Document a4gBRba43JywaXYe3MxKeGmKB

i In: Reviews on Drug Metabolism and Drug Interactions, Vol.IV#No.1tpp 1-48,Freund Publishing House Limited,London, 1982 44. ,SoHoc| , ads.1] specific covalent binding and toxicity of AUHMTIC HALOCENATED XENOUOTICS RdahoM J. Uib* Ab/eHungflf Toxikobgie fharmakoiogischet Institet derJohanna-Gutenberg-Univcnit&t ObereZafdbacherStr. 67, D4500 Mainz 1. Fed. Rep. ofGermany CONTENTS I. INTRODUCTION L RAUMUUtCS 2.1. Methyime chbrid* (Dichbeomeihnncl 2.2. Chbmform fTYichbroimtlmne) 2.3. Carbon letTW^inriAf (TfrmrhtntrTM*efhaHf I 2.4. I^Dickbroettmne, lJ-Dlbromoethane 2.5 1,1.1-TtiMoroethane("methyl chloroform"), IJ^-trichknoethane 2.6. I^'DibromoS-cMomproputte 3. HAUMUCEHE* XI. Vinylfluoride, vinyl chloride, rlnyl bromide (fluoro- ethane, ehhroethette, bromoeihme) X2. VbnBdene fluoride, rtnriidene chloride (l.I-difhto- rethene, l,1-tMchkeoethcnc) X3. ck-U-Dickbroethytcpe, tsms-1,2dlchloroethykne (tit-1J-dUMococthcac, tnm-IJ-dichhroelherte) 3.5. fi0^hmj*hvl^(TenwMmriktncl i CONCLUSIONS 4.1. Speckle anukat blading and cardnogentdiy 4.Z Specific covalent binding and (acute) toxicity 5. ACKNOWLEDGEMENT'S 6. REFERENCES ft%e 2 4 4 6 8 II 14 16 17 20 24 26 27 29 31 31 32 35 36 * TMi tado* u compiled dwtaf (ha Iconre of a Rcaeaicti Tramtae FeNowhlp at the latcnutianal Apacy fot Rcaeaidt on Cancel, Lyon, I'tance. 0334-2190/12/01000148 >1982 by Flared FaUbHi* Home Lid. AP000I0024 Vol IV. Ho. t, 1967 AHphdit HtlotmltJXenotiortct i. ikntoDUcnoN li (he past four dwdu there hat hem a tremendous Incmu h the production snd use of i wrier or hafogouted short chain hydrocarbon. They are used ki vast araotmli ar Industrial solventa for drgreasing, dry* dewing, food processing and paint removing purposes. In addition, some of them are fctdncliisRy impoatant plastic monomers; others ace lead acaveiigera (in petrol) of nt mod on large acale basis bi agrtatd- lure for a variety of purposes. Most of them compounds are refoued ki Incradng quenlltes hto tbe environment. Residues of techtdaSy fcn- portaut substances have been detected in drinking water (detailed Infor mation on production, we and occurrence la Included in references/I, 2,3ft. 1 The chemical and physical properties of hslegeastcd xenoMotfcs are welt documented. At can be sew from Fig. I.most of thehalogsnated hydrocarbons In question are Cj ea Cj compounds. In general, their chemical reactivity h relatively low, but (unttke many halogenated aromatic hydrocarbon pestlddei) many of these compounds (Fig. I) are resdly metabolzed. Some technically bnportant products have long been known as hepatotoxic agents. However, K was not until the discovery of tbs carcinogenJetty of vinyl ddoride that research on the mode of action of tliese compounds was greatly stimu lated. According to the present data, halogenated aliphatic hydrocarbons exert a variety of toxic effects which have been attributed to tbe fbrmaIbn of reactive metabottc intermediates. Such metabolites are capable of alcylaltag nucleophilic sites of different cclutae comthuents, resel ling In "covalent binding", i.en fa chemical modification of targets, (be biochemical function of which may be essential for (he cel. Carnal re lationship between covalent blnding of reactive hafogouted xenobkrilc metabolites to edhilar proteins and/or lipids and tissue necrosis has been suggested /4,5/. hritiatiM of paaxydative ttpid membrUM break down by halogenated reactive radical Mermodbtes /6/ may be respoaaible for parenchymal damage observed. Mutagentatty of liatogenated Epiialfc xenobfotfca has been thoroughly bivesligated hi different "short term assays" p,8,9/. With regard to DNAalkyfcHiow, the believed primary event in the process of chemferi CMChtogettesb. covalent binding of halogenated hydrocarbon metabolites to DNA has been eurained fa ritro and fa rfa /l 0,11/. Depletion of ccMotar glutathione hat also been investi gated. I R.J. Mi tfftrwi on Dmg MtlaboMstn and Druf Intcrocriont 3 AP000I0025 APOOO10026 ret IK Jfo I.1992 AUphatie Baiogeneud XenobMer Very recently, n increased acetone exhalation by rati exposed to various tudogemated alkanee and slkenes bat been (dated to a content binding of reactive metabolic taletmedlatn of there compounds to celular CoASli/l 1,12/. In addkkm, comUnationa connecting etmetores and metabolic reactivities of the chlorinated ethylene* have been pubMwd /13,14/. For most of the substance* of concent, resobi of long-term admal carctaogenlcby tests are now available /! ,2,3/. The oncogenic effect! of differ ent hafogenated ethytenes have been quantitated on the bads ofhistodtemkal examhution of preneopiastic nudeosids-S'- tripboaphstare (ATPase) deficient foci In rats exposed to there dhemlcds from the time of birth on /I4/. Furtheimore, the pharmacokinetics of there com pounds have been investigated /IS/. This now extendi the data bare for a toxicological evaluation of hatoatkanes and habaleearn. 2. KALOALKANES In conlrast to tbc halnalkenes C, and Cj haloaBnaes differ widely from each oilier in terms of mechanisms of reactive metabolite forma tion. and the dieaiical structure of Use reactive metabolites. Thus, these compounds, from s mechanistic point of dew, cannot he regarded as a uniform toxicological entity. 2.1. Methylene chloride fDtcMoromeihane) The non-flammability of methylene chloride whidi b widely used in paint removers and as a solvent in food processing, makes this com pound an attractive substitute for a replacement of other, more hazar dous, solvents /16/. Neither nephrotoxicity nor hepstotoxklty couM be observed after acute i.p. dosage of methylene ebbtide to mice /17,I8/, and hi a one year inhalation study (3500 ppm) with lalsouly minimal hepatoceHular siterations were reported /I9/. Hepalotoxlfc effects were observed in mice only withuHimately lethal doses /20/ and afler conti nuous inhalation of 5000 ppm. A carcinogenicity study in aide mice by i.p. fojeclfon (It/ revealed no significant difference in the results from treated and control aahnab. No malignant tumour increase was found in a two year Inhalation study in male or ferule liamsters, nor tat female rats, at exposure concentra tion! of $00, 1,500 and 3.500 ppm (6 hours per day, 5 days a week). -However, an apparent exposure related ssochifon between an Incveased incidence of malignant salivary gland tumours in male rats and pro- 4 Ht.Utb lUriewt on Drug MettboBan and Png tntcrecHoni longed exposure to 3,500 ppm methylene chloride was reported. Tilts observation was attributed to a viral infection of the salivary glands, which 1fleeted afl ms at the age or about 2-3 months /I9/ and was not Interpreted as of toxicological significance in the light of the extensive data on toxicity of methylene ddoride. With respect to the importance of this compound, reverd further studies are in progress (11/. in con trast to earHer observations which diowed a low teratogenic potential (see /23/) methylene chloride was reported to be neither embryotoxic nor teratogenic in mire and rati /24.2S/. Since (he findings that exposure to methylene chloride resulted hi elevated carboxyhemoglobin levels /26,27/ whidi were depended on the dose level admlnbtered /2B/ the metaboksm of this compound has been extensively investigated m vitro and hr rtvo /29-34/. Various lines of evidence drew that (he greatest portion of absorbed methylene chloride Is meUbollcaMy dimmated in rats and mice via dose dependent (saturable) pathways /30.31/. Mori probably, methylene chloride is mainly metabolized by a cyto chrome F-450 mediated oxidative reaction (see Tig. 2) to a hydroxy- rticNoromolhane intermediale. IICI clndmiion of the latter leads to formyl chloride, which decomposes, yielding the end product carbon monoxide. I aNAOFH1 -m 1 cytosel 65H -ho -Ha ic-o n^^HCWGSH enzymrSic ntymlc ''-HC0QH+GSH Hg. 2: MetsboEm of methylene chloride sccoidtaf lo Andcrr ft el (Ilf (pro posed reactive mctabofilei framed). As a second metabolic pathway glutitiiioiK-transrerare-medisled nu cleophilic attack of glutalhione.U suggested, leading to a chtororiKtliyiglutalhlone intermediale (Fig. 2). 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Ate I. I1S2 AHpkollc HnUjftitattd XaioHatia (Ions fa vivo. Furthermore, metabolic activation of chloroform in isolaicd hepatocytes caused protein alkylation, glutathione depletion and a lots in the hepatocytes' ability to repleaMi GSH from amino add pre cursors /43/; hi these experiments, ghitatMone depletion was foNowed by lipid pefoxydathm. However, (lie potency of cMorufbrat to induce BpM peroxydatton fn vtro, Indicated by determinations of pentane production in the rat, was only about 1/10 that of carbon tetrschlocfck /44/. Although irreversfcle binding of reactive<chl*rofotm melabolUes to proleins clearly occurs, so far al invealigationi reported /4,10,45,46/ bare failed to detect any significant binding to fiver RNA nr DNA from rats and mice after (oral) administration of ,4C-chlofoform. {Extreme ly low RNA binding was observed when RNA was Incubated with Hver microsomes and labelled chloroform pf.\ In accordance with these results, chloroform tt not mutagenic in & typhinuaim, with or without mctaboRc activation PL and N was thought that the reactive intermediate generated la the biological sys tem may not reach the target (the DNA of the lest bacteria), doe to a very short half-life. Sodi a view is eventually supported by metaboSm of chloroform to gencticalty active compounds tn Saccharoinycetceivvisae, an indicator organism containing a cytochrome P-450 dependent monooxygeaase system PI. Wilh regard to the carcinogenic properties of chloroform, there Is evidence that chronic llstue injury always precedes tumour develop ment /45/ and that tumours do not develop after doses of chloroform that are not ruffletent to cause tissue necrosis. The virtual absence of DNA-binding On rodents) suggests an epigenetic mechanlnnof tamoitgetUcily by chloroform f45f. 2.X Carbon tetrachloride Carbon tetrachloride, which is used in the industrial production of fluorocatbons. and as an industrial solvent, h tlae most hepntotoxlc chlorinated methane /47,20/. However, Its nephrotoxic potency Is much less linn that of chloroform /48,49/. As early as one hour after oral administration of a suffleteatiy high caibon tetrachloride dose, biochemical alterations Indicative of bepatotoxicity ate visible /4/. Such changes include early centrHobutar sup pression of gUco5e-6-phosphatase, lipid peroxydation, triglyceride ac cumulation, increase of seram enzyme activities due to monbrane dam B til U* XeitCMM DrugMeuMum and Drag bitcracikM* age, fatty degeneration and ceolriiobular ueevosia (4, lb. 50/. In Kuhmm, inhalation of high, but unknown levels of carbon tetrachloride has predominantly lad to kidney Injury, whilst oral intoifcatkms have resulted mainly in hepatic necroris /SI/. Long-term admtafatratioa or high levels of carbon tetrachloride to mice, rats and banters result In formation of hepatocellular evdnomas /3,52,53/. Two early studies In mice have demonstrated'the im pact of dose and dose intervals /S2,53/, and a correlation war found between the degree of necioda and the incidence of hepatomas obmrved /53/. Most probably, eatbon tetradderide is metabolized by cytochrome P-450 enzymes of the Uvei; an initial reductive dehdogenalioa step leads to a trfchioromethyl radical (see Fig. 4) /54, SS/. HOa nay be oxygenated by the microsomal mixed-function oxidase system to yield a tricldoromethanol latermediate ami, after HCMmuaalion, plwsgene /55/-Hydrolytic deddorinalioa of phosgene would then result hr mrbon dioxide formation, a major end product in carbon letmddoiide metabofism.bt vbo fS6, S7f and As ritro /57,58/. 'S ^ J ^[a-i eojvjna Fit. 4: HelttMha of eaibou trbulkddr according to Sail el d /SS/ (pro posed acadivo luelabolitaa banted). TricMofomelhyl radicals, released during carbon telnchloride melabofirn, may cilher abstract a hydrogen atom from Iti envimnment to yield chloroform, combine to bexadiloroethane, or bind covalently to proteins and lipids/I0,55/. Confetti binding of caibon telradiloride in rat Hver hr rim results in about the same extent of protein alkyialbn. 