Effects of diets enriched in eicosapentaenoic or docosahexaenoic acids on prostanoid metabolism in the rat

To clarify the effects of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) on prostaglandin biosynthesis, diets supplemented with oils rich in one fatty acid or the other were fed to rats over a 4‐wk period. Animals fed the Max EPA diet showed a significant decrease in plasma and tissue phospholipid arachidonic acid content. While plasma levels of DHA increased on a shark liver oil diet enriched in DHA, the liver and kidney phospholipid contents of DHA were not altered. In addiition, the DHA‐enriched diet did not decrease the arachidonic acid content of either liver or kidney phospholipids. Whole blood thromboxane and vascular prostacyclin synthesis were decreased by 65% and 36%, respectively, in animals fed the Max EPA diet. No such decrease was seen in the rats fed DHA‐enriched diets. We conclude from these results that in the rat DHA is not likely to have a significant effect on prostaglandin synthesis when given as a dietary supplement.