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Updated: Mar 23, 2026
Voltage-Dependent Potassium Current Recording on H9c2 Cardiomyocytes via the Whole-Cell Patch-Clamp Technique
Published on: November 11, 2022
A dual potassium channel activator improves repolarization reserve and normalizes ventricular action potentials
Kirstine Calloe1, José M Di Diego2, Rie Schultz Hansen3
1Danish National Research Foundation Center for Cardiac Arrhythmias, Department of Veterinary Clinical and Animal Science, University of Copenhagen, DK-1870 Frederiksberg C, Denmark.
Background:
A loss of repolarization reserve due to downregulation of K(+) currents has been observed in cultured ventricular myocytes. A similar reduction of K(+) currents is well documented under numerous pathophysiological conditions. We examined the extent of K(+) current downregulation in cultured canine cardiac myocytes and determined whether a dual K(+) current activator can normalize K(+) currents and restore action potential (AP) configuration.
Methods And Results:
Ventricular myocytes were isolated and cultured for up to 48 h. Current and voltage clamp recordings were made using patch electrodes. Application of NS3623 to coronary-perfused left ventricular wedges resulted in increased phase 1 magnitude, epicardial AP notch and J wave amplitude. Patch clamp measurements of IKr and Ito revealed an increase in the magnitude of both currents. Culturing of Mid ventricular cells resulted in a significant decrease in Ito and IKr density. NS3623 increased Ito from 16.4 ± 2.23 to 31.8 ± 4.5 pA/pF, and IKr from 0.28 ± 0.06 to 0.47 ± 0.09 pA/pF after 2 days in culture. AP recordings from 2 day cultured cells exhibited a reduced phase 1 repolarization, AP prolongation, and early afterdepolarizations (EADs). NS3623 restored the AP notch and was able to suppress EADs.
Conclusions:
NS3623 is a dual Ito and IKr activator. Application of this compound to cells with a reduced repolarization reserve resulted in an increase in these currents and a shortening of AP duration, increase in phase 1 repolarization and suppression of EADs. Our results suggest a potential benefit of K(+) current activators under conditions of reduced repolarization reserve including heart failure.
Insights
A novel dual potassium current activator, NS3623, normalizes reduced repolarization reserve in cultured cardiac cells. This compound restores action potential configuration and suppresses early afterdepolarizations, suggesting therapeutic potential for heart failure.
Area of Science:
- Cardiovascular Physiology
- Electrophysiology
- Pharmacology
Background:
- Downregulation of potassium (K+) currents reduces repolarization reserve in ventricular myocytes.
- This reduction is observed in cultured cells and pathophysiological conditions like heart failure.
Purpose of the Study:
- To investigate K+ current downregulation in cultured canine cardiac myocytes.
- To determine if a dual K+ current activator, NS3623, can normalize these currents and restore action potential (AP) configuration.
Main Methods:
- Isolated canine ventricular myocytes were cultured for up to 48 hours.
- Patch clamp recordings measured Ito (transient outward K+ current) and IKr (rapid delayed rectifier K+ current).
- Action potentials were recorded, and the effect of NS3623 on AP configuration and afterdepolarizations was assessed.
Main Results:
- Culturing led to significant decreases in Ito and IKr density.
- NS3623 treatment increased both Ito and IKr magnitudes in cultured cells.
- NS3623 restored the AP notch, shortened AP duration, and suppressed early afterdepolarizations (EADs).
Conclusions:
- NS3623 acts as a dual activator of Ito and IKr.
- It effectively increases K+ currents, shortens AP duration, and suppresses EADs in cells with reduced repolarization reserve.
- K+ current activators like NS3623 may offer a therapeutic benefit in conditions characterized by reduced repolarization reserve, such as heart failure.
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