EFFECT OF DIETS RICH IN LINOLEIC OR ALPHA-LINOLENIC ACID ON PHOSPHOLIPID FATTY-ACID COMPOSITION AND EICOSANOID PRODUCTION IN ATLANTIC SALMON (SALMO-SALAR)

Atlantic salmon post-smolts were fed diets rich in linoleic acid (sunflower oil, SO), alpha-linolenic acid (linseed oil, LO) or long-chain polyunsaturated fatty acids (fish oil, FO) for a period of 12 wk. In the liver phospholipids of fish fed SO, the levels of 18:2n-6, 20:2n-6, 20:3n-6 and 20:4n-6 were significantly elevated compared to both other treatments. In choline phospholipids (CPL), ethanolamine phospholipids (EPL) and phosphatidylserine (PS) the levels of 22:4n-6 and 22:5n-6 were significantly elevated in fish fed SO. In liver phospholipids from fish fed LO, 18:2n-6,20:2n-6 and 20:3n-6 were significantly elevated but 20:4n-6, 22:4n-6 and 22:5n-6 were similar or significantly decreased compared to fish fed FO. Liver phospholipids from fish fed LO had increased 18:3n-3 and 20.4n-3 compared to both other treatments while EPL and phosphatidylinositol (PI) also had increased 20.5n-3. In fish fed LO, 22:6n-3 was significantly reduced in CPL, PS and PI compared to fish fed FO. Broadly similar changes occurred in gill phospholipids. Production of 12-lipoxygenase metabolites in isolated gill cells stimulated with the Ca2+-ionophore A23187 were significantly reduced in fish fed either SO or LO compared to those fed FO. However, the ratio 12-hydroxy-5, 8, 10, 14-eicosatetraenoic acid (12-HETE)/12-hydroxy-5,8,10,14,17-eicosapentaenoic acid (12-HEPE) was significantly elevated in stimulated gill cells from SO-fed fish. Although mean values of thromboxane B2 (TXB2) and prostaglandin E2 (PGE2) were increased in fish fed SO, they were not significantly different from those of the other two treatments.