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Hypoxic-Ischemic Tolerance Induced by Hyperthermic Pretreatment in Newborn Rats

Department of Obstetrics and Gynecology, Miyazaki Medical College, Miyazaki, Japan

Tomoaki Ikeda, MD

Department of Obstetrics and Gynecology, Miyazaki Medical College, Miyazaki Japan tikeda{at}post1.miyazaki-med.ac.jp

Xiao Y. Xia, MD

Yi X. Xia, MD

Tsuyomu Ikenoue, MD

Department of Obstetrics and Gynecology, Miyazaki Medical College, Miyazaki, Japan

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 were separated on postnatal day 7 into two groups: 1) preheated (those exposed to 2 hours of hyperthemic 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 let 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 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 to 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.

Conclusion: Incidence of hypoxic-ischemic brain damage is consistently reduced by 2 hours of hyperthermic pretreatment in 7-day-old rats.

Key Words: Hypoxic-ischemic tolerance • hyperthermia • heat-shock protein • brain damage • newborn rat

Journal of the Society for Gynecologic Investigation, Vol. 7, No. 2, 102-105 (2000)
DOI: 10.1177/107155760000700204


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