title: Background potassium current active during the plateau of the action potential in guinea pig ventricular myocytes.
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+. Ba(2+)-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.
authors.affiliation: Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205.
authors.forename: P H
authors.initials: PH
authors.lastname: Backx
authors.forename: E
authors.initials: E
authors.lastname: Marban
mesh_terms: D000200:Action Potentials; D000818:Animals; D004553:Electric Conductivity; D005544:Forecasting; D006168:Guinea Pigs; D006321:Heart / Q000502:physiology*; D006352:Heart Ventricles; D009206:Myocardium / Q000166:cytology; D011188:Potassium / Q000502:physiology*; D015221:Potassium Channels / Q000502:physiology
chemical_list: D015221:Potassium Channels; D011188:Potassium