Comparison of ion channel distribution and expression in cardiomyocytes of canine pulmonary veins versus left atrium.
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 alpha-subunit ERG, the slow delayed-rectifier alpha-subunit KvLQT1, the beta-subunit minK, the L-type Ca(2+)-subunit Ca(v)1.2, and the Na(+),Ca(2+)-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, Ca(v)1.2 and Na(+),Ca(2+)-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(+),Ca(2+)-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.
Melnyk
Peter
P
Research Center, Montreal Heart Institute, 5000 Belanger Street East, Montreal, Quebec, Canada H1T 1C8.
Ehrlich
Joachim R
JR
Pourrier
Marc
M
Villeneuve
Louis
L
Cha
Tae-Joon
TJ
Nattel
Stanley
S
D000818:Animals; D001145:Arrhythmias, Cardiac / Q000378:metabolism*; D015153:Blotting, Western / Q000379:methods; D016466:CHO Cells; D020746:Calcium Channels, L-Type / Q000032:analysis; D006224:Cricetinae; D004285:Dogs; D000072237:ERG1 Potassium Channel; D004594:Electrophysiology; D051638:Ether-A-Go-Go Potassium Channels; D005260:Female; D006325:Heart Atria / Q000166:cytology / Q000378:metabolism; D007150:Immunohistochemistry / Q000379:methods; D007473:Ion Channels / Q000032:analysis / Q000378:metabolism*; D051656:KCNQ Potassium Channels; D051657:KCNQ1 Potassium Channel; D008297:Male; D018613:Microscopy, Confocal; D032383:Myocytes, Cardiac / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000032:analysis; D024661:Potassium Channels, Inwardly Rectifying / Q000032:analysis; D024642:Potassium Channels, Voltage-Gated / Q000032:analysis; D011667:Pulmonary Veins / Q000166:cytology* / Q000378:metabolism; D019831:Sodium-Calcium Exchanger / Q000032:analysis
D020746:Calcium Channels, L-Type; D000072237:ERG1 Potassium Channel; D051638:Ether-A-Go-Go Potassium Channels; D007473:Ion Channels; D051656:KCNQ Potassium Channels; D051657:KCNQ1 Potassium Channel; C490968:Kcnj4 protein, rat; C489461:Kir2.1 channel; D015221:Potassium Channels; D024661:Potassium Channels, Inwardly Rectifying; D024642:Potassium Channels, Voltage-Gated; D019831:Sodium-Calcium Exchanger