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Research

Reduced Ca²⁺ transport across sarcolemma but enhanced spontaneous activity in cardiomyocytes isolated from left atrium-pulmonary veins tissue of myopathic hamster

Yue-Xia Loh^1,5 , Kuo-Ho Wu^1,2 , Yao-Chang Chen³ , Chih-Hsiung Hsu⁴ , Jeng Wei⁶ and Cheng-I Lin¹

¹  Institute of Physiology, National Defense Medical Center, Taipei, Taiwan, ROC

²  Graduate Institute of Medical Sciences, National Defense Medical Center, Taipei, Taiwan, ROC

³  Department of Biomedical Engineering, National Defense Medical Center, Taipei, Taiwan, ROC

⁴  Section of Cardiology, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan, ROC

⁵  Chiayi Veterans Hospital, Taipei, Taiwan, ROC

⁶  Heart Center, Cheng-Hsin General Hospital, Taipei, Taiwan, ROC

author email corresponding author email

Journal of Biomedical Science 2009, 16:114doi:10.1186/1423-0127-16-114

Published:	29 December 2009

Abstract

Background

Several 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 Results

Whole-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 I_Ca,L and I_NCX than the healthy control. The currents I_TO, I_K, I_K1 and I_Ca,T are not significantly different in myopathic versus healthy cells.

Conclusions

Our 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.