ENHANCEMENT OF POTASSIUM-STIMULATED, AND ANGIOTENSIN-II-STIMULATED ALDOSTERONE PRODUCTION BY THE CALCIUM CHELATOR EGTA IN BOVINE ADRENAL GLOMERULOSA CELLS IN-VITRO

The present study was designed to assess the effect of the calcium che lator EGTA (ethylenglycol-bis-(beta-aminoethyl ether)-N,N,N',N'-tetraa cetic acid; 1.0 mM) on potassium (8 mM)- and angiotensin II (AII; 10 n M)-stimulated aldosterone production in bovine adrenal glomerulosa cel ls in vitro. The combined administration of EGTA and potassium, or of EGTA and AII, yielded a significant increase in the levels of aldoster one production. The net increment in aldosterone production after the combined administration of EGTA and potassium, or that after the combi ned administration of EGTA and AII was also significantly higher than the sum of that evoked by EGTA and potassium alone, or the sum of that evoked by EGTA and AII alone, respectively. at similar concentrations of extracellular ionized calcium ([Ca2+](out)) or magnesium, the leve ls of agonist-stimulated aldosterone production were markedly elevated by the administration of EGTA. These results indicate that lowering [ Ca2+](out) concentrations with EGTA enhances potassium- and AII-stimul ated aldosterone production in bovine adrenal glomerulosa cells in vit ro. This enhancement may be predominantly due to another effect of EGT A, in addition to the stimulation of calcium entry into the cells. (C) 1997 Elsevier Science Ltd.