Mechanism of the Effect of Ionizing Radiation on Sodium Uptake by Human Erythrocytes

Abstract

Measurements were made of sodium uptake by erythrocytes in saline suspension at 401 after exposure to radiation, sulfhydryl -blocking agents (PHMB [para-hydroxymercuribenzoate], chlormerodrin, and NEM [N-ethyl-maleimide]), radiation-protective agents (GSH [reduced glutathione] and MEG [2-mercaptoethyl guanidine]), and various combinations of these. The distributions of the protective agents and of chlormerodrin were studied, and the chemical changes in the protective agents during radiation were determined. Radiation-protective and sulfhydryl-blocking agents increase sodium uptake. Radiation and PHMB effects are additive up to a certain maximum response, when the mechanism is apparently saturated. GSH and MEG reduce the effect of both radiation and PHMB (or chlormerodrin). GSH must be present in the medium to protect the cells against radiation. It does not enter the cells. MEG enters the cells and protects against radiation by being in the medium and by being in the cells. MEG also reverses radiation effect when added after irradiation. These observations suggest that sulfhydryl groups of proteins on the cell surface and inside the cell are the radiation target. MEG may reverse radiation effect by reducing protein disulfides formed by radiation oxidation of protein sulfhydryl groups.