Tissue Distribution, Uptake, and Requirement for α-Tocopherol of Rainbow Trout (Salmo gairdneri) Fed Diets with a Minimal Content of Unsaturated Fatty Acids

Abstract

The metabolism of and requirement for α-tocopherol in rainbow trout fed diets containing 1% linolenic acid as sole source of unsaturated fat and graded levels of tocopherol (0.06–10 mg/100 g) were examined. Fish grew 5-fold over a 16-week period. In liver, tocopherol was concentrated in mitochondria with little in cytosol. Orally administered [³H]-tocopherol was rapidly taken up by plasma and liver but uptake into erythrocytes and white muscle was much slower; in most tissues radioactivity reached a plateau after about 3 days but in red muscle radioactivity increased over a 10-day period. Activities of enzymes that prevent free radical initiated tissue damage did not change in tocopherol deficiency. Tocopherol-deficient trout had no gross or subcellular pathologies even though liver and muscle were severely depleted of the vitamin. Ascorbic acid-stimulated lipid peroxidation in liver organelles indicated a tocopherol requirement of 2—3 mg/100 g diet; the molar ratios of polyunsaturated fatty acids to tocopherol in livers of trout fed diets lacking or supplemented with tocopherol (10 mg/100 g) were 980 and 170, respectively.