CONCENTRATION-DEPENDENT CHANGES OF PCB PATTERNS IN FISH-EATING MAMMALS - STRUCTURAL EVIDENCE FOR INDUCTION OF CYTOCHROME-P450

Data sets on CB concentrations in fish-eating mammals from five labora tories were combined to test and refine a pharmacokinetic model. Clear differences in PCB patterns were observed between species, The abilit y to metabolize chlorobiphenyl (CB) congeners with vicinal H-atoms onl y in the ortho- and meta-positions and with one ortho-chlorine substit uent generally increased in the order otter < cetaceans (harbor porpoi se, common dolphin) < phocid seals (harbor and grey seal), but the met abolism of congeners with vicinal H-atoms in the meta- and para-positi ons and with two ortho-chlorines increased in the order cetaceans < se als < otter. Both categories of congeners are probably metabolized by different families of cytochrome P450 (1A and 2B) of which levels appa rently differed between the cetaceans, the pinnipeds, and the otter. W ithin-species CB patterns differed in a concentration-dependent manner . The induction of cytochrome P450 enzymes offers the most likely expl anation for this phenomenon, but starvation could have a similar effec t on occasion.