Submitted on August 11, 2004
Accepted on July 13, 2005
Ischemic Preconditioning Enhances Scavenging Activity of Reactive Oxygen Species and Diminishes Transmural Difference of Infarct Size
Masahiko Morihira1, Naoyuki Hasebe1*, Baljinnyam Erdene1, Kazuhiro Sumitomo1, Tomoyuki Matsusaka1, Kazuma Izawa1, Takayuki Fujino1, Jun Fukuzawa1, and Kenjiro Kikuchi1
1 First Department of Medicine, Asahikawa Medical College, Asahikawa, Hokkaido, Japan
* To whom correspondence should be addressed. E-mail: haselove{at}asahikawa-med.ac.jp.
Reactive oxygen species (ROS) enhance myocardial ischemia-reperfusion (I/R) injury. Ischemic preconditioning (PC) provides a potent cardioprotective effects in I/R. However, it has not been elucidated whether PC diminishes ROS stress in I/R, and whether PC protects myocardium from ROS stress transmurally and homogeneously. Isolated rabbit hearts perfused with Krebs-Henseleit buffer underwent 30/60 minutes of I/R. Hemodynamic changes and myocardial damage extent were analyzed in 4 groups; Control underwent I/R alone. H2O2 group underwent I/R with hydrogen peroxide infusion (50 µM) first 1 minute of reperfusion to enhance oxidative stress. PC and H2O2+PC groups underwent 5/10 minutes of PC prior to Control and H2O2 protocols, respectively. Extracted myocardial DNA was analyzed for 8-hydroxydeoxyguanosine (8-OHdG), an indicator of oxidative DNA damage, using HPLC-ECD method. Glutathione peroxidase (GPX) activity and reduced form glutathione (GSH) were measured by spectrophotometric assays. The myocardial infarct size was significantly reduced in PC (19±2) compared to Control (37±4%, p<0.05), particularly in the subendocardium. H2O2 transmurally increased the infarct size by 59±4% (p<0.05), which was significantly diminished in H2O2+PC (31±4%, p<0.01). The GSH levels, but not GPX activities were well preserved transmurally in protocols with PC. The 8-OHdG levels were significantly decreased in PC, and were significantly enhanced in H2O2 (p<0.01). These changes in oxidative DNA damage were effectively diminished by PC. In conclusion, PC enhanced scavenging activity of GSH against ROS transmurally, reduced myocardial damage particularly in the subendocardium, and diminished the transmural difference in myocardial infarct size.