9 APOOO10029 Voi IV, No 1.19*2 Aliphatic HMogemird Xcnobioi/a t> chloroform. However, lipid alkylation by aihoi tetrachloride It about three times that of chloroform; and covalent binding of CCU b probably unspecific towards various lipid components (4f, It b wed known that the abstraction of a hydrogen atom from unsalomed lipids, e-g. by carbon tetrachloride derived radicab, initiates dpId pcraxydalion, and both the CtTj-(I) and the CQj-OJ - radical (II) have been suggested as being reiponsftk for the llpoperoxydallve mem brane damage observed /SO, 5S/. However, H b atH not clear whether the lesutUng ccd necrosis b due to covalent binding of the radicals) to microsowtal proteins and lipids, or to radical induced peroxydatiem membrane-bound RpMs. As a second reactive metabolite of CCIs, phosgene (III) /S5/ may be Involved In covalent binding to proteins and lipids. Iovertballons on nucleic add alkylation by reactbe carbon Miachloride metabolites revealed Inconsistent aod contradictory results. No covalent bindbig of radioactivity to RNA was reported after Incubation of 14C-caiboa tetrachloride with RNA and rat Rver ndcioaomes /I0/. When incubated with Rver mieioaomes from mice pretreated with melhylcholanlfvene, >4C-caiboa tetrachloride was covriently bound to various polynucleotides and DNA. Altec chromatographic separation of hydrolysates of (hb DNA, two distinct peaks of radioactivity, not coin ciding with the efolioo of the natural bases, were described /59/. Administration of ,4C-caibon tetrachloride to rats dfcl not result In significant amounts of covalent binding to nucleic adds of Hver/4/. In contrast, bw amountsofcarbon IctracMoride derived radioactivity could be detected In fiver DNA of mice, after preheatmerit of the anlmaii with melhylchobnthrene /59/ aad after administration of a toxie dore of non-radInactive carbon tetrachloride, together with the labelled coatpound f60t. However, in both sell of experiments, no detectable radio activity was eluted on chromatographic separation of the hydrolyzed DNA. Also, covalent binding to cytoplasmic RNA was not detected ht these experiments. This led the authors to speculate that reactive carbon tetrachloride mCtabofilcs, covalently blading lo DNA, may probably be generated by cytochrome P-450 enxymes of the nuclear envelope /60f. Oo the basis of these Investtuitions At riao It is difficult to decide whether carbon tetrachloride radkmcItvHy b h fact bound to the nu cleic add, or whether binding occurred to minute eo-teobted protein Impurities. In future experiments, proor of a deflnildy characterized alkylation product should be attempted. 10 R.I. Lmt Rcvicmom Drug MrtmboKtm and Drug httrraeikun Carbon tetrachloride was non-nmtagmic in S. lyp/ihnurhim and K eoB, both in the presence and absence of a microsomal activation sys tem /3,7/. As already suggested for chloroform, carbon tetrachloride metabolites, generated outside of the test organisms, may abn be loo short-lived lo reach the genetic material ofthe indicator mtero-oiganiun. The meefranbm of tumour formation by carbon tetrachloride shows rimibrilies to that described for ehlorofann. Uke chloroform, carbon tetrachloride produces tumours only hi animals heated with doses that are high enough to evoke hepatocellular necrosis. In the fight of llieae resuhi. It aeenw most likely that carbon tetra chloride, fin chloroform, acts at a luntorigen mainly via an epigenetic mechanism. which b triggered by chronic hepatic injury. 2.4 1.2-tHcNoroethatte, 1,2-Dibmmottlmte Became of lb uae as an Mermedble in the production of vinyl cWoride, 1,2-dicMorocthaae is among the "top 50 chemical products" (ranked according to the U.S. production volume /6l/). 1,2-dibroinoethane b much fesa used. Both hatoelhaoes are applied as lead scaven ger! In petrol and as grabs fumigants. and widespread human exposure has been suggested. A large amount of work hat been done on mutagenicity, csrebiogenicby and metabolism of these two haloethanes. Recently, a detailed review on genetoxk effects of 1,2-dkhloroetliane and 1,2-dlbromoethane /62/, and a report on I ,2-dfchlorocthaae in book form have been pubfished /63/. A brief synopsis of major toxicological manlfestalions and meiakhm of die two compounds, with special reference to covalent binding, b given below. The chemicals show acute hepototoxic effects In inhalation experi ments with rats (order : 1,2-dibronioctlianc > 1,2-dlchlorocllianeX * pecialy In fasted animals /64/, Chronic exposure to 1,2-dfchkwoetluiie caused fiver and kidney necrosis. Anti-fertility effects of 1,2-dfiironMvethane In various ^secies have been reported f2f. Roth chemicals have been found carcinogenic hi laboratory animals on various routes ofadadnbtration. I J-dleMoroethane was not as tumorigefiie as 1,2-dibrorooetkane. 1,2-dfiHomoethaue (but not 1,2-dicMoroetfcane) produced tumoun at the application sites: oral administration resulted In squa mous ceH carcinomas of the stomach, skin appUcaltoii in dun carcinoam. contrast, skin application of I ,2-dichlofoelbane produced lung tumourt bi mice. Hemangkttarcumas In male and mammary adeno- II APOOO10030 Pol tV, Ha. 1,1992 Afphttic Mogauttd XcmoNolles carcinomas in female rats were also reported. Male mice showed some Increase fa hepatucdMar tumours, and both sexes developed hint tu mours. From the only Jnhalatkui study with mice and rats no carcino genic effect of 1,2-dicfiIoroethane couM be deduced. Most probably (tie two I ,2-dihaloethanes are melabofaed ids two major metabolic pathways (see Fig. 5). One of thcae involves conjuga tion with glutathione by cytosolic glutathione Innsferaset giving rise to a "half-stdphur-mutfanr' (la) which may rearrange to an episutroahim fcm (lb). Further attack of glutathione on the cptartfoniam ion of S(2-haVtethyl) glatalhinne would lead to S^-ethylene-bbghitathlnnf or ethylene, whereas S-(2-hydioxyethyi) glutathione cotdd be formed by hydrolysis of the epfeulfonfcim ion. A second suggested pathway also leads to nercapiuric adds: it involves microsomal oxydatbn at one of the catbon atoms, to form a highly mutable gan-chlototiydria which would qronUneously dchydiohdogenale to the 2-haio-acrtyldehyde 00- Both the haloaccUkldiyde and the eptailfonium Ion are eleclro- Iu Ih A ft *ra'*1 l Aft * l sai|l} _x\w> > os-ch,-ch2-so FIs. S: Md<M metabolic pathways of I ,2-dichbtoeUune (XH?tJ and |,}Jbnlaoethme <X*Xrt accardlnf to Ramus er at I62f (pmpoaed reactive metobottes Craned). plittfc reactive metabolites, probably responsible for covalent blading to proteins and rndeic acids and for the observed mutagenicity. In general, lower concentrations of 1,2-dibfomoeihane, compared with 1,2-dicMoroetfcane are needed for achieving hepalotoxk, mutagenic or cvcinngenic effects; (his may he due to the higher reactivity of the bro mine- compared with chlorine- substituted compound. The direct muta genic effect of both haJoctlunes on typhtmurkm, la the absence of an exogenous metsboHzbtg system, has been attributed to theh aettva- 12 A/ a Rnituw on Dmg Meiabotknt and Drug latcraelkMi lion to the S-iialoethyl conjugates, because these bacteria exhibit ghifathioiin-S-tnnsfenM activity /62f. However, for 1,2-dihromnetltane direct chemical alkylation of p-nrtro-benzyipyridine and considerable blading to microsomal protein by a non-enzymic reaction ha been re purled. So, In addition to Its action via reactive metabohe inlermedtalex, a direct reaction of 1,2-dtbromoetbane as such cannot be excluded. Studies to deteratht whether covalent binding of the two haloethylenea is dependant on microsomal or cytosolic activation have re vealed contradictory results. In the presence of microsomal preparations from mouse, stomach or Rver, radioactivity of >4C-l^-dlchlnro-, or i4CI,2-dlhromoe<hanewss covalently bound to microsomal proteins and added DMA;binding was not signiHeart with denatured rakresotnes /65/. Furthermore. It was demoastrated that binding of 1,2-dfcMorocthane to lung microsomal proteins was significantly higher when hrrig microaomea from B6C3FI mice, a species susceptible to dichloroetltaneiuduced pulmonary tumorigenesis, were used, as opposed to OshoraeMendd rats which are resistant to lung tumor(genesis by dieMoroethane /66/. Lang cytosol did not catalyze dichlorocthane binding, and the addition of glutathione inhibited irreversible binding of dibromo- and (BcMoroethane In mtcroaomal systems of mutse Uver /66/. TNa would suggest that iiictosomal activation plays a prominent role in covalent binding of the two haloethinet. probably Ha lbe P-450 mediated meta bolic pathway (see Hg. 5). However, from a second study at vitm on covalent binding of dieMoroethane It was concluded that in the presence ofglutathione most ofthe DN|k-Mndfag results via cytosolc glutathionetnrtsfeme fSIf. After administration of l4C-diuonroethanc to rats, significant amounts of radioactivity became covalently bound to protein RNA and DMA of aB major tissues, with largest amounts of bound radioactivity in the liver and kidneys /68/. So far, no specific react ion product of baloetbane metabolites with DMA or protein baa been characterized. However, investigations on the specific type of todoa, after treatment with dibromo- or dichlorocthane lit row would be valuable in ctucidatluf the telatlve importance of the two major metaboHc pathways in haioelhane mediated toxicity and circbtogencUy. > oo o Ml Vol IV, Mr i, 1982 AKphttic Haiogenrtnt Xsitobioftct , 25. 1,1,1-Tridikmethau i"methyl chloroform"), /, 1,2-tricMorvdlutiK M.l-Tricfiloroethtne and 1,1,2-trichloroetliaae are chemical ktermedales In the ajnlhecb of vhiyHdcne chloride; 1,1,1 -Iriddaroethane is also extcnrively uaed aa an Industrial cleaning solvent /3/. In contrast to Its boater, M.l-tikhknoethane ("methyl ctdoroform'*) exhibits a very low tozle potential /3/, Hver damage occurring only after exposure of anhnah to nearly lethal levels. The oral LDta of 1.1.1- trichloroelhatK In rats and nice Is about It ft/kg; and death oc curs by central nervous depression (narcotic effect). Long-term carcino genicity assays with 1,1 .l-trkMoroethane have revealed no Increased In cidence of tumours hi ntt and mice, and also no ambryotoxicMy and teratogenicity wasobierved In inhalation experiments with that spades. More than 98% of 1,1,1-trlehloroethene administered b exhaled un changed /(W/ and the absence of specific organ toxicity may he viewed along with the km metabolc rate of the compound. There are also no reactive metabolites in the metabolic pathway yet propoxd for 1,1,1trkhloroetliane. Most probably, l,|.NricMoroelliane Is hydroxylated by cytochrome P-450 enxymes to IrkhloroetlimoL followed by subsequent conjuga tion with glucuronic add to yield trkhloroethinoi ghtetionide, or by oxidation to trfchloroacetate, both being major urinary metabolites of 1.1.1- lridiloroethane fTOf, A-slight mutagenic potential, described for 1,1,1-trichloroelhane In S. lyphimurium with end without metabolic activation, has beea attri buted to conlambialion wKh other potentially carcinogenic compounds PM- An elevated acetone exhalation during exposure or rats to 1,1,1trkhlnroetkane, as probable proof of formation of reactive metabolites has not been observed fl 2/. At present (here Is no evidence Tor mutagenic or carcinogenic effects of pure 1,1,1-lrlchloroetliane pi/. This b in agreement with the men tioned Insignificant metabolic rale and an absence of reactive metaboWet and may recommend this compound as a substitute for other (more loxlc) haiogenated hydrocarbons. Compared to I JJ-trieMoroethune, the oral LDj# of l,l,2-(rlcliloroethane in rats and mice b about 10 times lower /49/. The hepalotoxic potency of 1,1^-trkhtoruetbaiR Is considerably less than that of carbon tetrachloride and chloroform; however, Hk< chloroform. I.l^-trldiloroethane exerts marked nephrotoxic effects ^8,49/. 14 I i A/ Uib Rertort an Drag Mttabo&sm and Drug tnter*cHoni In fong-tetm carcinogenicity tests administration of (technical grade) l.l^-tricbloroethaiie has Incrcaaed lire Incidence of hepatocellular tomours and ndrenal phacoduomocytorus in mice. In rats, no signifkant increase in tumour incidence was observed/]/. No data are available on teratogenicity or embiyotoxfcjly of the compound. 