Ion Channels and Vascular Tone

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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 K + channels, 1 to 2 types of voltage-gated Ca 2+ channels, ≥2 types of Cl − channels, store-operated Ca + (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 Ca 2+ , SOC, and SAC channels provides a major source of activator Ca 2+ used by resistance arteries and arterioles. In addition, K + and Cl − channels and the Ca 2+ 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 Ca +2 influx through voltage-gated Ca 2+ channels, but also influences release of Ca 2+ from internal stores and Ca 2+ - sensitivity of the contractile apparatus. By controlling Ca 2+ delivery and membrane potential, ion channels are involved in all aspects of the generation and regulation of vascular tone.