Document 2jMNrmpdLxB58xwaw1XdwG03p
Beilrage zur Okologischen Cheinie LXXXIV+ Metabolism of Lower Polychlorinated Biphenyls-14C
in the Rhesus Monkey
by W. Gfeb, W. Klein, F. Coulston*, L. Golberg*, and F. Korte
Intlitui fur Okologische Chemie der Geselhchaft fur Strahlen und Umweltfortchung mbH, Munchcn D-5205 St. Augustin lt W. Germany
* Institute of Experimental Pathology and Toxicology Albany Medical College, Albany, N.Y. 12208
INTRODUCTION
Metabolism studies on PCB are important for estimating
the toxicity of. metabolites after knowing their identi
ty and biological pathway. Some pure PCB-isomers were
shown to be converted to hydroxylated products by rat
liver microsomes (GREB et al. 1974), rabbits (BLOCK
and CORNISH 1959), rats (HUTZINGER et al. 1972,
YOSHIMURA and YAMAMOTO 1973) and pigeons (YOSHIMURA
and YAMAMOTO 1973). The purpose of this study was to
identify all major metabolites after PCB-administration
to Rhesus monkeys and to measure the amounts of diffe
rent excreted metabolites. Correlation of conversions
and elimination pattern of PCBs with different chlorine
content might lead to conclusions about the behavior of
other PCBs.
:
The excretion rates of 2,4'-dichlorobiphenyl and 2,5,21-trichlorobiphenyl have been described elsewhere (GREB et al. 1973); we now wish to report the identifi cation of their metabolites.
EXPERIMENTAL
The PCBs investigated were 2,41-dichlorobiphenyl and 2,5,2'-trichlorobiphenyl, both major components^of the lower AROCLOR series. They were labelled with C. Fema le Rhesus monkeys were housed in metabolic cages and the PCB was injected once in the left forearm vein. Three animals received 2,4'-dichlorobiphenyl in doses of 16.8, 77.6 and 566y|fcg/kg, while 82.6/sg/kg of the 2,5,2'-trichlorobiphenyl were administered to one mon key. Urine and feces were collected daily. Conjugates were hydrolyzed by refluxing urine with an equal volume of 8 N H-SO. for one hour and extracted with ether. Fe ces were mixed with anhydrous sodium-sulfate and extrac ted for two days in a Soxhlet apparatus with CHjCl, end then with methanol. The combined extracts were conceri-
+LXXXIII. Communication: GREB, W., W. Klein, F.COULSTON L.GOLBERG,and F.KORTE: Bull.Environ.Contain. Toxicol., in press.
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TABLE 1
TLC -, GLC- and MS-Data of 2,41-Dlchloroblphenyl Metabolites In Monkeys
Data
OH-Metabo- OH-Metabo- CH-Metabo- (CH),-Meta- (OH)--Me-
lite Sx
1ite S2
lite S3
bolite S. bOl. Sg
K before methylation 1 (ch2ci2)
0.66
0.50
0.25
0.13
< 0.1
Rf after methylation 1 (ch2ci2)
0.82
0.70
0.66
0.59
0.64
OH)2--Me:abof. Sg
< 0.1 0.52
GLC after methylation (min.)
MS-fragment a|ter methylation M+
10.2/179C 12.1/185C 11.4/185C 14 .8/200C 13.1/200C 11.6/200C
for 9 min. for 9 min. for 8 min., for 8 min. for 8 min.,
then temp, then temp, then temp, then temp, then temp,
raised 5C raised 5C raised 5C/ raised 5Q raised 5 C/
min.
min.
min.
min.
min.
252 s
252 s
252 s
282 s
282 s
282 s
H m+-ch3 " metastable " M+-C1 " M+-HC1 " M+-CH3-CO
-
217 1
-
209 in
237 1
217 m
-
209 s
237 m 223* m
-
-
209 m
267 1 -
247 m 246 m 239 m
267 m -
247 m 246 m 239 1
267 m
-
239 1
" M+-CH3-C1
- - 202 1 -
--
" M+-CH3-C0-HC1 " M+-CH3-C0-C12
173 1 -
-
173 m 139 m
204 1
-
-
Peak-Intensities: s*strong, m-medium, l*low
**
n (n a: O W1 4' ^
TABLE 2
TLC-, GLC - and MS-Data of 2,5,2,-Trichlorobiphenyl Metabolites in Monkeys
Data
OH-Metabo- OH-Metabo- OH-Metabo- (OH) --Meta-i . (OH)--Meta (OH)3-Me-
lite Gx
lite G2
lite G3
bolite G4 bolite G5 tabol. Gg
Rf before methylation (ch2ci2)
0.49
0.25
0.25
0.11
<0.1
< 0.1
Rf after methylation' 1 (ch2ci2)
0.76
0.72
0.72
0.64
0.53
0.32
GLC after methylation Rfc (min.)
