Effect of captopril on plasma prostacyclin concentration in essential hypertensive patients

To determine the influence of captopril on prostaglandins, the levels of plasma 6-keto-PGF1 alpha and thromboxane B2, the stable products of prostacyclin and thromboxane A2, respectively, were measured in 9 essential hypertensive subjects by radioimmunoassay before, 1 hour after a single oral 25 mg dose of captopril, and 2 weeks after administration of oral 25 mg captopril twice daily. A significant increase in plasma 6-keto-PGF1 alpha levels occurred after 2 weeks (p less than 0.05), but after 1 hour the increment was not significant. Plasma thromboxane B2 remained unchanged. Mean blood pressure fell significantly (p less than 0.02 after 1 hour, p less than 0.005 after 2 weeks) and plasma renin activity increased significantly after both periods (p less than 0.01 after 1 hour, p less than 0.02 after 2 weeks). There was no significant correlation between changes in blood pressure and 6-keto-PGF1 alpha for either time period. These results suggest that the elevation of plasma 6-keto-PGF1 alpha by captopril therapy was not responsible for reducing blood pressure, while enhanced plasma prostacyclin as a chronic response may contribute to prevention of thrombotic disorders and organ damage.