Document JrORJ6d66yNq0Em2Mj1rw90x6

R&S 134712 t'''1 EuvimnutruOil Ih'tllh Prrxprctivr* Vol. 17, p/). 217-210, 1076 Studies on the Metabolism of Vinyl Chloride by H. tatweiler* Vinyl rVUiriHr tVOI) i* not rrrinofii*nie by it.s,-ir. it i.x hioaelivatrd in the hihly trarltst nlkyUlin^ otiran? rhlnroelhylcne oxide. Further metabolism, apparently, lead* ia an inlrrarliun uf the primary alkylating mrlabolilrx with glulalhinn In .S'*(2-rarboymclkylpeyslcifle and Ihindiaertic arid whirh are eliminated with Ihe urine, I'p to now. il lia mil bwii ascertained whether Ihe oxirane alone is the tssrnliil carcinogenic factor or whether other mrlaholitoi arc aim* imolved in carcinogenicity. I.ikewiee, il i still unknown whether the metabolite* excrelcd in the urinr might hr u*ed ax biological crilrtia for exposure In VC.\|. because these metabolites prubahly ran originate from a erte ul substance* other than Vl*\l, This problem rould stimulate investigation* on the pwwihir carcinogenic anility of these suhslances. Studies mi the puthwny of the carcinogenic era (>') and in 107a bv ltadwan and Ilenschler kl mutagenic activity if vinyl chloride (VC) (-i). ii"l mdy of intercut in relation to thin spe- llartsch and coller.gucs (5) then supposed i ml ijliftiiia i-. Siudi studies also allow further that the presumed intermediary motnlwilite, ii'-iiflit into tin1 possibly carcinogenic and muta- chloruethylene oxide, would lie really the active i'i iin mtvlttiiiixm of chemically related sub- alkylating substance liecause this substance 'ami'x which arc suspected to In? dangerous proved to lie a strong i .utugen as well as VC hi iicniiational e.\|iostire. Furthermore, the in the presence of an oxygenating system- Its 'Mniwledtfe o| carcinogenic metabolites may mutagenic activity in certain sensitive bacteria i irui-h us with liiochemital criteria to judge was superior to the activity of chlnroucctalde- n.e dimension of risk in exposure to potentially hyde and chloroacetic acid. .m'iiiiigenic and mutagenic substances. About the same time ( *`cn and Hathway Murei.wr research into the carcinogenic ac- (/!) as well as Norpoth and co-workers (,') i;\ ity nf \'( Ina-omex more and more interesting identified thiodiacctic acid ns u conjugated "lien we just learn that also tobacco smoke metabolite in the urine of rats which inhaled *uiiains about :jn ppb of VC, a concentration VC. This finding was in good agreement with which limy nut lie important /irr .*/, but which the statement of Hefner and colleagues that 'ii 1*1 n.-Mimc increased importance in connec- free SH-groups in the liver, not Isiund to pro ' with the other carcinogenic substances teins. are strongly used by VC and its meta "Ulaincd in I lie smoke (/), bolites respectively. Reynolds ct al. <.s'). bow. I want to report brielly some investigations ever, were not able to confirm a loss of Nil hii-li were |icrfornied in our country ipiite groups. On the contrary, they rejiorted an in iriitly by Norpoth and co-workers in a work- crease of SH groups. It is not vet dear if this >g grnu)i in .Munster in the Department of can be explained as a rebound effect. ` cupnlioiiid Medicine and the hypothesis dc- Hefner et al. supposed N'-(-*cnrboxymethy|l i`d from the results of these experiments. cystein to be a further metalwilite. This com In I!<}< Crigorescu and Tuba (j) had found pound has since Ik'cii confirmed a rnetnlmlite l"i'nncetic acid as a metabolite of VC. This of VC by Norpoth and co-workers. Since Yllnrr ir confirmed in 1071 bv Hefner and co-work- (;>. in) also found this substance and addi tionally also thiodiacctic acid to U* the main i niM-inlut IluMU'Iderf, IlusscMorf, \V. Germany. metabolite of chloroacetic acid in experiment* 'iMolwr 1978 217 R8*S 134713 on mice. Norpoth and co-workers were interin the problem of coincidence of metabo lism In mice and men. They analyzed urine samples of patient* who were given Ifosfamid. an analog of cyclophosphamide, and stated that a chloroethy! group is cleaved hy side-chain oxidation so that chnlnrouretaldehyde can he produced Indeed. its metabolites could l>e iden tified as thiodi.icctir acid and N-carboxymethyl cysteine. Estimation of the dechloroethylated product* shows nliout SO'; of the value related to these products to analyze ns thiodiacetic acid and .S'- <2-cn rim.xymethyl) cystein. Thus, the results in mice and men seem to be in agree ment < / /). S'orpoth and colleagues have found thiodi_ acetic acid also to he a metabolite of dichlorodi- ethyl ether. Thus, conversion to chloroacetnlde- hyde is vtry i>n>halile. C'hloroacetahlehyde itself may l>c a carcinogenic substance. With VC rertninly the additional formation of chloroothylene oxide is an imi*ortant factor. When we try to get u synopsis of the results in metabolic research of VC as presented in the reaction scheme (/). the first oxidation step is fodowed by a chain of detoxicating reactions, some of which occur spontaneously and some of which are enzyme-catalized. The first three >< II ( _ cci -- ----(l <_. S \IH-II , 1 ia*I / h'ii* i4r ii f CCI ii II \ I hlerwtNdriw K III I >1 ' o-t; ~ <ti n n.ii 's I kWr^rUklr^il p \ II R-C - c;-o i'i i'i I *-. t4f`-get****-. II f iitMx- rci-------------- II,C- COOII tt- none1- coon i`i -. / \K bit ^ co, i /\ fV OS- C-COOII L i'i i j t ii.n-cii-cooh ill'll 1 ^omiiiju' | ie<-jrtMitjv .'i.c-rooii I t-*i) met hylet sleiiir ll.C1 -COOll S I II,C - COOH 1 hsslurrtif ir.4 alkylating substances are of deerea-ing t. They can have biologically alkylating a*' or they may l*e detoxicated stepwi'e. i acetaldehyde and chloroacetir acid are i to Ik? toxic substances. New uuiui.tl c\|h ii by van Duuren (/-?), however, did not , chloroacetic acid to lx- a carcinogen. The results of investigations of Men and co-workers (/./) could l*e interpret, indicate that all precursors of oxiraiws v -, are not symmetrically halogen sidistituted . as trichloroethylene, and also \in\lnli-m ride, vinyl bromide, vinylideiie bromid*. haps also vinyl iodide, may I** carcinogen, Regarding the developnient of biolog!. a. teria for dangerous, carcinogenic, ami n, . genic exposure, we have still the pr--'!