ION CHANNELS IN VASCULAR ENDOTHELIUM

The functional impact of ion channels in vascular endothelial cells (ECs) is still a matter of controversy. This review describes different types of ion channels in ECs and their role in electrogenesis, Ca²⁺ signaling, vessel permeability, cell-cell communication, mechano-sensor functions, and pH and volume regulation. One major function of ion channels in ECs is the control of Ca²⁺ influx either by a direct modulation of the Ca²⁺ influx pathway or by indirect modulation of K⁺ and Cl⁻ channels, thereby clamping the membrane at a sufficiently negative potential to provide the necessary driving force for a sustained Ca²⁺ influx. We discuss various mechanisms of Ca²⁺ influx stimulation: those that activate nonselective, Ca²⁺-permeable cation channels or those that activate Ca²⁺-selective channels, exclusively or partially operated by the filling state of intracellular Ca²⁺ stores. We also describe the role of various Ca²⁺- and shear stress-activated K⁺ channels and different types of Cl⁻ channels for the regulation of the membrane potential.