Effects of Phenobarbital, 3-Methylcholanthrene and Polychlorinated Biphenyls on Sex-Specific Forms of Cytochrome P-450 in Liver Microsomes of Rats1 2

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Abstract
The effects of treatment with phenobarbital, 3-methylcholanthrene or polychlonnated biphenyls (PCB) on the amounts of sex-specific forms of cytochrome P-450, namely P-450-male and P-450-female, in male and female rats were studied. Although treatment with phenobarbital, 3-methylcholanthrene or PCB markedly increased the total amount of hepatic cytochrome P-450, P-450-male and P-450-female were rather decreased or not significantly changed. Thus, the percentages of P-450-male and P-450-female in the total cytochrome P-450 were decreased in liver microsomes from the treated rats. The increases in specific cytochrome P-450, such as P-448-H, P-448-L, and P-4501-c accounted for the increase in the total amount of cytochrome P-450 in the treated rats. The treatment with phenobarbital or PCB increased the activities of testosterone 16α-hydroxylase, benzo(a)pyrene hydroxylase and aminopyrine N -demethylase more markedly in female rats than in male rats. Similarly, the treatment with 3-methylcholanthrene increased benzo(a)pyrene hydroxylase more markedly in female rats. Therefore, the sex-differences in testosterone 16α-hydroxylase, benzo(a)pyrene hydroxylase, and aminopyrine N -demethylase activities became smaller after the drug treatment. These results indicate that sex-specific P-450-male and P-450-female were unaffected, or even depressed by the agents in some cases.

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