Effects of dietary fatty acids on eicosanoid-generating capacity, fatty acid composition and chemotactic activity of rainbow trout (Oncorhynchus mykiss) leucocytes.

Rainbow trout, Oncorhynchus mykiss, were maintained on isocalorific diets 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 their fatty acid composition and eicosanoid-generating capacity. Major changes in fatty acid composition were apparent within 4 weeks on the diets, 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 composition changes were greater in the sunflower-fed fish, but thereafter 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 B5 and lipoxin A5 compared with those cells from fish fed either menhaden or Fosol based diets. Unlike the fatty acid composition, differences in lipoxygenase product profiles between the dietary groups increased throughout the experiment and by week 24 the arachidonic acid/eicosapentaenoic acid derived product ratios were approx. 14:1 in the sunflower oil-fed fish compared with approx. 1:1.5 in the menhaden oil-fed fish. A functional consequence of these differing ratios was seen in the ability of supernatants 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.