Physiological Roles and Properties of Ion Channels in Corporal Smooth Muscle

Lee, Sung Won

Abstract

Decreased penile vascular resistance induced by corporal smooth muscle relaxation is the most important step in penile erection. The heightened tone of the corporal smooth muscles is considered a major cause in impotence. Modulation of corporal smooth muscle tone is a complex process requiring the integration of a host of intracellular events and extracellular signals. In intracellular events of corporal smooth muscle cell, the potassium channels and calcium channels play a major role. Functionally, potassium channels are important regulators of smooth muscle membrane potential in response to depolarizing stimuli and they counteract calcium channels. Potassium channels have been shown to play a fundamental role in both the physiologic and pathophysiologic regulation of smooth muscle tone in diverse tissues. Among the several subtypes of potassium channels, the calcium-sensitive potassium channel subtypes (KCa channel) and ATP-dependent potassium channel subtypes (KATP channel) are thought to be the most physiologically relevant in human corporal smooth muscle. With respect to intercellular communication, gap junction channels (connexin 43) are important in corporal smooth muscle cells. Thanks to gap junction channels, the signal of one cell can be spread to adjacent cells and coordination of corporal tissue response is possible. This report reviews the known details concerning junctional and nonjunctional ion channels in corporal smooth muscle and suggest the possibility of gene therapy targeting ion channels for erectile dysfunction