Potassium Channels in Regulation of Vascular Smooth Muscle Contraction and Growth.

Potassium channels importantly contribute to the regulation of vascular smooth muscle (VSM) contraction and growth. They are the dominant ion conductance of the VSM cell membrane and importantly determine and regulate membrane potential. Membrane potential, in turn, regulates the open-state probability of voltage-gated Ca channels (VGCC), Ca influx through VGCC, intracellular Ca, and VSM contraction. Membrane potential also affects release of Ca from internal stores and the Ca sensitivity of the contractile machinery such that K channels participate in all aspects of regulation of VSM contraction. Potassium channels also regulate proliferation of VSM cells through membrane potential-dependent and membrane potential-independent mechanisms. VSM cells express multiple isoforms of at least five classes of K channels that contribute to the regulation of contraction and cell proliferation (growth). This review will examine the structure, expression, and function of large conductance, Ca-activated K (BK) channels, intermediate-conductance Ca-activated K (K3.1) channels, multiple isoforms of voltage-gated K (K) channels, ATP-sensitive K (K) channels, and inward-rectifier K (K) channels in both contractile and proliferating VSM cells.