Dietary docosahexaenoic acid does not promote tissue lipid peroxide formation to the extent expected from the peroxidizability index of the lipids

Changes in susceptibility of tissues to lipid peroxidation were investigated in rats after ingestion of oxidation-prone docosahexaenoic acid (C22:6n-3). Lipid peroxide levels in the liver, kidney and testis increased concomitant with increases in the peroxidizability indices calculated from the fatty acid composition of tissue total lipids. However, even in these cases, the lipid peroxides were not increased to the levels expected from the peroxidizability indices of these tissues, and thus no tissue injury was recognized. When low level of vitamin E was given to rats, the lipid peroxide levels of liver, kidney and testis nearly coincided with the peroxidizability indices of these tissues, where the cell injuries were observed as well. The mechanisms of defense to suppress lipid peroxide levels below the peroxidizability indices in normal vitamin E administration were presumed to be due to enhanced antioxidative function in the tissues mediated primarily by vitamin E, ascorbic acid and glutathione, and also to increased incorporation of docosahexaenoic acid into neutral lipids and phosphatidylethanolamine in the tissues, probably leading to acquiring stability against oxidative attack. Owing to these suppressive mechanisms, physiological efficacy of n-3 fatty acids may be exerted effectively.