1. Selective Na(+) /Ca(2+) exchanger inhibition prevents Ca(2+) overload-induced triggered arrhythmias.
- Author
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Nagy N, Kormos A, Kohajda Z, Szebeni Á, Szepesi J, Pollesello P, Levijoki J, Acsai K, Virág L, Nánási PP, Papp JG, Varró A, and Tóth A
- Subjects
- Animals, Arrhythmias, Cardiac etiology, Cnidarian Venoms pharmacology, Dogs, Hypercalcemia complications, Myocytes, Cardiac metabolism, Papillary Muscles metabolism, Patch-Clamp Techniques, Purkinje Fibers metabolism, Action Potentials drug effects, Aniline Compounds pharmacology, Benzopyrans pharmacology, Calcium metabolism, Myocytes, Cardiac drug effects, Papillary Muscles drug effects, Phenyl Ethers pharmacology, Purkinje Fibers drug effects, Pyridines pharmacology, Sodium-Calcium Exchanger antagonists & inhibitors
- Abstract
Background and Purpose: Augmented Na(+) /Ca(2+) exchanger (NCX) activity may play a crucial role in cardiac arrhythmogenesis; however, data regarding the anti-arrhythmic efficacy of NCX inhibition are debatable. Feasible explanations could be the unsatisfactory selectivity of NCX inhibitors and/or the dependence of the experimental model on the degree of Ca(2+) i overload. Hence, we used NCX inhibitors SEA0400 and the more selective ORM10103 to evaluate the efficacy of NCX inhibition against arrhythmogenic Ca(2+) i rise in conditions when [Ca(2+) ]i was augmented via activation of the late sodium current (INaL ) or inhibition of the Na(+) /K(+) pump., Experimental Approach: Action potentials (APs) were recorded from canine papillary muscles and Purkinje fibres by microelectrodes. NCX current (INCX ) was determined in ventricular cardiomyocytes utilizing the whole-cell patch clamp technique. Ca(2+) i transients (CaTs) were monitored with a Ca(2+) -sensitive fluorescent dye, Fluo-4., Key Results: Enhanced INaL increased the Ca(2+) load and AP duration (APD). SEA0400 and ORM10103 suppressed INCX and prevented/reversed the anemone toxin II (ATX-II)-induced [Ca(2+) ]i rise without influencing APD, CaT or cell shortening, or affecting the ATX-II-induced increased APD. ORM10103 significantly decreased the number of strophanthidin-induced spontaneous diastolic Ca(2+) release events; however, SEA0400 failed to restrict the veratridine-induced augmentation in Purkinje-ventricle APD dispersion., Conclusions and Implications: Selective NCX inhibition - presumably by blocking rev INCX (reverse mode NCX current) - is effective against arrhythmogenesis caused by [Na(+) ]i -induced [Ca(2+) ]i elevation, without influencing the AP waveform. Therefore, selective INCX inhibition, by significantly reducing the arrhythmogenic trigger activity caused by the perturbed Ca(2+) i handling, should be considered as a promising anti-arrhythmic therapeutic strategy., (© 2014 The British Pharmacological Society.)
- Published
- 2014
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