Hepatic drug metabolism during ethanol ingestion in riboflavin deficient rats.

Riboflavin deficiency was induced by feeding rats a riboflavin-deficient diet for 1 month. In order to find out if there are any combined effects of ethanol and riboflavin deficiency on drug metabolism, a group of riboflavin-deficient rats were also given ethanol in their drinking water. At the end of the feeding period, hepatic drug-metabolizing enzyme activities were determined. The hepatic phospholipid and protein contents were the same in rats receiving a standard diet and in those on a riboflavin-deficient diet. However, ethanol ingestion in both groups enhanced significantly the phospholipid content. Ethanol ingestion also markedly enhanced the hepatic cytochrome P-450 concentration in rats fed either a standard or riboflavin-deficient diet. Ethoxycoumarin O-deethylase activity was significantly lower in riboflavin-deficient rat livers than in those of the controls. In both groups ethanol ingestion nearly doubled the activities. Aryl hydrocarbon hydroxylase activity was also significantly decreased during riboflavin deficiency. However, ethanol administration did not change the activities of this enzyme. UDP glucuronosyltransferase activity was slightly lower in riboflavin-deficient rat livers than in those fed a standard diet. No significant decrease was found in the epoxide hydrase activity in the riboflavin-deficient rats. However, the riboflavin-deficient rats had enhanced activity after the ethanol ingestion.