title: The effect of normothermic and hypothermic hypoxia-ischemia on brain hypoxanthine phosphoribosyl transferase activity.
abstract: OBJECTIVE
  Cerebral hypoxia-ischemia leads to the depletion of ATP. Hypoxanthine, a degradation product of ATP, can be salvaged by hypoxanthine phosphoribosyl transferase (HPRT) and used to reform high-energy purines. Hypothermia conserves ATP in hypoxia-ischemia, possibly by preserving HPRT activity. We hypothesized that cerebral hypoxia-ischemia would decrease the activity of this enzyme, and that this reduction would be attenuated by moderate hypothermia.
  
  
  METHODS
  Three groups of rabbits were evaluated. Normothermic rabbits were exposed to 8 minutes of hypoxia, 8 minutes of cerebral ischemia, and 30 minutes or 4 hours of cerebral reperfusion. Hypothermic rabbits were cooled to a brain temperature of 33-34 degrees C throughout identical injury and reperfusion periods. Control rabbits underwent the same preparation, without hypothermia or injury. HPRT activity in the cortex, hippocampus, thalamus, caudate, and cerebellum was measured spectrophotometrically.
  
  
  RESULTS
  There were no significant differences (p>0.05) in enzymatic activity when comparing the three groups of animals, regardless of reperfusion time or brain temperature. Within the control group, some regional differences in enzyme activity were noted.
  
  
  CONCLUSIONS
  The results indicate that brain HPRT activity is unaffected by hypoxia-ischemia, even after 4 hours of reperfusion and regardless of brain temperature. This study supports the importance of this enzyme in the conservation of brain purines after neurologic injury.
authors.affiliation: Department of Pediatrics, Division of Pediatric Critical Care, Harbor-UCLA Medical Center, Torrance, CA 90502, USA.
authors.forename: Tony
authors.initials: T
authors.lastname: Cherin
authors.forename: Maria
authors.initials: M
authors.lastname: Catbagan
authors.forename: Stephen
authors.initials: S
authors.lastname: Treiman
authors.forename: Richard
authors.initials: R
authors.lastname: Mink
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001794:Blood Pressure / Q000502:physiology; D004195:Disease Models, Animal; D007035:Hypothermia; D007041:Hypoxanthine Phosphoribosyltransferase / Q000378:metabolism*; D020925:Hypoxia-Ischemia, Brain / Q000201:enzymology* / Q000473:pathology* / Q000503:physiopathology; D011817:Rabbits; D015424:Reperfusion / Q000379:methods; D013053:Spectrophotometry / Q000379:methods; D013696:Temperature; D013997:Time Factors
chemical_list: D007041:Hypoxanthine Phosphoribosyltransferase