Increased central blood volume: a poosible pathophysiological factor im mild low-renin essential hypertension.

1. Patients with mild low-renin hypertension characteristically have increased central blood volume. The total blood volume is normal; the larger central blood volume reflects a shift of the blood from peripheral to central (cardiopulmonary) segments of the capacity system. 2. A relationship between central blood volume and plasma renin activity is demonstrable during tilting in normal and hypertensive subjects. In thirteen indivicuals there was a strong correlation between the decrease of the central blood volume and the increase in plasma renin activity in response to 12 min of 35 degree head-up tilt. 3. We propose that the elevated central blood volume causes greater stretch of cardiopulmonary mechanoreceptors and this in turn depresses renin release in mild low-renin hypertension.