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Effect of lentinan on the hepatic drug-metabolizing system was studied in ddY mice (unless otherwise stated). On the assay in vivo, lentinan (1 mg/kg, i.p.) decreased cytochrome P-4 5 0 content and the activities of aminopyrine N-demethylase, aniline hydroxylase, 7-ethoxycoumarine O-deethylase and biphenyl 2- or 4-hydroxylase in the hepatic 9,000 x g supernatant or microsomes. Decreases in the activities of aminopyrine N-demethylase, aniline hydroxylase and biphenyl 2-hydroxylase were not observed in vitro. On the other hand, the effect of lentinan was weak on the hepatic drug-metabolizing enzymes in C57BL/10, C3H/He and DBA/2 mice which are nonsensitive to lentinan or do not respond to aryl hydrocarbon hydroxylase. Furthermore, the depression by lentinan on the cytochrome P-448-dependent drug-metabolizing enzymes induced by 3-methyl-cholanthrene was more greater than that on the cytochrome P-450-dependent drug-metabolizing enzymes induced by phenobarbital. This result suggests that the depression by lentinan on the hepatic drug-metabolizing system was more specific to the cytochrome P-448 induced by 3-methylcholanthrene.

BCG is almost the only agent now used as the immuno-accelerator of cell-mediated responses1'3, but it has various biological side effects and a complicated chemical structure, so that it is not necessarily the most suitable agent. We reported that lentinan4,5 and pachymaran6 strongly inhibited the growth of transplanted tumours in mice, and these two polysaccharides are worth considering as excellent immuno-accelerators.