< n. : the specificity of the criterion. Thiodiacetic acid can probably *.rig.> from: 2-chlorocthanol, 2*bromacetic acid. > roaeetie acid, chloroacetaldchyde. hr* to.icetal s hyde. l.2-dichlori*ethane. i,2-dil*rtnctti<.and 1,1,2-trichloroelhane. All drugs containing oxidatively ek*i;i< chloroethy! side chains, such as cm lopho-t-i. mide, for instance, are supposed to cuu-c ilr opmeut of thiodiacetic acid. These hypotheses likewise might la* dis'iM-forN-(2-carlsixymelhyl)cysteine which ha- a lieen shown to Is* a naturally occurring stance in the intermediary mclal'oli^m. Most of these investigations ha\c l*een eluded in ritr tests in mutagenieitv. A* tinexists a dose correlation la-tween carcinogr: and mutagenic elfeets of chemical sub-'.-t I fee! that at present there exist, no la tii-i i sibility to learn alrout the melals.lic isiiwi', of carcinogenic substances ' in a r-a* iiic short time. It should la* con-idere*l al--* m. there are some dillictilties in the mlerpretai.ol such extierinienls, as. for example, m :* ease of Kuglish research worker* who o< recently were not able to find a motagenn i Ii in mice with tile dominant lelhal le-l w m they exposed the animal- to concentration- to :Hi.uuii ppm of VC. iM*:mti:.\<r.> 1. Il:fu*llTi muafnn\.aiMyl,, ri-thl-a-lr.i.ltr*hr-it.,nit-t..I..grjt.|*.l.-.1-...-.li'tni-Vi- Chirm. 1-: -IT i lUTfii, I * i ie-*i - u, I, uii'l 1'**'.i, i* II i --*i,,'s a. A'l-i-i-i*- .................. i*i*i ,-!r .. j I! - * i * i. IT: la-.t 11i. mt Environmental Health TVi-nwrlMe* 1, H<-fin-r, K. K,, Jr.. Wiitnnol>e, P. G., ami Gehring, J. l*n-l!minty studies of the fate of inhaled > mo | i-litori-le mfiiMHiMT In rain. Ann. N.Y. Acad. Mrt'. 2t: H.'! t lUT.'.l. 4. liadwan, Z., find Henechler. D. Uptake and metab- nlltn f vinyl chloride in the Isolated perfused rat liver preparation. Naunyn fkhmledebergs Arch. Exp. Path. I'harmak. .Suppl. 287: 100 (10751. ,i. Ma/avedle, C., ct al. Mutagenicity of vinyl chloride, rhhtrortliylvnoxiilr, chloroareUldehyde and chloro- ethanol, lhochem. Iliophy*. Re*. Comm. 671; 363 IID75). *. tlrwn, Th and Hmthway, 1*. E. The biological fate in mta of vinyl rhloriile in relation t>- it* oncogenicity, t'hctn. Hiol. Interaction* 11: 545 (1975), 7 Muller, (i., and NWpoth, K. Hestimmung zweier I'linnwtul-dit* dr* Vinylchlorid*. Natiirwii*. 62: 641 11075), 8. Reynolds, E. S., et al. Hepatotoxicity of vinyl chloride and 1,1-dichloroethylen*. Am. J. Pathol. 81: 210 (1075). 9. Yllner, S. Metalwlism of 1.2-diehlon>ethane-'*C` la the mou.se. Acta Pharmacol. Toxicol. .*): 257 (1971). 10. Yllner, S. Metabolism of rhloroacetate~l-,4C in lha mouse. Acta Pharmacol. Toxicol. :t'l; 60 (10711. It. Norpoth. K.: Studies on the metalnlium of tfoa* /amide in man. Cancer Treatmant Report*. 0: 437 (1976). 12. Van lluuren, B. L., Carcinogenic activity of alky lating agents, J. Nat. Cancer Inst. 53: C05 11974). 13, Greim, H., et al. Mutagenicity in rilru and potential earcinngenicity of chlorinated ethylene* u a fuaction of metalmlic oxirane formation, ltioehem. Phar macol. 24; 2013 (1075), I R&S 134714 etUr 1978 t * 219 R&S 134715 (('{<( - fo o ') 77 Chenospiiere ;.'o. 6, p? 309 - 329, 1977 Ferc^-on Pre=c. K- till -(/oo) p i`i'7-7 V Printed in Great Britair.. **w ' VimCHLORIDE HETA30LISM - A REVIEW Hans Plugge and Steven Safe Guelph Waterloo Centre for Graduate Work in Chemistry Guelph Campus, Department of Chemistry University of Guelph, Guelph, Ontario, Canada NIG 2W1 (Received in TCxe Netherlands 29 April 1977; accepted for publicat ion 13 Kay 1977) 0) In 1971 vinyl chloride (VC) was shown to be a carcinogenic chemical*1^; rats exposed to 2ft 7Q vinyl chloride levels as low as 50 ppm developed angiosarcoma, a rare type of liver cancer, * and approximately 50 human deaths have been attributed to this cancer.^ A syndrome occurring in VC and polyvinylchloride (PVC) fabrication and production workers was aptly called vinylchloridedisease and is characterized by extensive liver, lung and spleen damage-^>27,31,35Mortality among VC/PVC workers is extensively increased.In addition it has been established Chat in communities surrounding PVC production facilities cancer and congenital anomalies are statis- tically higher in comparison to similar towns in the same counties 19 . All these effects are con nected with VC and its transformation "in the body and thus an understanding of the metabolism of VC is essential in understanding the toxicity of this chlorohydrocarbon. This review attempts to discuss and summarize VC metabolism and to interpret seemingly contradictory data which appear in the literature. VINYIXHLORIDE URINARY ^TAB0L1TE5 The ^in vivo metabolism of VC has been studied by several groups^ * ^1 ^ and has led to a diversity of results and conclusions. The major metabolic pathway for the formation of the major urinary metabolites is shown in Figure 1. VC is metabolised by the liver mixed function oxidase system (MFOS) to chloroethyiene oxide which readily rearranges to chloroacetaldehyde. Chloroethyiene oxide and chloroacetaldehyde 30$ i i. V-S; 55S&gSBj sm55 s 310 o. 6 then either bind directly or enzymatically via glutathione-epoxide-transferase or other glutathione transferases ' to glutathione to fora S-fortaylmethylglutathione. Chloroacetaldehyde can also be directly oxidised to ehloroacetate presumably by an NAD+-dependenc aldehyde dehydrogenase. Chloro- acetate is then either excreted or bound to glutathione to fora S-carboxymethylglutathlone which can also be formed from S-formylaethylglutathione. S-Carboxymechylglutathione is then hydrolysed to S-earboxymethyleysteine which can be N-acetylated, excreted or deaminaced and decarboxylated to thiodiacetate/chiodiglycollace. The latter process undoubtedly involves pyridoxal phosphate and a Schiff base intermediate. Vinylchloride has also been shown to be metabolized by the in vitro KFOS system to chloroethylene oxide. This highly reactive intermediate was not isolated but trap ped as its addition product to 4-(4-uitrobeooyl)pyridine and the adduct was similar to the product formed with synthetic chloroethylene oxide.