Abstract
BackgroundSeveral lines of evidence point to a particularly important role of the left atrium (LA) in initiating and maintaining atrial fibrillation (AF). This role may be related to the location of pulmonary veins (PVs) in the LA. The aim of the present study was to investigate the action potential (AP) and ionic currents in LA-PV cardiomyocytes isolated from Bio14.6 myopathic Syrian hamsters (36-57 week-old) versus age-matched F1B healthy control hamsters.Methods and ResultsWhole-cell patch-clamp techniques were used to record AP in current-clamp mode and ionic currents in voltage-clamp mode. The results obtained show that in both healthy and myopathic LA-PV tissue spontaneously discharging cardiomyocytes can be found, but they are more numerous in myopathic (9/29) than in healthy hamsters (4/42, p < 0.05 by χ2 analysis). Myopathic myocytes have shorter AP duration (APD) with smaller ICa,L and INCX than the healthy control. The currents ITO, IK, IK1 and ICa,T are not significantly different in myopathic versus healthy cells.ConclusionsOur results indicate that in myopathic Syrian hamsters LA-PV cardiomyocytes are more prone to automatic rhythms. Also, they show altered electrophysiologic properties, which may be due to abnormal Ca2+ channels and may account for contractile dysfunction.
Highlights
The Biobreeders strain 14.6 myopathic Syrian hamster had been frequently used as an experimental model for the study of congestive heart failure (CHF) [1,2,3]
Action potential characteristics In driven cardiomyocytes, APD50 and APD90 were shorter in myopathic (n = 29) than in healthy hamsters (n = 42)
Active cardiomyocytes were present in both myopathic and healthy left atrium (LA)-pulmonary veins (PVs) areas, but they were more numerous in myopathic hamsters (9/29) than in healthy hamsters (4/42) (χ2 = 3.966, p < 0.05)
Summary
The Biobreeders strain 14.6 myopathic Syrian hamster had been frequently used as an experimental model for the study of congestive heart failure (CHF) [1,2,3]. In the left atrium (LA), the pulmonary veins (PVs) are an important source of ectopic beats, which frequently initiate paroxysms of AF. Previous studies in multiple or single cells from dogs [10,11] and rabbits [12,13] have shown that PVs contain cardiomyocytes, which may be either quiescent or show spontaneous activity It is not clear whether CHF enhances the arrhythmogenic activity of PVs. Several lines of evidence point to a important role of the left atrium (LA) in initiating and maintaining atrial fibrillation (AF). Several lines of evidence point to a important role of the left atrium (LA) in initiating and maintaining atrial fibrillation (AF) This role may be related to the location of pulmonary veins (PVs) in the LA. The aim of the present study was to investigate the action potential (AP) and ionic currents in LA-PV cardiomyocytes isolated from Bio14.6 myopathic Syrian hamsters (36-57 week-old) versus age-matched F1B healthy control hamsters
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