Smooth Muscle Ion Channels and Regulation of Vascular Tone in Resistance Arteries and Arterioles

Abstract

Vascular tone of resistance arteries and arterioles determines peripheral vascular resistance, contributing to the regulation of blood pressure and blood flow to, and within the body’s tissues and organs. Ion channels in the plasma membrane and endoplasmic reticulum of vascular smooth muscle cells (SMCs) in these blood vessels importantly contribute to the regulation of intracellular Ca ²⁺ concentration, the primary determinant of SMC contractile activity and vascular tone. Ion channels provide the main source of activator Ca ²⁺ that determines vascular tone, and strongly contribute to setting and regulating membrane potential, which, in turn, regulates the open-state-probability of voltage gated Ca ²⁺ channels (VGCCs), the primary source of Ca ²⁺ in resistance artery and arteriolar SMCs. Ion channel function is also modulated by vasoconstrictors and vasodilators, contributing to all aspects of the regulation of vascular tone. This review will focus on the physiology of VGCCs, voltage-gated K ⁺ (K _V) channels, large-conductance Ca ²⁺-activated K ⁺ (BK _Ca) channels, strong-inward-rectifier K ⁺ (K _IR) channels, ATP-sensitive K ⁺ (K _ATP) channels, ryanodine receptors (RyRs), inositol 1,4,5-trisphosphate receptors (IP ₃Rs), and a variety of transient receptor potential (TRP) channels that contribute to pressure-induced myogenic tone in resistance arteries and arterioles, the modulation of the function of these ion channels by vasoconstrictors and vasodilators, their role in the functional regulation of tissue blood flow and their dysfunction in diseases such as hypertension, obesity, and diabetes.