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 language | English (US) |
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Pages (from-to) | 890-900 |
Number of pages | 11 |
Journal | Circulation Research |
Volume | 72 |
Issue number | 4 |
State | Published - 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