title: Tissue oxygenation in brain, muscle, and fat in a rat model of sleep apnea: differential effect of obstructive apneas and intermittent hypoxia.
abstract: OBJECTIVE
  To test the hypotheses that the dynamic changes in brain oxygen partial pressure (PtO(2)) in response to obstructive apneas or to intermittent hypoxia differ from those in other organs and that the changes in brain PtO(2) in response to obstructive apneas is a source of oxidative stress.
  
  
  METHODS
  Prospective controlled animal study.
  
  
  METHODS
  University laboratory.
  
  
  METHODS
  98 Sprague-Dawley rats.
  
  
  METHODS
  Cerebral cortex, skeletal muscle, or visceral fat tissues were exposed in anesthetized animals subjected to either obstructive apneas or intermittent hypoxia (apneic and hypoxic events of 15 s each and 60 events/h) for 1 h.
  
  
  RESULTS
  Arterial oxygen saturation (SpO(2)) presented a stable pattern, with similar desaturations during both stimuli. The PtO(2) was measured by a microelectrode. During obstructive apneas, a fast increase in cerebral PtO(2) was observed (38.2 ± 3.4 vs. 54.8 ± 5.9 mm Hg) but not in the rest of tissues. This particular cerebral response was not found during intermittent hypoxia. The cerebral content of reduced glutathione was decreased after obstructive apneas (46.2% ± 15.2%) compared to controls (100.0% ± 14.7%), but not after intermittent hypoxia. This antioxidant consumption after obstructive apneas was accompanied by increased cerebral lipid peroxidation under this condition. No changes were observed for these markers in the other tissues.
  
  
  CONCLUSIONS
  These results suggest that cerebral cortex could be protected in some way from hypoxic periods caused by obstructive apneas. The increased cerebral PtO(2) during obstructive apneas may, however, cause harmful effects (oxidative stress). The obstructive apnea model appears to be more adequate than the intermittent hypoxia model for studying brain changes associated with OSA.
authors.affiliation: CIBER Enfermedades Respiratorias, Spain.
authors.forename: Isaac
authors.initials: I
authors.lastname: Almendros
authors.forename: Ramon
authors.initials: R
authors.lastname: Farré
authors.forename: Anna M
authors.initials: AM
authors.lastname: Planas
authors.forename: Marta
authors.initials: M
authors.lastname: Torres
authors.forename: Maria R
authors.initials: MR
authors.lastname: Bonsignore
authors.forename: Daniel
authors.initials: D
authors.lastname: Navajas
authors.forename: Josep M
authors.initials: JM
authors.lastname: Montserrat
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D002540:Cerebral Cortex / Q000378:metabolism*; D004195:Disease Models, Animal; D005978:Glutathione / Q000378:metabolism; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism; D000860:Hypoxia / Q000378:metabolism; D050356:Lipid Metabolism; D015227:Lipid Peroxidation; D008297:Male; D018482:Muscle, Skeletal / Q000378:metabolism*; D010100:Oxygen; D051381:Rats; D017207:Rats, Sprague-Dawley; D012891:Sleep Apnea Syndromes / Q000378:metabolism*; D020181:Sleep Apnea, Obstructive / Q000378:metabolism; D042442:Vascular Endothelial Growth Factors / Q000378:metabolism
chemical_list: D018840:HSP70 Heat-Shock Proteins; D042442:Vascular Endothelial Growth Factors; D005978:Glutathione; D010100:Oxygen