title: Gap junctional remodeling by hypoxia in cultured neonatal rat ventricular myocytes.
abstract: OBJECTIVE
  Altered gap junctional coupling of ventricular myocytes plays an important role in arrhythmogenesis in ischemic heart disease. Since hypoxia is a major component of ischemia, we tested the hypothesis that hypoxia causes gap junctional remodeling accompanied by conduction disturbances.
  
  
  METHODS
  Cultured neonatal rat ventricular myocytes were exposed to hypoxia (1% O(2)) for 15 min to 5 h, connexin43 (Cx43) expression was analyzed, and conduction velocity was measured using the Micro-Electrode Array data acquisition system.
  
  
  RESULTS
  After 15 min of hypoxia, conduction velocity was unaffected, while total Cx43, including the phosphorylated and nonphosphorylated isoforms, was increased. After 5 h of hypoxia, total Cx43 protein was decreased by 50%, while the nonphosphorylated Cx43 isoform was unchanged. Confocal analyses yielded a 55% decrease in the gap junctional Cx43 fluorescence signal, a 55% decrease in gap junction number, and a 26% decrease in size. The changes in Cx43 were not accompanied by changes in mRNA levels. The reduction in Cx43 protein levels was associated with a approximately 20% decrease in conduction velocity compared to normoxic cultures.
  
  
  CONCLUSIONS
  Short-term hypoxia (5 h) decreases Cx43 protein and conduction velocity, thereby contributing to the generation of an arrhythmogenic substrate.
authors.affiliation: Rappaport Faculty of Medicine, Technion, Haifa, Israel.
authors.forename: Naama
authors.initials: N
authors.lastname: Zeevi-Levin
authors.forename: Yaron D
authors.initials: YD
authors.lastname: Barac
authors.forename: Yotam
authors.initials: Y
authors.lastname: Reisner
authors.forename: Irina
authors.initials: I
authors.lastname: Reiter
authors.forename: Gal
authors.initials: G
authors.lastname: Yaniv
authors.forename: Gideon
authors.initials: G
authors.lastname: Meiry
authors.forename: Zaid
authors.initials: Z
authors.lastname: Abassi
authors.forename: Sawa
authors.initials: S
authors.lastname: Kostin
authors.forename: Jutta
authors.initials: J
authors.lastname: Schaper
authors.forename: Michael R
authors.initials: MR
authors.lastname: Rosen
authors.forename: Nitzan
authors.initials: N
authors.lastname: Resnick
authors.forename: Ofer
authors.initials: O
authors.lastname: Binah
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D001145:Arrhythmias, Cardiac / Q000378:metabolism* / Q000503:physiopathology; D015153:Blotting, Western / Q000379:methods; D018031:Connexin 43 / Q000032:analysis / Q000235:genetics / Q000378:metabolism; D017629:Gap Junctions / Q000737:chemistry / Q000378:metabolism*; D006329:Heart Conduction System; D006352:Heart Ventricles; D000860:Hypoxia / Q000378:metabolism*; D007150:Immunohistochemistry / Q000379:methods; D018613:Microscopy, Confocal; D032383:Myocytes, Cardiac / Q000737:chemistry / Q000378:metabolism*; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013997:Time Factors
chemical_list: D018031:Connexin 43; D012333:RNA, Messenger