Prolonged Ca 2+ 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 ([Ca 2+ ] i ) induced by ATP‐stimulation in the absence of extracellular Ca 2+ were observed in individual cells. No differences were observed between the exposure and sham‐exposure groups in [Ca 2+ ] i resting level before ATP‐stimulation, or in the [Ca 2+ ] i peak levels induced by stimulation. However, the duration of the initial transients in [Ca 2+ ] 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 [Ca 2+ ] i in both the exposure and sham‐exposure groups. The ATP‐receptor P2Y appeared to play an important role in the increase of [Ca 2+ ] 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.