Related Experiment Video

Updated: Oct 5, 2026

Contractions of Human-iPSC-derived Cardiomyocyte Syncytia Measured with a Ca-sensitive Fluorescent Dye in Temperature-controlled 384-well Plates
07:42

Contractions of Human-iPSC-derived Cardiomyocyte Syncytia Measured with a Ca-sensitive Fluorescent Dye in Temperature-controlled 384-well Plates

Published on: October 18, 2018

Inhibition of Na+/Ca2+ exchange by KB-R7943: transport mode selectivity and antiarrhythmic consequences

C L Elias1, A Lukas, S Shurraw

  • 1Institute of Cardiovascular Sciences, St. Boniface General Hospital Research Centre, University of Manitoba, Winnipeg, Manitoba, Canada.

American Journal of Physiology. Heart and Circulatory Physiology
|August 22, 2001
PubMed

Insights

The novel inhibitor KB-R7943 effectively suppresses cardiac arrhythmias by blocking calcium entry through the Na+/Ca2+ exchanger. This study confirms its antiarrhythmic properties in an ischemia-reperfusion model, highlighting the role of calcium influx in cardiac injury.

Area of Science:

  • Cardiovascular Physiology
  • Molecular Pharmacology
  • Cardiac Electrophysiology

Background:

  • The Na+/Ca2+ exchanger (NCX) is crucial for regulating intracellular calcium in cardiomyocytes, influencing cardiac function.
  • KB-R7943 is a novel inhibitor proposed to selectively block the reverse mode (calcium entry) of NCX, but its precise inhibitory mechanisms and efficacy are debated.

Purpose of the Study:

  • To rigorously evaluate the inhibitory effects of KB-R7943 on cardiac Na+/Ca2+ exchange currents.
  • To elucidate the mechanism by which KB-R7943 inhibits NCX activity.
  • To assess the antiarrhythmic efficacy of KB-R7943 in a preclinical model of cardiac ischemia-reperfusion injury.

Main Methods:

  • Utilized the giant excised patch-clamp technique on Xenopus laevis oocytes expressing the cardiac NCX1.1.
  • Investigated outward, inward, and combined NCX currents under various conditions.
  • Employed Langendorff-perfused rabbit hearts to evaluate antiarrhythmic effects during global ischemia-reperfusion, using ECG and left ventricular pressure measurements.

Main Results:

  • KB-R7943 demonstrated preferential inhibition of outward (reverse mode) Na+/Ca2+ exchange currents.
  • The inhibition mechanism involves direct interaction with the exchanger's transport machinery, not competitive ion binding.
  • Pre-treatment with 3 microM KB-R7943 significantly suppressed ischemia-reperfusion-induced ventricular arrhythmias (tachycardia and fibrillation) in rabbit hearts.

Conclusions:

  • KB-R7943 directly inhibits the reverse mode of the Na+/Ca2+ exchanger.
  • Calcium influx via reverse NCX activity plays a significant role in ischemia-reperfusion-induced cardiac arrhythmias.
  • KB-R7943 exhibits potent antiarrhythmic effects, supporting its therapeutic potential for managing cardiac injury during ischemia-reperfusion events.

More Related Videos

Voltage-Dependent Potassium Current Recording on H9c2 Cardiomyocytes via the Whole-Cell Patch-Clamp Technique08:11

Voltage-Dependent Potassium Current Recording on H9c2 Cardiomyocytes via the Whole-Cell Patch-Clamp Technique

Published on: November 11, 2022

Isolation and Kv Channel Recordings in Murine Atrial and Ventricular Cardiomyocytes11:33

Isolation and Kv Channel Recordings in Murine Atrial and Ventricular Cardiomyocytes

Published on: March 12, 2013

Related Concept Videos

Antiarrhythmic Drugs: Class III Agents as Potassium Channel Blockers01:12

Antiarrhythmic Drugs: Class III Agents as Potassium Channel Blockers

Class III antiarrhythmic drugs are a group of medications that can prolong action potentials in the heart. They achieve this by blocking potassium channels or enhancing inward currents from sodium channels. However, these drugs have a unique property of "reverse use-dependence," which is most pronounced at slower heart rates and can lead to torsades de pointes—a specific type of arrhythmia. However, it is essential to note that excessive QT interval prolongation—a measure of the heart's...
Antiarrhythmic Drugs: Class I Agents as Sodium Channel Blockers01:22

Antiarrhythmic Drugs: Class I Agents as Sodium Channel Blockers

Class I antiarrhythmic drugs are used to treat various types of arrhythmias or irregular heart rhythms. These drugs block the sodium (Na+) channels in the cardiac cells, thereby affecting the movement of electrical impulses across the heart. Class I antiarrhythmic drugs are divided into three subgroups: Class IA, Class IB, and Class IC, each with distinct mechanisms of action and effects on the heart.
Class 1A Antiarrhythmic Drugs: These drugs work by moderately blocking sodium channels,...
Antiarrhythmic Drugs: Class IV Agents as Calcium Channel Blockers01:20

Antiarrhythmic Drugs: Class IV Agents as Calcium Channel Blockers

Class IV antiarrhythmic drugs, such as verapamil and diltiazem, block calcium channels. They primarily affect the heart, slowing the conduction in calcium-dependent tissues like the SA and AV nodes. These drugs manage reentrant supraventricular tachycardia (SVT) and reduce ventricular rate in atrial flutter/fibrillation.
Verapamil, a calcium channel blocker, inhibits calcium movement across myocardial cell membranes and vascular smooth muscle. This results in the dilation of coronary and...
Antiarrhythmic Drugs: Class II Agents as β-Adrenergic Blockers01:24

Antiarrhythmic Drugs: Class II Agents as β-Adrenergic Blockers

Adrenergic stimulation generally impacts cardiac rate and rhythm. Specifically, stimulation of the β-adrenoceptors triggers an increase in intracellular calcium ion influx and pacemaker currents, which may cause arrhythmias. Catecholamines like adrenaline also demonstrate β2-adrenoceptor-mediated hypokalemia, impacting cardiac action potential and disrupting the normal cardiac rhythm. Class II antiarrhythmic drugs are β-adrenoceptor antagonists or β-blockers, which indirectly block calcium...
Antiepileptic Drugs: Potassium Channel Activators01:20

Antiepileptic Drugs: Potassium Channel Activators

Ezocgabine or retigabine, an antiepileptic drug of remarkable efficacy, has revolutionized the management of seizures. It is a potassium channel activator, explicitly targeting the family of Q subtype potassium channels. It enhances the transmembrane potassium currents, regulating neuronal excitability. This action stabilizes the resting membrane potential, a pivotal factor in mitigating the hyperexcitability that characterizes epilepsy.
Ezogabine has gained approval as an adjunctive treatment...
Antihypertensive Drugs: Action of Calcium Channel Blockers01:18

Antihypertensive Drugs: Action of Calcium Channel Blockers

Calcium ions are essential to contract smooth muscle cells in blood vessels. They enter these cells through voltage-dependent calcium channels, specifically L-type calcium channels in the cell membrane. These L-type calcium channels are integral to the excitation-contraction coupling process in smooth muscle. When a stimulus is received by smooth muscle cells, their membrane depolarizes. This alteration in membrane potential instigates the opening of L-type calcium channels. As a result,...