Oxygen-free radicals in traumatic brain oedema.

Oxygen-free radicals have been implicated as causative factors in ischaemic and traumatic processes. Oxygen-free radical scavengers can be used potentially to treat brain oedema. We investigated the effects of superoxide dismutase and dimethylthiourea on brain oedema. Vasogenic brain oedema was produced in 44 cats by a cortical freezing lesion. Animals were separated into three groups: (1) cold-induced oedema with sacrifice at 6, 24 and 48 h; (2) cold-induced oedema with sacrifice at 6, 24 and 48 h: subgroup A was pretreated with 10,000 u./kg polyethylene glycol and superoxide dismutase; subgroup B received a bolus injection of free superoxide dismutase (4 mg/kg) and then 1 mg/kg/min for 20 min; (3) cold-induced oedema with sacrifice at 6 and 24 h: this group was pretreated with 500 mg/kg dimethylthiourea. Brain water content was measured by the specific gravity method. Detection of superoxide radicals was carried out by the direct cortical application of nitroblue tetrazolium. Free and polyethylene glycol-superoxide dismutase did not prevent the development of brain oedema, but superoxide radicals were detected in the cold lesion. Dimethylthiourea prevented the development of brain oedema in the white matter adjacent to the lesion at 6 h but not at 24 h. These findings indicate that oxygen-free radicals are generated by the brain following cold injury and the demonstration of these radicals offers an important clue in the genesis of traumatic brain oedema.