Delayed rectifier potassium current in undiseased human ventricular myocytes

Iost, Norbert and Virág, László and Opincariu, Miklós and Szécsi, János and Varró, András and Papp, Julius Gyula (1998) Delayed rectifier potassium current in undiseased human ventricular myocytes. Cardiovascular Research, 40 (3). pp. 508-515. ISSN 0008-6363 (print), 1755-3245 (online)

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Abstract

Objective: The purpose of the study was to investigate the properties of the delayed rectifier potassium current (I-K) 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 degrees C. Results: An E-4031 sensitive tail current identified the rapid component of I-K (I-Kr) in the myocytes, but there was no evidence for an E-4031 insensitive slow component of I-K (I-Kb). When nifedipine (5 mu M) was used to block the inward calcium current (I-Ca), I-Kr activation was fast (tau=31.0+/-7.4 ms, at +30 mV, n=5) and deactivation kinetics were biexponential and relatively slow (tau(1) =600.0+/-53.9 ms and tau(2)-6792.2+/-875.7 ms, at -40 mV, n=7). Application of CdCl2 (250 mu M) to block I-Ca altered the voltage dependence of the I-Kr considerably, slowing its activation (tau=657.1+/-109.1 ms, at +30 mv n=5) and accelerating its deactivation ( tau=104.0+/-18.5 ms, at -40 mV, n=8). Conclusions: In undiseased human ventricle at 35 degrees C I-Kr exists having fast activation and slow deactivation kinetics; however, there was no evidence found for an expressed I-Ks. I-Kr 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.

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