1,1 ^-Trichloroethane b readily metabolized so that small amounts only are ehminiied by exhalation of the unchanged compound /72/. GSH corjugotkn F|,|i Metaboliniof l^.l-tricMoroeltimeftop) and |,|,2-lrlcMotoeMane (bot tom) according le Ivanetfcli tt at /TO) (propowd wc8w laelaMw framed). Several Hues of evidence suggest that 1,1,2-ltkWoroelhaiK Is metaboBzed by cytochroiue-P-450 enzymes (see Fig. 6, bottom) rig a higldy unstable dtlorahydrle, which after spontaneous dchycboltalugenation, yiebfe the reactive chloroacetyichkxide(l). Ilydrolysb of chloroacetykhkxMe then lends to chloranceUte, which U eliminated In mine or is conjugated wMh glutathione, leading to nrinaiy elimination of thiodlglycolic add ftOi. The formation of a reactive acybliog metaboUte (1) b consbteni with the observed hepatotoxk and nephrotoxic properties of 1,1,2-trichloroethane, but so far no date are available ou covalent maciomolecular bindfatg of thb compound. 1,1 ^-Tridilotoethane was not mutagenic ln OpMmrlM wHhand wlflioul metabolic activation f7.1/. Hepatic tumour formation occurred caperImentaBy with doses that also led to damage of the Over parenchyma. There Is some similarity in five toxl- 5 APOOO10052 Vol tV, No, t, 1932 AUpkaUc Hatofrnaied JTenoWotkt A|ical patterns or both 1,1 ,2-tridikwoethane and chloroform; also, Kis suggested reactive metabolic istennedkatea both have acylallag properties. 2.6. /J-Dibromo-3-cbfrropropene I ^Dibronio-3-chlonifnopane had pined widespread acceptance as a nenutocfcle and was used as a soil ium%ant. It was also present as an impurity in lro(2,3-<tthramopmpyl)pliosphete that was nsed as a flame retardant additive in synthetic textiles {3f. In 1977, employees at a chemical plant hi California, who had manu factured I ,24ibronK>-3-choropiopane were iaaad azoospennie or otigospermic. After subseqaenl surveys the U.S. Environmental Protection Agency In 1979 banned this compound for agricultural me in the USA n4/. Acute end subchronk hlialitba studies with l^-dtbromoO-chlofopropnne In different specks revealed toxic lesions in lung, Hvet, kidney and testes /76/. Severe atrophy and degeneration of the testa wereob served in rats, guinea |rigs and rabbits fi$f. Following repeated treat ment with l,2-dibromo-3-chk)ropiapane, tuanber and viability of sper matozoa were decreased hi male rats and oestrus was inhibited hi fe males/3/. I ^-Ubromo-3-cliloropfopane has carcinogenic properties in rats and mice with mainly a local action. It produces squamous ceM carcinomas of the forestomach in both species and adenocarcinomas of the mam mary gland in female rats PI. Chronic inhalation studies with 1,2-dibfomo-3-chloropropane resulted In carcinomas of the nasal eerily in rata and mice /76/. In two-stage carcinogenesis assay 1,2-dibrotno-3> chlnroptopane was an laitlalor of skin tumour when pborbol myrbtate acetate was applied asa promoter f77{. However, repeated ikin appHca* (ion to mice resulted ska in lung and stomach tumours, Indkating lhat l^-dlhronio-3-chloropmpsne acts not only al the site of application nv- When rats were orally treated with 20mg/kgorM{M,2-dibinm>-3chkiropmpane, 99% of lire dose was metabolized and the metabolites cHminated in urine, bHe and expired air. Radioactivity expired consisted mainly of '*00* /78/. As urinary metabolites the mcreapturk adds of S-(2,3-4)ihydroxypropyl)cystine and !,3-{bis-cystelnyJ)propan-2-ol, bromotacUte and /J-chtoroladale, have been idcnllfkd /79/. Because notably epkhlotohydrin (I) and eplbromoliydrin (I) produce the same lb R.J. LM Refitwt on Drug UeteboRm *ndt>a$ h/mnfMi urinary metabolites, tlie epihaiohydrina were suggested as metabolic Intermediates of dlbcoaMxfiloropropaHe /79/. OehyOohologefHition and oxyOobon x-gv.a Ft*. 7i MeMalw of |,2-dR>t*BK>-3-cUofopfopanc accgidhig In lone* el el 1791 (proposed reactive melabolfie* framed). It hu been speculated (see Fig. 7) that dehydrohak>gcnalion of di- bromo-chloropsopafie, followed by oxidation via monooxygenases, may result in reactive aliphatic cpitalohydrins (I). Opening of the epoxide ring by hydrolysis would produce a-hatoliydrini (II) which are known to undergo oxidation to fl-hakacetale and. via the respective aldehydes, to oxalate. This means that four reactive metabolites, epfchlorohydrln (I), epi- bromohydrin (IX e-chkuotiydrin (II) and a-brotnohydrin (II) have been suggested/79/. l^-Dfbfomo-3-chkHoprojsane showed llllle direct mutagenicity in the Salmonella test system. However, when activated to an tdlinuie mutagen with S-9 preparation (pine) dibioino-chlofopropeee was dear* ly mutagenic. Hie microsomal S-9 fraction alone wns responsible for metabolic activation of the compound, and glutathione Inactivated rather than activated tUbromochloropropane (SO), much In contrast to the findbip with 1,2-dtfiabetluoes (see aboveX In addition, covalent binding of l,2-dibromo-3-chloropmpaiie to mkrommal protein in film Is dependent oa enzymatically active mlcro- somes/81/. / 3. IIALOALKNE3 Tlie data available on metabolism of haloetiienes /9.13/ Indicate lhat compounds of elaas cliemkal class are uniformly btuliansformed to 17 AP00010033 Hot IV. Na 1,1992 Anphtlk Htto/mmmttd XmoHotk! (lie corresponding epoxides (oxlranes) by microsomal monooxygenases, located ai endoplmmic membrane*. The oxkanes vndergD rearrange ment lo halogenated aldehydes or acyl halide*, which cm be further converted to halogenated acetic adds. At different metabolic tombcon* jngation wkh gtatathloiie may lake place, reuriting hi final excretion of nlphur-coatsiniitg metsboltes (see Fig. B)/l 1,116/. According to the present data, reactive metabolic Intermediates or haloethenes are represented by the epoxides, and probably abo by re arrangement products thereof /9,13/. It Is w$B established that Indivi dual members of the baloctbene cbn differ widely in tcxmi ofboth re activities of their metabolites and to^lc adloni f9, II, 13/. A* toxic and caidnogerdc effects of individual Uodhenea have been attributed lo formatlou of reactive metabolic fartermedletee, difTerencea la toxkillee nay partly be dee torfiflerent metabofic rates of the compounds, pounds. Extensive studies on phmmacoklnetlca of the habethenes In ques tion have now revealed that the metabolc dtrdnalion of these com, pounds is a saturable, dose-dependent process /IS, 85/. When rats ire exposed to an atmospheric concentration of a halogenated elhene which exceeds "a point of saturation'', elimination h determined by * zero-order law. |j. Its rate Is independent of the Ibsae concentration ' of (he compound. Below saturation, metabolic elimination itdescribed by normal fittl order kinetics /15,85/. In Wbtar rats, under conditions of saturation, the metabolc rates of the dtffacnt hriocthcnes (V^, see Fig. 8), and hence the rates of formation of reactive metaboltea, range over two orders of magnitude. Thisclearly demonstrates that for quantitative toxicological cnnsldemtlons the rates of metabolic trans formation of these compounds must be taken into account /id, IS, B4/. Rclfflibiiiy consMeratloRs connecting the structure or chlorinated ethenes and Ihe activities of the initial epoxide Intermediates have been publkhed by Ibitschlei and coworkers. These authors have suggested that reactivities and lienee loddUra of the Individual chtoro-oxirane intermediales depend on the type of ddorhte substitution, hi that sym metric substitution mulcts the epoxMet cetattvety stable and not muta genic, whilst asymmetric substitutions cause unstable and therefore mutagenic epoxides /13, 83/. Trichloroethylene was exempted from this general rule, because Its epoxide^ although asymmetrically substitu ted and reactive,Is immediately farther tientformed (tithecytochrome P-450 site) to IridiloroacetalttShyde. From this point of view, hatogenated elhenST may be divided Into two dames, the symmetrical ones 18 R.J. Ltib Rertewton Dmg MttmMitm <mdfirut Inlfftlionr *WH B-bfVcV<]i yirtf* ItuorUa h. /H gm [Av'Vo"^! C--C -----* C--C. ; ' 'XI wwicMorida lis Ml t'-q C--C ---- > h' vBr j-v-j--?<. OSH conjugmtan "W ISSeiVjT vf ** K. vk^UJane SucrMa .o P "V-Cs'a,-- OSH cor*igaHon CHCtj-CtyOH ""Vs, -CMCI2-CC. Uonf-t3 rmwemqfane m' a UicHoroeUyhne [iK____ 'a] f pjimuWtyina cOfC^ --i cctj-ctyw \------- ------- ,0! * *Q C^<pj-^CaCv OH Fkli Metsbolc schema for dMfaent hateethene* aeoMdiag te Pome and Hv drier /l3/an4Bartaehefet to Fiber wriBott/iS/. awofAn* 19 AP00010034 ftd.lV.Ho. 1.I9S2 Altfhu/c iUlogemtcd Xenobiolfct (*- and MnB*!,2-dichk>roflthylem; pefckloiodhyleiK) which form stable epoxides and ate nol mutagenic and the imsymmetrical com pounds (vinyl chloride, vinyl fluoride, vinyl bromide, vhsylklene chlor ide and vinyNdene fluoride), with tricldoroethylene as dn exception (sec R*. *) -- 3. 1. Vinylfluoride, vinyl chloride, vinylbromide Vinyl fluoride, vinyl chloride and vinyl bromide are used in the manufacture or synthetic polymers in tlie plastics industry. Bycontrast to the vinyl chloride, only small aroounttof vinyl bromide are used asa co-monomer in plastic fibres. Vinyl Onorkle b used in tlw indualrial synthesis of polymen with improved chemical and phyded stabHHiea. These (luce hdogcoated etlienes do not show acute hepato* or nephrotoxicity in laboratory aahnals (except hi one study with mice) ft, 86/; pretreatment with selected inducers or the hepatic monooxy genase system being necessary for injury to become manifest /86/. After pretrestment with polychlorinated biphenyls the relative hepatotoxfc potencies of these compounds have been found similar; alto, the spectrum of murpiiologic changes waa the seme /86/. " The detection of carcinogenic properties of vinyl chloride In labora tory animals fSIf and in man /88/ has prompted many publications dealing with various toxfcologfcai and biochemical aspects. Literature on loxfcily, mutagenIdly, metabolbm and cwdnogenlcMy of vinyl drioride In anlmab and humans hat been thoroughly reviewed, and vinyl chloride b now conridered a human and animal carcinogen, with liver, brain, lung and haemo-lymphopoietic tyriem being target organs. Furthermore, it has been suggested that vinyl chloride b mutagenic to human 12f. Preliminary results of an inhalation study with vinyl bro mide in rets reported on increased Incidences of Urn angiosarcomas and zymbab gland carcinomas /&/. No data are avaflable on bag-term carci nogenicity studies with vinyl fluoride. However, after exposure of new born rats to etther vinyl fluoride, vinyl chloride or vinyl bromide, (he potency of vinyl fluoride to induce hcpalocetkitar preneoplastic "ATPwe" deficient foci has been demonstrated /I4/. Metabolic patlgyays for vinyl chloride In mao (99/ and in the rat [2f have been Investigated by several research groups. AM Ibe available evi dence shows/90/that vinyl cldortdc bepoxtdized by monooxygeuasefO (see Fig. 8) to diloroethylene oxide which liran rearranges lo chloroacelafdehyde. Chloroacetaldehyde b oxidized lo chloroacetic add. 20 HJ. Lett tfWfwjoh DrugMeubobtM eittf Drug Anrwrtmi Corrugation of these primary btermedbtes with glutathione is followed by modificalbn of the peptide moiely of lire glutathione conju gates, leading (o sulfur containing urinary excretion products. diloroethylene oxide (i) and chforoaceUldehyde (II), both being reactive electrophilic Intermediates m vbyl chloride metabolism, may be responsible for the toxicity and carcinogenicity observed /II/. No details are available on the metabolic pathway of vinyl bromide subse quent |o cpoxidalfon, although the implication of bromoethylene oxide in the metabolbm of tins compound has been suggested /8/. Several tines of evidence suggest that covalent binding of Ihe reactive mono-haboxiranes and hsloacclaldehydes might be involved In tissue damage observed. After exposure of rats to 14 C-vfnyl chloride, covalent binding of this M C radioactivity to proteins of various tissues, with pre ferential binding In the Bver, has been demonstrated /91,92,93/. Fur ther studies on protein alkylation by reactive vinyl chloride metabolites reveMed a preferential aBcytarion of Sttgroups of cysteine w rirro /94/ and the attachmeal of a 2-oxocthyl gioup to tire l-N and 3-N poritions of hbthllM in experiments in mice hi viro 1951. After incubation of l4C-vinyl bromide in a ral Rvcr microsomal sys tem, reactive nwtabotla of vinyl bromide also became covalently bound to microsomal protein /96/. Depletion of hepatocellular glutathione, most probably due to