^ Trapping studies with 3,4-dichlorobenzenethiol point to either chloroethylene oxide or chloroacetaldehyde as the primary vitro metabolites of VC. 13 Vlnylchloride metabolism in the KFOS is predominantly through the cytochrome P450 system20 ' 40,41. vivo VC metabolism was shown to be increased after administration of P-450 inducers such 20 40 41 as phenobarbital, Aroclor 1254 and hexachlorobenzene ' * as measured by the extent of liver damage measured by the release of alanine Icetoglutarate40 , glutamic oxaloacetic and glutamic pyruvic^ transaminases into the serum. Increased glutathione levels (due to short-term induction of glutathione?)^ and decreased cytochrome P-450^'^ , and c reductase (NADFU/ HADH dependent variety) levels were also observed (see Table 1). Table 1. Effect3 on cytochromes and cytochrome reductases of MF0S 24 hours afeer VC Pretreacment Exposure*1 ______ cytochrome______ cytochrome c reductase P-450_________________ NAB PH_________________________ NADH 3) nmoles/mg prot. nmoles/mg prot. min. C/3 Vehicle Air (A) 1.lit.05 1.730.06 6703 381013 Vehicle VCM (5) .810.07f 1.570.05 50053 377040 GO C* P3T ^s| -_L PBT Air (A) VCM (6) 2.42i.lld .82i.08 1.500.11 1.390.07 9105d 9809 27So45c 667o95f 'J A-1254 Air (5) 2.53o.09d 1.610.03 8703d 213026d A-1254 VCM (8) ,970,07f 1.440.07 8306 628044f a mean SEM b VCM exposure 51 x 6 hr. number In parenthesis Is number of animals c p<0.05 compared to animals receiving vehicle d p<0.01 compared to animals receiving vehicle e p<0.05 compared to animals receiving same pretreacment p<0.01 compared to animals receiving same pretreacment 'to. Cl H CH^CHCI-5^^ XC-C rearron^ vinylchloride gement H' V'O' \XH 00 chloroethylene- oxide CHgCICHO^^fe'a- CKCICOOH chloroacetaldehyde chloroacetate I G-S-CH,-CHO 2 -xaanldtheihnyedeoxoidxaidsaese^G-S-CH2-COOH S-formyimethyl- S-carboxymethyl- iglutalhione cys-S-CH2-CH2OH <- -cys-S-CH2-CHO^ S-(2-hydro xyefhyl)- S-formy!methyl- cysteine cysteine glutathione * ^cys-S-CH2-C00H S-carboxymethylcysteine I ^nh3 N-acetyl-S-fe-hydroxy- ethyD-cysteine o 00 detected in vivo |-^co2 H00C-CHrS-CH2-C00H detected in vitro thiodiglycollate 312 I'O, C Cytochrome P450 (P450) concentrations decrease during the _it\ vicro^0/In vivo'**' incubation/ exposure of liver homogenates fron phenobarbicol and Aroclor 1254 induced cacs^0,`,,1 and non- induced rats (Table 2). P450 was broken down Co cytochrone "P-420" as indicated by UV spectra and this breakdown uas inhibited to some extent (Table 2) by glutathione and by replacing the NADPH in the liver homogenate incubation mixture with NADP+. Table 2. The effects of incubation in the presence of VC on the levels of hepatic microsomal enzymes from variously Induced rats3'** Type of Induction None MC P3 Cyt P-450 (nnol/mg mic. protein) VC 0 min 15 min. Z loss Cyt P-450 - 1.251.08 1.021.05 - 1.501.10 + 1.351.05 - 2.361.05 2.101.10 1.981.10 2.041.03 2.161.01 2.201.08 1.231.09 0.92i.08c 1.481.06 1.241.02 2.321.06 1.431.lO51 1.991.16 1.581.03c 2.011.02 1.981.05 2 10 1 8 2 32 0 22 7 10 I Loss Cyt bj 104 100 102 106 , 103 100 - - X Loss NADPH - Cyt c Reductase 96 99 97 91 98 94 - R&S 134719 3 Samples contained microsomal suspension (2 mg protein/ml 0.02 M Tri3-HCl, pH 7.4). NADPH generating system and 0.2 mfi EDTA. References contained only microsoaes. Incubation was at 30" with shaking for 15 min. k Abbreviations used are VC, vinyl chloride (30 mil); cyt, cytochrome; mic., microsomal; MC, 3-methylcholanthrene; PB, phenobarbltal. C An absorbance peak centered at 420 nm was observed in these samples. d Minus NADPH generating system. g Plus 5 mM reduced glutathione. ^ C0:0,(80:20; v/v) was bubbled through the microsomal suspension after the addition of vinyl chloride. s NADH (0.6 mM) replaced the NADPH generating system. Induction with 3-methylcholanthrene, a "P448" inducer still gave rise to VC metabolism, although the decrease in "P448" was 25Z of the decrease in "P450" of PB induced liver microsomes and 30Z of the non-induced P448-P450 decrease*0 (Table 2). Cytochrome b5 and NADPH cytochrome c reductase were not reduced jut vltro^ or _ir: vlvo^ and in the latter study it was shown that NADH cytochrome c reductase uas increased after VC exposure. MFOS inhibitors had different influences Trichloroethyleneoxide Cl <5) H , Cl CoJ H in H20 'c---c -q shlft > CHCI,--COCh---'r--< \/ Cl- Cl dcNoroacetylchloride Cl Cl in vivo C\l yto^y\/;H Cl shift * CCI3-CH0 - Cl Cl trlchloro acetaldehyde i cci3-ch2oh trichloroethanol Chtoroethyleneoxide CCI3-COOH trichloro acetate * CH2CI -- CHO4 chbroacetaldehyde cl -fcSi H^ H 314 .'.'o. 6 on VC metabolism In vitro. SKF-525A inhibited binding to P450 but did not decrease NADPH consum ption whereas metyrapone did not inhibit P450 binding but reduced NADPH consumption by 702^, Metyrapone did not inhibit VC metabolism in vivo but other MFOS inhibitors did.