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Hypoxia-induced increases in hypoxic tolerance augmented by beta-hydroxybutyrate in mice
1Department of Physiology, University of Michigan Medical School, Ann Arbor 48109.
Stroke
|September 1, 1989
Summary
Acute hypoxic pretreatment significantly extends survival time in mice by inducing protective metabolic changes and hypothermia. This suggests a novel adaptation mechanism against hypoxia.
Area of Science:
- Physiology
- Biochemistry
- Environmental Medicine
Background:
- Hypoxia, a state of oxygen deficiency, poses significant physiological challenges.
- Understanding adaptive responses to hypoxia is crucial for survival and therapeutic strategies.
Purpose of the Study:
- To investigate if acute pretreatment exposures to hypoxia can enhance ultimate hypoxic survival time.
- To explore the metabolic and physiological changes associated with hypoxic preconditioning.
Main Methods:
- Adult male albino mice were subjected to graded hypoxic exposures (4.5% O2) with intervening normoxia.
- Hypoxic survival time, blood glucose, and ketone concentrations were measured.
- Effects of exogenous glucose, ketones, and beta-hydroxybutyrate were assessed.
- Body temperature changes and their role in survival were analyzed using Cox regression.
Main Results:
- Hypoxic pretreatment significantly increased mean hypoxic survival time from 108 to 403 seconds.
- Blood glucose and ketone levels elevated post-hypoxic pretreatment.
- Exogenous glucose or ketones alone did not improve survival.
- Beta-hydroxybutyrate with hypoxia increased survival time to 749 seconds and decreased body temperature.
Conclusions:
- Sequential hypoxic exposures induce metabolic adaptations that protect against lethal hypoxia.
- Decreased body temperature plays a partial role in enhanced hypoxic survival.
- Hypoxic preconditioning may involve altered substrate utilization and induced hypometabolic hypothermia.