Effect of polybrominated biphenyls on drug metabolizing enzymes in different tissues of C57 mice

Polybrominated biphenyls (PBBs) are structurally very close to polychlorinated biphenyls (PCBs) which are known to be potent inducers of xenobiotic biotransformation reactions. We have studied the effects of 2 industrial PBB-mixtures, "hexabromobiphenyl" (HBB) and "octabromobiphenyl" (OBB), on enzymes catalyzing drug hydroxylation, epoxide hydration, and conjugation reactions in different tissues of C57 mice. The enzyme activities were measured 10 days after a single i.p. injection of PBBs (75 mg/kg). HBB enhanced the activities of hepatic AHH (1.9-fold), ethoxycoumarin deethylase (5.7-fold), epoxide hydratase (1.5-fold), glutathione S-transferase (1.7-fold) and UDP-glucuronosyltransferase (1.5-fold). In the kidney HBB enhanced the activity of UDP-blucuronosyltransferase 1.5-fold. OBB caused in increase in the activities of liver AHH (1.5-fold), ethoxycoumarin deethylase (2.4-fold) and glutathione S-transferase (1.4-fold). A slight increase was also seen in the activity of UDP-glucuronosyltransferase in digitoninactivated liver microsomes of OBB-treated mice. In the kidney OBB caused a slight but statistically significant decrease in glutathione S-transferase activity. Intraperitoneally injected bromobiphenyls had no effects on these drug metabolizing enzymes in the lung of C57 mice. These results were similar to the effects caused by a mixture of PCBs.