Effect of dietary cholesterol on the release of prostacyclin from the mesenteric vascular bed in diabetic rat.

Streptozotocin-induced diabetic female rats and age-matched control rats were fed a regular chow with or without the addition of 1% cholesterol in the diet. The release of 6-keto-PGF1 alpha, a prostacyclin metabolite, from the mesenteric vascular bed was significantly increased in diabetic rats. The production of PGI2 in diabetic rats was significantly reduced whereas that in the control was not affected by cholesterol feeding. The examination of the fatty acid composition of phospholipids from the mesenteric vascular bed indicated that proportions of stearic (18:0), linoleic (18:2n-6) and dihomo-gamma-linolenic (20:3n-6) acids were higher whereas those of oleic (18:1n-9) was lower in diabetic rats than those in the controls. Cholesterol feeding had no significant effect on the levels of arachidonic acid (20:4n-6) in the controls but it significantly decreased those in diabetic rats. It is suggested that cholesterol feeding lowers the release of PGI2 from the mesenteric vascular bed possibly because of a reduced level of arachidonic acid, the major precursor for prostaglandin synthesis. This could be due to an impairment of delta-5 desaturase.