Gap Junctional Remodeling by Hypoxia in Cultured Neonatal Rat Ventricular Myocytes

Cardiovasc Res. 2005 Apr 1;66(1):64-73. doi: 10.1016/j.cardiores.2005.01.014.

Abstract

Objectives: 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.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Animals, Newborn
  • Arrhythmias, Cardiac / metabolism*
  • Arrhythmias, Cardiac / physiopathology
  • Blotting, Western / methods
  • Connexin 43 / analysis
  • Connexin 43 / genetics
  • Connexin 43 / metabolism
  • Gap Junctions / chemistry
  • Gap Junctions / metabolism*
  • Heart Conduction System
  • Heart Ventricles
  • Hypoxia / metabolism*
  • Immunohistochemistry / methods
  • Microscopy, Confocal
  • Myocytes, Cardiac / chemistry
  • Myocytes, Cardiac / metabolism*
  • RNA, Messenger / analysis
  • Rats
  • Rats, Sprague-Dawley
  • Reverse Transcriptase Polymerase Chain Reaction
  • Time Factors

Substances

  • Connexin 43
  • RNA, Messenger