Regulatory mechanism of calcium efflux from cultured bovine adrenal chromaffin cells induced by extracellular ATP.

The effect of adenosine-5'-triphosphate (ATP) on Ca2+ efflux from cultured bovine adrenal chromaffin cells was examined. ATP stimulated the efflux of 45Ca2+ from the cells in a concentration-dependent manner (0.01-1 mM). The 45Ca2+ efflux from the cells was also stimulated by adenosine-5'-O-(3-thiotriphosphate) (ATP-gamma s), alpha beta-methylene-ATP and adenosine-5'-diphosphate (ADP), but was not by adenosine-5'-monophosphate (AMP) and adenosine. The ATP-stimulated 45Ca2+ efflux was not affected by deprivation of the extracellular Ca2+ and Mg2+, but was dependent on the extracellular Na+ concentrations. ATP increased the influx of 22Na+ into the cells. These results indicate that ATP stimulates extracellular Na(+)-dependent 45Ca2+ efflux from cultured bovine adrenal chromaffin cells, probably through its stimulatory effect on membrane Na+/Ca2+ exchange.