| The Role of Myocardial Gap Junction
in Ischemia-Reperfusion Injury in Senescent Rabbit Myocardium |
(Department of Thoracic and Cardiovascular Surgery
and The Third Department of Internal Medicine*, Osaka Medical
College, Takatsuki, Japan)
| Yasunari Nakai |
Hitoshi Horimoto |
Hiroaki Shimomura* |
| Tetsuya Hayashi* |
Yasushi Kitaura* |
Keiichiro Kondo |
| Kunio Asada |
Shinjiro Sasaki |
|
|
Objective. We investigated whether
the aging-related decrease in gap junction expression affects
myocardial response against ischemia-reperfusion injury of the
rabbit myocardium. Methods. Isolated aged (≧135 weeks) or mature
(15-20 weeks) rabbit hearts were perfused with Krebs-Henseleit
solution via a Langendorff apparatus, and were divided into five
groups as follows: 7 mature hearts served as mature controls
(Group A), 7 mature hearts underwent ischemic preconditioning
(IPC) consisting of two cycles of global ischemia for 5 min followed
by reperfusion for 5 min (Group B), 7 aged hearts served as aged
control（Group C)，7 aged hearts underwent IPC (Group D) and 7
mature hearts received 1 mM of gap junction uncoupler heptanol
for 5 min (Group E). Then, all hearts were subjected to 1 h of
left anterior descending coronary artery occlusion followed by
1h of reperfusion. Left ventricular pressure, ischemic zone monophasic
action potential and coronary flow were measured throughout the
experiment and the infarct size (IS) was determined at the end
of the experiment. Gap junction expression was investigated by
the electron microscopy. Results. The IS of Group A was 39.1±3.8(%)and
that of Group B was 26.9±3.8（%)* (*p＜0.05 vs. Group A).
The IS of Group C was 19.3±1.6(%)*. That of Group D was 43.6±5.8(%)#
(#p＜0.05 vs. Group C). IS of Group E was 24.3±1.6(%)*.
Electron microscopic findings demonstrated that gap junction
expression in aged hearts was less prominent than in mature ones.
Conclusion. These data suggested that aged myocardium might be
more tolerant of ischemic insult than that of mature heart, and
that the mechanism might be related to the aging-related change
of gap junction expression.
Jpn. J. Cardiovasc. Surg. 30: 165-170 (2001) |
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