Diffusional water permeability of human erythrocytes and their ghosts.

Abstract

The diffusional water permeability of human red cells and ghosts was determined by measuring the rate of tracer efflux by means of an improved version of the continuous flow tube method, having a time resolution of 2-3 min. At 25.degree. C, the permeability was 2.4 .times. 10-3 and 2.9 .times. 10-3 cm/s-1 for red cells and ghosts, respectively. Permeability was not affected by a change in pH from 5.5-9.5 or by osmolality up to 3.3 osmole. Mn ions at an extracellular concentration of 19 mM did not change diffusional water permeability. A ground permeability of 1 .times. 10-3 cm/s was obtained by inhibition with 1 mM of either p-chloromercuribenzoate (PCMB) or p-chloromercuribenzene sulfonate (PCMBS). Inhibition increased temperature dependence of water permeability for red cells and ghosts from 21-30 to 60 kJ mol-1. Although diffusional water permeability is .apprx. 1 order of magnitude lower than osmotic permeability, inhibition with PCMB and PCMBS, temperature dependence both before and after inhibition, and independence of osmolality showed that diffusional water permeability has qualitative features similar to those reported for osmotic permeability, which indicates that the same properties of the membrane determine both types of transport. The PCMB(S)-sensitive permeability above the ground permeability apparently takes place through the intermediate phase between integral membrane proteins and their surrounding lipids.