Single-Cell Imaging of the Ca²⁺ Influx into Bovine Endothelial Cells Occurring in Response to an Alternating Electric Stimulus

Abstract

The electric control of cellular functions via Ca²⁺ was formerly suggested. From this viewpoint, the involvement of a Ca²⁺ channel was studied using bovine fetal arterial endothelial (BFAE) cells in which P2X4, an ATP-operated and fluid shear stress sensitive Ca²⁺ channel, exists predominantly. An electric stimulus (sine wave, 10 Hz, 10 V_PP, 30 s) caused a marked influx of Ca²⁺ into BFAE cells from an extracellular solution. The magnitude of the [Ca²⁺]_i change increased with a decrease in the frequency in the range from 100 Hz to 5 Hz. Regarding the pathway of this Ca²⁺ influx, single-cell imaging and an ATP depletion experiment strongly suggested the involvement of a pathway different from P2X4. This pathway was thought to be a non-specific one, because typical Ca²⁺ channel blockers, such as verapamil, Gd³⁺, and Co²⁺, could not inhibit the Ca²⁺ influx.