Acute effects of three natural corticosteroids on the acid-base and electrolyte composition of urine in adrenalectomized rats.

In acute experiments, aldosterone (aldo), 18-hydroxycorticosterone (18 OH B) or corticosterone (B) were administered to adrenalectomized rats and parameters related to acid-base balance measured in urine samples collected for 3.5 hours after injection. Aldo reduced sodium excretion but did not affect pH nor the outputs of K, NH4+, CO3H-, phosphates nor titratable acidity. 18 OH B increased the excretion of titratable acidity and reduced drastically that of CO3H-. The lowest effective dose (3 micrograms) promoted Na excretion while the highest dose employed (6 micrograms) reduced pH and Na excretion. B increased the excretions of phosphates and ammonium, the former drastically. Potassium output either increased or did not change, and pH augmented marginally. It is postulated that a) 18 OH B is a naturally occurring steroid eliciting urine-acidification not necessarily accompanied by sodium retention; and b) at least B and 18 OH B in the rat, possess hormonal roles according to which the latter promotes the presence of protons, and the former, that of acute proton-acceptors in the lumen of tubuli.