Effects of dietary fats on prostanoid production and aortic and plasma fatty acid composition in rats

Male Sprague-Dawley rats were fed diets with 10%, 30%, or 50% of energy derived from fat for two weeks. The fats used were beef tallow, olive oil, peanut oil and butter. Aortic prostacyclin (PGI₂) production, platelet aggregation and thromboxane A₂ (TXA₂) production and plasma and aortic phospholipid (PL) content were measured. Butter- and beef tallow-feeding reduced aortic PGI₂ production and collagen-induced TXA₂ production in a dosedependent manner as the level of fat in the diet increased. Neither olive oil nor peanut oil had any effect on aortic PGI₂ production or collagen-induced TXA₂ production. Butter-feeding also resulted in a decrease in collageninduced platelet aggregation; however, none of the other fats had any effect on collagen-induced platelet aggregation. The observed decreases in aortic PGI₂ and collagen-induced TXA₂ production were paralleled by similar decreases in aortic and plasma PL arachidonic acid content and an increase in eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Only the most saturated fats, butter and beef tallow, had significant inhibitory effects on prostanoid production and platelet aggregation.