Suppressive effect of interferon inducer, polyriboinosinic acid-polyribocytidylic acid on induction of uridine diphosphate-glucuronyltransferases and monooxygenases in liver microsomes of rats.

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Abstract
The effect of polyriboinosinic acid-polyribocytidylic acid [poly (I)·poly (C)] on glucuronyltransferase activities toward 4-nitrophenol and 4-hydroxybiphenyl in liver microsomes of Wistar rats was examined by its single or co-administration with 3-methylcholanthrene and phenobarbital. The increased 4-nitrophenol glucuronyltransferase activity by treatment with 3-methylcholanthrene was significantly suppressed following the coadministration with poly (I)·poly (C), although the activity was not affected by the treatment with poly (I)·poly (C) alone. In addition, 4-hydroxybiphenyl glucuronyltransferase activity decreased or tended to decrease by the treatment with poly (I)·poly (C) alone, and the activity induced by phenobarbital was strikingly decreased following the co-administration with poly (I)·poly (C). This result suggested that poly (I)·poly (C) comprehensively decrease the induction of glucuronyltransferases regardless of their multiple forms. Furthermore, contents of cyto chromes P-450 and b5 were also decreased by the treatment with poly (I)·poly (C) alone or the co-administration with the inducers. Concomitantly, arylhydrocarbon hydroxylase and benzphetamine N-demethylase activities were significantly decreased by the treatment alone or the co-administration with the inducers. These findings supported a view that the suppressive effect of poly (I)·poly (C) may be derived from the prevention of de novo synthesis of the apoprotein of the enzymes and/or the increased degradation.