Voltage dependent block of the cardiac potassium channel hERG by calcium and hydrogen

Abstract

Reduction of the current carried by the cardiac potassium channel HERG can lead to Long QT syndrome, an arrhythmia characterized by a rapid heart rate and reduced cardiac output, which can, in certain situations, be fatal. The effects of various extracellular electrolytes on the biophysical properties of the HERG channel have been studied in some detail. In particular, increases in extracellular divalent ions such as Ca2+, Mg2+, and Zn2+ as well as increases in extracellular H+ have been shown to slow channel activation, increase channel deactivation, and shift the G-V curve to more positive voltages.