1. We studied renin-aldosterone system behaviour in five renovascular hypertensive patients during central hypervolaemia by water immersion to the neck.
2. Water immersion significantly suppressed the high peripheral renin levels of the patients despite an autonomic renin secretion from the stenotic kidney, a significant reduction of mean blood pressure and an increase in distal tubule sodium concentration.
3. The effect of immersion on plasma aldosterone appeared to be primarily mediated via suppression of plasma renin activity (PRA).
4. Our data suggest that: (a) the renin secretion is mainly modulated by cardiopulmonary receptors activity; (b) the neurogenic reflex control of plasma renin activity is very effective in renovascular hypertension.