Chapter 84 – Potassium, Sodium, and Chloride Channels in Smooth Muscle Cells

The opening of potassium (K + ) channels mediates hyperpolarization and vasodilation of small arteries and arterioles, thereby modulating blood flow to critical organs and regulating blood pressure. Many gene families of K + channels with unique properties act in concert to determine the level of vascular tone, and also to mediate specialized dilator responses to endothelial factors, metabolic stimuli or mechanical stress. This chapter will emphasize several types of K + channels in vascular smooth muscle cells (SMCs) that provide a critical dilator influence in different vascular beds. Subsequently, we will focus on two of the lesser studied ion channels in SMCs, the voltage-gated Na + channels and the Cl - channel families, which may participate in the regulation of vascular SMC excitability. Our discussion of each ion channel also will briefly broaden to include the non-vascular SMCs of the respiratory and gastrointestinal tracts. Ultimately, the ion channel families expressed in SMCs will collectively modulate cell excitability so that SMC-containing organs can optimally perform their physiological functions.