Electron spin resonance (ESR) method is a simple method for detecting various
free radicals simultaneously and directly. However, ESR spin trap method is unsuited to analyze weak ESR signals in organs because of water-induced dielectric loss (WIDL). To minimize WIDL occurring in biotissues and to improve detection sensitivity to
free radicals in tissues, ESR cuvette was modified and used with 5,5-dimethtyl-1-pyrroline N-
oxide (DMPO). The tissue samples were mouse brain, hart, lung, liver, kidney, pancreas, muscle, skin, and whole blood, where various ESR spin adduct signals including DMPO-
ascorbyl radical (AsA(∗)), DMPO-
superoxide anion radical (OOH), and DMPO-
hydrogen radical (H) signal were detected.
Postmortem changes in DMPO-AsA(∗) and
DMPO-OOH were observed in various tissues of mouse. The signal peak of spin adduct was monitored until the 205th day postmortem. DMPO-AsA(∗) in liver (y = 113.8-40.7 log (day), R1 = -0.779, R2 = 0.6, P < .001) was found to linearly decrease with the logarithm of postmortem duration days. Therefore, DMPO-AsA(∗) signal may be suitable for detecting an oxidation stress tracer from tissue in comparison with other spin adduct signal on ESR spin trap method.