Potassium channels in the heart Cellular, molecular, and clinical implications.

Potassium channels are membrane-spanning proteins that regulate the flow of potassium ions across the cell membrane. Because of the electrochemical gradient for potassium ions in almost all cell types, opening of potassium channels causes an efflux, of potassium ions that in turn tends to make the interior of the cell more negative than its extracellular environment. During the last 5 years, there has been a rapidly expanding base of information about the structure, function, and pharmacologic regulation of this type of ion channel, and the integration of this information is particularly important to cardiac electrophysiology, where control of potassium efflux is relevant to the design of class-III antiarrhythmic agents and to the understanding of genetic basis of certain disorders. This brief review highlights the functional importance of various potassium channels to the electrophysiology of the heart and presents relevant molecular information about the structures that constitute this important family of integral membrane proteins.