DIETARY VITAMIN-A AND VITAMIN-E AFFECT DIFFERENTLY LIPID-PEROXIDATION IN RAT-HEART AND TESTIS

This study examines the susceptibility to lipid peroxidation of rat heart and testis microsomes, in relation to dietary vitamin PL and/or E status. Four groups of rats were fed different levels of the vitamins. After a period of 8 weeks, lipid peroxide levels estimated by thiobarbituric acid method, fatty acid composition and vitamins A and E were measured in serum or in microsomes. In heart, lipid peroxide levels were enhanced in dietary vitamin E deficiency; linoleic acid 18:2 (n-6), arachidonic acid 20:4 (n-6), and docosahexaenoic acid 22:6 (n-3) were significantly decreased. In testis, dietary vitamin A deficiency significantly increased lipid peroxide production and decreased docosapentaenoic acid 22:5 (n-6) and 20:4 (n-6). Supplementation of the diet with both vitamins A and E significantly decreased lipid peroxide production but did not change the fatty acid composition. Induced lipid peroxidation increased in the heart of vitamin E-deficient rats and in the testis of vitamin A-deficient ones. Both in heart and testis, we found a good correlation between spontaneous and induced lipid peroxides and also between lipid peroxides and polyunsaturated to saturated fatty acid ratio. Besides, lipid peroxide production was well correlated with polyunsaturated fatty acids/vitamin A in testis and with polyunsaturated fatty acids/vitamin E molar ratios in heart. Membrane susceptibility to lipid peroxidation varied greatly according to dietary status and organ. Vitamin E seemed to be a more effective antioxidant for heart, and vitamin A, for testis. Supplementation enhanced the beneficial role of each vitamin.