^ The inhibitors (dose applied in DMSQ, I inhibition) were; 3-bronophenyl-4(5)-imidazole (35 og/kg, 1002); 6-nitro1,2,3-beniothiadiazole (50 ng/kg, 762); SKT-525A (50 mg/kg, 762; and pyrarole (50 mg/kg, 662; 100 ng/kg, 1002; 100 mg/kg in H20, 712). Table 3. The effects of inducing agents on the interaction of vinyl chloride with hepatic microsomal cytochrome P-450 in vitro3. Pretreatment of Animals Cyt P-450 (nnol/mg mic. protein) Ks (mM) AA max (A385-A418) Km (nM) V max (nmol NADPH/ min/mg mic. protein) None MC PB 1.1 80f3Q 0.05i0.01 - 0.4i0.2b 1.7 126 0.030.01 - 0.6i0.2b 3.2 82 0.08i0.01 5+3 2.30.2 3 Abbreviations used are cyt P-450, total type P-450 cytochromes; mic., microsomal; MC, 3-nethylcholanthrene; PB, phenobarbital. b Apparent values measured at the highest concentration of vinyl chloride achievable by bubbling (30 mM). Chloroethylene oxide rearranges -to chloroacetaldehyde in aqueous solution^'^ with a halflife tine of 1.6 nin^. The mechanism of the rearrangement of chloroethylene oxide to chloroacet aldehyde is not clear but by analogy with trichloroethylene oxide the two mechanisms in Figure 2 may compete (i.e-): (i) in aqueous solution trichloroethylene oxide can rearrange to dichloroacetylchloride (dichloroacetate) by either of the two pathways as shown in Figure 2; (ii) trichloroethylene oxide rearranges in vivo to trichloroacetaldehyde which is further metabolised to trichloroethanol and trichloroacetate, 18 Clearly these metabolites are also formed via a 1,2-Cl rearrangement and further studies with isotopically- labeiled substrates are required to determine the precise mechanism involved. Chloroacetaldehyde has been found to bind to glutathione but only in situ^ and exposure a. m lev ttC." I' o. 6 315 of rats to 2000, 1000, 500, 250, 150 ppm VC for 1-7 hours resulted in a substantial reduction of liver non-protein sulfhydryl (thiol) levels.019 Exposure to 50 and 10 ppn of VC for 7 hours gave a slight reduction of sulfhydryl levels at the 50 ppm level and no reduction at the 10 ppm level. At the 150, 250 and 1000 ppm level an apparent maximum level of sulfhydryl depression was reached after 4-5 hours giving a 25, 35 and 37Z depression respectively. Exposure to 2000 ppm led to a sulfhydryl depression of 332 after 2, 47Z after 4 and 62Z after 7 hours. The metabolism of chloroacetaldehyde has not been studied in detail but chloroethanol 21 is metabolized _in vivo and ^in vitro (liver enzymes) to give S-carboxymethylglutathione which can be derived from either S-formylmethylglutathione or chloroacetate. In addition chloroacecate has also be "n detected as a chloroethanol metabolite09. Chloroacetate was metabolized to two major urinary metabolites, S-carboxymethylcysteine and thiodiacetate 52 and small amounts of glycollate were also detected (see below for explanation). S-Carboxymethylcysteine was detected in one study as a VC metabolite together with thiodiacetate 32 which is the product of S-carboxymethyl cysteine metabolism0', This latter metabolite was not reported in several VC studies14,40,49 which did identity thiodiacetate as a metabolic product. N-Acetyl-5-(2-hydroxyechyl)cysceine was shown to be the major metabolite from VC after oral administration and inhalation40,49. This could be derived from S-formylmethylcysteine/S-formylmethylglutachione which formerly were presumed either not to be formed or to be further metabolised to S-carboxymethylcysteine. 21 N-Acetyl-S-(2-chloroethyl)cysteine has also been reported as a VC metabolite 14 but this may be an artifact due to the iso lation procedure12 which involved boiling with HC1. S-(2-chloroethyl)cysceine has been synthesized by heating S~(2-hydrqxyechyl)cysteine with cone HC1.0,9 An unidentified major metabolite (30-40Z overall) was also reported and a possible structure could be (N-Acecyl)-S-Carboxynethyl cysteine. * 49 OTHER VIltYLCHLORlDE METABOLITES Administration of [14C)-vinyl chloride resulted in Che formation of levels were found (based on the amount of VC administered): and the following inhalation oral intragascric intrapericoneal 12.1Z (10 ppm) 12.3Z (1000 ppm) 49 9.OZ (0.05 cg/kg) 13-32 (1 mg/kg) 2.52 (100 mg/kg) 4S 13.52( 250 wg/kg)0.72 (450 mg/kg)14 11.02 (250 ug/kg) 0.72 (450 og/kg)14 m 49* zzLtzi s'ga Cl H ocetyl- 0 CHCl--CH2--1 C^C ------- >CH2CICH0------->CH2CICOOH thiokraie----- CH2Cl-C-SCoA h' 0 'h | Cl H tt H-C--C-H II OH OH glyoxylate -- second time through citric acid cycle -->MC02 acetate \ oxoloacelate V acetylCoA------- ^------- citrate -malate <-- succinate <l fumarate -1 - oxaloacetate 1 phosphoenot pyruvate J. 2- phosphogiycerate succinylCoA ^co2 a-keioglutcrate 4- 1. glutamate , l i. urea *cisaconitate i isocitrate irCOz -oxalosuccinate i,3diphospboglycerate <-- - 3-phosphoglycerate --CICHjCOOH 3-phosphog!yceraldehyde 3-phosphohydroxypyruvate l 3-phosphoserine 'CH, S-adenosythornocysteine -*-- S-adenosylmethionine i r. homocysteine--I--) methionine 'delected as metabolites serine -- -------7---------- telrohydrofcbte -> glycine** N5Nlomethylenetetrahydrofo!ate R&S 134724 CH?=CHCi Cl H * /C^C^ * CHpCICHO H 0 NH hydrolase a *h H-C--C-H - CHpCICOOH * S- carboxymefhyl cysteine/glulafhione / cysleine- acetate desulfhydrase? mono oxygenase OH OH hci CH2OHCHO CHoOHCOOH 1-chloroethane -1,2 diol glycolaldehyde glycollafe N' formylte rahydrofolate oxaioCoA CoASH NADH t NAD ate (-------------------- NADH CHOCOOH glyoxylate ---- - glycine - ocelylCoA CoASH N - formylteirahydrofolate citric acid cycler-------malate N,5,f,\,Tiomethy idenyiteirahydrofolafe--> N5N[0 methylenefetrahydrofolate homocysteine- i ------- > methionine detected as metabolite "CHj" S-adenosylhomocysteine -S -adenosylmethionine serine 31C :.c. 6 33 </) co ~vl ro ui 4 1 1 1 3 * ax J 1 l i i* $ m4 1 3 Two pathways can explain the generation of 14 CO^: (i) addicion/transfer of an (chloro)acecyl group to CoA followed by metabolism in the TCA cycle (Figure 3) or (li) the formation of glycollate followed by its oxidation to glyoxylace (Figure 4) after which it enters the C2 and Cj pools. From these two, the glycollate pathway seems to be preferred since by analogy chloroethyleneoxide is hydrated via a hydratase 36 to l-chloroethane-l,2-diol* and rearranges to glycolaldehyde which is oxidised to glycollate. Another pathway for glycollate formation involves the use of a monoox'ygenase hydrolase to convert chloroacetate to glycollate**52 , In addition 5-earboxymethyl- cysteine could be enzymatically cleaved to give either glycollate directly or acetate which could be oxidised to glycollate. This is not