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Circ Arrhythm Electrophysiol. 2012 Dec;5(6):1184-92. doi: 10.1161/CIRCEP.112.975425. Epub 2012 Nov 16.

Activation of glibenclamide-sensitive ATP-sensitive K+ channels during β-adrenergically induced metabolic stress produces a substrate for atrial tachyarrhythmia.

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1
Department of Pharmacology and Toxicology, College of Veterinary Medicine, Chonbuk National University, Jeonju-City, South Korea.

Abstract

BACKGROUND:

Cardiac ATP-sensitive K(+) channels have been suggested to contribute to the adaptive physiological response to metabolic challenge after β-adrenoceptor stimulation. However, an increased atrial K(+)-conductance might be expected to be proarrhythmic. We investigated the effect of ATP-sensitive K(+) channel blockade on the electrophysiological responses to β-adrenoceptor-induced metabolic challenge in intact atria.

METHODS AND RESULTS:

Atrial electrograms were recorded from the left atrial epicardial surface of Langendorff-perfused rat hearts using a 5×5 electrode array. Atrial effective refractory period and conduction velocity were measured using an S(1)-S(2) protocol. The proportion of hearts in which atrial tachyarrhythmia was produced by burst-pacing was used as an index of atrial tachyarrhythmia-inducibility. Atrial nucleotide concentrations were measured by high performance liquid chromatography. Perfusion with ≥10(-9) mol/L of the β-adrenoceptor agonist, isoproterenol (ISO), resulted in a concentration-dependent reduction of atrial effective refractory period and conduction velocity. The ISO-induced changes produced a proarrhythmic substrate such that atrial tachyarrhythmia could be induced by burst-pacing. Atrial [ATP] was significantly reduced by ISO (10(-6) mol/L). Perfusion with either of the ATP-sensitive K(+) channel blockers, glibenclamide (10(-5) mol/L) or tolbutamide (10(-3) mol/L), in the absence of ISO had no effect on basal atrial electrophysiology. On the other hand, the proarrhythmic substrate induced by 10(-6) mol/L ISO was abolished by either of the sulfonylureas, which prevented induction of atrial tachyarrhythmia.

CONCLUSIONS:

Atrial ATP-sensitive K(+) channels activate in response to β-adrenergic metabolic stress in Langendorff-perfused rat hearts, resulting in a proarrhythmic substrate.

PMID:
23159416
DOI:
10.1161/CIRCEP.112.975425
[Indexed for MEDLINE]
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