22 - Ion Channels in Nonexcitable Cells

Abstract

Publisher Summary This chapter describes the ion channels that are involved in the control of biologically important functions. A Na+-selective, amiloride-blockable ion channel regulates Na+ absorption and Na+ secretion in epithelial cells. Ca2+-activated nonselective cation channels provide in many non-excitable cells a pathway for the entry of Ca2+ and cause depolarization. Other nonselective cation channels are activated by extracellular agonists via G-protein- dependent mechanisms, are directly activated by extracellular messengers, such as adenosine triphosphate (ATP), or are directly gated by intracellular cyclic nucleotides. K+ channels are widely distributed in non-excitable cells. In many cells, they are activated by intracellular Ca2+ and modulate cellular signals, which are caused by various agonists. The chapter also explains that non-excitable cells act as mechanosensors. Various mechanically activated ion channels are involved in volume regulation of many cells. Moreover, non-excitable cells also express voltage-operated ion channels but do not fire action potentials.