co valent Interaction of tbe lattei with reactive meubofoes of vinyl chlor ide (97/ and vinyl bromide /98/ has been reported, and eoaridcntioits of the mechanistic background of interaction of both compounds with glutathione have been pubjtehed f99/. Exposure of rats to vinyl chloride resulted in deactivation of certain cytoehrooeP-450*ectes/100pl0l/. Very recently the pmsibHIty of covalent binding of reactive vinyl chloride luelabohles to coettzyme A has been proven /11/ and evidence was obtained for specific binding by a thfoether linkage. This, nod elec trochemical data on coenzyme A reactivity compared to that ofgluta thione, lends support to the suggestion (hat coenzyme A might be an even hotter target for reactive hafoethene netaboMles than ghstathioae /II/. Both reactive vinyl chloride metabolites (diloroethylene oxide and cMoroacetaldehyde) react with nucleic acid moieties, leading to defined alkylation products /11/ (see Fig. 9). Targets for alkylation in nucleic adds are adenine, cytosine and guanine residua of DNA and/or KNA. In RNA, both bi vitro and in vivo the principal alkylation products 21 H 0 APOOO10035 Vol IV. No. I, 1982 Afiphatk /Mogenakd XauMatict V _-r "til Ot c c a Ot o c a *T <V N X t /U-2 Z N* z w & 22 z X* nr Ot cc n o c o i u o o 1 c at 41 f Ot o ZX trt 0 1 IN \\ / 0 1 CM 1 r* Ot XLJ-7^2? c cM at o o o' X c at X c. "5 i e Z *-- N M * ModVM bam derived from covtlsnt btodisi of m a in v ta jrt cU uidt meabofltu is DNA ud/or ANA. fU. u Rttfevn on DrugflittabaHsm and Drug fawactioHf ate l,N* -clhenoadenosiiie and 3.N*-ethcaocylktine /102, 103/. Fur thermore, nril twounti of 7-oxoethylguaeine have been demonstrated in nt liver RNA afler exposure of the aaimals to 14C-vlnyl chloride /I04/. After chemical reaction of chtarmceuldehyde with DNA, NJ3etheaogiianine was formed as tlie only guanine alkylation product with in the nucleic acid /I05/, whereas chemical reaction of driorocthylene oxide with deoxyguaaoahw led to 7-(2-nxoelliyl)deoxyguanoslne (I) by introduction of a 2-oxoethyl group at (lie 7-N poshinn of the mole cule /I06/. This compound may nornully be present is 0*-7^i`hydnyethano>deoxyguanosine(ll) /I06/, thus representing a cyclic hendacctal form, which affects the 7-N as well as the 0*-podtfon, an important aspect in view of Ihe often dissimilar biological roles of 0*and 7-N afltylsllon ofguanine. 7-(2-Oxoethyl)guaniue, the major alkylation product, I Jd*-ethenodeoxyadeftosine and IJi4 elheno-deoxycylMine are readily formed in Him on Incubation of DNA with labelled vinyl chloride and rat Hver ndcfommet /I04/. However, the nature of the vinyl cMorMe-DNA adduds formed In vbo are stiS a mailer of controversy. Evidence for the occurrence of ] ft*-etbeno-deoxyadenosine and, 3Jd^-ethenodeoxycyUdine hi the liver DNA of cats, after receiving vinyl ditoride for two years in Iheir drinking water, has been presented /107/. Othirer re search poupe have detected only 7-(2-oxoethyl)ft*anine in liver DNA of rats/104/ and mice /95/ after acute exposures of the animals to t4Cvinyl chloride. N*3-theno-guaniae has not yet been identified as a product As afro. The rindlarky of vinyl bromide with vinyl chloilde h evident as both form the him ikybUoa products wMh RNA /108/, in vi/rv afterrricrororaal activation, and hr afro and with DNA in vitro fi 09/. Bxperhnenti In various systems*have been carried out /I l(M I3f to determine whether there adducts have miscoding properties or would after die processes of transcription and translation. Translation of poly A containing m-RNA In wheat germ celt free systems, resulted in a dif ferent pattern of the synthesized proteins when the m-RNA was tota led from livers of rata, 8 hours after exposure of the animals to vinyl chloride or vinyl bromide /110/. Transcription of different synthetic ternpines which contained l,N*-ethenoadenlne and/or 3/i4-ethenoeytoslne by DNA- or DNA-dependenl RNA polymerase revealed evi dence for mlscodlna properties of there afeyblkm produets, and it was suggested that the "ptomuiageoJc lesions'* evoked by l,N*-ctbenoade- 23 AP00010036 rot ir.fta t.tw Alfpfttttc HtioetmteUXentMoUct nine and 3,N4-etlenocytodn residues may represent the initial steps in vfciyl chloride induced carcinogenesis /111/. The available dala ou covalent binding to proteins and nucleic acids an consistent with the formation of haloethene oxide and hakacetaidehyde as reactive metabolites of vinyl chloride end vinyl bromide. Sig nificant direct bacterial mutagenicity was observed with chloroeiliylene oxide and ehioroacetaktefcjrde, but the former was approximately 20 limes more effective than tire aldehyde, on an equimolar baria /114/. Subcutaneous infections of chloeoelhylene oxide to mice revealed local sarcomas / IIS/. Chloioethylene oxide Induced ddn tumours in an initiation-promotion experiment whereas ddoroacelakldiyde did not /IIS, 77/. Furthermore, diloroaceialdehyde-dtaceUl has been reported to be non-carciftogenic /116/ ml bb-chloroethylethw, a sabstance part ly metabolised to dibroace(aldehyde In the organism, showed no car* dnogenietty In rats after oral administration /117/. Although chloroecetaldehyde haa not yet been studied in long-term carcinogenicity tests, the above arguments support the more or less ex clusive role of chloioethylene oxide as ultimate carcinogen hi vinyl chloride Induced carcinogenicity. 3.2. Vinylkienefluoride, PbryUdene chloride Vinylldene chloride it widely used for copolymerhallon with other monomers. Vinylkiene fluoride hat been round suitable for industrial synthesis of polymers of Improved stabrtky /119/; however, sufllckat toxicological data on this monomer are lacking. Acute inhalation tests in rsts/120, 121/ are lucocuhtoat, but suggest a much lower degree of acute toxicity of this compooed compand to vinylldene chloride /2/. Tills may be partly due to the slow metaboMc rale of vfciyRdene fluo ride vhkh b about 1/100 that of vtnyHdene chloride in the rat /122/. ' VinyHdene chloride exerted a masked toxic effect In a series of spe cies which was dependent on dietary parameters (fed or fasted anhnah) and the hepatic gtulstliioiie content /2, 123-125/. Liver and kidney in jury has been reported In animals exposed to 50 ppmvbiylkkne chloride (fth/day, 5days/week) for several months /123/. A continuous 90-dsy inhalation exposure to 48 pptn produced death In monkeys and guinea pigs, occurrence of morphologtcd changes In livers from monkeys, dogs and rsts. and kidney chaages In rats /I24/. In faated tats. Mm paren chymal cel injury was observed tiler a 4-hour exposure to 200 ppm vinyldene chloride /I26/. Acute Inhalation exposure to vinylldene 24 HI Lett Petitwt an Drag tDrm'lwxi ddoride mulled In a marked decrease In liver glutathione concentreHons /I27/. No teratogenic effect of vinylldene chloride was seen In either rats or rabbits, end some evidence of embryotoxlcity and fetotoxidty was aiaocbled with maleraal loxk leveb of exposore 12,128/. In a long-term carcinogenicity study hi rats, after oral admbiistration of vinylkiene fluoride, Kposaroomas were reported /129/, the biological slgaifkance of which b not dear. CarcinogenIcily of vinylidene chloride has oof been observed in several long-term studies with rats/130/;but another study reported about hemangiusarcomas in two rats, probably related to Ihb compound /I3I/. VinyHdene chloride induced kidney tumours hew been reported in mice, with a higher sensitivity of males 13, II/. However, vmylidenechlorideinhtdalion Induced abobroachioatveolar adenomas and angiosarcomas of the liver in thb species /131/. Its,potency to induce preneopfastic hepatocellular ATPase deficient foci In the rat was about one order of magnitude higher than that of vinylldene fluorMe, but ranged about three orders of magnitude below that of vinyl ddoride /I32/. Both aaymmetricaRy substituted 1,1-dihaloethenes are bioactivated .o mutagenic metabolites, but to much dff lerent extents. In experiments with vmylidene fluoride, a borderlfcie Hver-iracrosome-dependent mutagenic effect was observed, whereas vmylidene chloride showed a marc pronounced mutagenic response In ifphi. murium, espedely when activftled with liver and kidney fnctbns from mice /B, >3/. Most probably, vfciyHdene chloride b raetabolketty activated vf Ha epoxide (2,2-dlchlorooKirape) which rearranges to ddoroacetyichloride (an % 8) /|33, 13/. Hie latter compound b hydrolyzed to drioroaeetlc acid, which after eombtnatkra with glutathione and further de putation of the glutathione reddne leads to Ihlodiacetic add as a major metabolic end product /134/. No data are avertable on vtnyHdene fluoride metahoksra. 22-Dkltk)rooxin(ie and chloroacetylchloride, re dive Intermediates In vinyidene chloride metaboksm. hew been pro poeed as responsible for acute and chronic loxidly of (Ik compound observed in rodents. Furthermore, diloroacetlc addww proposed to lead to cellular damage by a biochemical mechanism of lethal synthesis (see 4.2)/127/. After inhalation exposure of rats tn 14C-vinyiidcne chloride, the radioactivity covalently bound to Mwr protein of the animals was great er in fasted than in fed rats, In parallel to the Ircpstotoxic effect, al though fasted animah metabolized less vinylldene chloride than did fed 25 APOOOI0037 Vnl IV. Ntt. I, fO*2 Ai&mtic Mbynuinf XrmMnlift rats /I3S/. Disulfham pretreatment, which reduced (he acute lethal and hepalotnxic effect of inhded vhsylldcne dilorkfe, also reduced 'the le vels of covdenlly bound radioactivity In the liver and kidney of mice after i.p. administration of1 'Gvtnyhdene clderide to the animals/IJ6/. This led the authors (o conclude ihsl an bciease In the covalent bind ing of reactive vfnytfdene chloride irHermedtales to target tissues may be associated with vinyNdene chloride toxidty /135,136/. Covalent binding of the epoxide and/or Its derivatives to elhaimtamlne moieties of membrane ffpfds has been suggested as being respon sible for the parenchymal damaging (fleet of vinyMctie chloride; and methyMMoacetominoetbaaol, a urinapr metabolite of rrbiyMdene chlo ride hi the rat, war tbooglit to be derived sis this reaction /I33/. DNA alkylation In Bver and kidneys of rats and mice after exposure of lire animals to 14C-vfayldeoe chloride baa been reported,and a low level of DNA repair In the kidneysof mice exposed to vtnyHdenechlo ride could be measured / 130/. Furthermore, these experiments revealed a 25-fold increase in DNA icpMcatlns hi the kidneys of mice, probably due to the tissue damage observed in (he tame organs /l30/. This led the author* to the conclusion that vfayKJene chloride appears to induce tumours primarily through epigenetic mechanisms. However, their re sults do tot necessariy Indicate that the tumours observed hi mice ex posed to tfnyIMfcMechloride, mlghtariae through effects of (he chendcat on non-geneUc components of (he cell, but may suggest that tunrorlgemc doses of (lib compound could range in the urn order ofmagnitude, where tissue damage la to be expected. 3.3. da/,2-OicMorrxthyIeme. tmo-l,2-dkhk*Vtkyletie tram- and c-1,2-Dtddoroethylenc are used ar industrial solvents. In various countries the TLV/MAK value of both homers has been set to 200 ppm, a concentration which b baaed on earlier publications on the narcotic properties of these compounds /137/. Animal experiments have dwwn dial exposure of rata to 200 ppm mans-or ds- 1,2-dichloroethylene Inhibit* ding metabolism by (he hepatic mixed function oxi dase /138/. Furthermore, exposure of rats to 200 ppm kmtf-l,2-dlchloroethylene for various time periods Induced filly degeneration of hepatoeyics mid of Kupfler cells/139/, Both hatoethenes have been re ported to be weakly nephrotoxic to the mouse, and rf*-l,2-dlchlor*etliylene seemed to be more toxic than the tram homer /17/. Thh may 26 it/ L>6 Rertrwf rm Dru% Metabofiim and Drug iilcrtrinms partly be due to the higher metabolic rate of rfs-l ,2-dicliloroelhyfenc /15/. (See Fig, *). Most probably, both hornets are metabolized nu primary interme diate oxiranes wHch rearrange to dichlotoacetaldehyde /13/. T he brier may them be oxidized to dkhioroaceiic acid nr reduced to dlcMomedurool; both metoboHles have been identified in perfusates or an isola ted ret liver preparation /140/. Although a reactive metabolic tatermedhte (i^-diehiorooxyranej h reggesled, no mutagenic activity ofrfr- or MU- 1,2-dichloroethytene could be detected In E. coS K12 with and without metabofic activation /83/. Thh b in accordance with (he abovementioned rule on structure settvky relationship /13, MO/, which pre dicts for those chlorinated ethenes which are metaboSred tie symsnetricaly aubatltuted epoxides no mutagenic or carcinogenic activity. 