POLYUNSATURATED FATTY-ACID COMPOSITION OF THE SALMON (SALMO-SALAR L) PINEAL ORGAN - MODIFICATION BY DIET AND EFFECT ON PROSTAGLANDIN PRODUCTION

To examine the influence of dietary polyunsaturated fatty acids (PUFA) on the lipid composition of the pineal organ and its production of pr ostaglandins, Atlantic salmon were fed diets containing either fish oi ls rich in long-chain n - 3 polyunsaturated fatty acids, or plant oils with high levels of 18:2(n - 6) (sunflower oil) or 18:3(12 - 3) (lins eed oil) for 12 weeks. Lipid content and lipid class composition of th e pineal organ were not greatly influenced by the type of oil fed to t he fish: choline phosphoglycerides were always the predominant lipid c lass and the proportion of polar lipids exceeded that of neutral lipid s. The pattern of PUFA present in total lipid and individual lipid cla sses was, however, related to that of the dietary oil. The major PUFA in pineal total lipid from all four dietary groups was 22:6(n - 3) and the proportion of n - 6 PUFA present was highest in lipid from salmon fed sunflower oil. Both PGE and PGF analogues of the 2- and 3-series were detected in pineal homogenates from all dietary groups with the f ormer prostaglandin being the most abundant, The ratio of PGE(2)/PGE(3 ) was greatest in fish fed sunflower oil and lowest in those fed linse ed oil. The results provide further evidence that despite its anatomic al location the pineal organ resembles non-neural tissues more than br ain in terms of lipid composition and prostaglandin production.