Volume independent stimulation of renin secretion by a single dose of amiloride in man

The regulation of renin secretion is not understood in detail. There is evidence that amiloride (CAS 17440-83-4) has a stimulatory effect on the renin secretion but it is still in question whether this is volume and/or sodium independent. The purpose of this study was to investigate whether a single dose of amiloride has a direct stimulatory effect on the renin secretion in humans independent of its diuretic effect. Blood pressure, plasma renin activities and plasma aldosterone concentrations as well as serum electrolytes and serum creatinine were assessed in 11 healthy male humans over a period of 6 hours after a single dose of 20 mg of amiloride (Midamor), or placebo. Furthermore every hour urine was collected for analysis of urinary creatinine and electrolytes. To avoid a possible effect on the renin secretion via augmented diuresis induced by amiloride the urinary volume loss was replaced by 0.9% NaCl solution. There was a decrease in plasma renin activities and plasma aldosterone concentrations after amiloride and placebo administration, but the plasma renin activity after amiloride was significantly higher compared with placebo. Also the plasma aldosterone concentration was higher after amiloride compared with placebo, but the difference did not reach statistical significance. Serum and urinary concentrations of sodium and potassium clearly confirmed the known potassium-saving and natriuretic effect of amiloride. Serum creatinine concentrations decreased and urinary sodium chloride concentrations increased due to the administered volume load using physiologic sodium chloride solution. The present study provides evidence that amiloride induces renin secretion by direct mechanisms in man, which might go along with augmented aldosterone secretion.