3.4. TftchlorDethyfeiK Today, (he overwhelming amount of trichloroethylene produced b used as a solvent, eg. for degreasing of metals or in Ibe dry cleanhg Industry. Due to Ms wide applications, an extensive literature on the loxidly of thh compound h mBabb which has been reviewed by several authors (see /3/). Although acute and long-term exposure has disclosed some cellular damage in Bver and kidney of experimental animats /3, 141/ no pronounced hepato- or nephrotoxicity could be attributed to thb compound. However, pretreatment of the animals with agents that induced hepatic monooxygenmes, resulted fas acute hepatic injury afler exposure to high IricMoroethybae conoenriatinni /I42,143/. In a tong-term carcinogenesis assay by garage to rats and mice, irlddocoethylease waa reported lo Induce nuBgnant liver (umoun In mice hut not In rats /I44/. hs thb study a technical grade preparation of tri chloroethylene waa uaed, which contained substantial amounts of cpfcWorohydrin and 1,2-epoxybutane, two weR-eslablbhed muiagens and carchtogCM /145/. A recent latulalory carcinogenicity study in tliree animal species revealed no indication for carcinogenicity of pure tri chloroethylene /I46/. Furthermore, trichbroethyfeiie did not Induce preneoplastk hepatocellular foci afler inhalation exposure to rats, from time of birth ostwwds/147/. Studies In rata and mice revealed no embyrotoxic or teratogenic potential of the compound /3/. 27 AP00010038 VoL IV, Mj. I, 1992 Atphatie IMofentltd IcmMlto AH the available evidence Aowt that irichbroelhyleaefemetafaotfzed by mixed function oxydases to 2,2J-tHcMotoethykue oxide /13,149/, which is farther converted to chlural /I3, 149/. CMonl is in pari re duced to trkiiloroelhaDol or oxidized to UfchJoroaceUc add, the major urinary metabolites of trichloroethylene In animals and in nun /I3,3/ (see l-1g. 9). Ghilathtane conjugates have not been Uentitled as ntelaboHies of trichloroethylene so far /ISO/, although an hepatic glutathione decrease has been reported In phenobeibMone pretreated animals after exposure to this compound /ISO/. For the apparently exclusive rear rangement of irichlofoettiykne epoxide to chloral hi rko, which It in contrast to the expectation from the thermal rearrangement behaviour, an explanation has been provided /149/. Thie suggests an Immediate Lewis add-type catalyzed rearrangement of the reactive epoxide to the non-reactive chloral whhin the hydrophobic environment of the monooxygenases, which would be consistent with the lacking carcinogenic potential of trichloroethylene. After microsomal activation, trichloro ethylene is mutagenic In coN, S. lypMimrirm and several strains of Sacdimmycet cerevtsiae /3, 83/. In one study the pure compound rfiowed no mutagenic activity. In presence or absence of a rat liver microsomal activation system /MS/. On incubation of ,4C-trkhloroetliyleae in liver microsomri systems from rats and mice,14Grad*oacUvity was covalently bound to fiver endoplasmic protein /ISI, 152/ and the binding was related to the activity of hepatic monooxygenases in the different species /I52,153/. Binding was decreased by addition of inhibitors of the monooxygenase, and enhanced by Inhibition of the microsomal epoxide hydrolase whit (ridtloroptopcne oxide /I52/. Microsomal trichloroethylene metabolites were bound not only to sulphydryl groups, hut also to anise groups of proteins wiiich were added lo lire incubation mixtureyi5l/. After exposure of rats to 14C-lrrchhxoethyieoe vapour, radioactivity was hreversitly attached to hepatic proteins /I5I/. An i.p.administra tion of the labelled compound lo mice revealed a distinct bindbig pat ient in the different cellular compartments, with highest values fit microsomal and lowest in cytosolic proteins /153/, poinihig also lo P450 centred rearrangement reaction. Incubations of '^-trichloroethylene with salmon sperm DNA in the presence of ndaosomnl preparations resulted in covalent binding of re active mHihotites to tin DNA. The amount of covalently bound radioacihrily was much higher in the presence of microsomal proteies of male than female mice, and could be enhanced by pretreatment of the 28 ft/ L*U> Veriewt m Drug MenboMpm mi tutertetiom animals with pitcnobarbital in vivo or by addition of trichloropropene oxide to the incubate /IS2/. After microsomal incubation of the nucleic adds with MC-trfchlo*oehyieiK, chromatographic separation of DNA or fWA hydrolysates revealed some radioactive peaks, but no major al kylation product could be detected hi positions of the duale which were characteristic foe aficyUtioa products of the chemically related vinyl chloride/147,154/. The possibility has been menlioned that the positive mutagenic results may have been partly due lo impurities in the test samples 13/ and that small amounts of reactive Impurities also In the commercial radioactive trichloroethylene preparations may have been the cause of "apparent" covalent binding /$/. However, purified ,4CMrichloroethy lene abo showed a considerable microsomal binding when incubated M vitro /153/. Possible structural differences of the metabolic activation system in vitro, compared with the in vivo situation, may have facilita ted the escape of tlte epoxide as such from the hydrophobic rearrange ment site, which may be pertly responsible for the effects observed tn vitro. Very recently, small amounts of covalently bound radioactivity Itave been reported in rat and mice liver DNA after i.p. administration of l4C-lrkhforoethy1efie to the animals /155/. In fniure experiments, proof of a definitely characterized alkylation product should be at tempted. 3.5. PcTckloroethykne Due to Its non-flammability and Hs excellent solvent properties, per- cfckuoethylene Is used as a dry-cleaning, fabric finishing and metal de pearing agent /3/. Perchloroethylene is absorbed mainly through the lungs and b pri marily elimlnaled unchanged in the expired ah. With repealed expo sures, U is stored partknhuly bi fatty tissues, and is retained unchanged within the body for prolonged periods of time /156, 157/. In laboratory sithnah end in man. Use predominant effect of acute perchbraethykae exposure h depression of the central nervous system /158, 159/ probably due to the pre-narcotic and narcotic actionoT the unchanged compound /I58/. Although perchloroethylene is generally regarded as being of low toxicity /159/, liver and kidney damage lias been reported in laboratory animals after high acute dosage, f3,159/ or after pretreatment with polychlorinated biphenyls /160/. Daily adinin- 29 APOOO10039 Vol IV, No. 1.1982 AUpkotic IMogemmted Seruybioikt Istmtion or high oral doses of percfdoroethyleiic produced an increase of hepatocellular carcinoma in mice. In rati, In the tame study /I6I/ pcrddoroelhylene was not Ivmorogenic. In addition, perchloroelhyteite did not induce prencoplastic hepatocellular fod after exposure of new born rati lo the compound/163/. Most probably, perddotoethyleae is metabolized by microsomal raonooxygcnaae(s) to tetraddorooxymne /I3, 140, 157, 164/. This epoxide may rearrange to tricMoroacetyl-chloride, which b sabseqvently hydrolyzed to trichloroacetic ndd /13, 164/. Another suggerted pathway, involving nudeopMIc attach by water, or enzymic reduction of the epoxide by epoxide hydrateae| wouM lend to n tetrad)lorhuted did intermediate. Spontaneous dehalogenalkm of the Intter and hydro lysis of the resulting acyl chloride would yield oxalic add /IS7/. Tri chloroacetic add and oxriic add have both been reported as major urinary mctabohtcs of pctchforoelhylene /157. 165/. No glutathione conjugates have been identified, and perddoroethyteue did not rhow glutathione depletion, which has been attributed to the very low meta bolic rate of the compound. Tetrachlorooxlrane (I) and/or tricMoroacetjdchloride (II), both reac tive metabolic intermediates of perddoroctliylene, have been suggested to acylale ceftutar constituents /140, 164/. On incubation of l4C-pcrchloroeihylene hi i rat or mourn Hver microsomal system, MCeadloactivity was covalently bound to microsomal protein of both apedes /I63, 164/ and microsomal Incubations of the non-labeled compound revealed significant amounts of the trichloroecyl moiely bound In ester or amide llakaga to the microsomal protein /I64/. SmiUr results have been obtained In the isolated perfused rat Hver preparation, where 3-5% of the total uptake of peteMoroethykne waa eovdently bound to rat liver tissue n acyl chloride. This type of covalent binding was suggested to undergo spontaneous or enzyme-catalyzed hydrolytic cleavage /140/. After exposure of rats and mice te 1 *C-perddoroethyiene. the greater extent of irreversibly bound *4C-iadloactivHy in hepatic rmcoraofeculei of the mouse was attributed to Ihe higher metabolic rate of the compound In this species /166/. PercUaroethyiene was nefthtn muta genic when tested in cofi K12/83/ or lyphirmrlum // In the pre sence of liver microsomal fractions, nor active as debt tumour initiator in a two-stage carcinogenesis assay on mouse skin /77/. Investigations on an anticipated differential sensitivity of the mouse (B6C3FI) and the rat to percWoroethylene revealed no covalent binding of percMorectlivtene anlaboftles to purified mourn Hver DNA /f 66/. However, ap- 30 8.1. l*ib Reriewt on Drug MrtahoKsm mtj Drug Intertetiont proxlmately a two-(bid increase in UNA synthesis and hlstopathologicri changes were observed in the liver of mice but not In tats after repealed and exit adminittratfcMi of perchloroelliylene, at doae levels which are tumorigeoie to mice In lifetime studlea. Thfa led the aatltom to the con clusion thet the spontaneous Incidence of liver tumours (in this highly susceptible mouse strain) has been enhanced by recurrent cytotoxicity, aid that levelsof perdrioroethyiene which do not induce organ toxidly Mve not Hkely to pose a carcinogenic ride to man". 4. CONCLUSIONS A comparison of the haloelkanes and hatoaftenei hi question reveals that these compounds, although dundcaHy closely related, differ wide ly In thek Iox(cities which are preferentialy directed towards Hver and kidney as the mahi target organs. 4.1. Specific cow/atl binding tnd cnrdnogemicity Factors (hat hsHuence the oncogenic potential are primarily the ex tent of formation of seactlve metabolic intermediates and the reactivity or stability of Ihe seactlve metaboBte(i) within the phydotogfcal en vironment. For the hatooxfcanea, It has been reasonably suggested tint successful DNA rikylallou requhes an optimum between stability (to leach the DNA target) and reactivity (to react with it); from that opti mum a further decrease In stabWty may render the oxirane too shortHved to reads the DNA. SlmHar consociations may be relevant for reac tive haloalcane metabolites which show a high (microsomal and cytoplanule) protein binding even when DNA binding h negligible or ab sent. In general, the fcttraceltuUr distance may become more important with hscsvasfog reactivity of the metabolic intermediate. Long-term carcinogenicity assays hi rats and mice revealed liver and kidney at pitedp* target organs (except for compounds acting directly at Ihe site of application; substances for which significant and specific covalent binding to Km and/or kidney DNA has been demonstrated have also been foutid carcinogenic In these species. To-date, chemicaly defined adducts of DNA alkylation for vinyl chloride (and vinyl bro mide) only have beet identified and related to the genotoxic and car cinogenic properties. No, or at least questionable, covalent binding lo Hver DNA could be attributed to some hriocarbons which have been found to be hepatocardnogeaJc. 