The authors studied the effect of short-term (20 min) hypobaric hypoxia at simulated altitudes of 7000 and 9000 m on the peroxidation of lipids in the cerebral cortex, subcortical formations, medulla oblongata and cerebellum of the laboratory rat. In 5- and 21-day-old rats, increased lipoperoxidation was recorded in all the studied regions of the brain. Differences were observed in sensitivity to the degree of hypoxia. In 5-day-old rats the response to both exposures was the same, but in 21-day-old animals exposure at 7000 m stimulated peroxidation in the cerebral cortex only (at 9000 m in all the parts of the CNS examined). In 35-day-old and adult rats, changes in the malondialdehyde concentration were likewise found after exposure at 9000 m, but not in every compartment (in 35-day-old rats in the cerebral cortex and subcortical formations and in adult rats in the cerebral cortex). In young rats, 30 and 60 min after exposure to hypoxia the malondialdehyde concentration was still higher than in older animals.
Carnitine administration (by intraperitoneal injection) to 21-day-old-rats prevents the increase of thiobarbituric acid-reactive substances (index of lipid peroxidation and free radical damage) induced by 30 min hypobaric hypoxia in four different parts of the brain (cerebral cortex, subcortical structures, medulla oblongata and cerebellum).
The effect of normobaric oxygen atmosphere on hypoxia-enhanced lipid peroxidation in the brain cortex, subcortical structures, medulla oblongata and in the cerebellum was observed in 7- and 21-day-old and adult rats. The production of free oxygen radicals causing lipid peroxidation was assessed by the method described by Ohkawa et al. (1979). The rats were exposed for 30 min to 100 % oxygen atmosphere which significantly stimulated the production of malondialdehyde (MDA) in all the studied regions of the brain in 7- and 21-day-old male rats, and in the brain cortex and subcortical structures of adult males. Higher levels of MDA were found in the brain cortex of 7-day-old female rats only. Reoxygenation with pure oxygen after 30 min hypobaric hypoxia corresponding to 9000 m increased MDA production in all studied parts of the brain on both male and female rats 7- and 21-day-old. In adult rats significantly increased MDA production was only found in the brain cortex of male and female rats and in the subcortical structures of males. The exposition to hypobaric hypoxia followed by reoxygenation by atmospheric air enhanced MDA production in all studied regions of the brain in 7-day-old males and in the cerebellum of females; in 21-day-old rats of both sexes a significant increase of MDA was detected in all parts of the brain. In adult rats were found higher MDA levels in the cerebral cortex of both males and females.