Hepatic and extrahepatic induction of drug-metabolizing enzymes in specific pathogen free and germ free rats

1. 1. The drug metabolizing enzyme activities were equal in the liver, kidney and intestinal mucosa of control specific pathogen free and germfree rats. 2. 2. The hepatic inducibility of ethoxycoumarin O-deethylase and p-nitroanisole O-demethylase activities by 3-methylcholanthrene was higher in germfree than in SPF rats. 3. 3. Aryl hydrocarbon hydroxylase activity was inducible only by 3-methylcholanthrene in the liver, kidney and intestinal mucosa of rats of both gnotobiotic states. 4. 4. Hepatic cytochrome P-450 level and p-nitroanisole O-demethylase activity were highest after phenobarbitone administration in rats of both gnotobiotic states. 5. 5. The hepatic UDPglucuronosyltransferase activity was enhanced 50% by phenobarbitone and 100% by 3-methylcholanthrene in trypsin-digested microsomes. Only slight induction by 3-methylcholanthrene was present in kidneys and no induction was seen in the intestinal mucosa.