Gap junctional remodeling by hypoxia in cultured neonatal rat ventricular myocytes.
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.
Zeevi-Levin
Naama
N
Rappaport Faculty of Medicine, Technion, Haifa, Israel.
Barac
Yaron D
YD
Reisner
Yotam
Y
Reiter
Irina
I
Yaniv
Gal
G
Meiry
Gideon
G
Abassi
Zaid
Z
Kostin
Sawa
S
Schaper
Jutta
J
Rosen
Michael R
MR
Resnick
Nitzan
N
Binah
Ofer
O
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
D018031:Connexin 43; D012333:RNA, Messenger