Abstract: To determine and evaluate the changes of free radicals in brain tissue after brain injury and the relationship between them and brain edema, 42 SD rats were used and divided into three groups: normal controls, sham group and operation group. The cerebral contusion model was produced by weight dropping. The brain injury model was built successfully. The contents of SOD and MDA in cerebral contusion tissue were measured, and so were brain water contents. The data from the normal control group and the sham group showed no significant difference. MDA values of the traumatic right hemisphere of the operation group were significant higher than that of the normal control group and sham group, so were brain water contents(P<0.05). SOD activity of the traumatic hemisphere was lower than that of the other two group(P<0.05). The results of this study suggests: ①lipid peroxidation takes place in the traumatic cerebrum, and free radicals play the role in tissue damage due to ischemia and bleeding; ②oxidative stress causes brain edema and vice versa.

Key words: brain injury, free radicals, brain edema, superoxide dismutase, malonyldialdehyde