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(Circulation. 1996;93:656-659.)
© 1996 American Heart Association, Inc.

Articles

ATP-Dependent Potassium Channel in Rat Cardiomyocytes Is Blocked by Lidocaine

Possible Impact on the Antiarrhythmic Action of Lidocaine

A. Olschewski, MD; M.E. Bräu, MD; H. Olschewski, MD; G. Hempelmann, MD; W. Vogel, PhD

From the Departments of Anesthesiology and Intensive Care Medicine (A.O., M.E.B., G.H.), Physiology (A.O., W.V.), and Internal Medicine (H.O.), Justus-Liebig-University, Giessen, Germany.

Correspondence to Dr. A. Olschewski, Physiologisches Institut, Justus-Liebig-University, Aulweg 129, D-35392 Giessen, Germany.

Background During myocardial ischemia, lidocaine has favorable antiarrhythmic properties. Malignant arrhythmias result from heterogeneity between ischemic and nonischemic regions in extracellular potassium concentration and action potential duration. These effects have been attributed to the activation of ATP-dependent potassium (K_ATP) channels. In this study, we investigated the action of lidocaine on the K_ATP channels to test the possible link between the antiarrhythmic properties of lidocaine and its action on the K_ATP channel.

Methods and Results The patch-clamp technique was employed on enzymatic dissociated cardiomyocytes of adult rats. Lidocaine was applied to the outer side of excised membrane patches by means of a multibarrel perfusion system. Lidocaine reversibly blocked the mean current of the K_ATP channels in a concentration-dependent manner (IC₅₀=43±4.7 µmol/L, E=0 mV, n=6), while the amplitude of the single-channel current remained unchanged. The half-maximum blocking concentration corresponds to the therapeutic range for the antiarrhythmic application of a lidocaine bolus in humans.

Conclusions The open probability but not the conductance of the K_ATP channel in the membrane of rat cardiomyocytes is blocked by lidocaine. This action may explain, in part, the favorable antiarrhythmic properties of lidocaine during acute myocardial ischemia.

Key Words: antiarrhythmia agents • electrophysiology • ischemia • myocardial infarction • potassium channel

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