SEROTONIN INCREASES NA-DEPENDENT CA2+ EFFLUX FROM BOVINE ADRENAL CHROMAFFIN CELLS IN CULTURE()

The effect of serotonin (5-hydroxytryptamine, 5-HT) on Ca2+ mobilizati on in bovine adrenal chromaffin cells in culture was examined. 5-HT (1 0(-5) M) did not increase secretion of catecholamine, uptake of Ca-45( 2+) and levels of intracellular free Ca2+ ([Ca2+](i)). However, 5-HT ( 10(-8)-10(-5) M) stimulated the efflux of Ca-45(2+) from cultured bovi ne adrenal chromaffin cells in a concentration-dependent manner. Its s timulatory effect on Ca-45(2+) efflux was inhibited by cyproheptadine (a 5-HT1A and 5-HT2 receptor antagonist) or mianserin (a 5-HT2 recepto r antagonist). The increase in 5-HT-stimulated Ca-45(2+) efflux was de pendent on extracellular Na+ concentration, but not extracellular Ca2 concentration. These results indicate that stimulation of the 5-HT re ceptors induces extracellular Na+-dependent Ca2+ efflux from bovine ad renal chromaffin cells in culture, probably by acceleration of Na+/Ca2 + exchange. (C) 1997 Elsevier Science Ireland Ltd.