[Metabolism of 3,3',4,4',5-penta- and 2,2',3,3',4,4'-hexachlorobiphenyls in rats].

Following the i.p. administration of 3,3',4,4',5-pentachlorobiphenyl (CB126) and 2,2',3,3',4,4'-hexachlorobiphenyl (CB128) to rats, blood, liver, lung, kidney, adipose tissue and feces were analyzed for the metabolites. CB126 was biotransformed to three hydroxylated metabolites identified as 4-OH-3,3',4',5'-tetraCB, 4-OH-3,3',4',5,5'-pentaCB and 5-OH-3,3',4,4',5'-pentaCB at about 1:7:2 ratio, whereas to two methylthio metabolites as 5-MeS- and 6-MeS-3,3',4,4',5'-pentaCBs at 1:2 ratio. Among the metabolites, only 4-OH-3,3',4',5,5'-pentaCB was detected in all tissues and blood. The ratio of metabolite/unchanged CB126 was 1:1.3 in blood and 1:162 in liver, indicating the high blood affinity of this metabolite. Trace amounts of 5-methylsulfonyl-3,3',4,4',5'-pentaCB was also detected in the liver. CB128 was biotransformed to 5-OH-, 5-MeS- and 6-MeS-2,2',3,3',4,4' hexaCBs which were excreted to feces in about 5:5:1 ratio. No metabolites were detected in blood and any tissues except for liver where trace amounts of 5-hydroxylated metabolite was present, indicating the low tissue affinity of hydroxylated metabolites from CB128.