31 APOOO10040 Vol IV, rt<l 1.1982 AUfhttic IMogtmted Xenobtotks Tills has nM (he question as to whether an "epigenetic** mechan ism of haloesiboa-tndticed tumour formation, possibly triggered by cellular Injury due to chronic administration or cylotoxic doses, does exist. Recurrent cytotoxicity, leadtag to increased cell division during tbsue regeneration, has been considered lo be the responsible for a promotioa of inherent or spontaneous mutettana, thus euhanehg ths tumorigenic process. An "epigenetic" mechanism of tumour formation,Malted to enhanced ceWidar pfollferatioa evoked by tissue Injury would imply the necessity for differential risk assessment procedures for "epigeactlcsily" acting haiocarhona compared to those causing tumours by genetic damage. For the "epigenetic" mechanism threshold principles dioaU apply. In that exposure to doses which fail to induce tissue Injury thould be un likely to came cancer. However, the preseally avadable data do not yet provide a suffiefenily sound bash for such a procedure of risk assess ment, but ideasIn this direction are being developed /I7I/ d_2. Specific covalent bindingmd(acute) toxkity la many publications on this subject toxicity of halocarbont hat been attr&uled lo the covalent binding of reactive mettboHc interne* dlates to proteins. Aa quantitative measures the radioactivity covalently attached to total (thane, cytoplasmic, microsomal) protein, and binding of reactive metabolites to free sidphydryl groups ware moat rnianxinly used. After Induction of balocarhon metabatbm, the enhanced toxicity of the tingle compounds waa paralleled by the increase in corelent bind ing to cellular protein constituents. However, when rehtied to the dose metabolized, the amount of covalent protein binding did not coincide with Ihe toxicity observed ami often, bdoorboet of low toxtrity showed protein blading comparable lo that of tlie acute toxic ones. Titus, covalent protein binding seems to represeat a measure of the amount of reactive metaholc intermediates generated, rather than of toxic potencies of the latter. Chloroform, carbon tetrachloride, 1,1 ,2t;kfcloroethaoe and vinylldene chloride are regarded as highly toxic compounds evoking ante tivet and kidney Injuries in experimental animals, lipid peroxidation b thought to be responsible Tor carbon tetrachloride-produced cellular damage. However, out of the substances evaluated here, only chloro form seems to induce, to a much lesser extent than carbon tetraddo 32 it/, tot* Rewitwt on Drug Heubvtbm ami Drug hMwrtbmi ride, a lipoperoxldative mechanism. Furthermore a general refal toasfup between UpoperoxUathm and hepatotoxicity is not established /167/. To explain (he vinylidene chloride induced ccHuiar damage, faeger /127/ hat suggested that chtoroacctate (as a metabolite of this com pound) could Mock the citric add cycle In mitochondria hy the ereehanbna of `'lethal synthesis". This was hypothesized in analogy to the wdMmotra biochemical effect of fluoreacetate, which involves an en zymic "acttvalton" of the latter to ftuoroacelyl-CoA before catering tin citric add cycle aa Ifciordtrale and blocking cfr-aconltase (sec Fig. 10, I) /I68/. However, the relative LDSa potency ratio of chloroacetae/fluoroaceUte in rats It 21,6 / 169/ which points to a much lower extent of eozyrelc activation or a distimlsr btading mechanism of chtoroacetate (Fig. 10, 2a,b). Furthermore, vinylidene chloride toxicity in rets waa reduced by timukaneous exposure to vinyl chloride, which is of km acute toxicity but generates chkxoacetate as a metabolic intermodisle /64/. This raises some doubt as lo a major role of ddoroacetate in the mechanism of acute toxicity. A commas) feature In the metabolism of chloroform, carbon tetra chloride, i ,1,2-trichkuoethane and vinylidene chloride, which they only share with percMoroethyteM b the generation of halogcnated acyhltag tateonediales Mke phosgene and cMoroacetylctilovide. With regard lo the theory of Jaeger /127/, these haloacylattag Inter mediates would be reactive enough to generate "activated" htioacyleocazymc A derivatives by direct chemical acylation (Fig. 10, 3a. The making hrioecyi-coensyme A derivatives, possessing a reactive chlorine function, would represent "active rito-dkeded gents'* and might bo able lo read) hey posittons to the extremely Important mctibdOc ftmctiOM of "aettvated" coenzyme A derivatives. There, spedfie covalent btodk* mediated by the reective chlorine function may block metabolic reactions of vital Importance of lire ctU. Although forming an tudoacylaliag metabolic Intermediate, perehkmeUtyleae may not share the acute toxic action of the other com pounds due to its vary low metabolic rale and/or the low alkylating potency of the tricMoromelhyl residue (Fig. 10,3c). Recently, increasing attention was drawn to a covalent binding of re active metabolic toteimedlates to coenzyaie A. A iMechanistic treatise had arrived at the conclodoa that the sulphydryt group of ooenzyme A should be a preferred target for electrophilic reactive metabolites /170/. aad the possibility of covalent btading of reactive vinyl chloride meta bolites to coenzyme A (m a thioetber linkage) has been proved /II/. In- 33 AP0001004I Vni IV. Wft /, 1992 AUpMt lUogentfeA Xmcbtotki -S-H + %-lr CoA-S-C-t-F U CoA ho' * oc,Kra,ion 1? 2aJ CaA-S-H + C-C-CI h6 A H0 W CoA-S-H Cl-t-C - A c* ?? - CoA-s-c-c-a A P , - CoA-S-C-C H OH 3a) CoA-$-H + J`a qV b CaA-S-H + C-C-a aA q? d CoA-S-H * c-c~a a6 -s-?-a CoA -f coA-s-?-c-a A 9? * CoA-s-c-c-a a Fl. IOi SfecUk cmlnt bMIng l MucrMetMlMi la aMifm A-SH (ww tcxtk creased acetone ahtUUn by rata exposed to various halogenated al kanea and atkenea hu been (dated to a depletion of ceHtdar coeaiyme A by reactive metabolic Intermediate* of theae compound* /I2/. In view of Ibex data, the hypothesis on (be involvement of a apedflc coenzyme-blnding in acute toxicity of haloa(kanea and haloalkenee may provide basis for productive further investIgaltorn on toxidtles evoked by hriogeaated aliphatic xcnoblotlcs. 34 tU.UA Rerirwt n Dmg Mrttboftottmd Drug InKrtciimtf 5. ACXNOWLEDGEMFXTS The author thanks Professor ll.M. Boll for critically reading the manuscript. Use author's own experimental work wn supported by the Deutsche Forschuagagcmdnschan. The award of an IARC Research FatlowsHp itgmtefuBy acknowledged. The anthor thanka the HermannSchfesm-SUflang for fimndal support. The author k indebted to Mrs. Bmssfeux and IHebm-KoMIng for secretarial aM. NOTE ADDED IN PROOFS During the time of editorial proceadng of the manuacript, two experi mental stadias on covalent binding of trichloroethylene to DNA have puHvhad or accepted for {attention /I72,173/. The authoaa* report an extremely Mgh covalent binding of ndkmctlvtty to proleim of the Iver nnefear pellet, after adminislmtion of14CIrtchbroethylene to experimental animab /I73/. The small amount of radioactivity associated with liver DNA of these anlmala /I72, 173/ could be feather diminished by subsequent procedure* of DNA purtfkaHon /I73/. Analyab in dHTercnt chromatogiaphfcsl aeparatlon systems of tver DNA hydrolysrtes revealed DNAearocfatad isdtoacllrity either an phyriotogtanNy Incorporated into the natural nucleosides (bases) or fat the early fractions when protein eoatandnanta of DNA were ex pected to elute /172, 173/. Furthermore, DNA fragmentation ki the tkalae sucrose gradhstl,ladkat!te of phoaphotriester formalioe, could not be observed after admUsIratlon of trichloroethykne to mice /173/. HrisfwUwr supports the view, that there b no indication of a gmotoxk action of tricfdoroelhybae. 35 AP00010042 Vol IK, Ate /. 1992 Aliphatic Iklojcnilcd Xcnobialki 6. REFERENCES 1. IARC Monographt on (Ik n-atoatkia of the carctoogcalc rbk to town. IS, Some fumigants, Ibe herbicides 3,4-0 and 2,4.5-T, chtorbtiled Mbened^ oxto* and mbMiltMmii industrial chemicals, l.yva (1980). 2. (ARC Motmuphe on (be enhAbi f Ibe amiw(tilc rbk to Imnmm, H, Some momncn. ftastks tad tymhctk dMoMl, iM Acrolein, Lyon (1979). 3. (ARC HtMfnpki on ibe enMbi of Ibe caidnofeaic rbk to bomoiu, 20, Seme hafageaoted hydrocarbons. Lyon (1979). 4. REYNOLDS, B.S. and YF.E, A.G. Uw pmanrfiynul CflR 1*0ry. V. Retatkmahip* IwIwm prltern of rtdowmathine C1* hwipenlfai halo contifiMnlt of Brer *r *#o and ceRahr bdoiy. ld. Amt, 18, 591-603 (1967). 5. [LICIT, F.K., REID. W.P,, SIPES, I.G., and KRISHNA,G. CMoroforai toxfcRy in mice: Cbrrefaihm of amal awl hepatk nocroak wKb coratari Ibitlag of metabolites to Ibm mcninohakt. Exp. JMk MM, If, 215-229 (1973V 6. REITCNAGEL, R.O, GLKNDE, E.A^ and HRUSKEWYCZ, A M. Cbamfad mecfcanbm in carbon tetracMoride toxkRy. In: Free ndfeak to Biology, VoL III (W.A. Pryor,ed), Aoademie ham, New York,*7-132 (1977). 7. UEHLEKE. H-, WKRNER, T., GRBM. H, ami KRAMER, U. Meiabolk cUvadna of InlMkiMt ad tottito rime Toe mntagenkRy. XfmMotkm, 7, 393-400(1977). . BARTSCII, H.. MALAYEILLE. C, BARBIN, A., awl PLANCHE. G. Mato(enic and akyMfai lactaboUies of luto-cthylenm, cMorabotadleaea and ddilonitolcM produced by rodent at buma Km Ifaam Arth. Toxical. 41.349-271(19791. 9. CAUEN, PJ7., WOLF, C.R.. and PHMJOT. R.U. Cytechfomc-F-4S0 amdialed genetic activity of awen htkgeaaied aBpbfllc hydrocatbom to Sacckxromyctx cererMae. Mutxt. Research. 77,55-63(1980). 10. UKHLEKR, H. Btodbit *t hrioafttnc* to Nrer mtenuamm. to: Rbbakalre active Intenaediilea: Eormriba, loildty and faadtvatlae (JoBow, D.L, Kocab, J.J., Snyder, R., Vainto. IL,odi.) PtmoaiPrem, New York, 431-445 (1977). 11. BOLT. H.M., PIL3ER, J.G.. and LAIB, RJ. Ciwaknt faMiag of hrioethykne*. BJotogfcMreatriretaterwedtilw2,Snyder, (L, Parka, D.V,,Koedc, JJ,, JoBow, D.J.,<ili..Advances toExperimcatilMedidwnawd Btotofy, VoL I36A, Tbxnun Press, New York, pp. 667-683(1982). 12. FILSF.R, J,G,, JUNG, r,, and BOLT. H.M. Increased acetone exMMfontodnoed by melaboUie*of hatogcruled C, aadC] coaqmnoda Arch. Toxicol, 40,187-116(1982). 13. BONSE. G, and HRN8CHLFR. D. Chemical reactivity, bfetraMfcratotloo and toxicity of potycbfcwtinted aliphatic compounds. CRC Oil. Rea. ToxtMt. 8. 395-409(1976). 36 R.J. Mb SrNrw m Dm MmMlm mf Ana 6 ara-Am 14. BOLT, H.M., LAUt, R.J., ut I-ILSKK. I.G. Rmdive Mint catvi. nofiwby of totogowtad etbykac*. Biochem. fhmmmtot., 71.1-4)1962). 15. FtLSFJt. 143, and BOLT, II.M. Pharwacublaelict of hatogenaUd etbykne* to rata. Arth. fiufaot,42, 123-136(1979). 14. Anon. Clnmlcd briefer melbyleae chloride. Oicwl Arck, October. SB. (1976V 17. PLAA. C.L., and CARSON, R.E. ReWba napbmtoalc propmtte* of cbtori- aatad mitbane. ethane and ethylene dernalirer in mice, Toxicol. Appl fta imeet. 7.37-44(1965). IB. KLAASEN, CD^ and PLAA, C.L Raletiva cfTeeta of wtooa ddcibuird hydroemboai on liver and kidney fandiawin nOoe. Toxicol, Appl Fhorm* eoL. 8.139-151 (1966V 19. Dow Chcmicd USA: Report to ETA, Nooember 14. I960. JL GEHRING, PJ. Hepatotoak patency <f vartoar cMotinated hytoocarboa aapoait retafka to tbdr narcotic and lethal poleocka to nke. Toxtcof. Appl. HmmacoL. 17.287-296 (1968). 21. TWBSS. J.G, STONER, CD, SHIMKIN, 14.8.. and WEISBURGER. E.K. Teal for cardnogenidly of organic contaaitoanti of UnRed Stales drinking water* by pabnoaary taoou mpome in attain A mice. Cwicer Ret., 27, 2717-2730(1977). 22. IARC - Information baBetln on the wtney of dwanieale beiag taned lor car- ctoofcnkOy Na.B, Lyon, pp. 333,350,4|6 (1979V 23. HEMMINKI, K. Occapattoaal ritemkaN leued (or tetatogeaietiy. Imt. Am*. Optup. Emtroo. HUM., 47,191-207(1910). 24.8CHWETZ, 8A, LBONG. IKJ, and GEHRING. PJ. The effect of ante*. aoBy tobatod tricMorocthyfcaK, peictoorocthykne, atetbyl cMwofnrm. and Htliylena ridetide on aadirjiiwl and fatal dmetapmeat in mice and tala Toxicol Appl Itonnet, 82,84-96 (1975V 25. HARDIN, BJ>. and MANSON. J.E. Abaento >rdhMotome<bM Mratogenl- city with inhalation mpcUr* la tat*. Toxicol Appl ftomeeat. E2, 22-26 (1980). 26. STEWART. R.D, RSHER, T.M..IIOSKO, U.l^ PETERSON, LE^BARET- TA, E.D., and POOD, H.C Experbnenlal totnun expentre to melhykma chloride. Arch. Andwt MmbK 28, 342-348 (1972). 27. STEWART, R.D., FISHER. TJf^ HOSKO, bLJ. PETERSON. J.E., BARETTA, E.DH and DODD, ILC Carbonyhemogtobto ftaralioo afur expontia lo dkblBfomathaaa. friewce. 178. 295-296(1972). 21. KUBIC, V.U ANDERS. M.W., ENGEL, R-R-, BARLOW. C.H.. and CAUGHEY, WA. Matabotom of dicMeroaralhanea lo cmbon aMaoxblc. to rfpo atodka. Diug Memk Ob., 2.53-57 (1974). 29. RODKEY. F.L., and 00LUS0N, A.H. Bfolntkal osydalton of l4C-metby- leoo chloride to aAn monoxide and cartion dioxide by Ibc rat Toxicol Appl Phxnmcol, 40,33-38(1977). 