Essential fatty acids alter the activity of manganese‐superoxide dismutase in rat heart

The effects of oil‐derived dietary essential fatty acids on the activities of mitchondrial Mn‐SOD (manganese‐superoxide dismutase) and cytosolic cupric zinc‐superoxide dismutase (Cu/Zn‐SOD) were investigated in rat heart. A control group of rats was fed a stock diet for 29 d, and a second group was fed on a fat‐free diet. Three other groups were fed fat‐free diets that were supplemented with (i) borage oil, which is rich in linoleic (18∶2n−6) and γ‐linolenic (18∶3n−6) acids, (ii) fungal oil, which is rich in γ‐linolenic, but low in linoleic acid, or (iii) evening primrose oil, which is rich in linoleic acid and low in γ‐linolenic acid. An increase in the percentage composition of arachidonic acid (20∶4n−6) in both the choline and ethanolamine phospholipids, together with a decrease in linoleic acid in ethanolamine phospholipids, were found in heart membranes after feeding the rats with diets containing borage oil or fungal oil as compared to those fed the stock diet. The respective activities of Mn‐SOD in rats fed the borage or fungal oil diets were also significantly higher than in rats fed the stock diet alone. No change in cytosolic Cn/Zn‐SOD activity was observed. Dietary supply of linoleic acid‐rich evening primrose oil resulted in an increased proportion of choline phospholipid linoleic acid without any changes in arachidonic acid content or in the activity of Mn‐SOD. By contrast, a reduction in the activity of Mn‐SOD was detected in rats fed a fat‐free diet. These results show that the activity of heart mitochondrial Mn‐SOD is influenced by dietary essential fatty acids, whereas the activity of cytosolic Cu/Zn‐SOD remained unaffected.