In the present study, the changes of the supexoxide radical production and the activities of superoxide dismutase(Superoxide:superoxide oxidoreductase, EC 1. 15 1 1, SOD) and catalase(Hydrogen peroxide: hydrogen peroxide oxidoreductase, EC 1. 11. 1. 6) in the rat brain which exposed to 85`% 0, or 95% 0, were observed.
The results were as :follows:
1. All homogenates prepared from the brains of rats exposed to 85% 0, showed considerably higher activity of Cu,Zn-SOD in comparison with those of the control group(p<0.01). The activity reached to the peak at 5 days after the exposure to 85 % O2.
2. Homogenates prepared from the brains of rats at 3 days, and 5 days after the exposure to 85% O2 showed considerably higher activity of Mn-SOD in -comparison with those of the control group(p<0.01). The activity reached to the peak at 3 days after the exposure to 850/0 0,
3. After the exposure to 95 To O2, all homogenates of brains of rats showed considerably higher activity of Cu,Zn-SOD in comparison with those of the control group(p<0.01). The activity reached to the peak at 2 days after the exposure to 85% 02-
4. Only at 2 days and 3 days after the exposure to 95% 02, the homogenates of the brains of rats showed considerably higher activity of Mn-SOD in comparison with those of the control rats(p<0.01). The activity reached to the peak at 3 days after the exposure to 95% 02-
5. At 3 days after the exposure to 85% O2 and at 2 days and 3 days after the exposure to 95% 02, the homogenates prepared from the brains of rats showed considerably low superoxide radical production in comparison with those of the control group(p<0.01).
6. The activities of catalase o the brains of rats exposed to 85 To 0, were higher than those exposed to 95% 02. The activities of catalase of the brains of rats exposed to 95% O2 were similar to those of the control group.
The activities of Cu,Zn-SOD of the rat brains.increased in higher oxygen concentration. However, the production of superoxide radical decreased. In conclusion, it seems likely.that the superoxide dismutase plays an important role in the defense mechanism of the brain when exposed to hyperoxic state.
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