DIETS RICH IN EICOSAPENTAENOIC ACID AND GAMMA-LINOLENIC ACID AFFECT PHOSPHOLIPID FATTY-ACID COMPOSITION AND PRODUCTION OF PROSTAGLANDINS E(1), E(2) AND E(3) IN TURBOT (SCOPHTHALMUS-MAXIMUS), A SPECIES DEFICIENT IN DELTA-5 FATTY-ACID DESATURASE

Duplicate groups of juvenile turbot, (Scophthalmus maximus), were fed diets containing either Marinol K (MO), a marine fish oil rich in eicosapentaenoic acid (EPA; 20:5, n-3) or borage oil (BO), rich in gamma-linolenic acid (GLA; 18:3, n-6), for a period of 12 weeks. Individual phospholipid fatty acid compositions from hearts of fish fed BO had significantly more 18:2, n-6, GLA, 20:2, n-6, dihomo-gamma-linolenic acid (DHGLA; 20:3, n-6) and total n-6 polyunsaturated fatty acids (PUFA), but significantly less arachidonic acid (AA; 20:3, n-6), compared to fish fed MO. In both phosphatidylcholine (PC) and phosphatidylethanolamine (PE) from heart, the DHGLA was increased by over 50-fold in fish fed BO while AA was reduced by over two-thirds, compared to fish fed MO. In brain, EPA was the major C-20 PUFA, i.e. potential eicosanoid precursor in all phospholipids from fish fed MO, with the EPA level being twice that of AA in brain phosphatidylinositol (PI). DHGLA was the major C-20 PUFA in all phospholipid classes from fish fed BO. In kidney and gill, EPA was the predominant C-20 PUFA in all phospholipid classes, except PI, in fish fed MO. In kidney of fish fed BO, DHGLA was the major C-20 PUFA in all phospholipid classes, except PE. In gill of fish fed BO, DHGLA was the major C-20 PUFA in all phospholipid classes, including PI, where DHGLA was over 2.5-fold greater than AA. In homogenates of heart, kidney and gill from BO-fed fish the prostaglandin E(1) (PGE(1)) concentration was significantly increased compared to MO-fed fish. In heart and kidney homogenates from fish fed MO the PGE(3) concentration was significantly increased compared to fish fed BO. The ratio of PGE(2)/PGE(1) was significantly reduced in brain, heart, kidney and gill homogenates from fish fed BO compared to those fed MO.