Angiotensin Effects on Calcium and Steroidogenesis in Adrenal Glomerulosa Cells*

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Abstract
The role of cellular Ca pools in angiotensin II-stimulated aldosterone synthesis in bovine adrenal glomerulosa cells was investigated. Angiotensin II decreased the size of the exchangeable cell Ca pool by 34%, consistent with previous observations that angiotensin II causes decreased uptake of 45Ca2+ into cells and increased efflux of 45Ca2+ from preloaded cells. Atomic absorption spectroscopy showed that angiotension II caused a decrease of 21% in total cellular Ca. Angiotensin II caused efflux of 45Ca2+ in the presence of EGTA and retarded uptake of 45Ca2+ when choline was substituted for Na, suggesting that hormone effects on Ca pools do not involve influx of trigger Ca or Na. Cells incubated in Ca free buffer and 0.1 mM or 0.5 mM EGTA synthesized reduced (but still significant) amounts of the steroid in response to hormone. Cells incubated in increasing concentrations of extracellular Ca contained increasing amounts of intracellular Ca and synthesized increasing amounts of aldosterone in response to angiotensin II. The participation of intracellular Ca pools in angiotensin II-stimulated steroidogenesis and the importance of extracellular Ca maintaining these pools was suggested.