Effect of 7,12-dimethylbenz(a)anthracene administration on hepatic drug metabolizing enzymes in female rats fed corn, primrose, and menhaden oils.

Female rats receiving a diet containing 20% menhaden oil beginning at 10 weeks of age and continuing for 13 weeks had hepatic benzo(a)pyrene [B(a)P] hydroxylase activity significantly higher than similar rats fed diets containing 20% corn oil or 20% oil of evening primrose. Compared to microsomes recovered from rats fed the corn oil diet, a significant increase in microsomal cytochrome P-450 content along with an increase in the activity of cytochrome P-450 mediated ethoxycoumarin O-dealkylase was evident in rats fed menhaden oil. Glutathione S-transferase activity of the cytosol of hepatocytes was increased twofold by the feeding of 20% menhaden oil, compared with the feeding of corn or primrose oil. Administration of 7,12-dimethylbenz(a)anthracene (DMBA) 21 days before instituting the diets enhanced B(a)P hydroxylase in all animals, with the activity greatest in those fed the menhaden oil. DMBA also caused a significant increase in ethoxycoumarin O-dealkylase in rats fed menhaden oil.