Cellular electrophysiology of canine pulmonary vein cardiomyocytes: action potential and ionic current properties.
Pulmonary vein (PV) cardiomyocytes play an important role in atrial fibrillation; however, little is known about their specific cellular electrophysiological properties. We applied standard microelectrode recording and whole-cell patch-clamp to evaluate action potentials and ionic currents in canine PVs and left atrium (LA) free wall. Resting membrane potential (RMP) averaged -66 +/- 1 mV in PVs and -74 +/- 1 mV in LA (P < 0.0001) and action potential amplitude averaged 76 +/- 2 mV in PVs vs. 95 +/- 2 mV in LA (P < 0.0001). PVs had smaller maximum phase 0 upstroke velocity (Vmax: 98 +/- 9 vs. 259 +/- 16 V s(-1), P < 0.0001) and action potential duration (APD): e.g. at 2 Hz, APD to 90% repolarization in PVs was 84 % of LA (P < 0.05). Na+ current density under voltage-clamp conditions was similar in PV and LA, suggesting that smaller Vmax in PVs was due to reduced RMP. Inward rectifier current density in the PV cardiomyocytes was approximately 58% that in the LA, potentially accounting for the less negative RMP in PVs. Slow and rapid delayed rectifier currents were greater in the PV (by approximately 60 and approximately 50 %, respectively), whereas transient outward K+ current and L-type Ca2+ current were significantly smaller (by approximately 25 and approximately 30%, respectively). Na(+)-Ca(2+)-exchange (NCX) current and T-type Ca2+ current were not significantly different. In conclusion, PV cardiomyocytes have a discrete distribution of transmembrane ion currents associated with specific action potential properties, with potential implications for understanding PV electrical activity in cardiac arrhythmias.
Ehrlich
Joachim R
JR
Department of Medicine and Research Center, Montreal Heart Institute and University of Montreal, Montreal, Quebec, Canada.
Cha
Tae-Joon
TJ
Zhang
Liming
L
Chartier
Denis
D
Melnyk
Peter
P
Hohnloser
Stefan H
SH
Nattel
Stanley
S
D000200:Action Potentials / Q000502:physiology*; D000818:Animals; D002118:Calcium / Q000378:metabolism; D020746:Calcium Channels, L-Type / Q000502:physiology; D020747:Calcium Channels, T-Type / Q000502:physiology; D051668:Delayed Rectifier Potassium Channels; D004285:Dogs; D005260:Female; D008297:Male; D032383:Myocytes, Cardiac / Q000502:physiology*; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000502:physiology; D024661:Potassium Channels, Inwardly Rectifying / Q000502:physiology; D024642:Potassium Channels, Voltage-Gated; D011667:Pulmonary Veins / Q000166:cytology / Q000502:physiology*; D012964:Sodium / Q000378:metabolism; D015222:Sodium Channels / Q000502:physiology
D020746:Calcium Channels, L-Type; D020747:Calcium Channels, T-Type; D051668:Delayed Rectifier Potassium Channels; D015221:Potassium Channels; D024661:Potassium Channels, Inwardly Rectifying; D024642:Potassium Channels, Voltage-Gated; D015222:Sodium Channels; D012964:Sodium; D002118:Calcium