REPEATED ORAL BENZENE EXPOSURE ALTERS ENZYMES INVOLVED IN BENZENE METABOLISM

Benzene is a known carcinogen and hematopoietic toxin in humans and ex perimental animals. The effect of acute, high-dose exposure to benzene on hepatic bioactivation and detoxication enzymes has been defined wh ile little is known about the effect of repeated, low-dose benzene exp osure on these enzymes. Our objective was to determine whether repeale d, oral benzene exposure alters enzymes involved in benzene metabolism . Specifically, we were concerned with cytochrome P-450-2E1, a bioacti vation enzyme, and glutathione transferase and aldehyde dehydrogenase, two detoxifying enzymes. Female CD-1 mice were treated by gavage for 3 wk with benzene doses of 5 mg/kg (0.064 mmol/kg) or 50 mg/kg (0.646 mmol/kg) in corn oil. These doses of benzene produced 0.048 and 0.236 pmol muconic acid/d, respectively. We found that repeated exposure to 50 mg benzene/kg/d decreased P-450-2E1 activity by 34% and induced glu tathione transferase activity by 30% without affecting aldehyde dehydr ogenase activity. These changes in enzyme activities may serve a prote ctive role against repeated exposure to benzene.