Influence of dietary PUFA content on cytochrome P450 and transferase activities in atlantic salmon ( salmo salar)

Abstract

Hepatic biotransformation activities were measured in salmon after maintenance for 4 months on diets containing different ratios of ( n−3) and (n6) polyunsaturated fatty acids. Cytochrome P4501A (ethoxyresorufin-O-deethylase. EROD) activities in fish fed high seed oil diets (45% 18:2 ( n−6): ( n−3)/( n−6) = 0·2) were double and phenol UDP-glucuronosyltransferase (UDPGT) activities half those in fish fed diets containing high-quality fish oil (( n−3)/( n−6) = 6). In both groups the total cytochrome P450 levels and glutathione- S-transferase (GST) activities were constant. Analyses of membrane lipids showed that there were no significant differences in lipid class compositions between dietary groups: however, there were marked differences in the fatty acid species composition of the phospholipids. Phosphatidylinositol contained a low (n−3)/(n−6) ratio in both groups. The fatty acid compositions of the other phospholipids reflected those of the diets: e.g. the (n−3), (n−6) ratio of phosphatidylcholine was 1·9 in the sunflower oil group (compared with 21 for the fish oil diet). The results indicate regulation of microsomal biotransformation activities by dietary modification of the fatty acid composition of the endoplasmic reticulum bulk phospholipids.