Copyright © 2004, European Society of Cardiology
Comparison of ion channel distribution and expression in cardiomyocytes of canine pulmonary veins versus left atrium
Research Center, Montreal Heart Institute, 5000 Belanger Street East, Montreal, Quebec, Canada H1T 1C8
Departments of Pathology and Pharmacology and Therapeutics, McGill University and Department of Medicine, University of Montreal, Canada
* Corresponding author. Research Center, Montreal Heart Institute, 5000 Belanger Street East, Montreal, Quebec, Canada H1T 1C8. Tel.: +1 514 376 3330; fax: +1 514 376 1355. Email address: nattel{at}icm.umontreal.ca
Background: Cardiomyocytes in pulmonary vein (PV) sleeves are important in atrial fibrillation (AF), but underlying mechanisms are poorly understood. Pulmonary veins have different ionic current properties compared to left atrium, with pulmonary vein inward-rectifier currents being smaller and delayed-rectifier currents larger than in left atrium.
Methods: Expression and distribution of the inward-rectifier subunits Kir2.1 and Kir2.3, the rapid delayed-rectifier 
-subunit ERG, the slow delayed-rectifier -subunit KvLQT1, the β-subunit minK, the L-type Ca2+-subunit Cav1.2, and the Na+,Ca2+-exchanger were quantified by Western blot on isolated cardiomyocytes and localized by immunohistochemistry in tissue sections obtained from canine hearts.
Results: Western blotting indicated significantly greater expression of ERG (by 28%, P<0.05) and KvLQT1 (by 34%, P<0.05) in pulmonary vein versus left atrial (LA) cardiomyocytes, but smaller Kir2.3 and similar Kir2.1, Cav1.2 and Na+,Ca2+-exchanger expression in PV. Kir2.1 exhibited weak transverse tubular distribution in both regions. Kir2.3 localized to intercalated disks in both regions, and to transverse tubules in left atrium but not pulmonary vein. ERG staining was more intense in pulmonary vein than left atrium, localizing to transverse tubules in both regions and intercalated disks in pulmonary veins. KvLQT1 was more intensely expressed in pulmonary veins, with a transverse tubular and intercalated disk localization, versus a more diffuse signal in left atrium. The Na+,Ca2+-exchanger localized to transverse tubules, plasma membranes and intercalated disks with similar intensity in each region.
Conclusions: Greater ERG and KvLQT1 abundance in pulmonary vein cardiomyocytes, lower abundance of Kir2.3 in pulmonary veins and differential pulmonary vein subcellular distribution of Kir2.3, ERG and KvLQT1 subunits may contribute to ionic current differences between pulmonary vein and left atrial cardiomyocytes.
KEYWORDS Arrhythmia (mechanisms); ECG; Ion channels; Repolarization
Time for primary review 20 days
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