Effects of chronic treatments with adrenal steroids on acid-base homeostasis in the rat.

Urinary parameters related to acid base homeostasis were studied in adrenalectomized rats (ADX) as well as in ADX treated with physiological doses of corticosterone (B), aldosterone (aldo) or 18-Hydroxycorticosterone (18HOB) during 1, 3 or 5 days, under basal conditions and after gravage with 200 mM HCI. The results showed: a) persistent effect of B and 18HOB increasing titratable acidity principally in response to acidosis; b) an increased phosphate elimination in acidotic B treated ADX on the first day, and in 18 HOB treated ADX on days 3 and 5; c) pronounced increases in blood pH and blood bicarbonate levels provoked by the three steroids on day 1; d) increments of ammonium elimination in response to acidosis by aldo treatments on the first day, while B and 18HOB increase ammonium elimination under almost all conditions during the whole experiment; e) the effects of B and 18 HOB would be independent of an increase in sodium retention as well as glomerular filtration rate.