[Tissue retention of hydroxy and methylsulfonyl metabolites of 2, 2', 4, 4'-tetrachlorobiphenyl in rats].

Previously, we have identified a large number of methylsulfonyl metabolites in tissues of mink treated with Clophen A50. Most of them were found to be derived from CBs with a 2, 5-dichlorophenyl or a 2, 3, 6-trichlorophenyl ring. It is further necessary to investigate if CBs with a 2, 4-dichlorophenyl ring could be biotransformed to the sulfur-containing metabolites in animals. In the present study, 2, 2', 4, 4'-tetrachlorobiphenyl (TCB) was administered i.p. to rats, and liver, lung, kidney, adipose tissue and blood were analyzed for the unchanged CB and its metabolites. Both hydroxy and methylsulfonyl metabolites were detected in all tissues analyzed. Major metabolites were identified as 3-OH-2, 2', 4, 4'-TCB, 5-5-OH-2, 2', 4, 4'-TCB, 5-MeSO(2)-2, 2', 4, 4'-TCB and 6-MeSO(2)-2, 2', 4, 4'-TCB. Total level of the four metabolites was estimated to be 1.5 micrograms/g wet weight in the liver, corresponding to similar level of the unchanged CB. The concentration ratios of 3-OH- to 5-OH-TCB and 5-MeSO2- to 6-MeSO(2)-TCB were about 2:3 and 2:1, respectively, in liver and kidney. These results indicate that CBs with a 2, 4-dichlorophenyl ring can provide both hydroxy and methylsulfonyl metabolites that are retainable in tissues of rats.