Alterations in β-carotene and vitamin e status in rats fed β-carotene and excess vitamin A

Abstract

The effects of feeding various levels of vitamin A with and without various levels of β-carotene on vitamin E and β-carotene status and hepatic biodegradation capacity were examined. Male weanling Sprague-Dawley rats, 10/group, were fed ad libitum for 8 wk diets containing vitamin A and β-carotene in a 3×3 factorial experimental design. Vitamin A palmitate was given at the National Research Council's recommended requirement level of 4,000 IU/kg of diet (control), 10 times the requirement (vitamin A1) and 100 times the requirement (vitamin A2). Each of these groups was given β-carotene at either 0,48 (BC1) or 480 mg/kg (BC2) of diet. Liver vitamin A levels increased dramatically and were 100-fold higher in vitamin A2 groups than in the control group. Retinyl esters increased in the liver; retinyl stearate increased as a result of β-carotene treatments. Liver β-carotene levels were significantly reduced in vitamin A1-BC2 and vitamin A2-BC2 groups compared to the control-BC2 group. In the vitamin A2-BC2 group, plasma vitamin E was reduced 77% compared to the control group; hepatic microsomal cytochrome P-450 and its isozyme, benzephetamine demethylase, were significantly lower; and the specific activity of glutathione S-transferase was increased. These findings suggest that vitamin E status can be altered by ingesting excessive vitamin A or β-carotene and that vitamin A and β-carotene changed the biodegradation and detoxification capacity of the liver in rats.