likely to be a major metabolic pathway since S-carboxy- 52 oethylcysteine produced very little C02 during its metabolism. Glycollate is further oxidised to glyoxylace. Glyoxylate can be transaminated into glycine, a product of chloroacetate meta bolism or can be converted into formate, oxalate and oxalo CoA, all of which can yield formate. Formace can either enter the Cj pool, explaining the occurrence of labelled serine and methionine in urine of rats administered [ 14C]-VC14 or it can be oxidised to C02. Further metabolites detecced in the study 14 were urea, glutamate and chloroacetate, whose occurrence can be ration alized as shown in Figures 3 and 4. VC BINDING TO PROTEINS In vitro protein binding of VC (metabolites) was shown to be dependent on the thiol content of proteins 21" and protein binding was NADPH22 ' 23 and oxygen23 dependent. Incubation with nitrogen gave i502 of control metabolism but only 62 of the protein binding (Table 4). Glutathione slightly ` 23 increased metabolism and decreased protein binding (Table 4) 1,1,1-Trichloropropyleneoxide, an 972 effective hydratase inhibitor 36 , increased metabolism by only 102 but effectively doubled protein binding due to the _in vitro accumulation of chloro ethyleneoxide (and therefore chloroacetaldehyde and chloroacetate) which is available for protein binding2'3 (Table 4), Generation of superoxide radicals with HADH and phenazinemethosulfate, also gives VC metabolism and protein-bln^lhg at approximately 102 of the control level, using a liver 23 * Hyoratase activity is responsible for approximately 402 of VC metabolism in vitro ** Chloroacetate autohvdrolyses to glycollate very slowly at pH 7 which can not account for its in vivo metabolism3-. ter ide ch aid sed me tent ogen ghtly 1 ism e ;n lsc :.o. 6 319 microsomal preparation with added NADPH,^ Table 4. 14 Uptake and irreversible protein binding of C-vinyl chloride by hepatic microsoces of rats Uptake3 (nmol/ml) Percentage of control With NADPH (control) 50.8t8.7c,d (n-8) Without NADPH 4.1i0.69C (n-8) Wich NADPH under nitrogen 27.isl.3d (n-4) With NADPH under 952 CO/52 02 2.4t0.4d (n-4) Without NADPH under 952 CO/5% 02 0.310.09d (n-4) With NADPH + L-glutathione (1 mM) 60.0H2.2 (n-8) With NADPH + L-glutathione (1 mM) + cytosol (1 mg protein/ml) 65,8i5.6c (n-8) With NADPH + trichloropropene oxide (10 uM) 56.918.1 (n-6) 100.0 8.0 53.5 4.7 0.6 118.0 130.0 110.0 Protein binding (nmol/mg micro somal protein). 0.44t0,05c,d (n-3) x0.001c (n-8) 0.0610.01d (n-4) 0.01l0.002d (n-4) <o.ooid (n-4) 0.33i0.03C (n-8) 0.23 (n-2) 0.9810.06c (n-6) Percentage of control 100.0 -13.6 2.3 -- 75.0 63.6 222.5 3*t fCrx I'l vis 30 \r (/) 03 -4 N> a> m Uptake is expressed as nanomoles of vinyl chloride taken up per 1.0 ml of incubation mixture. b Protein binding is expressed as nanomoles of vinyl chloride metabolites irreversibly bound per 1.0 mg of microsomal protein. Microsomal protein concentration was 1.0-1.2mg/ ml. Incubation time 60 min, and partial pressure of vinyl chloride 2.0-4,0 Torr. c,d Differences are statistically significant within both experiments C p<0.001 (paired comparison); d psQ.001 (group Student's t test). In vivo binding of VC to microsomal proteins has also been reported. 4 Table 5 shows the levels of total metabolites and irreversibly protein bound metabolites directly and 48 hours after the termination of an exposure to 44 ppm VC for 5 hours. Protein-binding is relatively constant on a 48 hour time scale except in the kidney where an approx. 162 decrease in protein bound meta bolites occurred over this period. Extractable and cotal-procein bound metabolites decrease a 320 ::o. 6 Table 5. Metabolites of ^C-vinyl chloride and irreversible protein binding in different 14 tissues of rats after 5 hours exposure to C-vinyl chloride. Initial concentration of vinyl chloride in atmosphere - 44 ppm Uptake per rat (200 g) " 6.5 umol vinyl chloride Radioactive Metabolites immediately Radioactive Metabolites 48 hours after after Exposure beginning of Exposure nmol metabolites/100 mg tissue . nmol metabolltes/100 mg tissue * Total Metabolites Irreversibly Protein Bound Metabolites Total Metabolites Polar, Ex tractable Metabolites Irreversibly Protein 3ound Metabolites Liver 33 R Spleen (/> Kidnev 11.4511.84 2.2510.30 13.1512.63 CD Lung n.d* "J to Small Intestine 'si n.d. Brain 1.0510.05 Adipose Tissue 1.3610.17 Muscle (M.psoas) 1.9710.44 1.4610.47 0.8810.02 1.1810.14 n.d e n.d. 0.1310.04 0.2610.06 0.13i0.01 2.16*0.14 1.21*0.08 1.3710.19 1.0U0.08 1.0410.08 0.2210.03 0.3010.03 0.3210.07 0.3810.03 0.3310.01 0.4010.04 0.30*0.11 0.3310.04 n.d. n.d. n.d. 1.45i0.06 0.8310.06 0.9910.07 0.7710.01 0.7210.07 n.d. n.d. n.d ,, Figures show x - S.D.; n-3 n.d. " not determined BINDING OF VC TO KMA AMD DMA VC binds to RNA22 _in vitro and to RNA and DNA vivo 4. DNA binds 34 tines more meta bolites chan RNA on a molecular basis although the total amounc of RNA which reacts is about 34 tines as great as the DNA (Table 6) which reacts, all measured at their peak values. DNA binding reaches its maximum value immediately after exposure and declines rapidly in the next 6 hours probably due to the excission of alkylated bases, most probably ethenoadenosine and echenocytidine, by DNA repair enzymes. / / pea DNA [2. dih arc lit 3< bel anc vit ca: 6 321 Table 6. Irreversible binding of mecabolites of ^4C-vinyl chloride to DMA and RN'A of liver of rats exposed to 14 C-vinyl chloride Initial concentration of 14 C-vinyl chloride in atmosphere - 145 ppn Time of exposure - 5 hours Uptake per rat (210 g) - 16.4 pmol vinyl chloride Time after begin ning of exposure 5 hours (immediately after exposure) 12 hours 24 hours 43 hours pool metabolites bound tO 1 mg DNA RUA 132 15.9 55 19.6 61 42.5 37 36.6 pool metabolites bound per g liver (vet weight) DNA R2JA 102 118 46 164 43 340 22 307 RUA binding levels peak after 24 hours; some of the possible explanations for this delayed peak are a long turnover time, continuous reaction with metabolites and a building-in of excised DN'A bases, Chloroacetaldehyde is known to bind to adenosine to form 3-3-U-riboturanoxylimidato [2,1-1] purine or l.N^-ethenoadenoslne^'^'^. Cytidine gives a similar reaction to form 5,6dihydro-5-oxo-6-S-D-ribofuranosylinidaao [1,2~6J pyrinidine or 3,N^-ethenocytidine. The structures g8 .