Potassium-chloride cotransport in resealed human red cell ghosts.

Furosemide-inhibitable K influx is threefold higher in resealed ghosts of human erythrocytes than in intact cells. The enhancement is specific for K in that furosemide-inhibitable Na influx is the same in resealed ghosts and intact cells. The enhanced K influx resembles K-Cl cotransport in intact cells in that it requires Cl but not Na. N-ethylmaleimide (NEM), which stimulates furosemide-inhibitable K influx in intact cells, is without effect (or slightly inhibitory) in resealed ghosts. The failure of NEM to enhance the flux was not due to low ATP in the ghosts. These findings suggest that enhancement of the K flux in ghosts occurs by oxidation of membrane protein sulfhydryl groups, known to occur with lysis, the same sulfhydryl groups at which NEM acts by alkylation. This conclusion is supported by two observations: dithiothreitol completely prevents the increase in K influx in ghosts; this agent inhibits both oxidation of sulfhydryl groups and alkylation of them by NEM; and K influx in resealed ghosts is sensitive to changes in cell volume, just as it is in NEM-treated intact cells.