29 - Ion Channels in Nonexcitable Cells

Abstract

This chapter discusses ion channels in nonexcitable cells and focuses on a selection of ion channels in epithelial cells. The chapter focuses on those that function as secreting or electrolyte and fluid-reabsorbing cells, endothelium, tumor cells, and endocrine cells. Ion channels in nonexcitable cells have been less extensively studied at the functional level than the channels involved in fast signaling processes via voltage-operated ion channels. It is mentioned that Na+ reabsorption is a well-understood mechanism for vectorial transport that occurs in renal cells, intestine, colon, frog skin, and several other cell types. The chapter discusses several types of ion channels in nonexcitable cells— amiloride-sensitive Na+ channels, K+ channels, nonselective cation channels, mechanosensitive cation channels, Ca2+-entry and store-operated Ca2+ channels, and Cl– channels. These channels appear to be involved in the control of biologically important functions. The chapter also addresses the functional role of the ion channels in volume regulation and fine-tuning of the driving force for Ca2+ influx, and their involvement in vectorial transport, which is intimately linked to their localization at strategic sites of the cells and usually requires the cooperation of several channel types. In the final part of the chapter some physiological functions of ion channels coupled to other transporting proteins are discussed.