MS-fragment ater methylation M
" m+-ch3
n M+-C1 ,,+ " M -CH3-CO
13.8/180C
286 s 271 1 251 m 243 m
15.4/185C 16.2/185C 17.0/200C 13.7/200C 17.8/200C
for 8 min., for 8 min., for 8 min.,
then temp, then temp. then temp,
raised 5C/ raised 5C/ raised 5C/
min.
min.
min.
286 s 271 1
286 s -
316 s 301 1
316 s 301 1
346 9 -
243 1
251 1 24 3 1
281 1 273 m
273 1
-
" M+-CH,-C1
-
-
-
266 1
-
-
n M+-C1
186 1
-
-
246 1
246 s
276 1
4.
" M -CH3-C0-C12
173 1
173
-
203 1
-
-
OSM 0 2 5 9 4 9
Peak-Intensitie31 s=> strong, m *> medium, l*=low
After inethylation all purified metabolites showed in the mass spectra -OCH_-groups indicating that the original metabolites were phenolic derivatives. In both cases a number of isomers had been formed. Isomers only dif fered in peak-intensities. All isolated compounds showed the typical isotopic distribution pattern corresponding to the number of chlorine atoms in the parent PCB. For 2,4'-dichlorobiphenyl there was no conversion exceeding the Introduction of 2 OH-groups per molecule. For the 2,5,2'-trichlorobiphenyl we observed a metabolite with three OH-groups. Corresponding to its formation the monohydroxy-metabolite with the lowest concentration should be the precursor of the highest concentrated di hydroxy-compound. Only three monohydroxy-derivatives were formed although six (resp. seven for the trichloro biphenyl) structures are possible. For each PCB a highly polar zone of 1 and 4% resp. of radioactivity could not be identified. Data of the metabolites are shown in Table 1-2.
Comparing the excreted amounts (in % of totally excreted radioactivity) of metabolites formed, the dichlorobi phenyl was mainly excreted as monohydroxy-derivatives, while the trichlorobiphenyl was mainly eliminated as di hydroxy-compounds (Table 3).
TABLE 3
Comparison of Metabolites formed of PCBs by Rhesus Monkeys
Metabolites
Dichloro biphenyl
Trichloro biphenyl
Monohydroxy-metabolites
Dihydroxy-metabolites
Trihydroxy-metabolites
Polar metabolites, unidentified
66.6% 32.4%
-1%
7.8% ' 82.2%
6% 4
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The following might explain this different behavior. Due to the additional chlorine atom, the trichlorobiphenyl is more lipophilic than the dichlorobiphenyl. The monohydroxy-metabolltes react in the same way: the monohydroxy-dichlorobiphenyl is excreted rapidly, while the water solubility of the monohydroxy-trichlorobiphenyl is still low. After further hydroxylation the trichlorobiphenyl-metabolites reach a polarity to be easier eli minated. A dihydroxy-trichlorobiphenyl thus should correspond to a monohydroxy-dichlorobiphenyl as regards speed of elimination. For higher chlorinated BPs, a higher degree of hydroxylation is necessary and will cause a longer retention time of the compound in the bo dy, that is, a slow excretion rate. This might explain their accumulation.
CONCLUSION Metabolism of PCB with high chlorine content will be dif ficult and proceed slowly. Concerning lower chlorinated biphenyls, however, this study reveals that total degra dation to hydroxylated metabolites and the rapid excre tion of the PCBs investigated in primates indicate that accumulation of lower chlorinated biphenyls at low doses will not occur.
REFERENCES BLOCK, W.D., and H.H. CORNISH: J. Biol. Chem.' 234 ,
3301 (1959). DE BOER, Th. J., and H.J.BACKER: Org. Syn. Coll.
4, 943 (1963). GREB, W., W. KLEIN, F. COULSTON, L. GOLBERG, and
F. KORTE: Chemosphere 2^, 143 (1973) . GREB, W., W. KLEIN, F. COULSTON, L. GOLBERG, and
F. KORTE: Bull. Environ. Contam. Toxicol., in press (1974). HUTZINGER, 0. et al.: Science 178, 312 (1972). VOIGT, K.D. in H.D. BERGMEIER: Methods of Enzymatic Analysis. Acad. Press 1965, p. 462. YOSHIMURA, H., and H. YAMAMOTO: Chem. Pharm. Bull.n, 1168 (1973).
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