Renin and aldosterone responses to short-term NaCl or NaHCO3 loading in man

We compared the effects of 500 ml of 0.15M NaCl or 750 ml of 0.15M NaHCO2, infusions on PRA and PAC in 16 normal NaCl-restricted men. More positive sodium balance, greater natriuresis, and lower serum chloride, potassium, and hydrogen ion concentrations were observed after NaHCO3 infusion. PRA decreased (13.8 +/- 1.0 ng/ml angiotensin I per hour to 6.6 +/- 0.70) and PAC did not change (98 +/- 15 ng/dl to 86 +/- 15) after NaCl infusion. Conversely, PRA did not change (9.9 +/- 1.6 to 10.1 +/- 1.6) and PAC decreased (85 +/- 9 to 44 +/- 5) after NaHCO3 infusion. Plasma cortisol declined in both groups. These results suggest that in sodium-restricted man chloride is more important than sodium for the suppression of PRA by NaCl loading and that potassium or hydrogen ion is a more sensitive modulator of aldosterone secretion than is renin.