Effect of Dietary β-Carotene on Hepatic Drug-Metabolizing Enzymes in Mice

The effects of dietary supplements of β-carotene (20-500 mg per kg diet) on hepatic microsomal drug-metabolizing enzyme activities were studied in mice. Supplementation for 14 days resulted in marked reductions in the concentrations of cytochrome P-450 and biphenyl 4-hydroxylase. The antipyrine N-demethylase and β-nitroanisol O-de-methylase activities, however, were unchanged. Also apparently unchanged were the hepatic concentrations of microsomal protein, lipid peroxides, and superoxide dismutase. Supplemental β-carotene was weakly protective against the acute toxic effects of an injection of 1,2-dimethylhydrazine (DMH), as indicated by a lowered mortality. This anti-carcinogenic action of β-carotene, including a protection against DMH-induced colon carcinogenesis, suggests an alteration by this carotenoid in the metabolism of carcinogens by the liver.