EXCHANGEABLE SODIUM IN ANGIOTENSINOGENIC AND NONANGIOTENSINOGENIC RENOVASCULAR HYPERTENSION

Prerious studies have suggested that angiotensin II and sodium can act as alternative mechanisms in maintaining high blood pressure in chronic renovascular hypertension. In the present study, exchangeable sodium was measured in rats in which angiotensin II had been confirmed or excluded as the main cause of the hypertension. To determine the degree of participation of angiotensin II in the maintenance of the high blood pressure, we studied the mean blood pressure response to an angiotensin antagonist (l-Sar-8-Alaangiotensin II) and to a converting enzyme inhibitor (SQ20.881). Rats with a decrease hi blood pressure of less than 20 mm Hg, in response to both inhibitors, were classified as nonresponders; those with a decrease of 20 mm Hg or more, as responders. Fifty percent of the rats with two-kidney hypertension were nonrespooders, and they had lower blood pressure and plasma renin activity than the responders. Further, these two-kidney, hypertensive, nonresponder rats had normal exchangeable sodium. The two-kidney hypertensive responders, on the other hand, had significantly higher exchangeable sodium than both the two-kidney, hypertensive nonresponders and the two-kidney control rats. These results suggest that angiotensin II and exchangeable sodium do not play a major role in the maintenance of the high Mood pressure in the two-kidney hypertensive nonresponders. However, there appears to be an abnormal relationship between renin and exchangeable sodium in the two-kidney hypertensive responders that could contribute to the maintenance of the hypertension. © 1979 American Heart Association, Inc.