INVOLVEMENT OF SULPHHYDRYL GROUPS IN RADIATION DAMAGE TO HUMAN ERYTHROCYTE MEMBRANE

X-irradiation produces effects on several membrane permeability parameters of human erythrocytes (K+, Na+, choline+ movements; volume; hemolysis) similar to those produced by the sulphhydryl reagent parachloromercuribenzene sulfonate (PCMBS). However, X-irradiation does not alter glucose transport, in contrast to the inhibition resulting from PCMBS treatment. The results of additivity and subtractivity experiments are consistent with the proposal that PCMBS and X-irradiation produce increased K+ permeability by acting on common sites (-SH groups) in the membrane. The kinetics of K+ efflux at room temperature and the increased rate of K+ efflux at low temperature suggest the existence of membrane repair processes. Doses of X-irradiation which alter K+ permeability also result in the loss of membrane -SH groups, and part of this loss is due to disulfide formation. It is suggested that these changes of -SH groups after X-irradiation are primary events in the alterations of membrane structure leading to the increased K+ permeability observed.