2,4,5,3',4',5'-HEXABROMOBIPHENYL IS BOTH A 3-METHYLCHOLANTHRENE AND A PHENOBARBITAL-TYPE INDUCER OF MICROSOMAL DRUG-METABOLIZING ENZYMES

The effects of 2, 4,5, 3′, 4′,5′-hexabromobiphenyl (HBB) on hepatic microsomal drug metabolizing enzymes have been determined. Male rats were injected ip with 90 mg HBB/kg and sacrificed 7 days later. HBB increased liver weight and microsomal protein, and strongly induced NADPH-cytochrome P450 reductase, cytochrome P450, aminopyrine demethylation, benzo[a]pyrene hydroxylation, epoxide hydratase, and p-nitrophenol-UDP-glucuronyltransferase activities, and several microsomal hemoproteins. The microsomal CO difference spectral maximum was shifted from 450 to 448.5 nm. HBB unilaterally causes a mixed-type induction similar to that caused by both phenobarbital and 3-methylcholanthrene and is therefore a highly unusual type of microsomal inducing agent. © 1978 Academic Press, Inc.