Abstract
Summary
In cholestasis, 4 days after bile duct ligation, the activity of aminopyrine demethylase was greatly decreased, while the content of cytochrome P-450 and the activities of aniline hydroxylase, NADPH-cytochrome c reductase, and cytochrome P-450 reductase were only slightly decreased in the microsomes of the rat livers. Binding of type II substrate to cytochrome P-450 was unimpaired and its modifier effect on P-450 reductase was intact. The binding of type I substrate was greatly decreased, and its stimulating effect on P-450 reductase was abolished, suggesting that the effect of cholestasis on the hepatocellular smooth endoplasmic reticulum is to alter the type I binding sites, which is responsible for the hypoactivity of the biotransformation system.
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