Biochemical and morphological changes in rat brain synaptosomes after exposure to normobaric hyperoxia in vivo

Adult rats were submitted to normobaric hyperoxia for 1 to 24 h, then the brain synaptosomes were isolated and their metabolic and morphologic properties were studied. Hyperoxia lasting 1-2 h significantly increased the content of thiobarbituric acid-reactive material (TBAR) and decreased the level of protein thid groups. During the next 5-8 h of hyperoxia SH groups as well as TBAR content became almost normal, reflecting adaptation of the animals to an elevated oxygen tension. After 24 h of hyperoxia a maximal increase in the TBAR content and parallel fall in protein thiol groups were noted. Simultaneously, significant morphological differences between control synaptosomes and synaptosomes isolated from rats exposed to 24 h oxygenation were observed in electron microscopy. The high-affinity dopamine uptake in hyperoxic synaptosomes was significantly increased in all experimental groups. A specific high sensitivity of the dopamine uptake system in synaptoplasmatic membranes to the free radical modification of the membrane structure is suggested.