Properties of Epithelial Potassium Channels

This chapter reviews some of the properties of potassium (K) channels in epithelial cells. The chapter focuses on one general feature of K channels, namely, diversity. This diversity of channel types creates the expectation that different cell functions (or responses) that involve alterations in cell membrane K permeability may be subserved by different populations of K channels that are activated or inactivated under a variety of circumstances. K-related cell functions or responses may be served by distinct populations of K channels, which can be differentiated according to their physical properties. The chapter discusses the general properties of ion channels and emphasizes the experimental strategies that can be employed to differentiate one type of K channel from another. The application of single-channel techniques offers the opportunity to explore the diversity of channel types which may be involved in epithelial cell function. In view of the diversity of K channels, it is necessary to develop experimental systems where it is possible to keep track of different K channels at various levels of organization—from the cell layer to the isolated membrane patch—to permit the ion translocation process at the single-channel level to be related back to the transport function of the epithelium.