QUANTITATIVE ESTIMATION OF PHYSIOLOGICAL EFFECT OF N-3 AND N-6 POLYUNSATURATED FATTY ACIDS IN RATS

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Effects of dietary linoleic, gamma-linolenic, arachidonic, alpha-linolenic, eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids on lipid metabolism were quntitatively estimated in rats. Dietary EPA and DHA lowered serum and liver triglyceride concentration. Dietary DHA also lowered serum cholesterol concentration. The triglyceride lowering effect of EPA and DHA was thought to be due to the suppression of fatty acid and triglyceride synthesis in liver. Secretion of triglyceride and cholesterol from liver estimated by the injection of Triton WR-1339 was suppressed by dietary EPA and DHA.Dietary gamma-linolenic and arachidonic acids increased arachidonic acid content in serum, liver, heart, aorta and platelet phosphatidylcholine and phosphatidylethanolamine. In contrast, dietary n-3 polyunsaturated fatty acids (PUFA) decreased the arachidonic acid content. DHA was most effective to lower arachidonic acid in the phospholipids. Arachidonic acid content in brain phospholipids were not influenced by the dietary PUFA.Production of platelet thromboxane A2 was decreased by the feeding of n-3 PUFA.DHA was most effective to lower the production. In contrast, production of aortic prostacyclin was enhanced by the feeding of gamma-lonolenic and arachidonic acids, although dietary n-3 PUFA had a comparable effect with linoleic acid. The ratio of protsacyclin and thromboxane A2, an index of inhibition of platelet aggregation, was higher in dietary EPA and DHA than the other PUFA groups. Dietary DHA suppressed systolic blood pressure in spontaneously hypertensive rats. The results suggest that EPA and DHA are more hypolipidemic and antithrombotic than the other PUFA.