The effect of lentinan (1 mg/kg/12h×4, i.p.) on the hepatic cytochrome P-450 molecular species and the cytochrome P-450-dependent monooxygenase activities was observed in ddY and C57BL/6 mice treated with phenobarbital (8 or 40 mg/kg/d×2, i.p.) or 3-methylcholanthrene (80 mg/kg, i.p.). The activities of aminopyrine N-demethylase, aniline hydroxylase and biphenyl 4-hydroxylase were elevated by 20-37% by the treatment with phenobarbital, and these increases were unaffected by concurrent administration of phenobarbital and lentinan. The activities of 7-ethoxycoumarin O-deethylase and biphenyl 2-hydroxylase were increased by 74-192% by the treatment with 3-methylcholanthrene, but these increases were depressed by the combination treatment with 3-methylcholanthrene and lentinan. It was found by an sodium dodecyl sulfate-polyacrylamide gel electrophoretic study that the suppression by lentinan of the elevation of cytochrome P-450-dependent monooxygenase activities induced by 3-methylcholanthrene was caused by a decrease in the hepatic microsomal cytochrome P-450 content.
