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  • Title: Gap junctional remodeling by hypoxia in cultured neonatal rat ventricular myocytes.
    Author: Zeevi-Levin N, Barac YD, Reisner Y, Reiter I, Yaniv G, Meiry G, Abassi Z, Kostin S, Schaper J, Rosen MR, Resnick N, Binah O.
    Journal: Cardiovasc Res; 2005 Apr 01; 66(1):64-73. PubMed ID: 15769449.
    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.
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