Glucose metabolism and molecular mechanism in hypoxic ischemic brain injury using fresh brain slices and positron based imaging technique

2002 Fiscal Year Final Research Report Summary

• Project/Area Number: 12670861
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Radiation science
• Research Institution: Fukui Medical University
• Principal Investigator: MURATA Tetsuhito Fukui Medical University, University Hospital, Assistant Professor, 医学部附属病院, 講師 (80200294)
• Co-Investigator(Kenkyū-buntansha): FUJIBAYASHI Yasuhisa Fukui Medical University, High Energy Research Center, Professor, 高エネルギー医学研究センター, 教授 (50165411)
• Project Period (FY): 2000 – 2002
• Keywords: Brain slice / Ischemia / Hypoxia / Glucose metabolism / Free radical / Excitatory amino acids / Hypoxic tolerance / Gene expression

Research Abstract

Fresh rat brain slices were incubated with [^<18>F]2-fluoro-2-deoxy-D-glucose ([^<18>F]FDG) in oxygenated Krebs-Ringer solution at 36℃, and serial two-dimensional time-resolved images of [^<18>F]FDG uptake in them were obtained on imaging plates. The fractional rate constant (= k3^*, proportional to the cerebral glucose metabolic rate) of [^<18>F]FDG from pre-loading of ischemia (O2 and glucose deprivation)/hypoxia (O2 deprivation) to the reperfused/reoxygenated post-loading phase was quantitatively evaluated by applying the Gjedde-Patlak graphical method to the image data. Against ischemia the NMDA antagonist and hypothermia, but not the free radical scavenger, showed a protective effect when administered during ischemia, whereas no such effect was achieved with any of the above agents when administered after reperfusion. Against hypoxia, there was no protective effect with any of the above agents when administered during hypoxia, although an effect was noted with each when administer ed after reoxygenation. Excitatory amino acids during ischemia loading were found to be the main factor in the neuronal damage associated with ischemia, while in hypoxia, excitatory amino acids working in tandem with free radicals immediately after reoxygenation were implicated. Next, we prepared rat brain slices following sublethal hypoxic pretreatment (preconditioning) and untreated (control) rats, and measured the cerebral glucose metabolic rate (CMRglc) by dynamic positron autoradiography with [^<18>F]FDG before and after originally lethal 20-min hypoxic loading. In the regions of interest such as the frontal cortex, the CMRglc before hypoxic loading did not differ between the preconditioning and control groups. The CMRglc after reoxygenation was markedly lower than that before hypoxic loading in the control group but did not significantly differ from the preloading value in the preconditioning group. Thus, hypoxic tolerance induction by preconditioning was demonstrated using the maintenance of CMRglc as a neuronal viability index. In addition, profiling of gene expression using an Atlas Rat Stress Array suggested the involvement of the expression of genes such as stress protein in hypoxic tolerance induction.