The effect of angiotensin II and noradrenaline alone and in combination on renal sodium excretion in man.

Abstract

1 The renin-angiotensin-aldosterone-system is important for the maintenance of sodium balance in man. Recent animal evidence suggests the anigiotensin II can modulate the effect of the renal sympathetic nervous system on renal function. We have investigated the possible interaction of physiological doses of angiotensin II and noradrenaline on sodium excretion in man. 2 Seven normal volunteers were studied on four occasions during maximum water diuresis sustained by oral hydration. Samples were obtained during a baseline and four subsequent 20 min periods (A-E). Placebo or noradrenaline was infused over periods B-E, and angiotensin II infused over period C. 3 There was no change in systemic blood pressure, heart rate or creatinine clearance caused by infusion of either angiotensin II, noradrenaline or both in combination. 4 Noradrenaline alone caused a significant fall in absolute and fractional sodium excretion. Angiotensin II when infused with placebo caused a 37% fall in absolute sodium excretion and a 32% fall when infused with noradrenaline (no significant difference between the 2 days). Similar changes were seen for urinary flow and fractional sodium excretion. 5 We have therefore found no evidence to support a postsynaptic interaction of low doses of angiotensin II and noradrenaline on renal sodium excretion in man.