EFFECT OF A CALCIUM ENTRY BLOCKER ON BLOOD PRESSURE, PLASMA RENIN ACTIVITY, ALDOSTERONE AND CATECHOLAMINES IN NORMOTENSIVE SUBJECTS

The effects of the calcium entry blocker nifedipine on blood pressure, heart rate, plasma renin activity, aldosterone, noradrenaline and adrenaline were studied in 23 normotensive subjects in the supine and upright positions. Nifedipine, 10 mg administered sublingually, lowered mean blood pressure and increased heart rate, plasma noradrenaline and renin activity without increasing plasma aldosterone in the supine position. The increase in plasma aldosterone in response to upright posture was inhibited by nifedipine, whereas the rise in plasma noradrenaline was augmented. These results suggest that intracellular calcium is important as a regulator of aldosterone secretion as well as of vascular tone in normotensive subjects.