ATP-INDUCED CHLORIDE CURRENT AND TONIC INCREASE OF INTERNAL CA2+ CONCENTRATION IN VASCULAR ENDOTHELIAL-CELLS

The effect of ATP on membrane currents and the intracellular Ca2+ concentration was investigated in cultured human aortic endothelial cells. ATP (10 mu M) activated the Cl- current within a few minutes following a rapid activation of the K+ current. Fura-2 fluorometry showed that ATP increased [Ca2+](i) with a biphasic time course. The tonic phase was markedly depressed by both an increase in [K+](0) to 140 mM and a decrease in [Cl-](0) to 20 mM. ATP activated not only Ca2+-activated K+ channels but also Cl- channels to regulate the membrane potential related to the tonic phase of the [Ca2+](i) increase.