INVESTIGATIONS INTO THE ROLE OF CALCIUM IONS IN THE CONTROL OF STEROID PRODUCTION BY ISOLATED ADRENAL ZONA GLOMERULOSA CELLS OF THE RAT

Abstract

An increase in the concentration of extracellular potassium from 3·6 to 8·4 mmol/l had only a small delayed effect on the uptake of radioactive calcium by isolated adrenal glomerulosa cells. However, the same stimulus had a rapid and highly significant effect on the efflux of radioactive calcium from glomerulosa cells preloaded with ⁴⁵Ca²⁺. Cells incubated in medium containing 8·4 mmol potassium/l had retained approximately 15% more radioactivity than control cells after 2·5 min and this difference was maintained for up to 90 min. There was an increase in the production of steroids by the glomerulosa cells in the presence of 8·4 mm-potassium. No effect on calcium efflux was observed in similar experiments with isolated fasciculata cells; it has been established that this concentration of potassium does not affect steroidogenesis in fasciculata cells, indicating that the effect on glomerulosa cells may be causally linked to steroidogenesis. There was no significant change in the total calcium content of glomerulosa cells in the presence of 8·4 mm-potassium. Exchangeable calcium in these cells was found to be 60% of the total calcium content.