Kir2.1

Inwardly rectifying K+ channel 2 family (Kir2.1, 2.2, 2.3) underlies the Ik1 current in the heart. Among the subunits of Kir2 family, Kir2.1 channels are the main contributor, accounting for 70-90% of the Ik1. Ik1 sets the resting membrane potential in atrial and ventricular cells. IK1 also makes a significant contribution to phase 3 repolarization stage of the cardiac action potential. Loss of function mutation of Kir2.1 (LQT syndrome 7, or Andersen-Tawil syndrome) down regulates Ik1, which leads to prolongation of action potential duration and in severe cases, recurrent episodes of polymorphic ventricular tachycardias. Drug inhibition or potentiating of Ik1 could induces long QT or short QT and subsequent severe cardiac arrhythmias.

Pharmacore Labs currently provide manual patch clamp assay using acutely isolated animal cardiomyocytes to test drug's inhibition or potentiating effect on Ik1 mainly contributed by Kir2.1 channels. This assay is one of the recommended preclinical cardiac safety assays in the pharmaceutical industry.

In vitro electrophysiology IK1 assay in primary cardiomyocytes:

Note: 1) Positive control: 20 μM BaCl2 is used in the assay to ensure cell quality and normal response of Ik1 channels.

Ik1 current in guinea pig cardiomyocyte and blockade effect of 20 μM BaCl2