Delayed potassium channels in the heart: Regulatory and molecular properties

Abstract

Potassium channels are ubiquitous membrane spanning proteins that regulate the flow of potassium ions across the membranes of virtually all cell types [1]. Currents through potassium channels are important to maintaining the normal electrical activity in most excitable cells, and are particularly important to the electrical activity of the heart, where the characteristically long-lasting cardiac action potential must adjust to physiologically-induced changes in heart rhythm. Because the plateau phase of the cardiac action potential is maintained by a balance of small ionic currents [2,3]. One class of potassium channels, the so-called delayed rectifier channels, is particularly important to maintenance of the cardiac action potential plateau. Regulation of these channels by neurohormones underlies, in part, the adjustment of cardiac electrical activity that must accompany acceleration of the heart with sympathetic stimulation. The cellular, molecular, and regulatory properties of the cardiac delayed rectifier currents are described in this chapter.