EFFECTS OF DIETARY FATTY-ACIDS ON EICOSANOID-GENERATING CAPACITY, FATTY-ACID COMPOSITION AND CHEMOTACTIC ACTIVITY OF RAINBOW-TROUT (ONCORHYNCHUS-MYKISS) LEUKOCYTES

Rainbow trout, Oncorhynchus mykiss, were maintained on isocalorific di ets in which either sunflower, menhaden or Fosol oils were used as the dietary source of fatty acids. At intervals over a period of 6 months , head kidney leucocytes were isolated and used for the analysis of th eir fatty acid composition and eicosanoid-generating capacity. Major c hanges in fatty acid composition were apparent within 4 weeks on the d iets, with fish fed sunflower oil diets showing a 2.1-fold increase in total n - 6 fatty acids and a 2.3-fold decrease in n - 3 fatty acids, compared with the original basal levels. By week 8 the fatty acid com position changes were greater in the sunflower-fed fish, but thereafte r remained relatively stable to the end of the experiment at week 24. Leucocytes from the fish maintained for > 8 weeks on the sunflower oil containing diet produced significantly lower percentages of 5-series lipoxygenase products derived from eicosapentaenoic acid including 12- hydroxyeicosapentaenoic acid, leukotriene B-5, and lipoxin A(5) compar ed with those cells from fish fed either menhaden or Fosol based diets . Unlike the fatty acid composition, differences in lipoxygenase produ ct profiles between the dietary groups increased throughout the experi ment and by week 24 the arachidonic acid/eicosapentaenoic acid derived product ratios were approx. 14:1 in the sunflower oil-fed fish compar ed with approx. 1:1.5 in the menhaden oil-fed fish. A functional conse quence of these differing ratios was seen in the ability of supernatan ts containing these products to cause the in vitro locomotion of trout neutrophils. Supernatants from sunflower oil-fed fish were less chemo -attractive than supernatants from menhaden or Fosol oil-fed fish.