title: Estimation of free radical formation by beta-ray irradiation in rat liver.
abstract: In vivo free radical reactions in rat liver as a result of exposure to low-dose beta-radiation was evaluated with electron paramagnetic resonance (EPR) spectroscopy by monitoring the reduction of the nitroxyl spin probe after intravenous administration. The EPR signal intensity of a nitroxyl probe as a function of time in bile flow was monitored by cannulating the bile duct through the cavity of an X-band EPR spectrometer. The results show that the rate of nitroxyl signal loss was higher in rats whose livers were exposed to beta-rays compared to unexposed rats. However, the rate of signal loss was lower in animals whose organs were exposed to air by opening the abdominal cavity. In vitro experiments also showed that the nitroxyl EPR signal loss was greater in an atmosphere of nitrogen than in air. Results suggest that under low levels of tissue oxygen, exposure to beta-rays results in nitroxyl signal loss, which may be mediated by free radical dependent pathways. When tissue oxygen were higher, hydrogen peroxide mediated oxidation of hydroxylamine may predominate resulting in a signal loss of smaller magnitudes. This study shows possible evidence of reactive oxygen species formation by low-dose beta-ray irradiation in a living animal.
authors.affiliation: Radiation Biology Branch, Center for Cancer Research, National Cancer Institute, Bethesda, MD 20892-1002, USA.
authors.forename: Ken-ichiro
authors.initials: K
authors.lastname: Matsumoto
authors.forename: Aya
authors.initials: A
authors.lastname: Okajo
authors.forename: Takenori
authors.initials: T
authors.lastname: Kobayashi
authors.forename: James B
authors.initials: JB
authors.lastname: Mitchell
authors.forename: Murali C
authors.initials: MC
authors.lastname: Krishna
authors.forename: Kazutoyo
authors.initials: K
authors.lastname: Endo
mesh_terms: D000818:Animals; D001610:Beta Particles; D004578:Electron Spin Resonance Spectroscopy; D005609:Free Radicals / Q000032:analysis / Q000378:metabolism* / Q000528:radiation effects*; D006861:Hydrogen Peroxide / Q000378:metabolism; D019811:Hydroxylamine / Q000378:metabolism; D008099:Liver / Q000378:metabolism*; D008297:Male; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism; D011827:Radiation; D051381:Rats; D017208:Rats, Wistar; D017382:Reactive Oxygen Species / Q000378:metabolism / Q000528:radiation effects
chemical_list: D005609:Free Radicals; D017382:Reactive Oxygen Species; D019811:Hydroxylamine; D006861:Hydrogen Peroxide; D010100:Oxygen