METABOLISM OF 2,3',4',5-TETRACHLOROBIPHENYL BY CYTOCHROME-P450 FROM RATS, GUINEA-PIGS AND HAMSTERS

The metabolism of 2,3',4',5-tetrachlorobiphenyl (TCB) was compared usi ng liver microsomes and six isoforms of cytochrome P450 purified from rats, guinea pigs and hamsters. In microsomal study, the following spe cies differences were observed: 1) Untreated guinea pigs and hamsters but not rats can metabolize this TCB to 3-hydroxy- or 4-hydroxy-2,3',4 ',5-TCB, 2) Guinea pig microsomes showed only 3-hydroxylating activity , whereas hamster microsomes showed higher activity of 4-hydroxylation than that of 3-hydroxylation. In common with three species, the 3-hyd roxylation was accelerated by phenobarbital. The 4-hydroxylation in ra ts and hamsters was increased by pretreatment with 3-methylcholanthren e and 3,3',4,4',5-pentachlorobiphenyl. The hydroxylation activities of liver microsomes from the three species could be explained by an invo lvement of different isoforms of cytochrome P450. In addition, it is a pparent that hamster CYP1A2 as well as hamster CYP2A8 is involved in t he 4-hydroxylation of 2,3',4',5-TCB although it has no activity for 2, 2',5,5'-TCB. (C) 1998 Elsevier Science Ltd. All rights reserved.