The Open Circulation & Vascular Journal

2010, 3 : 95-102
Published online 2010 August 20. DOI: 10.2174/1877382601003010095
Publisher ID: TOCVJ-3-95

Revisit of the Cardiac Inward Rectifier Potassium Current I

Gui-Rong Li and Ming-Qing Dong
L4-59, Laboratory Block, FBM, Li Ka Shing Faculty of Medicine, The University of Hong Kong, 21 Sassoon Road, Pokfulam, Hong Kong SAR China.

ABSTRACT

Inward rectifier potassium currents are present in different types of cells. In the heart, the inward rectifier potassium current IK1 plays a crucial role in maintaining cardiac resting membrane potential and excitability. It is generally believed that the strong inward rectification of cardiac IK1 channels makes it conduct substantial current near the resting potential but carry little or no current at depolarized potentials. However, recent studies in native cardiac myocytes and HEK 293 cell line stably expressing human Kir2.1 gene have demonstrated that a significant transient outward current carried by IK1 channels is activated by the upstroke of action potential. This review will revisit cardiac IK1 channels, especially the previously-ignored transient outward component of IK1 carried by Kir2.1 channels.

Keywords:

Inward rectifier potassium channels, cardiac inward rectifier potassium current, I, Mg, polyamines.