The relationship between metabolism of 2,3,4,5,3′,4′,5′-heptachlorobiphenyl and its ability to induce both cytochromes P-448 and P-450

Male CD rats received i.p. injections of 2,3,4,5,3′,4′,5′-heptachlorobiphenyl (7CB) under conditions resulting in induction of both benzphetamine demethylase (cytochrome P-450-dependent) and ethoxyresorufin deethylase (cytochrome P-448-dependent) activities. To test the possibility that one class of induction ( P-450) was due to the parent compound and the other ( P-448) to a metabolite, liver, adipose, bile, urine and feces were analyzed for the presence of 3,4,5,3′,4′,5′-hexachlorobiphenyl (6CB) (the major photolysis product of 7CB) and/or 2-hydroxy-3,4,5,3′,4′,5′-hexachlorobiphenyl (OH-6CB), another known P-448 inducer. To allow for the possibility that 6CB might be a transient intermediate, 3H-labeled 7CB was given along with unlabeled 6CB in a trapping experiment. The results supported the hypothesis that 7CB is a true ‘mixed inducer’, not requiring metabolic alteration for its dual activity.