Ionic channels in vascular endothelial cells
Vascular endothelial cells respond to neurohumoral and physical stimuli to secrete mediators that modulate blood pressure and tissue perfusion. The initial response of endothelial cells usually involves an elevation of cytoplasmic Ca2+, due to Ca2+ release from intracellular stores and Ca2+ influx from the extracellular space, and subsequent activation of Ca2+-dependent enzymes. The activation of cell-surface receptors by vasoactive substances stimulates Ca2+ entry via plasmalemmal ion channels and the rate of Ca2+ influx depends on the electrochemical gradient, which is modulated by the resting membrane potential. Membrane potential is regulated by a variety of voltage- and ligand-gated potassium channels that may function to repolarize the stimulated endothelial cell. This review focuses on ionic channels involved in receptor-mediated Ca2+ entry and control of the membrane potential that are critical to stimulus-secretion coupling in vascular endothelium.