Prolonged Ca2+ transients in ATP-stimulated endothelial cells exposed to 50 Hz electric fields

Human umbilical vein endothelial cells were exposed to sinusoidal electric fields of 0.3 or 30 kV/m, 50 Hz, for 24 h. Changes in intracellular calcium concentration ([Ca2+]i) induced by ATP-stimulation in the absence of extracellular Ca2+ were observed in individual cells. No differences were observed between the exposure and sham-exposure groups in [Ca2+]i resting level before ATP-stimulation, or in the [Ca2+]i peak levels induced by stimulation. However, the duration of the initial transients in [Ca2+]i following an ATP stimulus was significantly prolonged by exposure to a 30 kV/m field. The inositol trisphosphate receptor inhibitor, xestospongin C, inhibited the ATP-induced elevation in [Ca2+]i in both the exposure and sham-exposure groups. The ATP-receptor P2Y appeared to play an important role in the increase of [Ca2+]i. The present results suggest that an extremely low-frequency electric field affects the function of vascular endothelial cells by a mechanism involving activation of P2Y.