LIPID-PEROXIDATION AND ANTIOXIDANT STATUS IS AFFECTED BY DIFFERENT VITAMIN-E LEVELS WHEN FEEDING FISH-OIL

The protective role of vitamin E and changes in the status of several physiological antioxidants after feeding rats a fish oil diet were investigated. Six week old male Sprague-Dawley rats were divided into four groups and fed experimental diets for 8 wk. Three fish oil (FO) groups were fed a menhaden fish oil and soybean oil (SO) (9:1) mixture as 10% (w/w) of the diet. These groups were provided with less than or equal to 3, 45 or 209 IU of vitamin E/kg diet. One SO group was used as control and was fed less than or equal to 45 IU of vitamin E/kg diet. Plasma vitamin E levels, when expressed as vitamin E per mt plasma, were extremely low in the group fed FO and less than or equal to 3 IU of vitamin E, and were lower in the groups fed FO than in the group fed SO. However, plasma vitamin E levels when expressed per mg plasma lipid were higher in the FO groups provided with less than or equal to 45 and 209 IU of vitamin E than in the SO group. Compared with the SO group, plasma levels of thiobarbituric acid reactive substances (TBARS), when expressed per mg lipid, were higher in the three FO groups, plasma retinol levels were lower in the FO groups provided with less than or equal to 3 and 45 IU of vitamin E, and ascorbic acid levels were lower only in the FO group provided with less than or equal to 3 IU of vitamin E. Blood glutathione (GSH) levels were lower in all three FO groups than in the SO group. Liver vitamin E levels increased as the dietary level of vitamin E increased, but all FO groups had higher liver levels of TBARS than the SO group. The dietary vitamin E levels were correlated positively with plasma vitamin E (r = 0.71) and negatively with TBARS in both the plasma and liver of rats fed FO. Among the antioxidants measured, correlations were found between plasma retinol and vitamin C (r = 0.64), and plasma vitamin C, uric acid (r = 0.72) and blood GSH (r = 0.60). Weaker correlations were found between plasma retinol, uric acid and blood GSH. It is concluded that vitamin E requirements are higher when feeding fish oil. Vitamin E seems necessary to prevent enhanced lipid peroxidation and to maintain appropriate levels of other physiological antioxidants.