EFFECTS OF DIETARY GAMMA-LINOLENIC ACID-RICH BORAGE OIL COMBINED WITHMARINE FISH OILS ON TISSUE PHOSPHOLIPID FATTY-ACID COMPOSITION AND PRODUCTION OF PROSTAGLANDIN-E AND PROSTAGLANDIN-F OF THE 1-SERIES, 2-SERIES AND 3-SERIES IN A MARINE FISH DEFICIENT IN DELTA-5 FATTY ACYL DESATURASE

The effects of gamma-linolenic acid-rich borage oil (BO), in combinati on with different marine oils, namely an eicosapentaenoic acid (EPA) r ich oil (MO) or a DHA-rich oil (TO), on tissue fatty acid composition and prostaglandin production were investigated in turbot, a species wh ich lacks appreciable Delta 5 fatty acyl desaturase activity. The juve nile turbot grew well on the experimental diets and there were no sign ificant differences in final weights between dietary treatments. Irres pective of the marine oil component, both the BO-containing diets incr eased tissue phospholipid levels of 18:2n-6 and 18:3n-6, and their res pective elongation products, 20:2n-6 and 20:3n-6, compared to fish fed a control diet containing a standard Northern hemisphere fish oil. Bo th the BO-containing diets increased the production of 1-series prosta glandins (PG), this being observed across all tissues investigated wit h PGF and especially PGE. The BO/MO diet also reduced 20:4n-6 in tissu e phospholipids without affecting 20:5n-3, whereas the BO/TO combinati on decreased 20:5n-3 but increased 20:4n-6. The production of 2-series and 3-series PGs was also altered by the dietary treatments but the c hanges were less dependent upon the tissue levels of their respective precursor fatty acids, 20:4n-6 and 20:5n-3. The BO-containing diets ha d very significant effects on gross fatty acid compositions of the pho spholipids including increased proportions of saturated fatty acids an d n-6 polyunsaturated fatty acids (PUFA) and decreased proportions of monounsaturated fatty acids and n-3 PUFA. Overall, this study shows th at eicosanoid production in turbot tissues can be influenced by dietar y fatty acids, not only by changes in the absolute and relative levels of specific eicosanoid precursor PUFA in tissue phospholipids, but al so by general effects on membrane composition, structure and function induced by gross fatty acid compositional changes.