title: Hypoxia and reoxygenation modulate the arrhythmogenic activity of the pulmonary vein and atrium.
abstract: Ischaemia and reperfusion contribute to the genesis of AF (atrial fibrillation). PVs (pulmonary veins) and the atria are important foci for AF initiation and maintenance. However, the effect of ischaemia and reperfusion on PVs and the atria has not yet been fully elucidated. In the present study, conventional microelectrodes were used to record the APs (action potentials) in isolated rabbit PV, LA (left atrium) and RA (right atrium) specimens during hypoxia and reoxygenation, and pharmacological interventions. Hypoxia reduced the PV beating rates from 1.8±0.1 to 1.3±0.2 and 0.8±0.1 Hz at 30 and 60 min respectively (n=8, P<0.005), and induced EAD (early after depolarization) in three (37.5%) of the PVs and DAD (delayed after depolarization) in one (12.5%) of the PVs. Reoxygenation increased the PV spontaneous rate to 1.4±0.2 Hz (P<0.05) and induced PV burst firings (3.5±0.1 Hz, P<0.001) in six (75%) of the PVs. Hypoxia shortened the AP duration in the LA and PVs, but not in the RA. Pretreatment with glibenclamide attenuated hypoxia-induced decreases in the PV spontaneous activity and the shortening of the LA and PV AP duration. Similar to those in hypoxia, the K(ATP) (ATP-sensitive potassium) channel opener pinacidil (30 μM) decreased PV spontaneous activity and shortened the AP duration. Pretreatment with 5 mM N-MPG [N-(mercaptopropionyl)glycine; a hydroxyl (•OH) free-radical scavenger] or 300 μM chloramphenicol [a cytochrome P450 inhibitor that reduces ROS (reactive oxygen species)] attenuated the rate changes induced by hypoxia and reoxygenation, and also decreased the burst firing incidence. In conclusion, hypoxia and reoxygenation significantly increased PV arrhythmogenesis and induced different electrophysiological responses in the RA and LA, which may play a role in the pathophysiology of AF.
authors: Division of Cardiovascular Medicine, Taipei Medical University, Wan Fang Hospital, Taiwan.
authors: Yung-Kuo
authors: YK
authors: Lin
authors: Mei-Shou
authors: MS
authors: Lai
authors: Yao-Chang
authors: YC
authors: Chen
authors: Chen-Chuan
authors: CC
authors: Cheng
authors: Jen-Hung
authors: JH
authors: Huang
authors: Shih-Ann
authors: SA
authors: Chen
authors: Yi-Jen
authors: YJ
authors: Chen
authors: Cheng-I
authors: CI
authors: Lin
mesh_terms: D000200:Action Potentials / Q000187:drug effects / Q000502:physiology*; D000818:Animals; D001145:Arrhythmias, Cardiac / Q000503:physiopathology*; D001281:Atrial Fibrillation / Q000503:physiopathology; D015153:Blotting, Western; D002701:Chloramphenicol / Q000494:pharmacology; D005905:Glyburide / Q000494:pharmacology; D005998:Glycine / Q000031:analogs & derivatives / Q000494:pharmacology; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism; D006325:Heart Atria / Q000187:drug effects / Q000378:metabolism / Q000503:physiopathology; D007004:Hypoglycemic Agents / Q000494:pharmacology; D000860:Hypoxia / Q000503:physiopathology; D066298:In Vitro Techniques; D008297:Male; D010100:Oxygen / Q000378:metabolism* / Q000494:pharmacology; D020110:Pinacidil / Q000494:pharmacology; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D011667:Pulmonary Veins / Q000187:drug effects / Q000378:metabolism / Q000503:physiopathology*; D011817:Rabbits; D017382:Reactive Oxygen Species / Q000378:metabolism; D008625:Tiopronin / Q000494:pharmacology; D014665:Vasodilator Agents / Q000494:pharmacology
chemical_list: D018840:HSP70 Heat-Shock Proteins; D007004:Hypoglycemic Agents; D011500:Protein Synthesis Inhibitors; D017382:Reactive Oxygen Species; D014665:Vasodilator Agents; D002701:Chloramphenicol; D020110:Pinacidil; D008625:Tiopronin; D010100:Oxygen; D005905:Glyburide; D005998:Glycine