Aldosterone Production by Isolated Glomerulosa Cells: Modulation of Sensitivity to Angiotensin II and ACTH by Extracellular Potassium Concentration.

Abstract

The influence of extracellular K concentration of adrenal sensitivity to angiotensin II and ACTH was studied in isolated canine adrenal glomerulosa cells. When K was absent from the incubation medium, the aldosterone response to angiotensin II or ACTH was completely abolished. At physiologic angiotensin II concentrations (2.5 .times. 10-11M), aldosterone formation increased 4-fold when K concentration was increased from 2.5 to 5.0 mM, and rose 6-fold as K was increased from 2.5 to 7.5 mM. In the absence of angiotensin II, the same changes in K concentration increased aldosterone production only to 2-fold and 3.5-fold, respectively. The effect of K concentration on the aldosterone response to ACTH was similar but less marked. The concentration and binding affinity of angiotensin II receptor sites in glomerulosa cells were not changed by increasing K concentrations from 0 to 7.5 mM. These observations demonstrate that the aldosterone response of the glomerulosa cell to angiotensin II is K dependent within the physiological range for each of these stimuli. Such an interaction suggests that the in vivo effect of K upon aldosterone secretion includes a significant modulating action upon adrenal sensitivity to angiotensin II, and a direct action of K upon the adrenal glomerulosa cell.