Organ and phospholipid class fatty acid specificity in response to dietary depletion of essential n-3 fatty acids inAtlantic salmon (Salmo salar L.)

The cell membrane phospholipid composition is of major importance for normal cell functions. However, it is not known how complete depletion of both shorter and longer chain omega-3 fatty acids in salmon diets influences fatty acid composition of phospholipid subclasses in different organs of Atlantic salmon. We describe here the fatty acid composition in phospholipid subclasses of liver, muscle, heart and intestine in Atlantic salmon after 18 months of dietary n-3 essential fatty acids deprivation. The percentage of 22:6n-3 was markedly reduced in almost all phospholipid subclasses, and except for muscle phosphatidylcholine, phosphatidylethanolamine (PE) and phosphatidylinositol (PI), phospholipids in deficient fish were totally devoid of 20:5n-3. As compensation, we observed significant increases in 20:4n-6, and especially in 20:3n-9 (Mead acid) and 22:5n-6, varying among phospholipids and organs. High amounts of 20:3n-9 were found in liver and intestinal PE, little in PE from heart and muscle. For 22:5n-6, we saw a small incorporation in PI in liver and intestine compared to heart and muscle. Generally in PI, the preference for 20:4n-6 to 20:5n-3 differed significantly between organs. Overall, changes upon n-3 deprivation seemed to be strongest in liver and intestine, the lipid-secreting organs, and less in muscle and heart.