Brain edema was produced in rats and cats by freeze treatment, implanted balloons or triethyltin (TET) injection and metabolic activities were studied. An increase in water and sodium and a decrease in potassium content of white matter, resulting in a sharp rise of Na: K ratio, were observed. In total protein, nucleic acid and lipid content no significant changes were observed between normal and edematous brains. However, level of ganglioside was elevated markedly in both gray and white matter of cold induced brains. On the other hand the level of proteolipid protein showed a marked increase in the gray matter and a decrease in the white matter of both cold induced and TET intoxicated brains.
In the edematous brains the concentrations of the energy-rich phosphates, creatine phosphate and adenosine triphosphate, were decreased markedly whereas inorganic phosphate was increased.
The increased level of lactate was observed in the cold induced brains which suggested an increase of glycolysis in this condition. However, in the cold induced and epidural compressed gray and white matter, the most remarkable fact was that the protein synthesis was increased markedly after production of edema. In the experiments, protein synthesis increased for twenty-four hours following injury, reached a maximum between seventy-two and one hundred and twenty hours, and then gradually decreased. These findings correlate with the macroscopic changes of swelling of the brain. The same phenomenon was observed in the white matter of TET intoxicated cat brains to which TET was injected at the daily dose of 1 mg/kg, that is, the protein synthesis of the white matter increased remarkably on the fifth day, when its prominent edematous changes had already been confirmed. The proteolipid protein synthesis was also increased markedly in the cold induced gray and white matter and in the TET intoxicated white matter of the brains.
These findings suggest that turnover of the structural protein may be increased and the structural component of the membrane may be changed.
Incorporation of [5-3H] uridine into RNA was also increased in this condition. However, there was a sharp decrease in respiratory response to cationic and electrical stimulation. These findings are discussed in this paper in relation to other aspects of metabolic activity and to the mechanism of brain edema.
