Stimulation of Plasma Renin Activity by Captopril in Renovascular Hypertensive Conscious Dogs

The increase in plasma renin activity induced by captopril is used in the clinical evaluation of renovascular hypertensive patients. This increase in plasma renin activity could result from either the concomitant fall in systemic pressure or other effects of captopril, such as the removal of an angiotensin II inhibitory effect on renin release, the increased production of bradykinin or prostaglandins, etc. To examine the effect captopril has on plasma renin activity, independent of changes in systemic pressure, captopril (5, 10 and 50 micrograms/kg iv) was administered to conscious dogs before and following the development of 1 clip-2 kidney Goldblatt hypertension. Plasma renin activity, under normal conditions remained unchanged, while during hypertension it increased 2.0, 2.8 and 3.5 fold respectively in response to the three doses of captopril. These results suggest that the development of renovascular hypertension sensitized the kidney to release renin when challenged by captopril and that the effect is independent of changes in systemic pressure.