UDP-Glucuronosyltransferase(UDPGT) activity was studied in hepatic microsomal prepararion from rats treated with infedipine. The substrates 1-naphthol, P-nitrophenol, 40methylumbelliferone and bilirubine were used. With 1-naphthol, nifedipine 2 and 4 weeks treatment caused 6- and 7.3-fold, respectively, increase in activity over the control value. With 4-methylumbelliferone, nifedipine 2 and 4 weeks treatment caused 5- and 6fold increase in activity over the control value. With P-nitrophenol, nifedipine 2 and 4 weeks treatment caused both approximately 3-fold increase in activity over the control value. However bilirubin-UDPGT activity was not affected by this inducer effects of nifedipine on the hepatic monooxygenase system in rats were investigated. P-Nitroanisole-O-demethylase, NADPH-cytochrome C reductase activity and cytochrome P-450 content in nifedipine treated rats were significantly increased to 390, 290, and 150% of control rats, respectively.
The selectivity of nifedipine of UDP-glucuronosyltransferase was investigated in rat liver microsomes and compared with their effect on monooxygenase reactions. Similar to 3-methlycholanthrene-type selectively stimulated the glucuronidation induced both UDPGT₁and monooxygenase activity, probably through a common receptor protein.
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