Ion channels and vascular tone

Abstract—Ion channels in the plasma membrane of vascular muscle cells that form the walls of resistance arteries and arterioles play a central role in the regulation of vascular tone. Current evidence indicates that vascular smooth muscle cells express at least 4 different types of K1 channels, 1 to 2 types of voltage-gated Ca21 channels, $2 types of Cl2 channels, store-operated Ca1 (SOC) channels, and stretch-activated cation (SAC) channels in their plasma membranes, all of which may be involved in the regulation of vascular tone. Calcium influx through voltage-gated Ca21, SOC, and SAC channels provides a major source of activator Ca21 used by resistance arteries and arterioles. In addition, K1 and Cl2 channels and the Ca21 channels mentioned previously all are involved in the determination of the membrane potential of these cells. Membrane potential is a key variable that not only regulates Ca12 influx through voltage-gated Ca21 channels, but also influences release of Ca21 from internal stores and Ca21- sensitivity of the contractile apparatus. By controlling Ca21 delivery and membrane potential, ion channels are involved in all aspects of the generation and regulation of vascular tone. (Hypertension. 2000;35[part 2]:173-178.) Key Words: muscle, smooth, vascular n arterioles n potassium channels n calcium channels n vascular resistance n vasoconstriction Vascular tone, the contractile activity of vascular smoothmuscle cells in the walls of small arteries and arterioles, is the major determinant of the resistance to blood flo