Background potassium current active during the plateau of the action potential in Guinea pig ventricular myocytes

Peter H. Backx, Eduardo Marban

Research output: Contribution to journalArticlepeer-review

Abstract

Background outward K+ currents in guinea pig ventricular myocytes were characterized over a broad range of membrane potentials, including those corresponding to the plateau of the action potential. The background current that is blocked by 1 mM Ba2+ (IK,p) activates within 5 msec at positive potentials, does not inactivate, and deactivates very rapidly on repolarization. IK,p is insensitive to Cl- channel blockers, internal or external [Cl-], dihydropyridines, and sulfonylureas. In contrast, the delayed rectifier K+ current (IK) was not completely blocked even by 30 mM Ba2+. Ba2+-sensitive current density increased progressively from 0.16±0.04 pA/pF at 0 mV to 0.52±0.21 pA/pF at +80 mV (n=13, mean±SEM). The background current remains present when [K+]o is reduced to 0 mM, which suppresses the inward rectifier K+ current (IK1). These and other features suggest that IK,p is generated by K+ channels that are distinct from IK1 or IK. The kinetics and voltage dependence of IK,p render it capable of modulating both the height and duration of the cardiac action potential.

Original languageEnglish (US)
Pages (from-to)890-900
Number of pages11
JournalCirculation Research
Volume72
Issue number4
StatePublished - Apr 1993

Keywords

  • Action potential duration
  • Action potential repolarization
  • Class III antiarrhythmic agents
  • Patch clamp
  • Potassium channels

ASJC Scopus subject areas

  • Physiology
  • Cardiology and Cardiovascular Medicine

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