AJP - Cell Physiology, Vol 235, Issue 5 269-C278, Copyright © 1978 by American Physiological Society
Influence of pH on elastic deformability of the human erythrocyte membrane
E. D. Crandall, A. M. Critz, A. S. Osher, D. J. Keljo and R. E. Forster
Fresh human blood was diluted 1:5000 in buffered saline-sucrose solution
and titrated to a pH varying from 4.5 to 10.5 with 0.1 N HCl or 0.1 N NaOH.
Circular regions of the membrane of individual cells were then deformed at
25 degrees C by aspiration into a micropipette having an internal tip
diameter of 0.9-1.4 micron. A membrane surface elasticity modulus, mu
(dyn/cm), was computed from the relationship between length of the
aspirated membrane and the deforming pressure according to a
two-dimensional membrane model. Surface elasticity increases with
decreasing pH and with time after the cell suspension is acidified, rising
several orders of magnitude with a t1/2 of 1--5 h as pH is lowered from 7.2
to 4.6. This increase in mu is only partially reversible. pH greater than
7.2 had little effect on mu. Membrane surface elasticity is not affected by
variations in external [Ca2+] over the range of 0--50 mM, tonicity of the
suspension medium from 275--400 mosM, or age of 0--50 h. Addition of 50 mM
NaHCO3 to the medium increases the rate of change of mu at a given pH.
These results suggest that the elastic properties of the red cell membrane
are largely determined by interactions among structural proteins located on
the cytoplasmic surface of the membrane and that these interactions are
initiated by changes in intracellular pH.
