Basics of Microcirculation

**3**

**Chapter 1**

**Abstract**

microcirculation

**1. Introduction**

rectifier (Kir) K+

Ion Channels and Their Regulation

Vascular smooth muscle excitability is exquisitely regulated by different ion channels that control membrane potential (Em) and the magnitude of intracellular calcium inside the cell to induce muscle relaxation or contraction, which significantly influences the microcirculation. Among them, various members of the K<sup>+</sup> channel family, voltage-gated Ca2+ channels, and transient receptor potential (TRP) channels are fundamental for control of vascular smooth muscle excitability. These ion channels exist in complex with numerous signaling molecules and binding partners that modulate their function and, in doing so, impact vascular smooth muscle excitability. In this book chapter, we will review our current understanding of some of these ion channels and binding partners in vascular smooth muscle and discuss how their regulation is critical for proper control of (micro)vascular function.

**Keywords:** ion channels, signal transduction, vascular tone, vascular smooth muscle,

Vascular smooth muscle cells wrapping around small resistance arteries and arterioles are crucial for vascular reactivity [1]. These cells enable dynamic, moment-to-moment control of vessel diameter and pressure-induced contraction (e.g., vascular tone). This control is central to autoregulation of resistance vessels, maintenance of vessel caliber independently of changes in blood pressure, and

To regulate arterial diameter, vascular smooth muscle receives and integrates many inputs, including changes in intraluminal pressure, vasoconstrictor and vasodilatory signals from endothelial cells lining the inner arterial wall, and nerve terminals innervating the vessels [2]. These inputs regulate vascular smooth muscle excitability, at least in part, by modulating the activity of a number of ion channels to control membrane potential (Em) and the magnitude of intracellular Ca2+ concentration ([Ca2+]i) [1]. Among the many ion channels, transient receptor potential (TRP) channels, voltage-gated (KV), Ca2+-activated (BKCa) and inward

mental in transducing mechanical force, establishing Em, and regulating [Ca2+]i [1]. Mechanisms for the regulation of vascular smooth muscle ion channels, including those mentioned above, involve agonist-independent and agonist-dependent activation of Gq and/or Gs protein-coupled receptors (GxPCR) [3]. The optimal

channels, and voltage-gated Ca2+ channels (VGCC) are funda-

proper perfusion to meet the metabolic demands of a given tissue.

in Vascular Smooth Muscle

*and Madeline Nieves-Cintrón*

*Arsalan U. Syed, Thanhmai Le, Manuel F. Navedo* 
