BACKGROUND POTASSIUM CURRENT ACTIVE DURING THE PLATEAU OF THE ACTION-POTENTIAL IN GUINEA-PIG VENTRICULAR MYOCYTES

被引:89
作者
BACKX, PH [1 ]
MARBAN, E [1 ]
机构
[1] JOHNS HOPKINS UNIV,SCH MED,DEPT MED,DIV CARDIOL,720 N RUTLAND AVE,BALTIMORE,MD 21205
关键词
PATCH CLAMP; POTASSIUM CHANNELS; ACTION POTENTIAL DURATION; ACTION POTENTIAL REPOLARIZATION; CLASS-III ANTIARRHYTHMIC AGENTS;
D O I
10.1161/01.RES.72.4.890
中图分类号
R5 [内科学];
学科分类号
1002 ; 100201 ;
摘要
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+ (I(K,p)) activates within 5 msec at positive potentials, does not inactivate, and deactivates very rapidly on repolarization. I(K,p) is insensitive to Cl- channel blockers, internal or external [Cl-], dihydropyridines, and sulfonylureas. In contrast, the delayed rectifier K+ current (I(K)) 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 (I(K1)). These and other features suggest that I(K,p) is generated by K+ channels that are distinct from I(KI) or I(K). The kinetics and voltage dependence of I(K,p) render it capable of modulating both the height and duration of the cardiac action potential.
引用
收藏
页码:890 / 900
页数:11
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