The effect of high altitude and dietary restriction on protein oxidation in rat brain

Both, exposure to high altitude (HA) and dictary restriction (DR) implicated to alter free radical generation. Brain can be especially sensitive for the attack of free radicals as it has relatively low antioxidant capacity and contains significant amount of iron. The aim of the present study was to evaluate the effects of 4 wk chronic exposure to 4,000m of HA and 60% of DR of control (C) rats on protein oxidation in brain. Eighteen rats were assigned to DR, HA and C rats. Reactive carbonyl derivatives (RCD), marker of protein oxidation, was measured by Western blot. In addition, the activity and protein content of glutamine syntethase (GS) were determined. The activity of GS can easily depressed by free radicals. The body mass of C rats was significantly higher (P<0.001) than that of HA and DR groups. The quantified signal intensity of RCD was significantly stronger in C rats than in HA and DR rats. The activity of GS was higher (120%) in samples of HA rats than in C rats while in DR rats tend to be decreased (80%) compared with C group. The intensity of immuno blot signals of GS was stronger in C and HA rats than in DR group and the relative activity of GS in samples of HA and DR rats was significantly higher than in C rats. The data of the present study support the former observations that decrease in RCD level might be a result of increased protein degradation in HA group or increased antioxidant protection in DR group. Activity of GS might be a marker of oxidative stress, however the specific activity is important to evaluate the extent of oxidative stress. Finally, both HA and DR decrease the accumulation RCD in brain, however the underlying mechanism of the decrease seems to be different.