THE EFFECT OF DIETARY LINOLEIC-ACID ON THE FATTY-ACID COMPOSITION OF INDIVIDUAL PHOSPHOLIPIDS AND LIPOXYGENASE PRODUCTS FROM GILLS AND LEUKOCYTES OF ATLANTIC SALMON (SALMO-SALAR)

Diets containing either fish oil or sunflower oil, both of which supplied the minimum required level of n-3 fatty acids, were given to Atlantic salmon (Salmo salar) post-smolts for a period of 16 weeks. In fish f ed sunflower oil, the phospholipids of gills showed increased 18:2n-6 (2-13-fold), 20:2n-6 (4.5-12-fold) and 20:3n-6 (2-8-fold). In addition, phosphatidylethanolamine had increased 20:4n-6 (1.5-fold). Changes of a similar magnitude were observed in the phospholipids of blood leucocytes except that, in addition, 20:4n-6 was elevated in phosphatidylserine (1.7-fold) and phosphatidylinositol (1.4-fold). Both tissues showed a general decrease in phospholipid 20:5n-3 (up to 3-fold), which caused an increase in 20:4n-6/20:5n-3 ratio (1.3-6-fold). The elongation and desaturation products of 20:4n-6, 22:4n-6 and 22:5n-6 were not increased as a result of feeding sunflower oil. When isolated gill cells were stimulated with the calcium ionophore A23187, 12-hydroxy-8, 10,14,17-eicosapentaenoic acid (12-HEPE) was the major lipoxygenase product from salmon given fish oil. 12-HEPE was significantly reduced in salmon given sunflower oil. When stimulated with A23187, the lipoxygenase products derived from whole blood of fish given sunflower oil showed decreased levels of leukotriene B5, 12-HEPE and 12-hydroxy-5,8,10,14-eicosatetraenoic acid.