Chloride transport in human erythrocytes and ghosts: a quantitative comparison.

Abstract

Homogeneous preparations of resealed ghosts with intracellular KCl concentrations between 15-900 mM were prepared. Virtually all ghosts were sealed to Cl-. The Cl- transport system was not damaged: a quantitative comparison of the self-exchange of 36Cl- across intact and resealed membranes showed that both the transport capacity and a number of characteristic properties were identical. Due to the absence of intracellular titratable buffers, intracellular Cl- concentration in ghosts varied only slightly between pH 5 and 11. The unidirectional exchange flux was constant between pH 7 and 11, showing that the transport system did not have a functionally important titratable group in the alkaline range, as previously assumed. The decrease of transport below pH 7 was similar in intact-erythrocytes and ghosts. Mean cellular volume of the resealed ghosts was a function of the amount of KCl added at reversal, before the ghosts are sealed. The ghosts shrank by osmosis when KCl was added to the suspension of unsealed ghosts. The reflexion coefficient of sucrose was larger than that of KCl. Volume changes apparently did not affect the Cl- transport across the human red cell membrane. Unidirectional Cl- fluxes at a KCl concentration of 165 mM were independent of ghost volume.