Evening primrose oil, a dietary prostaglandin precursor, diminishes vascular reactivity to renin and angiotensin II in rats.

Polyunsaturated fatty acids (PUFA) are biosynthetic precursors of prostaglandins (PG). Endogenous biosynthesis of PG in vessel wall and kidney contributes to the regulation of arterial blood pressure. By increasing the fraction of PUFA in the diet systemic blood pressure can be lowered while PUFA deficient diet leads to an increase in blood pressure. To evaluate the effect of an enhanced PG biosynthesis by dietary PG precursors on vascular reactivity and vascular formation of prostacyclin-like activity, the pressor response to intravenous renin and angiotensin II in rats pretreated p.o. for 3 months with evening primrose oil (EPO, 1 ml/day) was determined and the antiaggregatory activity released by aortas of treated rats studied. EPO is unique in that it contains beside linoleic acid (72%), gamma-linolenic acid itself (9%). In contrast to olive oil treated rats EPO pretreatment diminished vascular reactivity to the vasopressor stimuli of renin and angiotensin II and increased the formation of vascular prostacyclin-like activity (p less than 0.05). These studies imply the possibility of a selective modulation of PG production by dietary maneuvers.