Lipid Peroxide, α-Tocopherol and Retinoid Levels in Plasma and Liver of Rats Fed Diets Containing β-Carotene and 13-cis-Retinoic Acid

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Abstract
The effect of feeding large amounts of β-carotene and 13-cis-retinoic acid (RA) on plasma and liver levels of α-tocopherol, lipid peroxides and retinoids was studied. Groups of young male rats were fed semipurified diets supplemented with 0, 100 mg/kg β-carotene, 20 and 100 mg/kg 13-cis-RA. After feeding the various diets for 11 weeks, rats were killed and the concentrations of lipid peroxides, α-tocopherol, and retinoids were measured in blood plasma and liver. Peroxide levels were increased and α-tocopherol levels were decreased in plasma as well as liver of rats fed diets containing 13-cis-RA; this effect seems to be dose dependent. β-Carotene had no significant effect on either of the above parameters. There was a decrease in the liver and plasma concentrations of retinol in rats fed 13-cis-RA; the levels of RA were generally higher in these two groups. The results suggest that the mechanism whereby 13-cis-RA increases the tissue peroxide levels may be related to its ability to decrease a-tocopherol levels.