Radiation damage and recovery of sulfhydryl groups of erythrocyte membranes have been studied by irradiating suspensions of human erythrocytes or isolated ghosts with X-rays and measuring the remaining membrane sulfhydryl groups with 5′5-dithiobis-(2-nitrobenzoic acid). Decomposition of the nonexponential dose-response curves indicated that the membrane sulfhydryl groups consist of two classes with widely different radiosensitivity, the most radiosensitive fraction constituting about 10% of the total number of -SH groups. Factors expected to influence the structure of the membrane altered the percentage of radiosensitive -SH groups. The loss of -SH groups was greater when isolated ghosts were irradiated than when intact cells were exposed. Disulfide formation, as revealed by sodium borohyride reduction, accounted for the major part of the -SH lost on irradiation. In erythrocytes incubated for 1 hour at 37°C in the presence of glucose after exposure, about 60% of the -SH lost on irradiation reappeared. No recovery of -SH groups occurred either at low temperature, in the absence of glucose, or in isolated ghosts. Direct measurements of the membrane disulfide content indicated that the reappearance of -SH groups after exposure was due to reduction of radiation-induced disulfides. The data presented demonstrate that human erythrocytes possess a mechanism permitting them to reduce membrane disulfides under conditions of active metabolism. This mechanism may explain the repair of permeability observed under similar conditions by previous authors.

This content is only available as a PDF.
You do not currently have access to this content.