-Ss are shown in Figure 5. Guanosine was reporced to be unreactive with chloroacetaldehyde^ but pre liminary work in our laboratory has shown the presence of a product with a mass similar to that of 3 (Figure 5). Both the ethenoadenosine and cytidine derivatives are easily Hprprrphle at concentrations 10" 2 26 below M . Chloroacetaldehyde also readily reacts with DMA in vitro , Chloroethylene oxide and VC + microsomal preparation produced 1,N^-ethenoadenosine on Incubation with adenosine in vltro^. The forcationof the ethenoadenosine and cytidine has been proposed as the basis of the 44 carcinogenic action of VC H H ` " --- -- _ H e N H 0^" ribose :i;ure 5. (Possible) Products of VC reaction of 1 ,N-ethenoa d enosine(l^) , 3 , N~-echonocytldine(2^ and 1etheaoguanoslneO) R&S 134729 PREPARATION OF VC METABOLITES CHLOROETHYLENEOXIDE (CEO) Different methods have been proposed to prepare chloroethyleneoxide. The earliest synthesis used tert-butylhypochlorite and ethylene oxide to yield CEO after irradiation at -10*C Molecular photochlorination of ethyleneoxide was suggested as an alternative^ to the earlier reactionA 7 both of which were not very successful 13 . A modified version. Including design of glassware has been published. 39 Extreme care should be taken in handling this compound as it is 10,000 times as reactive a mutagen as methylnethanesulfonate and ethylene oxide^. CKL0R0ACETAI.DEHYDE (CA) This compound is commercially available as either 301 or 452 aqueous solutions which are "somewhat" impure. Commercial 451 CA solutions were found to consist of a 40:60 mixture of the monomeric and dimeric hydrates of CA^, Synthesis of CA was first reported In 1882^* and in our laboratory a modified version of this method is used to prepare CA. Chloroacetaldehyde dimethylacetal (20 ml) was refluxed at 70* - 80* with 52 HjSOi, (80 ml) until a light brown color developed. The solution is then distilled at 150* and the fraction coming over between 87 and 94* is col lected and cooled in a dry ice-acetone mixture. This is presumed to be pure chloroacetaldehyde. Pure CA can also be prepared by cracking the trimer at 100*^'^. Synthesis of this trimer from chloroacetaldehyde dimethylacetal 39 and commercial 452 CA10 has been described. S-(2-HYDROXYETHYL)CYSTEINE/GLUTATHI0NE S-2 hydroxyethyleysteine/glucathione are prepared by the addition of ethyleneoxide to 2i 33 cysteine/glucachione - An additional synthetic cethod has also been published. S-FORMYLCYSTEINE/GLUTATHIONE S-FormyInethyl glutathione cannot be prepared directly from CA due to polymerisation at pH > 7. However preparation of CA in situ by reduction of 2 chloroethanol by alcohol dehydrogenase 2i at pH 7.8 in the presence of cysteine resulted in the preparation of this metabolite. S-CAR SOXYMETKYLCY STEIN E/CLUTATHI0NE S-Carboxymethylcystelne/glutathione was prepared by the reaction in a basic environment of cysteine/glutatione with either chloro- 52 or iodoacetate 21 Cl anhyc THIOl sulp) 1. 2. 3. 4. 5. 6. 7. 9. 10. 11. 12. 13. 14. 15. 16. 17. 13. 19. 20. -ga 1- ped. nase No. 6 323 n-acetyl-s-careoxymethylcysteine The synthesis of N-acetyl-S-carboxymethylcysteine through the acetylation with acetic anhydride of $-carboxymethylcysteine has been described. 37 TV. IODICLYCOLLATE /ACETATE This compound is commercially available or can be synthesized by the reaction of sodium sulphite with chloracetic acid. f 33 l 9" ' (/> W CO o REFERENCES 1. 3arbin, A., Bresil, H. , Croisy, A., Jacquinon, F., Malavellle, C., Montesano, R., and Bartsch, H., Blochen. Biophys. Res. Comnun.. 67. 596-603 (1975). 2. Barrio, J.R., Secrist III, J.A., and Leonard N.J., Biochem. Bloohvs. Res. Commun,, 46, 597-604 (1972). 3. Bolt, H.M., Kappus, H., Buchter, A., and Bolt, W. , Arch. Toxicol., 35, 153-162 (1976). 4. Bolt, H.M., Kappus, H., Kaufmann, R., Appel, K.E., Buchter, A., and Bolt. W.. INSERT, 52. 151164 (1976). 5. 3onse, G., Urban, Th., Reichert, D,, and Henschler, D., Bloch. Pharmacol.. 24. 1829-1834 (1975). 6. Carson, J.F., and Wong, F.F., J. Org. Chem.. 29. 2203 (1964). 7. Chasseaud, L.F., Glutathione-S-cransferases in "Glutathione" p 90-119, Flohe, L., Benohr, H. Ch., Sles, H., Waller, H.D., and Wendel, A. Eds. Academic Press, New York 1974. 8. Clegg, J.W., and Baerse, A.E., Industr. Eng. Chem., 42, 1222-1225 (1950). 9. Connors, T.A., and Ross, W.C.J., Chem. Ind , 366 (1958), 10. Elmore,'J.D., Wong, J.L., Laumbach, A.D., and Streips, U.N., Blochlm. 31ophvs. Acta. 442, 405419 (1976). 11. Fjellstedt, T.A., .Allen, R.H. , Duncan, B.K., and Jakoby, W.B., J. Biol. Chem., 248, 3702-2707 (1973). 12. Gehrke, C.W. and Stalling, D.L., Separation Sci., 2. 101-138 (1967). 13. Gothe, R., Calleman, C.J., Ehrenberg, L. , and Wachtoeister, C.A., Amblo. 3, 234-236 (1974). 14. Green, T.,and Hathway, D.E., Chem. Biol. Interactions, 11. 545-562 (1975). 15. Gross, H., and Freiberg J., J. Prakt. Chem., 311, 506-510 (1969). 16. Hefner Jr., R.E., Watanabe, P.C., and Cehring. F.J., Ann. N.Y. Acad.Sci., 246. 135-143 (1975). 17. Hussain, S., Osterman-Colkar, S. , Chem. Biol. Interactions. 12. 265-267 (1976). t IS. Ikeda, M., and Ohtsuji, M., Br. J. Ind. Med.. 29, 99-104 (1972). 19. Infante, P.F., Ann. N.Y. Acad. Sci.. 271, 49-57 (1976). 20. Ivanetlch, K.M., Aronson, I., and Kate, I.D., 3iochem. Bioohvs. Res. Cor--un. , 74(4), 1411-1418 (1977). -- f. it 324 i i 21. Johnson, M.K., 31ochea. Pharmacol.. 16. 185-199 (1967). No. 6 22. Kappus, H.,, Bolt, H.M., Buchter, A., and Bolt. W., Nature. 257. 134-135 (1975). 