Angiotensin II, plasma renin and sodium depletion as determinants of blood pressure response to saralasin in essential hypertension.

To evaluate the role of the renin-angiotensin system and sodium depletion in the hypotensive response to 1-sarcosine-8-alanine-angiotensin II (saralasin), 15 male patients with essential hypertension were studied on a diet containing 120 mEq of sodium and 100 mEq of potassium per day. After a 5-day control period, all subjects had a mild pressor response to the saralasin infusion (p less than 0.01). After 5 days of the diuretic metolazone (5 mg/day), eight of the 15 patients had a vasodepressor response; these responders had a significantly greater increase in plasma renin activity and angiotensin II concentrations than did the non-responders. Sodium deficit differed markedly (p less than 0.001) between the two groups (361 +/- 121 mEq (SD) vs 52 +/- 26 mEq sodium, respectively). The addition of spironolactone (400 mg/day) for 5 days resulted in saralasin responsiveness in all but two patients, both of whom had small sodium deficits. Thus, variability in the natriuretic response to diuretics may affect saralasin testing and limit its clinical utility.