Pathological impact of hyperpolarization-activated chloride current peculiar to rat pulmonary vein cardiomyocytes.
Pulmonary veins (PVs) are believed to be a crucial origin of atrial fibrillation. We recently reported that rat PV cardiomyocytes exhibit arrhythmogenic automaticity in response to norepinephrine. Herein, we further characterized the electrophysiological properties underlying the potential arrhythmogenicity of PV cardiomyocytes. Patch clamping studies revealed a time dependent hyperpolarization-activated inward current in rat PV cardiomyocytes, but not in left atrial (LA) myocytes. The current was Cs(+) resistant, and was not affected by removal of external Na(+) or K(+). The current was inhibited with Cd(2+), and the reversal potential was sensitive to changes in [Cl(-)] on either side of the membrane in a manner consistent with a Cl(-) selective channel. Cl(-) channel blockers attenuated the current, and slowed or completely inhibited the norepinephrine-induced automaticity. The biophysical properties of the hyperpolarization-activated Cl(-) current in rat PVs were different from those of ClC-2 currents previously reported: (i) the voltage-dependent activation of the Cl(-) current in rat PVs was shifted to negative potentials as [Cl(-)]i increased, (ii) the Cl(-) current was enhanced by extracellular acidification, and (iii) extracellular hyper-osmotic stress increased the current, whereas hypo-osmotic cell swelling suppressed the current. qPCR analysis revealed negligible ClC-2 mRNA expression in the rat PV. These findings suggest that rat PV cardiomyocytes possess a peculiar voltage-dependent Cl(-) channel, and that the channel may play a functional role in norepinephrine-induced automaticity.
Department of Cell Physiology, Akita University Graduate School of Medicine, Akita, Japan.
Yosuke
Y
Okamoto
Department of Cellular and Organ Pathology, Akita University Graduate School of Medicine, Akita, Japan.
Koichi
K
Kawamura
Department of Cell Physiology, Akita University Graduate School of Medicine, Akita, Japan.
Yuta
Y
Nakamura
Department of Cell Physiology, Akita University Graduate School of Medicine, Akita, Japan. Electronic address: onok@med.akita-u.ac.jp.
Kyoichi
K
Ono
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D017920:Antiporters / Q000235:genetics / Q000378:metabolism; D002104:Cadmium / Q000494:pharmacology; D002586:Cesium / Q000494:pharmacology; D018118:Chloride Channels / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D002712:Chlorides / Q000378:metabolism*; D015870:Gene Expression; D006325:Heart Atria / Q000166:cytology / Q000378:metabolism; D032383:Myocytes, Cardiac / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D009638:Norepinephrine / Q000494:pharmacology; D027361:Organic Anion Transporters / Q000235:genetics / Q000378:metabolism; D009994:Osmolar Concentration; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000378:metabolism; D011667:Pulmonary Veins / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D012964:Sodium / Q000378:metabolism; D014662:Vasoconstrictor Agents / Q000494:pharmacology
D017920:Antiporters; D018118:Chloride Channels; D002712:Chlorides; D027361:Organic Anion Transporters; D014662:Vasoconstrictor Agents; C515964:citrate-isocitrate carrier, rat; D002104:Cadmium; D002586:Cesium; D012964:Sodium; D011188:Potassium; D009638:Norepinephrine
4,4′-diisothiocyanostilbene-2,2′-disulfonic acid; 9-AC; 9-anthracene carboxylic acid; AF; Atrial fibrillation; Ca(2+) activated Cl(−) channel; Cl(−) channel; Cm; DIDS; GAPDH; I(ClCa); I(K1); I(KH); I(f); I(ti); LA; NE; PV; Pulmonary vein; atrial fibrillation; cell membrane capacitance; glyceraldehyde-3-phosphate dehydrogenase; hyperpolarization-activated K(+) current; hyperpolarization-activated cation current; inward-rectifier K(+) current; left atrium; norepinephrine; pulmonary vein; qPCR; quantitative polymerase chain reaction; transient inward current