37 APOOO10043 Vol IV. No. 1.1992 AOphedc MmmMnf XenobioUe* 30. HOOKEY, F,l, ud CDUiSOtiA.il EHcd gf dlfiatogciwlcd methanes aa the *i rint production of carbon monoxide and methane by rate. Toxicol. Aptd fbomoool, 4*. 19-41 (197?). 31. VESAIR, D.W., SCHEMS, iX. and USS, R.H. Dorn rebtod (durmacoklnolict of '^C-merbyicae cMeride in mix. Fed. Aoeu, 31,998 (1977). 32. ANDFJUt, M.W, KUMC, V.L, and AHMED. A.E. MetoboEna o( balogtni led meitrues an! aracaomoteortar blading. /. ftdwx fOthol Toxicol, I, 117-124(1977). 33. AHMED, A.C.. and ANDERS. M.V. Mctatnllne of dtoatoreethaan In for* maWehpde eed hmrpalc heBdc -- IL Sludla on Oh neditrdnn of (be rcno UoniMtcm. ftarawt. 27,2021-3023 (19781. 34. McKENNA, MJ.. nnd ZEMPEL, J.A. Tbe dew dependent aHtabolmi of MC-nethleac chtotlfe >oRowing on^adtntefctnUoa to mis. Fd Comet Toxicol. 99,73-71 (1980). 33. JONGEN, WJ4.F., AUHK, G.M.. and KOEMAN, I.H. Metageafc eftail of ddilwiwiHbM on fataoneRe typhimmrkwa. Mm in., 89, 243-248 (1978). 36. MEIIER, J, DE FBERRE, l.W, and RAHNUG, U. Mcatmenm* of drag RKtaboizbw I?sterna In JMnonedb ijptiOmMium stretor 046, TAI553, TA I00,TAI5)8, andTA98. Chtm.-BkA. Internet, 81,247-254 (1988). 37. JOHNSON, IlK. The Wlacncc of some aiphatlc composnds on rat 8m (hitilhtoae leveb. Bktchewt. fkwnmaL. 14.1383-1)83(1965). 38. WINSLOW. S.G, and GERSTNEft, 110. IfeeRIt aspects of cMorofocm - A Reslew, (bagand ChfmfcofIVwfcofogy. 1,239-275(1978). 39. TORRELSON. T.E, OYEN, F., and ROWE. V.E.The toxfctt?of ehtetoform aa detenubed bp stogie and repealed expoaoie if laboratory aidraale. dm. Ind. Hyg. dense /, 37.697-70J (1976). 40. HELL, R.N, CLEMENS. T.L, UU. D.K, and VE3ELL, E.S. Oenetic control of chtoroform toalcRp bi mice. Science, m. 1S9-UI (1973). 41. ESCHEN0RENNER. Ail., end MILLER, E. tadnetton of hepatomas hi mice bp repealed oral admlnittratlon of cMorofotm whh abeetvaHaas on tax ttf(ciences. /. Nett Oncer Nit. . 2SI-2S3 (IMS). 42. POHL, L.R., MARTIN. J.L, and GEORGE, l.w. Merhaalire of metshoOc scthatlea of chloroform bp nl Km nkratmn dinedcm. Atfirecet, 20. 3271-3276(1980). 43. EKSTROM, T, and HOG*ERG. 1. Chtoroform todneed gtotaMotw deptotton and loxkMp In freddp Isolated hepntoepten. dfodtotrt Itownmt 29, 3039-3963 < 1980). 44. SAGA1, M., and TAPEL, A.L. Uptd pwontdatton todneed bp eonm hatomethim < fncnmrcd bp to who pantana ptodacUsa In the rat Toxicol Appl PhmoMcwt. 49. 283-291 (1979). 45. REITZ, R.H., QDAST, I.F, STOTT, W.T,, WATANA8E. F.O., and GEIIRING, FJ. Fhaitnacofcbmtlcn and nracromotecolai effects In rata nnd ndeo; 38 (U. tolb Rexievt cm DrugMitMum and Drug hrmrfpM ImpRcaltoiw for carcinogenic ridt ntllndbt. Ik Water cblotimatinB- Enolroamantal Impact and health affects (JoRey. ILL., Orange W.A, Cunratog, R.R,ode.) Vet 3,923-992, Arm Arbsr, ffrlrnrn (ITBO) 46. DIAZ GOMEZ. MJ, and CASTRO, I.A. Crmfem btodlag of chloroform areteboOtae to tmdear proteins -- no rrldnau for Mndlig to nacdalc scMe. Causer Letter*. 9, 213-211 (1990). 47. FLAA, G.L, EVANS, E.A., and NINE, CH. Relath* hapatotaxldlr of taren balogematnd hydrocarbons. / ffurm. Exp. Tier.. 923.224-229(1938). 48. FLAA, C.L, and LARSON, R.E. Rctatire nephrotoxic properties of chforlsated methane, atbane and ethylene derirathree to mice. Toxicol Appl Mmmoeol. 1, 37-44 (1963). 49. KLAASSEM, CD., and FLAA, C.L Reislira effecti of vottooe rdibthmled hydwctobone on Rm and kidney hrnetion la mice, Toxicol Appl TEmm0*2.8,139-151 (1966). 50. REOCNAGEL, |L0, and GLENDE, E.A. Carbon lettacMorMa hepatotoxlcRy: An eeumgrte of kUM dem^c. CRC Oil Rex. Toxicol. X 263-297 (IW3). 51. NEW, FX, LU8ASH, C D., SCIIERR, L, and RUMN. A.L Acute renal faints nnoehled whh carbon MmcMotMe tatoxkatton. 7. Am. Med. Aimc, 181,983-906 (1962); 52. EDWARDS, ML, and DALTON, AJ, Indodfoa of driltoaii of tbe 4m tnd of hepatomas hi mice whh carbon tchacMwMe. / M CatcerInO., 3,19 (1942). 53. ESO(BRENNER, AJ, and MILLER, E. Sledlet on hepalomat L Size ead pacing of mnltiplr doeet In 8ie todadba of carbon tetreehtorlde hepatomne. J. ttHt Oncerhot. 4,383-388(1944). 34. AHR, HJ, RING. LI, NASTAINCZYK. W, and ULLRICH, V. The mech anism of chtoroform and carbon monoxHe (ormatkm from carbon tclracMorMe bp mfcroaomal cytochrome P-450. Ruintt Fharmnoot, 29.28352861 (1980). S3. SAH, J, HARTMAN, &F, and WEINHOUSE, S. Formalton of ratbonyl cktorMo to carton tobachloride awtaboBam hy rat Mver to rHro. Oncer Rewere*. 30.3942-3947(1979). 36. McCDLUSTER. D.D. BEAMTER. WJL, ATCHISON, GJ, and SFENCER, H.C. The akeorptioa. dltohnka and elbntoatlon of radfoadlre ctabon IctracMatMe bp monhaya npan exposure to tow eapoor conccalratloM J. normocot Exp Tier, 983.112-124(1951). 57. GARNER, R.C, end McLEAN, A.E.M. Increaaed MSceptlhRRp to cmbon MrecbhwMa pohontog to (be eat after piettealmenl with oral pheoobarMfane. Rfodkem. Ntomawl, 18,643-650(1969). 51.3EAWRIGHT, A.A, sad McLEAN, A.EJ4. Tlw effoct or dial on ctobon IctraehterMcmetabeOew.BtodHot/, 908.1035-1060(1967). 59. RODIN, P, FRODL G, GRILU, S, and FERRER1, A.M. At ton* and to 39 APOOO10044 Vol IV. No. i, 1962 AHpkttfe KrfaftiwriJrawMorics Him binding of uhnn fetiacMocMe wHft mkMo idii ind pwidw m nl uwi mansetfier.lot. t. Cmeer, 11,419*435(1973). 60. DIAZ GOMEZ, M l.. inf CASTRO, J.A. Cor start blndb oT cwhon trim- chloride MdabotUei to Urer necdeai DNA, pwlilwmlllfMa Toxicol Appl HtrnmmU. M. 199-106(1980). 61. Criaiial and Engineering Nan. Top SO CVwfcib. fltna fig Mem. *7, 19(1919). 62. RANNUG, U. CeaManle effect* of 1.1 iHnniwmthina and 1,3-dkhtMo- ethane.Mfuta/bnItrawri, 7B. 269-29$ (14*0). 63. Banbury Report S. Ethylene 4talk*Me: A putsntki forth rid? (Anet, R, Infante. P., Reitz. R,, aria.). OM Spring Harbor Laboratory, USA (19(0). 64. JAEGER. RJ,, Comly. R.R. and MURPHY, S.D. Short-term bihrialioo toxicity of tsabgenaled hydrocarbon*. Arch fMrot Jienftk. 30, 36-31 (1973). 65. BANERJEE, S. and VAN DUUREN, B.L Bledit of catdMealo helo- gonated hydroembont to cel maeronoieenjea. J M CmccrbttL, M, 707- 711(1979). 66. RANERJEE, S.. VAN DUUREN, B.L. and ORUAMBO. FJ. Micmome mediated covalent blndiaR of UdUilnMilnK to Mag microeons! protein and salmon vena DNA. Grocer lemn*, 41.2170*2173 (1900). 67. CUENCERICH, CRAWFORD, W.M, DOMORAOZJU, |.Y,, MAC. DONAU), T,l_, and WATANARE, P.G. Ac Ht*o actfisfloa of IJ-diddoroethane by microsomal and cyloioBc enzymez. Toxicol Appl ftunmtvl, SB. 303*317(1910). 68. mu, D.L, SIR, T., JOHNSTON, T.F., and STRUCT, ILF. MacmmotewJar binding and mctaboHm of tbe caidnogca I.T imiinnunrtla--n Cemxr Re- temreh. M, 2438-2442 (1978). 69. MONSTER, A.C. DHTctcnco In uptake, elmteation and oteUbofltm M expo nce to tricktoroethyhoc, I ,1,1-trfcttMoctfiane and tetrachkroetfcyfcac. Aft. Arab. Occup. fiwtM Heollh, O, 311-317 (1919). 70. rVANCTICH, K.M. and VAN DEN RONERT, L.H. CMntnrttmari: ftelr melakollsni by hepatic cytoefcmne P-4SQ to rim. ChKtMgmerir. X. 641- 102(1911). 71. HENSCHLER. D,, REICHERT. D., tri METZLBR. M. IdMUffinttoa of potenlM emetoogena hi tocdiatcal ptAe 1,1.1-nkMoroetbmw. fit Ardt Ocatp. Bn*att llettOk, 47. 243-260 (1980). . 72. YLLNER, 8. tdetobolan of t.I.l-tsfchferocthmm-l.l^C to If* mown. AcUphenoaeot ei taxkol. M, 248*156(1971). 73. RANNHO, U,, SUNDVALL, A, and RAMEL, C Tin onstage* effect of 1,2-dichloioelhane on S. tjphimutrium. L Actuation Uuough confugallon with glutathione to tpro. Cbeut-Btal hotrod.. , 1-16(1971). 14. BABK3I, H, DAVIS, D.L, sod STATZKI, G. MbtoamWotoprapun: A to vicv.&d. Total EnHnto.. 17, 207-221 (1981). 40 ft/ L*U> Kcriawton OrugMctabofommnd Drug iMenctkm* 75. TORKBL50N, TJL. SADET. S.B, ROWE. V.K, KODAMA. I.K., ANDER SON. H.H.. LOQUVAM. G.S., and NINE, C.ll. T<nklogtc taxntfcallmis of 1,2 dRaomn J-chtosopiopMm. Toxicol Apr* IlmnmaA. 3.545*55911961). 14. REZNIK, IX, STINSON, S.F., and WARD, J.M. RpkCwr pathology to arts and mica aftor tohalstion of 1,2-dltoeam 3 ckfoce|.ie|mto or 1,2-dibronwtliair Cor 13 Hckadtri. Toaieol. to, 2)3-24941980). 77. VAN DUUIEN, B.L, GOLDSCHMIDT, lit.. LOWEENGART. a, SMITH. AXL. MELCHIONNE, S, SEIDMANN, 1., and ROm, D. Carcinogenicity of halogensted oWhrie and alpfialic hydrocarbons to mice. /. Nail Ctmctr to*. 0,1433-143941974). 78. KATO, Y., SATO, K.. MAKI. S.J.. MATAN0.0.. md GOTO. S. Metabolic fain of ir7dlbromo 3 diioropropaae (DBCP) in rain/. JfeffJe. Set, 4, 196204(1979). 79. JONes, A.R^ FAKHOUU, G^ and GAHEL P. The ateribolisni of the soil hnS>4 U dlbsoino J ckbropropme to the sat. Expetientia, 36, 14321424 (1979). a BILES, R,, CONNOR, T., TfUEFF, ft, and LEGATOR. M. Chancierisation af S-9 actfiatioa of DBCP In the salmoaela lest tyrieoi ttunuaeologM. 20, 155(1978). 81. KATO, Yh NATANO, and GOTO, S. Covnlenl Undlv of DHCP to pro* letnrtovJtoo. Tacieol tell. X 299-302(1979). 12. VAN DUUREN, B.L, GOLDSCHMDT, B.H., KATZ, C. SEDH4ANN. I., and PAUL J-3. Carctoogralc actfily of skylattog agents- /. Afittf Onsecr Rut. BS, 695*700(1974). 83. GROM, IL ROME, tX, RADWAN. Z,. REICHERT, D-, and HENSCHLER, D. MntagenMty to WAtr and poteatM uidoagealdlr of cUorinled elhy* leaes as a Inaction of matahoBc axinne forsanllon. Rlochewt Amarcri, 24.2013*2011(1975). I 84. GEHRING, PJ^ WATANABE, P.G^ and PARK. CN. Reaohitioflof dosetejpoase twrlrity data fee chcmlcafi teqablng metsbottc aclfiatlon: example vhqtlchloride. IferctooC Appl PBameoaC, 44.501-591 (1974). BS.F1LSER, I.&, and DOLT, ILM. tntolntlon pharmacokinetics bawd on gas nptako riudlcc. L Impswrsmuat of ktotofc models. An*. Toxicol, 47, 279292(1901). 06. CONOLLY, R.L JAEGER, RJ, sad SZABO, 3. Acntc hrpaiotorielly of ethylana, rtoyrl ftoorHa.Ttoy! chloride and riayi bromide after Acodos 1254 psariaatmart. Bxp. Atotoc tOthol. 28,25*33 (1978). 87. MALTOM, C, and LEFEMINE. C. Cmcinugmirlty btonMayi of vtoyl cUorldo. I. Research plan nod early resale Briton. Are. 7, 387-405 0974). IK CREECH, J.S, and JOHNSON. M.N. Argiosarcoaia of here to the MsmlncNmo of ootrviayt ddoride. / Oetmp. Med.. 10,150*151(1974). 19. MULLER. G.. NORPOTII. and ECKARD, R. Idenlilieslson ot too urine 41 APOOO10045 Vol IV. No. 1. 1992 Aliphatic AfapwWXenohiotia meiabotBa of rtayt chloride br GC-MC Inof^lbi). hi. Arch. Oecup. EmArm ttekti. 38, 69-75 (1976). 90. BOLT, H.M. MetaboBc tdhMtoo of MegemKd Ahjrtem. In: Primary Lfvet Turnon(Rmni, M_, BoM, RM., Bammh, f,mf Tojiyti,R, eda), MTP Piem, Lancmter, UK, fV 285-294 (1*78). 91. BOLT, H.M., KAPPUS, R, KAUFMANN, APPEL, K.R, BUCHTRR, A., and BOLT, W. MetebeBm of ,4C-vtayf cMorHe * Afro and tat Are. INSERMSymp. Scr . B2, 151-1*2(1976). 92. WATANABE, P.G., ZENPEL, I.A, PEGG, D.G.. and GEHRB4G, P.H. Hepa tic ntaeHtnnlrabr tending Mbh| expeattta to vinyl cMotlft. TbxicoL Appl Ihettmtel., 44, 571-579(1978). ). GUENGERKJL P.P., and WATAHABt, P.G. MetaboBnn of ,4C- and **(> labeffcd vteyl (UnMehitao mdhpBo. OtocAetW.ftanouul, 2S.58959*11*7*), 94. KAPPIIS. R. BOLT. HJd., BUCHTER. A., and BOLT, V. KM Hn ndoevotne* catalyte covalent binding of ^Citarl chloride to reecromolcmlm. Nature. BBT. 134-135(1975). 95. OSTERMANN-GOLKAR. HULTUARK, D,, BEGERBACK, D., CALLSMANN, G.I., GOTHE, EI1RENBERG. L, nod WACHTMEtSTER. CA. ABcylallon ofDNA and pnrtrina k micee*pored (9 vinyl chloride.Btockem. Ekrphyt Re*. Coavmm., 7B, 259-2*4(1977). 9*. BOLT, H.M., FIUSER, LG, and UNDERER, RJC. Ral Bps mfoownuf up take and hrevmlMr protein binding of l,2.*4Cvtejl brandda. TexUoi. Appl. Pharmacol, 44,481-489 (1978). 97. WATANABE. P.G., HEFNER, R.F., and GEHRING, PJ. Vfay| chloride Indoted depreaaion of hepatic nen-pielelo mriphydiyt content and eBecta on bromomlyhaHa dearanca In tala TbxtcolotP, t, 1-8 (197*). *. DREW, R.T., PATEL, J.K, and VAN STEE, E.W. Tin tffodi of vinylbro mide In rata pretreated U pfnnobatbBal or dkthytmaleate. Toxicol. Appl Pharmacol. 3P, 17-l 77(197*). 99. BOLT. H R, FILSER, LG.. LAIR. RJ. and OTTENWALDER, H. Bfcdh* Unettca of vinyl chloride and vinyl baomlda al very pm dam, Are*. Toxi col, SnppL 3.129-142(1910). 100. REYNOLDS, E.S.. TRQHEN-MOSUM, JR, SZABO.S^ and JAEGER. R.J. Vinyl chloride Indaced deactivationof Cytaduonw PASO and olfcei componenla of the Ever mixed fandfon oxydaae ayrtem: An h after rtody. Ret Comm. Chem. Pathol PtmmacoL, 12,685(94 (1975). 101. PESSAYRE, D., WANDSCHEER, J.G. DESCAT01RE, V,, HOLDER, A., DEGOrr.C.and BENHAMOU, J-P. Ctamnktfo effect* nf remated Ivm of cotnpoandi tiinrfoMned Into readhe mcteboBte*. Bfoehtm. Bwiwnit, 28,1041-1047 (1*110). 