Nutritional factors affecting drug-metabolizing enzymes of the rat

Abstract Feeding diets rich in thiamin depresses aniline hydroxylase, cytochrome P-450 and cytochrome b 5 within 9–14 days. Pair-feeding experiments suggest that the depression of aniline hydroxylase, cytochrome c reductase and ethylmorphine demethylase is due to the thiamin; however, the depression of cytochrome P-450 and b 5 may be due primarily to the increased amount of carbohydrate ingested by rats fed the enriched diet. When starch was substituted for sucrose, cytochrome P-450 was not lowered by high thiamin ingestion, although cytochrome b 5 and NADPH cytochrome c reductase were depressed similarly to that of rats fed high thiamin levels in a sucrose-based diet. Although aniline hydroxylase and ethylmorphine demethylase activities were significantly depressed by both high thiamin diets, this effect was more pronounced in rats fed the sucrose-based diet.