Separable detection of lipophilic- and hydrophilic-phase free radicals from the ESR spectrum of nitroxyl radical in transient MCAO mice.

Free radicals are believed to be key factors that promote ischemia reperfusion injury in the brain. This study used the characteristic spectrum of methoxycarbonyl-PROXYL to detect free radical reactions in hydrophilic and lipophilic compartments in a transient middle cerebral artery occlusion (MCAO) mouse model. Methoxycarbonyl-PROXYL, which has a high water/octanol partition coefficient, allows the detection of nitroxyl radical in both compartments simultaneously. Free radicals generation was analysed from the enhanced ESR signal decay rate of methoxycarbonyl-PROXYL. The signal decay rate in the lipidic compartment was significantly enhanced 1 h after reperfusion following MCAO. The enhanced signal decay rate was significantly suppressed by Trolox. The accumulation of lipid peroxidation products increased by 6 h post-reperfusion and was suppressed by methoxycarbonyl-PROXYL or Trolox. These results demonstrate that information pertaining to different sites of free radical generation in vivo can be obtained simultaneously and that lipid-derived radicals are generated in transient MCAO mice.