Studies on the Effects of Antioxidants and Inhibitors of Radical Generation on Free Radical Production in the Reperfused Rat Heart Using Electron Spin Resonance Spectroscopy

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Abstract
Reperfusion of the heart after a period of ischaemia can precipitate ventricular arrhythmias and lead to an exacerbation of tissue injury. Direct evidence to suggest the involvement of free radicals has been obtained using electron spin resonance (esr) spectroscopy and the spin trap N-tert. butyl-α-phenyl nitrone (PBN). In the present study, we have used esr spectroscopy and PBN to examine the individual effects of superoxide dismutase (SOD), catalase. allopurinol or desferal on radical production in the isolated. reperfused rat heart. A burst of radical production was observed in the control group during the first 5 minutes of reperfusion; the peak occurred during the first minute, when signal intensity had increased by almost 300%. but returned to the baseline by 15 minutes of reperfusion. The esr signals were consistent with the trapping of either alkoxyl or carbon-centered radicals (aN = 13.6 and aH = 1.56G). In the desferal-treated group, a burst of radical production was observed during the first five minutes of reperfusion; this was maximal during the second minute, when signal intensity had increased by almost 200%, but had returned to the baseline value by 30 minutes of reperfusion. In the SOD-treated group, a burst of radical production was observed during the first 10 minutes of reperfusion; signal intensity was maximal during the tenth minute of reperfusion, when signal intensity had increased by almost 200%. but had returned to the baseline value by 30 minutes of reperfusion. In the allopurinol- and catalase-treated groups, no significant burst of radical production could be detected. These data further support the concept that cytotoxic, oxygen-derived species are formed upon reperfusion and that hydrogen peroxide and/or hy-droxyl radicals, are likely to be involved.