23. Kappus, H.,, Bolt, H.M., Buehter, A., and Bolt, W., Tox. Annl. Pharmacol.. 37. 461-471 (1976) 24. Kochetkov. N.K., Shibaev, V.N., and Kost, A.A.. Tet. Letters. 22, 1993-1996 (1971). 25. Lange, C.E., JCihe, S. , Stein, G., and Veltman, G., Ann. N.Y. Acad. Sci., 246, 10-21 (1975). 26. Lee, C.H., and Wetmur, Y.G., Blochen. Blophys. Res. Cocmun., 50(3). 879-884(1973). 27. Lilis, K., Anderson, H., Nicholson, W.J., Dawn, 5., Fischbein, A.S., and Sellkoff, I.J., Ann. N.Y. Acad. Sci., 246, 22-41 (1975). 28. Maltoni, C,, and Lefemine, G., Environ. Res., 7_, 387 (1974). 29. Maltoni, C., and Lefemine, G., Ann. N.Y. Acad. Sci.. 246, 195-218 (1975). 30. Marstellar, H.J., Lelbach, W.K., Muller, R., and Gedigk, P., Ann. N.Y. Acad. Sci., 246, 95-134 (1975). 31. Miller, A., Teirstein, A.S., Chuang, M., Sellkoff, I.J., and Warshav, R., Ann. N.Y. Acad. Sci.. 246, 42-52 (1975). 32. Muller, G., and Norpoth, K., Naturvlssenschaften, 62, 541 (1975). R&S 134731 33. Nachtomi, E., Alumot, E., and Bondi, A., Israel J. Chem., 4_, 239-246 (1966). 34. Natterer, K., Monatsh. Chen.. 443-464 (1882). 35. Nicholson, U.J., Hammond, E.C., Seidman, H., and Sellkoff, I.J., Ann. N.Y. Acad. Sci., 246, 225-230 (1975). 36. Oesch, F., Kenoblotlca, 3(5) , 305-340 (1973). 37. Ozawa, H., Bull. Chem. Soc. Jap.. 36, 920-922 (1963). 38. Pabst, M.J., Habig, W.H., and Jakoby, W.B., Blochea. Blophys. Res. Common-, 52(4), 1123-1128 (1973). 39. Rannug, U., Cothe, R. , and Wachtraeister, C.A., Chem. Biol. Interact., 12, 251-263 (1976). 40. Revnolds, E.S., Moslen, M.Y., Szabo, S,, Jaeger, R.J., Murphy, S.D., Amer. J.Pathol., 81_, 219236 (1975). 41. Reynolds, E.S., Moslen, M.Y., Szabo, S.. and Jaeger, R.J., Res. Comm. Chem. Pathol. Pharaacol., 12(4) . 685-694 (1975). 42. Secrist III, J.A., Barrio, J.R., Leonard, N.J., and Weber, C., Blochealstrv.11(19). 3499-3506 (1972) . 43. Tabershav, I.R., and Caffey, W.R., J, Occup. Med., 16, 509-518 (1974), 44. Van Duuren, B.L., Ann. N.Y. Acad. Sci.. 246, 258-267 (1975). 45. Veltman, C,, Lange, C.E., Juhe, S., Stein, C., and Bachner, U,, Ann. N.Y. Acad. Sci., 246. 6- 17 (1975). '1 46. Viola, P.L., Biogotti, A., and Caputo, A., Cancer Res. , 31, 516-522 (1971). 47. Walling, C., Fredericks, P.S., J. Amer. Chem. 5oc., 34. 3326-3331 (1962). No. 6 325 48, Wacanabe, P.C-,, McGowan, C.R and Gehring, P.J. Tox. Appl. Pharaoacol.. 36, 339-352 (1976). 49. Watanabe, P.G. i, McGowan, G.R (1976). .Madrid, E.O. and Gehring, P.J., Tox. Appl. Phana.. 37. 49-59 50. Watanabe, P.G., Hefner Jr., R.E., Gehring, P.J., Toxicology, 6^, 1-8 (1967). 51. Waxueiler. R.J., Stringer, W. , Wagoner, J.K., Jones, J., Falk, H., and Carter, C., Ann. N.Y. Acad. Sci. . 271, 40-48 (1976). 52. Yllner , s. . Acta.Pharm. Toxicol,. 30, 69-80 (1971). 53. Yllner . s.,, Acta. Pharn. Toxicol. , 30,' 257-265 (1971) R&S 134733 Data are presented on the levels of all chemical contami nants resulting from environmental pollution which have been found in human tissues including blood, urine, breast milk, and tissue samples obtained at autopsy. Most data results from specific surveys to determine health hazards. The roles of trace elements and recognition of the need to determine baseline levels of chemicals introduced into the environment are factors which have motivated surveys by individual investigators. Thus, most data'on chemicals in human tissues record levels of pesticides (e.g,, DDT and metabolites), levels of trace metals such as lead, cadmium, and mercury, or levels of nutritionally essential elements such as zinc, copper, manganese, and fluoride. Data available on iron and calcium are not presented as their presence in the environment is generally not considered hazardous. Data on several uncommon chemicals, such as indium and ytterbium, are included basically as items of in terest and to further document their presence in healthy in dividuals. Baseline data were presented where available to provide perspective as to chemical levels which might be expected under conditions where exposure could be con sidered normal or not directly related to a pollutant source. Nearly 600 cited surveys or investigations, most of which were reported within the'past decade, are listed. Ninetyfour different chemical contaminants, primarily trace metals and organochlorine pesticides, are reported. It is estimated that over 75% of the data published during the past 30 years on chemical contaminants derived from en vironmental pollution and found in human tissue in the United States are represented in this report. (ERA citation 04:019820) '7//-O ) I '--Highlight-- L -S 1 Vinyl Chloride: A Review, 1835--1975;. an Annotated Literature Collection, 1976--1975; a Literature Compilation, 1976-1977. H. S. Warren, J. E. Huff, and H. B. Gerstner. Toxicology Information Response Center, Oak Ridge, TN. Nov 78. 218p ORNL/TIRC-78/3 Price code: PC E13/MF A01 Vinyl chloride (CH sub 2 CHCI) (VC) is a colorless gas, produced and marketed in large volume primarily as the base for its versatile and relatively inert homopolymer, polyvinyl chloride. The toxicological problem posed by VC has broad ramifications rooted in the long interval between the industrialization of the VC/PVC processes and the first recognition of the potential carcinogenicity of the VC monomer. This time delay represents the latent period of the carcinogen within the human organism and may mean that the VC-associated cancer cases detected to date represent only the beginning of a growing clinical statistic. This report on vinyl chloride consists of three parts: Part I provides a review of vinyl chloride and its health-related aspects as summarized from the literature through 1975: Part II comprises an annotated, keyworded. indexed collec tion of 555 references (1835--1975) which emphasizes biological effects and includes references concerning analysis and control in both workplace and environment: Part III is an updated collection of references which ex