J. Biol. Chem., Vol. 258, Issue 4, 2225-2228, Feb, 1983
Disruption of erythrocyte membranal organization by superoxide
GM Rosen, MJ Barber and EJ Rauckman
Human erythrocyte ghosts were covalently labeled with 4-maleimide-
2,2,6,6-tetramethylpiperidinooxyl. Electron paramagnetic resonance (EPR)
spectrometry revealed two major binding environments representing strongly
(S) and weakly (W) immobilized species. The disorder parameter, W/S,
determined from the respective peak amplitudes, was shown to be
irreversibly elevated following treatment of the labeled ghosts with
superoxide, indicating an increase in membrane fluidity. Labeled ghosts
reduced with ascorbate showed no nitroxide EPR signals. However, following
exposure of these membranes to superoxide, the nitroxide spectrum returned
with a W/S ratio of 25. In contrast, the disorder parameter for
spin-labeled ghosts decreased following exposure to hydroxyl radicals
suggesting decreased fluidity, as a result of lipid peroxidation. This
effect could be prevented by the inclusion of mannitol. These changes in
membrane fluidity and/or protein mobility observed by EPR are compared with
previous results obtained by other methods and provide additional evidence
for physiologic alterations initiated by superoxide.
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