Effects of ANG II and K+ on Ca efflux and aldosterone production in adrenal glomerulosa cells.

Abstract

A comparison was made of the effects of angiotensin II (ANG II) and K+ on aldosterone secretion and calcium efflux from porcine adrenal glomerulosa cells. In the presence of 1.25 mM Ca2+ in the perifusion medium, both 1 x 10(-9) M ANG II and 12 mM K+ caused a 3-fold increase in rate of aldosterone secretion. ANG II caused a 3.5-fold increase in the fractional efflux ratios of radiocalcium from cells prelabeled with 45Ca, but K+ caused only a 1.5-fold increase. When the perifusate contained no Ca2+ or the Ca2+ was replaced by 0.6 mM Sr2+, the effects of K+ on both 45Ca efflux and aldosterone production were abolished. On the other hand, ANG II still caused approximately the same increase in the fractional efflux ratio of radiocalcium and 25-50% of the normal increase in aldosterone production rate. When the perifusate contained 1.25 mM calcium and 25 microM dantrolene, K+ produced the same 1.5-fold increase in calcium efflux and the same maximal rate of aldosterone production as seen in the absence of dantrolene. In contrast, dantrolene greatly inhibited ANG II-induced increase in the fractional efflux ratio of calcium, 1.5-fold compared with 3.5-fold in the absence of dantrolene. Likewise, dantrolene delayed the onset of the ANG II-induced increase in aldosterone secretion and reduced the maximal rate of secretion to 50%. Cells incubated with both dantrolene and media containing no Ca2+ or containing Sr2+ in place of Ca2+ showed no response to ANG II either in terms of calcium efflux or aldosterone production.(ABSTRACT TRUNCATED AT 250 WORDS)