Calcium ionophores inhibit the release of endothelin-1 from endothelial cells

We have determined the effect on endothelin-1 (ET-1) release of stimulating cultured endothelial cells for 24 h with Ca2+ ionophores. The results obtained using cultured bovine aortic endothelial cells (BAECs) were compared with those using the human endothelial cell line (EA.hy 926). ET-1 was measured using a radioimmunoassay specific for the C-terminal ET[16-21] sequence. Ionomycin (1 microM) lessened ET-1 accumulation over 24 h in the conditioned medium from BAECs (-37%) and EA.hy 926 (-25%). A23187 was a more potent inhibitor of ET-1 release. With BAECs, ET-1 release was inhibited by 28% and 77% at 0.1 microM and 1 microM A23187, respectively. The corresponding decreases for EA.hy 926 were 20% and 98%. A23187 at 0.2 microM lowered ET-1 concentrations in the medium after 24 h by 44% and 24% for BAECs and EA.hy 926, respectively. Neither NG-monomethyl-L-arginine (0.2 mM) nor indomethacin (10 microM), either alone or in combination, affected the inhibition by A23187. Thus, this inhibitory effect is not dependent on the stimulation of nitric oxide or prostacyclin synthesis. Additional factors in endothelial cells, activated by elevated Ca2+ levels, may be important in exerting an inhibitory influence on ET-1 formation.