102. LAIB, R.., and BOLT. RM. Alkylation of RNA by vinyl chloride metabo- 42 RJ. Le Retiemon Prut HetaMhui sndDnqc fotetoctknu Mtca hi thro and In afro: formation of l,N*-<lhenoadewidne. Toximtn*y. B. 185-195 (1977). M3. LAM, RJ-, and BOLT. HAL Formation of 3,N4-etbeaecy(Miacin<iletteite RNA by vinyl ddarlde metabolite* hi Atro and hi rfro. Arch. Toxicol. 38, 235-240(1978). 104. LAB. RJ.. GWINNER, LM, and BOLT, H.tL DMA aRytetion by vinyl chloride metabolic*: dlnadiilwl)iw er 7-afcyk<ion of guardne. CVvtRM. Interact. 37,219-231 (1911). 105. DOERJER, G. and OESCR F. Iwlatlon of gnanlne derivative* te (he rea Non ot chteraaceuMehirde vKh DNA In Atro. J. Oncer Ret OR Oncol. 9B, AZ4 (1981). 10*. SCHERER, E.. VAN DER LAKEN, GJ., GWINNER. L.M., LAIB. R.J., and EMMELOT, P. ModVieMtea of daoxypianotenc by dtlowetliytene eehto. GvchvogeMate. 2,671-477 (1981). 107. GREER T, and HAT1IWAY, D.E iMetaclioM of vinyl driotlde arilk ral Over DNA ia Aro. Chem-BM. Internet.. 22.211-224(1978). 108. OTTENWALDER, IL. LAM, RJ,, and BOLT, RN. ARytethrn of RNA by vtnyt breailde meteboNiei hi tetrp and ha the, ArrA. Toxicol., 41.279-28* (1979). 109. OTTENWALDER, R. LAM. R.J. FILSER. J.O^ ami BOLT. II.M. Dtepod (Ion and mvtebollc acdvallon of vinyl bramMa In rat*. 7ih IntennL Cengr. Phreraacol, Path, Abtetad 719(1978). 110. LAM. RJ^ OTTENWALDER, and BOLT, RM. AKylallnn of RNA by vinyl chkxMe and vteyl bromide metaboBtca hi Aros died oa proletebhrynUieais. In: Proceeding* In LBe Sdenca (Gate* al, ed*,) 319-122(1981). 111. BARBIM, A, BARTSCH, M, LECTONE. P.. and RADMAM, R SHieliM on the mbonding pnperifct of l^*-dhnmtenhn and 3,N4-elbenocy(o*bte, DNA caadlom pieteid* of vinyl chterMe mdaboBlea, daring hi Atm DNA tyadiad*. MndricAt*NAm. B, 375-387(1981). Ill HA1X, JA^ 8IIAFFIIILL, R., GREEN, T, and IIATHWAY. D.E. The tedodlon of aaiori dnrtag ht Atro DNA qmlhetb follotviMC cMotnacelaMohydv trialaim! efpofy-fdA-dT) and poly-<dCriG) template*. Crtebaegeneth. 2,141-146(1981). 13. SPGNGLER, &, and SINGER, B. Tnwcriplteml enwiaed ambkohy ren4Ibg from Mm yremain ef |J4*-etbenoadeatdn* or LN^^tkaMylMn In pMyrfcniwcfcmUdia MaddcAdd Ret. 2,3*5-373 (1981). 114. RANNUG. GOTHE, R, and WACHIMEISTER, A. The metegenMIy of chlareeiiiyieiM oxide, ddoroacc(aldehyde, 2-cMorodhanet end dboioacetic add, eanm^rable ractaboRea af vinyl difaride. Oam.-RM Interact., (2. 251-2*3(197*). US. ZAJDELA, F.. CROISY, A.. BARBIN. A., MAIAVEILLE. C. TOMATU, L., and BARTSCH. II. CudnogenlcUy of cklororthyicweoRidc, an animate mdhi mdaboWa of vinyl gMhHd, and bla<clilMoadliyl)etlMi aflca nab- 43 AP00010046 Vol IV, No. 1.1982 Alfphfiic Htktgnxled XtnobMa oriawou cdndntoialton and to toRMIofr|noeot*>a expqbattle min. UawReam*,, 332-336 (1910). I IS. VAN DUUREN, B.L. KATZ, C, GOLDSCHMIDT, B.M, FRENKEL, K, and StVAK. A-Ctntoofenicby of babelhot. ||. SknctofeacIMty reMbe*Wp* of ambgi of MffeMofonMhrOetfw. I AML Career MU, At, 14311439(19121. 111. WEISOURGF.R, E.K., ULLAND, AM, NAM, J, CART, U, aM WEISBURGER, I.H. Carcinogenfcjty MU ifnMumillWlllMllld MwIM ehemidki Mail COKer/mt. 7,7S-0(|9t). lit. BOLT. H.M.. LAB. RJ, FILSER. J.G, OTTEMWALDER, H., aad OUCHTER, A. Vinyl dlwM ml tabled canpouada: Mr-rbudno ofaction on ftp tow. la: Frozen to tow Abeam (Beak, TjC,, aad CMmi, PD., edL). TMem/SaaMoa, New Yrk (I9BI). 119. Teetotal Report DP-6 "Vinyl Amide, vbytokae (tootMe", El. da Pontda bemoans A Co, Wtonfeigta* Del, 1969. 120. LESTER. D., aad GREENBERG, LA. Acale aad ckroafo taaldtr A tome bibgfailed defheike* of awlbaae aad Ahae.dnk. Mte On- Omp Ifcrf, 2, 135-344 (1950). 121. CARPENTER. CP, SMYTH, IIP, and POZZANL U.C. The away of acale npoai loxldly, tod Ac ending and ialeipwttliea of renH* of 90 amtpoandt J. MAat. Hj* ToxkoL at. 343-34* (1949). 122. STOCKLE, C,, LAI*. RJ, FILSER. J.G. aad BOLT. HJL VtoyRdea* (botWe: Metabolic* and ladacltoa of |wnn|ilmlli kepaifc fod la ecbttoa l rtaji cklerMc. Taxkohgy Ltticrt, 3,337-342(19791. 123. IRISH, D.I). ABpkatfc kakgenated hyAnmboaa A: ladubMIHygiene and Toxicology, VoL II (Pally, F.A, ad.), 2ad ad. New Yofc feMnebaca Peb Btbert, pf. 1303-1307 (IMS). 124. PRENDERGAST, I.A., JONES. RA. JENKINS, U, aad SIEGEL J. Bf. (Beta on eaperbrnAal lalmib of Mntfem totadalba of McMoraeAyfeae, carOoa trttacMoride. l.t.HrtdkfatoaAane, 'Hi*--`fffinnnmTtlnna. aad 1.1 taMatoetliylcne. ToxkeLApf*. HmmoeeL, 10,270-2S9(l967. 123. ANDERSEN. MA. THOMAS. O.E, GARGAS, M L, JONES, R-A. aad 1ENKIN3. JJ. The rtgnSIcaieo of nmlllpfc detoxBleattoe yrtbaaya to ieacHea awMbotlet to the toxicity of l.l-dkAloeocAytoac. Ibxteot AppL HmmaeoL, M, 423-432 (I9MJ, I2. REYNOLDS, E.S, MOSLEM. M.T.. SZABO, 3., JAEGER. RJ.. aad MURPHY. S.D. HepaiotoxMly af *M cMotMc aad 1,1-dfcktofoeUiykiic. Am./. Pathol, Bl,219-236(1973). 127. JAEGER. R.f, SHONER. LG, aad COFFMAN. L l.l-Didiloraatbrleaa bcpalatoxicky: Punpotnd meebeahm of aetba aad dlttfaillM aad Mndhg f 14Cfadtoactkriir foBowbg takablton oponn to rad. AAw ItoM Anpecr, 21, 113-119(1977). |2t. MURRAY.F.J.. MITSDIKE,K.D.,SMITH, F.A, jpHN, J.A,HUNMICTON, 44 tti Mb Rertfws chi Drug Mruboliun ami Drug brtcrocucmt C.G., RUA5T, J.F., aad SCHWETZ, B.A Teratology aad fepndartioa rtw- dfea afvteyttdene cMotkfc la tali end rabMU Toxicol Apft PbermxcoL. 46. 341 (I97t>. 129. MALTOM. C, and TOVOU, D. f-krt expoMental evidence at Ac catdao- gewfc effect, of rtayidene cfclortle. Med. Uroro, 70.363-360 (1979). 130. RETTZ. RJL. WATANABE. P.C, McKENNA. M.J.. QUAST, JP, ami CEII- RING, PJ. HMief vbyUdeaertilHldeeaDNA aynAcdtand DNA reptk la Ae nl aad moan: A conpuetNa ttody M daelkirMtioaaiDe. TaU- cU ApptnumooeL. . 357 370(I$t0. 131. LEE, C.C, BHANDARI, J.C, WINSTON, J.M., aad HOUSE, W.l. Carclno- fOdcRir of rtayl cMotHa and rtnyBdcne ddeiide. / Toxteol Birim. MmM.4, 13-30(1970). IJL LAB, RJ, KLQM, K.P, KAUFMAN, J, nd BOLT. H.M. Zar fia* der KatstoogetolM mi VtorBdaathbwd (l.I.-DkAlaeoalliylenL KrrA. 9mA Gec.4r6cRMwdtMa.21,AW.GantaMVckg, Slotlgart, pp. 277-201 (1901). 133. REICHERT. D, WERNER. H.W, METZLER, M, aad HENSOILER, l>. MofecnW nwduinfara of l,l-4hAtonelliyteae toiMly: Eaeialad metofcoSte* lereat dlffriral ^Hnvnya of reaclhre blewwedialaa AwA Toxicol, 42,139- 169(1979). 134. HATHWAY, D.E. (tonpanlba ninuAiioMtabolaa ofvtoyl cMarkle and vtoyOdene chleelda in aebUon to oncogenb patanlM. ftfim. Hexttk Ftr tpccL. 21.55-39 (1977). 133. McKEJMA, MJ, WATANABE, PC, aad GEHRING, PJ. RutatacoAtoeifca af vtoyMaae cUortda to Ae tat Erwin*. HemUk Awpecr, 2L 99-105 (1977). 136. SHORT, RJ>, VINSON, J.M., MINOR, J.U SEfFTER, J, aad LEE, G Ef fect of vvtoaa WaUaaateon toxidlr ofialnlcd rtayBdeae rttbtlde. Bttrinm. itoaM . iw-imwn. 137. fhirtii la Tmai fcammaiirtarhafl TnHinli|iirh Tftirtlinir rtrlnliifr Btgribv- dtoW * MAK-Wmlaa, do-, Mm-1 J-Dbldonlkyiea. Vwkg Ckmfe,Wde- Mia. 1974. 130. FREIMDT, KJ, aad MACltOLZ, J. (ntlMba of mtoot-baeAw enUbea to M Mm by into- aad cto-1,2 dkhtotoeihykae. Toxicoktr. 10, 131-139 (1970). 139. PREUM3T. KJ, LIEBALDT, GP, aad LEBERWMTH. E. Tortdly atodiet aatwawlJ dkMaanelkytew Toxkoiofy, 7, Ul-lSJ (1917). 140. BONSE, G, URBAN, T, REICHERT, D.. aad HENSCHLER, D. Ckaadert rcactirky, aaatokoHe aulnae fonnaUM and Mntoglral Mactwity ofcfabriaaMd alhrfcaet to Ae Metaled paibted nl lira ptepweiton. Btocktm. Phtr- bmooL 24.1019-1134 (1975). 141. Daaltcka Foncfcwigaagfrtnwlafl. Tartkob|laclarl>*ICinedlrtabetoBe- giaadnag oaMAK-Watlcn.TricUa(aAylea.VaMg Ckenda, Veinhelm. 1973. 142. CARLSON. C.P. Eiduawmatf of Ike twyaloloxidty of lilckbroatliyleae by 45 AP00010047 VoL tV. No. I. m? Aliphatic NahpnrM XenoMottes imhKcrs of draft atrtaboKna. Kri. CVirrvn. Orem. Pathol Pharmacol, 7, (]7640(1974). 143. REYNOLDS. ES-, aad MOSLEM. M.T. Dame 4 hepntie ttRobt amkiaa by eMMinated nkOn wbfe erephoh *ygjre tad Emmrm. Health Penpect,. 91.137-147 <1977). 144. Nall Cancer Iml., Careinogenwh Btoataey or btcWorocdiykne. Caretrtogeacalx Tack Rep. Sc*. No. 2.DHEWhU No.<NIN) -f "7 --anhlaglnn. DC 1916. 145. IKMSCHLF.R, D, EDER, R, NEUPECKER, T., and METZLER. M. Caretnogenidly of iricMnaocihyleae: Fact f artefact? Arch. Toxicol, 37, 233236(1977). 146. IIENSCIILER, D, ROMEN, W, EL^ASSER, H.M, REICHERT, D., EDER, E.. cad RAOWAH, Z. CaahregtnlcBy Rady of tikNocoethylene by bagterm Miafetina M three aaliaal apedet. Attk. Tooted, 43, 237-241 (19801, 147. LAIR, R.I., STOCK LF, O. BOLT, H.M., aad KUNZ.W. VinylchbrHcand trkhbtocthylme: Compariam of alkylating affect* of metaboMc* and bp Ridba of prcnaeplaaliccwaymcdeflciBocfcaln rat Ira.;, (knr fu (HR. Ooml. 04.139-147(1979). 148. UEIILEKF, II, POPLAWSKI-TABARELLL S. Spectral evUence for 2,2,3trichlofooxyuneTormalba daring nlaamul tekhloiocthj'lMMoaydattoiL Arch. Toxicol, 37.95-105(1977). 149. IIENSCHLER, D.. HOOS, WJt., FETE, II., DALLMEIER, t, and METZLER, M. RMtfoai of Irldalotodhytenc tpilUc hi aqneou* ayatema. lb fhtni. Pharmacol. 2*. 543-548(1979). 150. MOSLEM. M.T., REYNOLDS. ES,, ROOR. PJ., PAYLEV, K., and SZABO, S. TrUblnrodhylene ladaced desdhralbn of cytochrome MSI and law of Rra glaiatliiaac dr who. Net. Cammim. Cham. Ibrt. FItorMaori, la, 109. 120(1977). 151. BOLT, IUL, and FILSER. I.C. Irccrndble binding of cMaHnatad cthyfcirei to macromoSeenlet Eminw. Health ftnprcf, 39,107-112 (1977). 152. BANIEREF, S.. and VAN DUUREN. L. Corafent Undlmofthe edaogen birtilorocthytene In hepatic mktoanmal pratetna aad to cangaaoiw DMA hr vitro. Cancer Rex. 3, 776-788(1978). 153. UEIILEKE. It., and POMAWSKI-TAIARELU. S. toevenlbt* btodiw of MC-bbe0ed irkhkHoelbytene ta mice Brer comIMacMxfrr Hfoand/a Him. Arrh. ThxkcA.. ST. 289-294 (1917). 154. BOLT, HR, aad LAI9, RJ. Cordent btodtag; of drag meUbnSlea to DNA A tool of predictive vibe? Arch. Toxicol. 46.171-180(1966). 155. PAROMAN, L.G.. and MAGEE, p. Profhretkw of MCOj from trichloroetbytenc ia ial* and mlee and a posdhk Interaction of a likbbrocfhylene melatmHIewtth DNA. Torffipt Appl Pharmacol. AI53(I980). 156. DeniacheFonchanftgoneintchaR ArbeWMawitalnbdUoaBwilogkche Bcpttin- dung ton BAT-Waten Pmchlmdhyteih VnbgChetnie.Webihelm, 1982. 46 KJ. lai Rrriem m Drug Metabolism omit Drug burractinm 157. PBGG, D.C.. ZEMPEL, I.A.. BRAUN. W.IJ, and WATANARK, P.G. Dhporf(ion of telraddom (^Qeltyfcne lolbohe wd and inliaiatian enpomre in tala. Toxicol Appl Bimaioeol. B1,465-474(1979). 158. STEWART, R.. BARLTTA, E, DODD. H., and TORKKLSON, T. Eapwl- mrMrt harem ertpomre to teitacMotodhykne. dreft. iMm Health. 20. 224-229(197(0. >59. Current IntifHgmce Bulkdln, No. 20, Tehaddorocthylrwi (PercMoroe1lrIen4, UR. Departaieat of lieaRh. Edacathm and WetTare. PIIS, MDSIt. Janaary. 1978. 160. MOSLEM, M.T, REYNOLDS, E.S., and SZARO. S. Enhancement of Ihe mabhoMmi and hcipalotoaidly of (rlcMoraelhytene and peachkaocthykne. BmAmh. Aaawat, 28, 369-375(1977). 161. Naltanal Cmm hreittuta. Bkwanya f IdtacNaroediylcne for pondhle car- chuatlidy, DHEW PnfaBcalfen No. 77-805. 162. RAMPY. L.W, QUAST, LEONC. B.KJ., and GEHRIND, PJ. RemBa of bag-leam hidalht toabRy atodfca on iU of l.l.i-trkbioroettianeaad pwAfaaoaHiybna fanMiathma. In: Proceeds** of (he Fht international CoiRteaa onTaxicalagy (Plan, G.L., and Dacan W.A.,ds.). Academic Pica, New Ywk. 1978. 163. BOLT. H.M., and UNR, B- Zur TmcBcofagle von PcccMwolIhrlen. Vwh. DMck Gca AibehamdUn, 2B. A.W. Ccadaet Vetlaa. Slullgart. pp. 463-470 (1980). 164. COSTA. AL, and 1VANETCH. K.M. Tckaddotoelliylenc mctaboRam by the IrepnUc mfemaonMl qrtocfnoiwe P450 ayttcat. Biodttm. norvucoL. 20, 2863-2869 0980). 165. YLLNER, S. Uitoay aretabcBlea of MC-teto*diiotoethyleBe In mko 8200961). 166. SCHUMANN, A.M, QUAST. I.P.. and WATANABE. P.C. The pharmaco- Unelka and mactonwtecntat interaction* of perchforocthj>lent h ndcc and nti u related to aacagenldty. Toxicol Appl fttormaeoL, B, 207-219 (1910). 167. COLBY, H.D* BROGAN, W.C. and MILES, P.R. Cwbon tetrachloride ln- daoed cfcaagetf halmd nktmtad miaed-hmetlon oaydaaea and tSpid peroayditio*. TbjrieoL Appl fhonmol. BB, 482-499(1981). 168. PETERS, RA, and WAKELIN. R.W. The tynthed* of fluoroacetk acM and Ht hMbBbn b acetate. Shxftem. J.. 87.280-286 < 1957). 169. HATES. P-D, SHORT, RAL, and GIBSON. l.E. Differential toxkMy of annoddMoaoefato, wonoOaotoaeetiK and monofodoatetatc la rata. Tod- eol Appl Mrnatonf., 26,93-102 (1973). 170. SCKOENTAl, R. Afeyfadon of cocnzyaie* and (he acute wteclt of aBtyla- ttog hapatorthw. FEBSUlL, 61.111-114 (1976). 171. Ta* Force ea Hepatocardnomat. ECCTOC, BmneU(1987). 47 1