Measurement of hydroxyl-radical formation in the rat striatum by in vivo microdialysis and GC-MS

Vien Nguyen, Darius V. Bonds, Laszlo Prokai

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Abstract

A GC-MS method was developed for measuring hydroxyl-radical capture products of salicylic acid, a common trapping agent for this reactive oxygen species, in samples obtained by in vivo cerebral microdialysis experiments. The assay employed liquid-liquid extraction followed by derivatization of 2,3- and 2,5-dihydroxybenzoic acid, along with 3,5-dihydroxybenzoic acid added as an internal standard. Due to their simple electron ionization mass spectra featuring [M-57]+ ions through the loss of tertiary alkyl group from the corresponding molecular ions, tert-butyldimethylsilyl (TBDMS) derivatives afforded straightforward method development based on selected-ion monitoring. In addition, tandem mass spectrometry probing collision-induced dissociation of [M-57]+ ions obtained from the isomeric tert-butyldimethylsilyl derivatives revealed characteristic differences in the resultant product-ion spectra. Our work has demonstrated the applicability of GC-MS for the assay of microdialysates for 2,3- and 2,5-dihydroxybenzoic acid by confirming that local administration of the excitotoxic glutamate into the rat striatum significantly increased in vivo hydroxyl-radical production in this brain region and that subsequent systemic administration of α-phenyl-tert-butylnitrone reversed glutamate-induced oxidative stress.

Original languageEnglish
Pages (from-to)S57-S62
JournalChromatographia
Volume68
Issue numberSUPPL. 1
DOIs
StatePublished - 1 Oct 2008

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Keywords

  • Derivatization
  • Dihydroxybenzoic acid
  • Gas chromatography-mass spectrometry
  • In vivo intracranial microdialysis
  • Oxidative stress

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