© 1998 by European Society of Cardiology
Copyright © 1998, European Society of Cardiology
Delayed rectifier potassium current in undiseased human ventricular myocytes
aDepartment of Pharmacology, Albert Szent-Györgyi Medical University, Szeged, Hungary
bDepartment of Cardiac Surgery, Albert Szent-Györgyi Medical University, Szeged, Hungary
* Corresponding author. Tel.: +36-62-311-760, +36-62-455-681; fax: +36-62-321-107; e-mail: papp@phcol.szote.u-szeged.hu
Objective: The purpose of the study was to investigate the properties of the delayed rectifier potassium current (IK) in myocytes isolated from undiseased human left ventricles. Methods: The whole-cell configuration of the patch-clamp technique was applied in 28 left ventricular myocytes from 13 hearts at 35°C. Results: An E-4031 sensitive tail current identified the rapid component of IK (IKr) in the myocytes, but there was no evidence for an E-4031 insensitive slow component of IK (IKs). When nifedipine (5 µM) was used to block the inward calcium current (ICa), IKr activation was fast (
=31.0±7.4 ms, at +30 mV, n=5) and deactivation kinetics were biexponential and relatively slow (1 =600.0±53.9 ms and 2=6792.2±875.7 ms, at –40 mV, n=7). Application of CdCl2 (250 µM) to block ICa altered the voltage dependence of the IKr considerably, slowing its activation (=657.1±109.1 ms, at +30 mV, n=5) and accelerating its deactivation (=104.0±18.5 ms, at –40 mV, n=8). Conclusions: In undiseased human ventricle at 35°C IKr exists having fast activation and slow deactivation kinetics; however, there was no evidence found for an expressed IKs. IKr probably plays an important role in the frequency dependent modulation of repolarization in undiseased human ventricle, and is a target for many Class III antiarrhythmic drugs.
KEYWORDS Cell isolation; K-channel; Human myocytes; Ventricular arrhythmias
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