Effects of angiotensin I converting enzyme inhibitor (SQ 14,225) on the responses of blood pressure and steroid hormone to angiotensin II and ACTH infusion in hypertensive subjects

The effects of the converting enzyme inhibitor, SQ 14,225, on the renin-angiotensin system, adrenal function and blood pressure were investigated in 14 hypertensive patients, i.e., 10 with essential hypertension (EH) and 4 with renovascular hypertension (RVH). The mean blood pressure (MBP) and plasma aldosterone showed significant decreases in the EH with normal renin (NR) group and in the RVH group but no significant changes in the EH with low renin (LR) group. Plasma renin activity (PRA) increased significantly in the EH and NR group and in the RVH group but showed no significant change in the EH with LR group. Significant correlations were found between the fall in MBP after SQ 14,225 treatment and the pretreatment levels of PRA or plasma aldosterone. In an ACTH infusion study, the response of plasma aldosterone to ACTH revealed significant decreases after SQ 14,225 administration. In an angiotensin II (A II) infusion study, the response of plasma aldosterone was unchanged after SQ 14,225 administration. However, the pressor responses to A II infusion with SQ 14,225 were significantly higher than those without SQ 14,225. From these findings, it is concluded that the antihypertensive mechanism of SQ 14,225 may be due mainly to the decrease in levels of endogenous A II and that the reduction in plasma aldosterone after SQ 14,225 were significantly higher than those without SQ 14,225. From these findings, it is concluded that the antihypertensive mechanism of SQ 14,225 administration may be due to reduction of endogenous A II levels by converting enzyme inhibition.