The effect of converting enzyme inhibition with SQ20,881 on plasma and urinary kinins, prostaglandin E, and angiotensin II in hypertensive man.

The relationship between levels of angiotensin II, kinins, and prostaglandin E and the depressor response to 1 or 3 mg/kg of the conrerting enzyme inhibitor SQ20.88I was studied in recumbent hypertensive subjects during 109 mEq and 9 mEq/day sodium intake. In 13 sodium-replete patients, SQ20,881 decreased angiotensin II from 46.7 ± 9.2 (mean ± SEM) to 31.7 ± 5.1 pg/ml and plasma aldosterone from 6.8 ± 0.9 to 2.9 ± 0.6 ng/dl (p < 0.003) without compensatory elevations of plasma renin activity and angiotensin I. Administration of SQ20.881 had no effect on plasma bradyklnin but it increased mean immunoreactive prostaglandin E from 143 ± 17 to 302 ± 75 pg/ml (p < 0.02) and in some patients it increased urinary kinin excretion. The distribution of the mean 2-hour depressor response was bimodal as four patients had a fall in diastollc pressure of at least 11 torr (mean 14 ± 1 torr) and nine had a minimal depressor response £ 4 torr, (-1 ± 1 torr); patients with a greater decrease in blood pressure showed an increase in urinary kinin excretion rate, whereas the other patients showed a fall (471 ± 121 vs 99 ± 106 ng/hr; p < 0.005); both had similar control levels and responses of plasma angiotensin II, aldosterone, immunoreactive prostaglandin E, and brad} kinin. In nine sodium-depleted patients, SQ20.881 slightly decreased mean angiotensin II from 30.5 ± 4.5 to 22.4 ± 4.3 pg/ml early after drug administration, but because this was accompanied by rapid compensatory elevations of angiotensin I (which increased from < 14 pg/ml to levels as high as 513 pg/ml) and mean plasma renin activity from 43 ± 1.6 to 13.9 ± 43 ng/ml/hr, levels of angiotensin II returned toward control soon after drug administration. We found that SQ20381 had no effect on plasma bradykinin but increased urinary kinin excretion by 203 ± 63 ng/hr (p <0.02) and in some patients increased plasma prostaglandin E. The distribution of the mean 2-hour depressor response in these nine sodium-depleted patients was also bimodal as flve sodium-depleted patients had a depressor response to drug of at least 7 torr (10 ± 1 torr) while four sodium-depleted patients had a minimal response (-1 ± 1 torr). The patients with a greater decrease in blood pressure showed a greater (p < 0.05) increase in both immunoreactive prostaglandin E (248 ± 99 vs 20 ± 12 pg/ml) and urinary kinin excretion (270 ± 69 vs 83 ± 75 ng/hr) whereas decrements in plasma angiotensin II and aldosterone were similar. Thus, the depressor response to SQ20,881 correlated better with alterations in urinary kinins and plasma prostaglandin E than with changes in plasma levels of angiotensin II. (Hypertension I: 416-426, 1979)