title: Hypoxic-ischemic tolerance induced by hyperthermic pretreatment in newborn rats.
abstract: OBJECTIVE
  We investigated the effect of hyperthermic pretreatment 24 hours before hypoxic-ischemic exposure on neuronal cell damage in 7-day-old rats.
  
  
  METHODS
  Newborn rats were separated on postnatal day 7 into two groups: 1) preheated (those exposed to 2 hours of hyperthermic pretreatment at 42-43C) (n = 29), and 2) nonheated (n = 20). At 24 hours after the hyperthermic stress, rats from both groups were subjected to left carotid artery ligation followed by 2 hours of hypoxia (8% oxygen/92% nitrogen) at 33C. All rats were killed 1 week after hypoxia-ischemia, and brains were extracted for histologic study. A different group of 7-day-old rats (n = 8) was placed in the same hyperthermic environment as mentioned above for 2 hours, and 24 hours after heat exposure brains were extracted for immunohistochemistry of heat-shock protein 70.
  
  
  RESULTS
  The total incidence of hypoxic-ischemic brain damage significantly decreased in the preheated group (12 of 25 [48%]) compared with the nonheated group (17 of 20 [85%]; P < .03). The induction of immunoreactive heat-shock protein 70 was observed mainly in glial and vascular endothelial cells and, in a lesser amount, in neuronal cells of the cerebral cortex and hippocampus.
  
  
  CONCLUSIONS
  Incidence of hypoxic-ischemic brain damage is consistently reduced by 2 hours of hyperthermic pretreatment in 7-day-old rats.
authors.affiliation: Department of Obstetrics and Gynecology, Miyazaki Medical College, Japan.
authors.forename: A
authors.initials: A
authors.lastname: Ota
authors.forename: T
authors.initials: T
authors.lastname: Ikeda
authors.forename: X Y
authors.initials: XY
authors.lastname: Xia
authors.forename: Y X
authors.initials: YX
authors.lastname: Xia
authors.forename: T
authors.initials: T
authors.lastname: Ikenoue
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D001921:Brain / Q000473:pathology; D018840:HSP70 Heat-Shock Proteins / Q000032:analysis; D006979:Hyperthermia, Induced; D020925:Hypoxia-Ischemia, Brain / Q000473:pathology*; D007150:Immunohistochemistry; D009474:Neurons / Q000473:pathology*; D051381:Rats
chemical_list: D018840:HSP70 Heat-Shock Proteins