Effect of hydrogen ion concentration on aldosterone secretion by isolated perfused canine adrenal glands

The direct effects of changes in extracellular hydrogen ion (H+) concentration on aldosterone secretion under basal, angiotensin II- and potassium-stimulated conditions were studied in isolated, perfused canine adrenal glands. Changes in extracellular H+ concentration were induced by altering either the partial pressure of CO2 (pCO2) or the HCO3- concentration of the perfusate. Acid-base disturbances had a more pronounced effect on aldosterone secretion under stimulated than under basal conditions. Increasing H+ concentration enhanced angiotensin II- and potassium-stimulated aldosterone secretion, whereas decreasing H+ concentration markedly inhibited the secretory response to these stimuli. Because changes in H+ concentration, whether produced by varying extracellular pCO2 or extracellular HCO3- concentration, had similar effects on angiotensin II-stimulated aldosterone secretion, the data suggest that H+ concentration per se is the important determinant of the aldosterone secretory rate. Interestingly, during the immediate recovery period from pCO2-induced alkalosis under both angiotensin II- and potassium-stimulated conditions, aldosterone secretion always returned to a value significantly higher than that obtained just before alkalosis. The results of this study demonstrate that changes in extracellular H+ concentration influence the rate of aldosterone secretion, possibly via changes in intracellular pH, by a direct action on the canine adrenal gland. Therefore, when evaluating the control of aldosterone secretion, the acid-base status of the whole animal or of in-vitro adrenal tissue must be considered.