Adrenocortical hormone secretory response to chronic NH4Cl-induced metabolic acidosis

We examined the effect of chronic metabolic acidosis on adrenocortical hormone production by administering NH4Cl for 5 days to four normal subjects. Plasma aldosterone concentration, aldosterone secretion, and urinary excretion of aldosterone-18-glucuronide increased significantly, whereas there were no significant changes in the plasma concentrations of cortisol, corticosterone, or deoxycorticosterone, or in the urinary excretion of 17-hydroxycorticoids. By day 2, plasma renin activity (PRA) and concentration (PRC) were not significantly different from control, and the slope of the regression line relating plasma aldosterone concentration to PRA was significantly greater than the slope in the control period, i.e., the sensitivity of aldosterone secretion to renin stimulation was increased. By day 5, however, PRA and PRC were increased above control. Plasma potassium concentration did not change significantly. Thus chronic NH4Cl-induced acidosis induces a sustained stimulation of aldosterone secretion in the absence of a change in adrenocorticotropin-dependent adrenocortical hormone secretion. Factors other than an increase in renin secretion and plasma potassium concentration may be involved in at least the early phase of aldosterone stimulation, suggesting that plasma hydrogen ion concentration might be a separate regulator of aldosterone secretion.