Active transport of GSSG from reconstituted erythrocyte ghosts

Human erythrocyte ghosts were loaded with 35S-labeled GSSG and with a sucrose marker, and the transport of GSSG to the suspending medium was studied. GSSG transport from ghosts occurred only when ATP was also present in the ghosts, proceeded against a concentration gradient, and was inhibited by fluoride. The rate of transport was dependent upon the intracellular concentration of GSSG. The relationship between GSSG concentration and rate of transport was sigmoidal. Half-maximal transport was observed at a GSSG concentration of approximately 9.6mM. The maximal velocity was estimated to be in the range of 0.27 umole GSSG per ml of ghosts per hr. These data suggest that the rate of GSSG transport a physiologic concentrations of GSSG is not sufficiently rapid to account for the turnover of glutathione by red cells. It seems more likely that the GSSG transport system serves an emergency function of erythrocytes.