Biochimica et biophysica acta
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Biochim. Biophys. Acta · Mar 1983
Hydroxyl free-radical spin-adduct in rat brain synaptosomes. Observations on the reduction of the nitroxide.
Understanding the prevalence and action of hydroxyl free-radicals, damaging species in biological systems, is improved by spin-trapping techniques. The hydroxyl free-radical rapidly adds to the spin-trap 5,5-dimethyl-1-pyrroline-1-oxide (DMPO) to form a relatively stable nitroxyl free-radical spin-adduct (DMPO-OH), but it was found that DMPO-OH becomes diamagnetic, presumably by chemical reduction, when it is added to rat brain synaptosomes. DMPO-OH reduction by synaptosomes was a time-dependent process, starting immediately and continuing up to 20 min or more, when almost all the spin-adduct is reduced. ⋯ Experiments with 1-octanol to obtain a measure of the membrane partition of DMPO-OH demonstrated that the octanol/water distribution was 1.83. Experiments with glass microfibre filtration to determine synaptosomal binding revealed that DMPO, as well as apparently DMPO-OH, were not specifically retained by synaptosomes. All of these results combined with past work on nitroxide reduction by biological systems, suggest that DMPO-OH reduction by synaptosomes is due to its interaction with and reduction by electron transport carriers of mitochondria within the synaptosomes.