[Free radical centers in isolated rat heart tissue in a normal state, in ischemia, and reperfusion]

EPR spectroscopy was used to measure paramagnetic species in rat hearts freeze-clamped during control perfusion by the Neely procedure, after 25 min of normothermic global ischemia or 20 min of total reperfusion with oxygenated perfusate. The analysis of spectral and relaxation parameters measured at -40 degrees C showed that in all three cases free radicals in heart tissue were semiquinones of CoQ10 and flavins. Ischemia increased the amount of free radical species (mostly flavosemiquinones) in myocardium about two times, the beginning of reflow of perfusate resulted in decrease of the intensity of the EPR signal to an initial level. The saturation curves were different for control, ischemic and reoxygenated postischemic samples, and they demonstrated the heterogeneity of free radical centers in cardiac mitochondria.