The Journal of General Physiology, Vol 79, 791-819, Copyright © 1982 by The Rockefeller University Press
Diffusional water permeability of human erythrocytes and their ghosts
J Brahm
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
ms. At 25 degrees C, the permeability was 2.4 x 10(3) and 2.9 x 10(3) cm
s-1 for red cells and ghosts, respectively. Permeability was affected by
neither a change in pH from 5.5 to 9.5, nor by osmolality up to 3.3 osmol.
Manganous ions at an extracellular concentration of 19 mM did not change
diffusional water permeability, as recently suggested by NMR measurements.
A "ground" permeability of 1 x 10(3) cm s-1 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 to 30 kJ mol-1 to 60 kJ
mol-1. Although diffusional water permeability is about one 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. It is suggested that the PCMB(S)- sensitive permeability above
the ground permeability takes place through the intermediate phase between
integral membrane proteins and their surrounding lipids.
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