Increased activity of certain hepatic drug-metabolizing enzymes due to subchronic exposure to bromobenzene.

Male Sprague-Dawley rats were treated i.p. with different doses of bromobenzene (0, 0.1, 0.2, 0.3 and 0.5 mmol/kg) in corn oil for 4 weeks. The animals were killed 24 h after the end of the treatment for hepatic drug metabolism studies. A significant induction of the activities of microsomal aniline hydroxylase (51%) and aminopyrine N-demethylase (58%) was observed at 0.5 mmol/kg dose level. Liver microsomal cytochrome P-450 content was significantly increased (approx. 38%) at subchronic doses of 0.3 and 0.5 mmol/kg. Hepatic glutathione (GSH) concentrations were increased (approx. 30%) in comparison to control values at subchronic doses of 0.3 and 0.5 mmol/kg, whereas a significant induction (46-72%) of the activities of conjugating enzymes, cytosolic glutathione S-transferases was noticed at any subchronic dose level of bromobenzene studied. These results suggest that, under certain conditions, subchronic pretreatment with bromobenzene may have the potential to modify the acute toxicity of its own as well as those of other environmental pollutants which require metabolic activation.