Lysophosphatidic acid as a stimulator of Na(+)-dependent Ca2+ efflux from adrenal chromaffin cells

The effect of lysophosphatidic acid (LPA) on Ca2+ efflux from cultured bovine adrenal chromaffin cells was examined. LPA stimulated the efflux of 45Ca2+ from the cells in a concentration dependent manner (10(-7)-10(-5)M). Other lysophospholipids (lysophosphatidylcholine, lysophosphatidylethanolamine, lysophosphatidylinositol and lysophosphatidylserine), phosphatidic acid, monoolein and oleic acid had not significant effect on 45Ca2+ efflux from the cells. The LPA-stimulated 45Ca2+ efflux was dependent on the extracellular Na+ concentration and was inhibited by amiloride, inhibitor of Na+/Ca2+ exchange. LPA increased 22Na+ uptake into the cells and this effect was also sensitive to amiloride. These results indicate that LPA stimulates extracellular Na(+)-dependent 45Ca2+ efflux from cultured bovine adrenal chromaffin cells, probably through its stimulatory effect on membrane Na+/Ca2+ exchange.