Effect of captopril on brain converting enzyme in the spontaneously hypertensive rat.

The effect of oral captopril (30 mg/kg per day) on the blood pressure, plasma aldosterone concentration, urinary electrolytes and brain angiotensin-converting enzyme activity of spontaneously hypertensive rats of the Okamoto strain was examined. Over a seven day period, captopril caused a progressive fall in blood pressure with increased sodium excretion and urine volume and a significant fall in plasma aldosterone concentration. Following captopril, angiotensin converting enzyme activity increased significantly in the midbrain and medulla oblongata; the pituitary level of angiotensin converting enzyme activity was significantly decreased. The hypotensive action of captopril in the spontaneously hypertensive rat is associated with changes in body sodium, water and plasma aldosterone concentration. The alterations in brain angiotensin-converting enzyme activity following captopril treatment suggest that, with chronic administration, captopril can alter the activity of the brain renin-angiotensin system.