The rate of dehydration of K+ permeabilized red cells is influenced by their Cl- permeability (PCl). In instances of pathological K+ permeabilization, cell-to-cell differences in PCl may determine which red cells dehydrate most. The present study was designed to investigate whether PCl differed significantly among red cells from a single blood sample. 2. Previously available methods measure only the mean PCl of red cell populations. We describe a 'profile migration' method in which dilute red cell suspensions in low-K+ media were permeabilized to K+ with a high concentration of valinomycin, rendering PCl the main rate-limiting factor for cell dehydration. As the cells dehydrated, samples were processed to obtain full haemolysis curves at precise times. Variations in PCl among cells would have appeared as progressive changes in the profile of their haemolysis curves, as the curves migrated towards lower tonicities. 3. Red cells from five normal volunteers showed no change in profile of the migrating haemolysis curves, suggesting that their PCl distributions were fairly uniform. Quantitative analysis demonstrated that intercell variation in PCl was less than 7.5%. 4. Results obtained with this technique were analysed using the Lew-Bookchin red cell model. The calculated PCl was within the normal range described in earlier studies.
