Inducibility of mucosal drug-metabolizing enzymes of rats fed on a cholesterol-rich diet by polychlorinated biphenyl, 3-methylcholanthrene and phenobarbitone.

Abstract

The results show that a cholesterol-rich diet changes the composition of mucosal membranes. A high cholesterol diet increases mucosal cholesterol and phospholipid contents. Cholesterol enhanced mucosal NADPH cytochrome c reductase and aryl hydrocarbon hydroxylase activities as well as mucosal UDP glucuronosyltransferase activity. When phenobarbitone or Clophen A 50 or 60 were administered intraperitoneally to cholesterol-fed rats, the hydroxylation and glucuronidation activities decreased to a lower level. 3-Methylcholanthrene was, however, able to maintain or increase mucosal hydroxylative enzymes and UDP glucuronosyltransferase. These results indicate that the drug-metabolizing enzymes of the intestinal mucosa behave very differently from those in the liver. Diet apparently has a regulatory effect on the induction of drug-metabolizing enzymes because only a very potent inducer, 3-methylcholanthrene, was able to maintain and even induce mucosal drug-metabolizing enzymes in rats fed on a high cholesterol diet, possibly through changes in the microenvironment of enzymes caused by cholesterol.