FATTY ACYL DESATURATION IN ISOLATED HEPATOCYTES FROM ATLANTIC SALMON (SALMO-SALAR) - STIMULATION BY DIETARY BORAGE OIL CONTAINING GAMMA-LINOLENIC ACID

The effects of different dietary oils on the fatty acid compositions o f liver phospholipids and the desaturation and elongation of [1 -C-14] 18:3n-3 and [1 -C-14] 18:2n-6 were investigated in isolated hepatocyt es from Atlantic salmon. Atlantic salmon smolts were fed diets contain ing either a standard fish oil (FO) as a control diet, a 1:1 blend of Southern Hemisphere marine oil and tuna orbital oil (MO/TO), sunflower oil (SO), borage oil (BO), or olive oil (OO) for 12 wk. The SO and BO diets significantly increased the percentages of 18:2n-6, 18:3n-6, 20 :2n-6, 20:3n-6, and total n-6 polyunsaturated fatty acids (PUFA) in sa lmon liver lipids in comparison with the FO diet. The BO diet also inc reased the percentage of 20:4n-6. Both the SO and BO diets significant ly reduced the percentages of all n-3 PUFA in comparison with the FO d iet. The OO diet significantly increased the percentages of 18:1n-9, 1 8:2n-6, total monoenes, and total n-6 PUFA in liver lipids compared to the FO diet, and the percentages of all n-3 PUFA were significantly r educed. With [1 -C-14]18:3n-3, the recovery of radioactivity in the pr oducts of Delta 6 desaturation was significantly greater in the hepato cytes from salmon fed SO, BO,and OO in comparison with the FO diet. Th e BO diet also increased the recovery of radioactivity in the products of Delta 5 desaturation. Only the BO diet significantly affected the desaturation of [1 -C-14]18:2n-6, increasing recovery of radioactivity in both Delta 6- and Delta 5-desaturation products. In conclusion, di etary BO, enriched in gamma-linolenic acid (18:3n-6), significantly in creased the proportions of both 20:3n-6 and 20:4n-6 in salmon liver ph ospholipids and also significantly increased the desaturation of both 18:2n-6 and 18:3n-3 in salmon hepatocytes. The possible relationships between dietary fatty acid composition, tissue phospholipid fatty acid composition, and desaturation/elongation activities are discussed.