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Related Experiment Videos

Characterization and functional consequences of delayed rectifier current transient in ventricular repolarization.

G A Gintant1

  • 1Cardiology Division, Department of Internal Medicine, and Department of Pharmacology, Wayne State University School of Medicine, Detroit, Michigan 48201, USA. gary.gintant@abbott.com

American Journal of Physiology. Heart and Circulatory Physiology
|March 10, 2000
PubMed
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The rapidly activating delayed rectifier current (I(Kr)) provides a crucial outward transient during ventricular repolarization, aiding in action potential termination. Its heterogeneous voltage dependence offers a new way to modulate this vital cardiac current.

Area of Science:

  • Cardiology
  • Electrophysiology
  • Molecular Biology

Background:

  • The role of the rapidly activating delayed rectifier current (I(Kr)) during cardiac repolarization, particularly its recovery from inactivation, remains unclear.
  • Understanding I(Kr) dynamics is essential for comprehending cardiac action potential generation and stability.

Purpose of the Study:

  • To characterize the behavior of I(Kr) during ventricular repolarization.
  • To compare the properties of I(Kr) with the inward rectifier current (I(K1)) during repolarization.

Main Methods:

  • Utilized voltage-clamp techniques with waveforms simulating cardiac action potentials.
  • Applied these methods to canine ventricular, atrial, and Purkinje myocytes.

Main Results:

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  • In ventricular myocytes, I(Kr) showed a transient increase during repolarizing ramps, peaking after 150ms depolarizations.
  • This I(Kr) transient was identified as a key factor in terminating the action potential plateau.
  • While peak I(Kr) density was uniform, its voltage dependence was heterogeneous, unlike the narrower voltage range of I(K1).

Conclusions:

  • Rapidly activating I(Kr) generates a delayed, voltage-dependent outward transient during ventricular repolarization, indicative of fast recovery from inactivation.
  • The observed heterogeneity in I(Kr) voltage dependence presents a novel mechanism for regulating its contribution to cardiac repolarization.