Sodium and angiotensin in the pathogenesis of experimental renovascular hypertension.

The effects of simultaneous angiotensin blockade and sodium depletion on the development of one-kidney renovascular hypertension were studied in rats. In sodium-replete rats, systolic blood pressure (SBP) increased from 102 +/- 2 to 153 +/- 11 mmHg by the 12th day after unilateral nephrectomy and subsequent partial occlusion of the renal artery with a 0.22-mm silver clip. When changes in body fluid volume were minimized by sodium restriction in a second group of rats, the increase in SBP from 98 +/- 4 to 149 +/- 7 mmHg after clipping was not different from that in sodium-replete animals. Inhibition of the angiotensin-converting enzyme with SQ 14,225 during sodium restriction prevented the SBP from increasing above 101 +/- 3 mmHg by the 12th day after nephrectomy and clipping. Once SQ 14,225 administration was discontinued, SBP rose significantly to 148 +/- 5 mmHg within 5 days. Because previous studies have shown that neither sodium depletion nor angiotensin blockade alone prevented the development of one-kidney renovascular hypertension, it is concluded that the increase in blood pressure resulting from renal artery constriction and contralateral nephrectomy was prevented only by suppression of both the renin-angiotensin system and body fluid volume.