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Am J Physiol Heart Circ Physiol 283: H2495-H2503, 2002. First published August 15, 2002; doi:10.1152/ajpheart.00389.2002
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Vol. 283, Issue 6, H2495-H2503, December 2002

Properties of potassium currents in Purkinje cells of failing human hearts

Wei Han1,3, Liming Zhang1, Gernot Schram1,2, and Stanley Nattel1,2,3

1 Research Center, Montreal Heart Institute, Montreal, Quebec H1T 1C8; 2 Department of Medicine, University of Montreal, Montreal, Quebec H3C 3J7; and 3 Department of Pharmacology and Therapeutics, McGill University, Montreal, Quebec H3G 1Y6, Canada

Cardiac Purkinje fibers play an important role in cardiac arrhythmias, but no information is available about ionic currents in human cardiac Purkinje cells (PCs). PCs and midmyocardial ventricular myocytes (VMs) were isolated from explanted human hearts. K+ currents were evaluated at 37°C with whole cell patch clamp. PCs had clear inward rectifier K+ current (IK1), with a density not significantly different from VMs between -110 and -20 mV. A Cs+-sensitive, time-dependent hyperpolarization-activated current was measurable negative to -60 mV. Transient outward current (Ito) density was smaller, but end pulse sustained current (Isus) was larger, in PCs vs. VMs. Ito recovery was substantially slower in PCs, leading to strong frequency dependence. Unlike VM Ito, which was unaffected by 10 mM tetraethylammonium, Purkinje Ito was strongly inhibited by tetraethylammonium, and Purkinje Ito was 10-fold more sensitive to 4-aminopyridine than VM. PC Isus was also reduced strongly by 10 mM tetraethylammonium. In conclusion, human PCs demonstrate a prominent IK1, a time-dependent hyperpolarization-activated current, and an Ito with pharmacological sensitivity and recovery kinetics different from those in the atrium or ventricle and compatible with a different molecular basis.

ion currents; cardiac Purkinje cells; potassium channel blockers


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