tends the bibliography through September 1977. This bibliography was compiled from the major scientific ab stract literature. Current journals in appropriate disciplines were also scanned. References are arranged alphabetically by first author s name. A permuted title index is appended for easy access to the bibliography. (ERA citation 04:024713) --Highlight-- Methods Dev lopment for Assessing Air Pollution Control Ben fits. Volume I. Exp rfmerits In the Economics of Air Pollution Epidemiology. Thomas D, Crocker, William D. Schulze, Shaul Ben-Dav and Allen V, Kneese. Wyoming Univ., Laramie. Feb 79, 177p EPA/600/579/001A See also.Volume 2, PB-293 616. Also available in set of 5 reports PC E14L PB-293 614-SET, PB-293 615/1WP Price code: PC A09/MF A01 The volume employs the analytical and empirical methods of economics to develop hypotheses on disease etiologies and to value labor productivity and consumer losses due to air pollution-induced mortality and morbidity. In the mor tality work, 1970 city-wide mortality rates for major disease catagories have been statistically associated with ag gregate data from sixty U.S. cities on physicians per capita, per capita cigarette consumption, dietary habits, air pollu tion and other factors. The estimated effect of air pollution on mortality rates is about an order of magnitude lower than some other estimates. Nevertheless, rather small but important associations are found between pneumonia and bronchitis and particulates in air and between early infant disease and sulfur dioxide air pollution. The morbidity work employed data on the generalized health states and the time and budget allocations of a nationwide sample of individual heads of household. For the bulk of the doseresponse expressions estimated, air pollution appears to be significantly associated with increased time being spent acutely or chronically ill. Air pollution, in addition, appears to influence labor productivity, where the reduction in productivity is measured by the earnings lost due to reduc tions in worktime. Supplementary Data System, Microdata File, Michigan, 1976. Norman Root, and Wayne Drawdy. Bureau of Labor Statistics, Washington, DC. Office of Occupational Safety and Health Statistics. 1976, mag tape BLS/DF-79/044 Source tape is in EBCDIC character set. Tapes can be prepared in most standard 7 or 9 track . recording modes for one-half inch tape. Identify recording mode desired by specifying character set, track, density, and parity. Call NTIS Computer Products if you have questions. Price includes documentation, PB-288 258. PB-293 669/8WP Price code: CP T02 Tape contains records of individual occupational injuries and illnesses. Selected injury and illness factors were clas sified in accordance with standard definitions used in the Supplementary Data System of the Bureau of Labor Statistics. Each case record contains year, month and day of occurrence: nature of injury or illness, part of body af fected. type of accident or exposure, and source of injury or illness; and industry, age. and sex, of injured or ill em ployee. Technical documentation is available: PB-288 258, Supplementary Data System, Microdata Files, User's Guide, 1976-77. Data were compiled by the Michigan Bu reau of Safety and Regulations from workers' compensa tion reports of cases which occurred during 1976 and which resulted in death or seven or more lost workdays. Data include cases arising in private and public employ ments with these principal exceptions: Those employed by certain nonagricultural employers with less than three em ployees: those employed by agricultural employers of less than three regular employees; those employed by certain agricultural employers with three or more employees; and ENVIRONMENTAL POLLUTION A CONTROL 645 88: 32773q Metabolism of vinyl chloride: destruction of the heme of highly purified liver microsomal cytochrome P-450 by a metabolite. Guengerich, F. Peter; Strickland, Thomas W. (Cent. Environ. ToticoL, Vanderbilt Univ. Sch. Med., Nashville, Tenn.), Mol. Pharmacol 1977, 13(6), 993-1004 (Eng). The NADPH-dependent, vinyl chloride 175-01-4] -mediated destruction of cytochrome P-450 [9035-51-21 was demonstrated in rat liver microsomes and in highly purified reconstituted enzyme systems contg, SADPH-cytochrvme P-450 reductase (NADPH: ferricytochrome oxidureductase, EC 1.6.2.4) [9023-03-4] and cytochrome P-450. The loss of cytochrome P-450 could be attributed to heme [14875-96-8] destruction, but not to lipid peroxidn. or binding of electrophiles to free sulfhydryl groups. The system required aH components necessary for mixed-function oxidn., including mol. 0, and was inhibited by CO. suggesting strongly that oxidative metab. of vinyl chloride by cytochrome P-450 is necessary for the obsd. destruction. The NADPH-cytochrume P-450 reductase-catalyzed destruction of free and cytochrome P-450-bound heme was also obsd. in reconstituted systems in the absence of vinyl chloride. Inhibition expts. with Co and catalase suggest that the vinyl chloride-mediated destruction of cytochrome P-450 heme differs from these processes. Two proposed metabolites of vinyl chloride, vinyl chloride epoxide [7763-77-1] and 2-chloroacet~ aldehyde [107-20-0], do not appear to be responsible for the heme destruction. Evidence for the involvement of free radicals could not be demonstrated when the reaction was examd. by EPR spectroscopy or when attempts were made to inhibit cvtochrome P-450 destruction with radical-trapping agenta. R&S 134734 K-nn - (ico) fj R&S 134735 fi-'.oseqi. Safeguarding the health of worker* exposed .IXim X". .Aiwi =WTW H" liSr'fTM of pvc. Manet. Jozef; Kaleta Jerry Uns^ Ekon. Pnem. PKsam Krakow Pol.) Poltmery (Warsaw) 19m, 22(2;. b* o (PoT"' general discussion is given of safety precaution*, mubeo&. during the manu and handhng oU^ cMor.dc 175-01-41 and its Dolvmers. E- Ac A,r polUhdAl d>id * \Joi 21 / I c!rt~h