1. The converting-enzyme inhibitor captopril has been given in doses up to 450 mg daily to hypertensive patients with renal artery stenosis and to patients resistant to other therapy.
2. Captopril alone was effective in controlling hypertension in renal artery stenosis, irrespective of whether pretreatment plasma angiotensin II was raised or normal, except in one man with overall renal impairment.
3. In one woman with the hyponatraemic hypertensive syndrome secondary to renal artery thrombosis, captopril restored depleted exchangeable sodium and potassium to normal. In the other cases of renal artery stenosis with normal renal function, exchangeable sodium and total body potassium were not significantly altered, and there were no marked changes in plasma sodium and potassium.
4. The combination of captopril with a diuretic controlled blood pressure long-term in every case of previously resistant hypertension.
5. Within 2 h, captopril induced highly significant falls in arterial pressure, in plasma angiotensin II and aldosterone, with converse increases in plasma active and total renin and blood angiotensin I.
6. The initial fall in plasma angiotensin II was closely related to the concomitant fall in diastolic pressure.
7. The pattern of change in circulating renin, angiotensins I and II and aldosterone was maintained during long-term therapy, whether or not a diuretic was added. There was no tendency for plasma angiotensin II to increase despite sustained elevation of active renin and angiotensin I.
