title: In vivo monitoring of hydroxyl radical generation caused by x-ray irradiation of rats using the spin trapping/EPR technique.
abstract: Measurement of hydroxyl radical (*OH) in living animals irradiated with ionizing radiation should be required to clarify the mechanisms of radiation injury and the in vivo assessment of radiation protectors, because generation of *OH is believed to be one of the major triggers of radiation injury. In this study, *OH generation was monitored by spin trapping the secondary methyl radical formed by the reaction of *OH with dimethyl sulfoxide (DMSO). Rats were injected intraperitoneally with a DMSO solution of alpha-phenyl-N-tert-butylnitrone (PBN). X-irradiation of the rats remarkedly increased the six-line EPR signal in the bile. The strengthened signal was detectable above 40 Gy. Use of 13C-substituted DMSO revealed that the signal included the methyl radical adduct of PBN as a major component. The EPR signal of the PBN-methyl radical adduct was completely suppressed by preadministration of methyl gallate, a scavenger of *OH but not of methyl radical. Methyl gallate did not reduce the spin adducts to EPR-silent forms. These observations indicate that what we were measuring was *OH generated in vivo by x-irradiation. This is the first report of the in vivo monitoring of *OH generation at a radiation dose close to what people might receive in the case of radiological accident or radiation therapy.
authors.affiliation: Redox Regulation Research Group, National Institute of Radiological Sciences, Chiba 263-8555, Japan.
authors.forename: Keizo
authors.initials: K
authors.lastname: Takeshita
authors.forename: Kaori
authors.initials: K
authors.lastname: Fujii
authors.forename: Kazunori
authors.initials: K
authors.lastname: Anzai
authors.forename: Toshihiko
authors.initials: T
authors.lastname: Ozawa
mesh_terms: D000818:Animals; D001646:Bile / Q000737:chemistry; D003497:Cyclic N-Oxides; D004121:Dimethyl Sulfoxide / Q000737:chemistry / Q000494:pharmacology; D004307:Dose-Response Relationship, Radiation; D004578:Electron Spin Resonance Spectroscopy; D016166:Free Radical Scavengers / Q000737:chemistry / Q000494:pharmacology; D005707:Gallic Acid / Q000031:analogs & derivatives* / Q000737:chemistry / Q000494:pharmacology; D017665:Hydroxyl Radical / Q000032:analysis* / Q000378:metabolism; D008297:Male; D009589:Nitrogen Oxides / Q000737:chemistry; D051381:Rats; D019097:Spin Trapping / Q000379:methods*; D014965:X-Rays
chemical_list: D003497:Cyclic N-Oxides; D016166:Free Radical Scavengers; D009589:Nitrogen Oxides; D017665:Hydroxyl Radical; C029217:phenyl-N-tert-butylnitrone; C052082:methyl gallate; D005707:Gallic Acid; D004121:Dimethyl Sulfoxide