Implication of endogenous prostaglandin system in the antihypertensive effect of captopril, SQ 14225, in low renin hypertension.

The role of endogenous prostaglandins in the antihypertensive mechanism of orally active angiotensin I-converting enzyme inhibitor in low renin hypertension was investigated. In the SQ 14225-responders with low renin hypertension, blood pressure was elevated to control level and antihypertensive effect of SQ 14225 was attenuated after the inhibition of endogenous prostaglandin synthesis with indomethacin, while no significant change in blood pressure was found in the SQ 14225-responders with normal renin hypertension. Urinary prostaglandin E excretion was not significantly increased after the SQ 14225 administration but significantly decreased after the administration of indomethacin. There was no significant difference in urinary prostaglandin E excretion between normal renin hypertension and low renin hypertension. These results suggest that SQ 14225 may potentiate extrarenal vasodilating prostaglandin system, probably vascular prostaglandin system, contributing to the antihypertensive mechanism in SQ 14225-responders with low renin hypertension. The augmented renin release following SQ 14225 administration was inhibited by indomethacin, suggesting that endogenous prostaglandin system may contribute to the negative short feedback mechanism of renin release.