The effect of dieldrin-contaminated feed on rat hepatic microsomal epoxide hydrase and aryl hydrocarbon hydroxylase

Adult male rats were exposed to dieldrin-contaminated rations. The hydroxylation of benzpyrene (AHH) and hydration of styrene oxide (EH) by the hepatic microsomal fraction were followed. At dieldrin levels of 5 to 25 ppm for one week, the EH activity increased from 19% to 115% above control levels respectively. Animals exposed to 25 ppm developed elevated EH activities after a few days, with a maximum increase of 2.5 times control levels after two weeks. AHH activity was not elevated over control levels at any dose or time studied. Slight but significant increases in levels of cytochrome P-450 were observed. Pentobartibal sleeping time was decreased to 61% of control levels after exposure to 20 ppm dieldrin-contaminated food for 7 days. Two days of intraperitoneal administration of technical grade dieldrin, analytical grade dieldrin and analytical grade aldrin gave similar increases in EH activity within this group. Again, no changes in AHH activity were seen.