UNILATERAL BRAIN INJURY IN THE RABBIT; REVERSIBLE AND IRREVERSIBLE DAMAGE OF THE MEMBRANAL ATPases

Modifications of some membranal enzymatic activities in rabbit brain edema induced by cold injury were studied. The edema was characterized by the tissue H₂O content and the K⁺/Na⁺ ratio. Comparison of the respiratory rate of isolated mitochondria in the state 3 and 4 and the ADP/O ratio suggested an alteration in the ATP synthesis mechanism. The oligomycin sensitive ATPase activity was severely reduced in mitochondria isolated from edematous cells. The alteration of the ouabain sensitive Na⁺-K⁺-ATPase was first qualitative in the sense where the response of the ATPase to the K⁺/Na⁺ ratio was modified. A loss of the total activity was then observed. Intravenous injection of CDP choline induced a regression of the edema, a restoration of the sensitivity of the mitochondrial ATPase towards oligomycin and a restoration of the sensitivity of the Na⁺-K⁺-ATPase to the K⁺/Na⁺ ratio. These results suggest that the reversible damages of the cells induced by cold injury were due to a disorder at the protein-lipid interaction level.