Free-Radical Generation in Regional Ischemic Myocardium Assessed by Electron Paramagnetic Resonance Spectroscopy and Chemiluminescence in Reperfused Canine Heart.

Abstract

The aim of this study was to clarify the role of free radicals generated in the postischemic myocardium in a canine coronary occlusion (90min)-reperfusion (5h) model of myocardial infarction. Myocardial samples were taken from the central infarcted region (infarct), the noninfarcted region within the area at risk (risk), and the endocardial-to-epicardial border between the infarct region and the area at risk (border). Free-radical generation was assessed by electron paramagnetic resonance (EPR) spectroscopy using a spin trapping agent, 5, 5-dimethyl-1-pyrroline N-oxide (DMPO) and a luminol-enhanced chemiluminescence assay. DMPO-adducts detected by EPR spectroscopy consisted of DMPO-OH, which markedly increased after reperfusion in the ischemic myocardium, especially in the border, and showed a peak after 3h of reperfusion (p<0.01). Similarly, a marked increase in the chemiluminescence of the border was observed after reperfusion, which showed a peak after 3h of reperfusion (p<0.01) and thereafter declined. The generating activity of free radicals in the border increased significantly (p<0.01) after reperfusion and its peak was also observed at 3h after reperfusion. However, the activity in the infarct was nearly zero after 1h of reperfusion. Administration of a free-radical scavenger, CV-3611 (5mg/kg, i.v.), before reperfusion reduced the free radical generation in the border. These results indicate that the increased generation of free radicals at the peri-infarcted site may relate to the extension of reperfusion-associated myocardial injury.