title: Imaging of reactive oxygen species in focal ischemic mouse brain using a radical trapping tracer [(3)H]hydromethidine.
abstract: BACKGROUND
  Reactive oxygen species (ROS) have been implicated in the pathophysiology of the brain after ischemic stroke. In this study, we investigate the generation of brain ROS after transient focal ischemia in mice using a radical trapping radiotracer, [(3)H]-labeled N-methyl-2,3-diamino-6-phenyl-dihydrophenanthridine ([(3)H]hydromethidine), which we recently reported as a ROS imaging probe. We also examined the effect of dimethylthiourea (DMTU), a hydroxyl radical scavenger, on brain ROS generation and infarct volume after transient focal ischemia in mice.
  
  
  METHODS
  [(3)H]Hydromethidine was intravenously injected into mice at 1, 2, 5, and 7 h after transient middle cerebral artery occlusion (tMCAO), and then, the brain autoradiogram was acquired at 60 min after tracer injection. Brain infarct volumes at 24 h after tMCAO were assessed by 2,3,5-triphenyltetrazolium chloride staining.
  
  
  RESULTS
  Accumulation of radioactivity was observed in the ipsilateral striatum and cortex at 1 h after tMCAO. The increase of radioactivity was attenuated at 2 h after tMCAO and then became maximized at 5 h. The high accumulation of radioactivity remained until 7 h after tMCAO. DMTU treatment significantly attenuated the accumulation of radioactivity in the ipsilateral hemisphere at 1, 5, and 7 h after tMCAO. Brain infarct volumes were also significantly reduced in DMTU-treated mice at 24 h after tMCAO.
  
  
  CONCLUSIONS
  These results indicated that [(3)H]hydromethidine is a useful radiotracer for detecting in vivo brain ROS generation such as hydroxyl radical after ischemic injury.
authors.affiliation: Department of Drug Metabolism & Pharmacokinetics, Research Laboratory for Development, Shionogi & Co., Ltd., 3-1-1 Futaba-cho, Toyonaka, Osaka, 561-0825, Japan, kohji.abe@shionogi.co.jp.
authors.forename: Kohji
authors.initials: K
authors.lastname: Abe
authors.forename: Misato
authors.initials: M
authors.lastname: Tonomura
authors.forename: Miwa
authors.initials: M
authors.lastname: Ito
authors.forename: Nozomi
authors.initials: N
authors.lastname: Takai
authors.forename: Natsumi
authors.initials: N
authors.lastname: Imamoto
authors.forename: Takemi
authors.initials: T
authors.lastname: Rokugawa
authors.forename: Sotaro
authors.initials: S
authors.lastname: Momosaki
authors.forename: Kazumi
authors.initials: K
authors.lastname: Fukumoto
authors.forename: Kenji
authors.initials: K
authors.lastname: Morimoto
authors.forename: Osamu
authors.initials: O
authors.lastname: Inoue