Reduced free radical generation during reperfusion of hypothermically arrested hearts |
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Authors: | M Renuka Prasad Xuekun Liu John A Rousou Richard M Engelman Randall Jones Anna George Dipak K Das |
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Institution: | (1) Cardiovascular Division, Department of Surgery, Surgical Research Center, University of Connecticut Health Center, 06030 Farmington, Connecticut, USA |
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Abstract: | Several studies indicate the presence of hydroxyl radical (OH·) as well as its involvement in the myocardial reperfusion injury. A transition metal-like iron is necessary for the conversion of superoxide anion (O2
–) to a highly reactive and cytotoxic hydroxyl radical (OH·). In the present study, we have examined the generation of OH· and free iron in reperfused hearts following either normothermic (37°C) or hypothermic ischemia (5°C). Employing the Langendorff technique, isolated rat hearts were subjected to global ischemia for 30 min at 37°C or 5°C and were then reperfused for 15 min at 37°C. The results of the study suggest that both the OH· generation in myocardium and free iron release into perfusate were significantly lower in hearts made ischemic at 5°C as compared to 37°C. Release of myoglobin and lactic acid dehydrogenase into perfusate also followed a similar pattern. Furthermore, in in vitro studies, chemically generated O2
– at 5°C caused a significantly lower rate of oxidation of oxymyoglobin as well as generation of OH° and free iron as compared to 37°C. These results suggest that (1) reperfusion of hypothermic ischemic heart is associated with a reduction in the generation of OH· and cellular damage compared to that of normothermic ischemic heart, and (2) myoglobin, an intracellular protein, is a source of free iron and plays a role in the reperfusion injury mediated by free radicals.Abbreviations OH·
hydroxyl radical
- O2
–
superoxide anion
- ODFR
oxygen-derived free radicals
- KHB
Krebs-Henseleit buffer
- LDH
lactate hydrogenase
- SOD
superoxide dismutase |
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Keywords: | hydroxyl radical hypothermia reperfusion injury cardiac surgery iron |
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