Synergistic effects of oxidation and deformation on erythrocyte monovalent
cation leak
PA Ney, MM Christopher and RP Hebbel
Department of Medicine, University of Minnesota Medical School,
Minneapolis.
The normal red blood cell (RBC) membrane is remarkable for its durability
(eg, preservation of permeability barrier function) despite its need to
remain deformable for the benefit of microvascular blood flow. Yet, it may
be hypothesized that the membrane's tolerance of deformation might be
compromised under certain pathologic conditions. We studied this by
subjecting normal RBC in viscous suspending medium (20% dextran) to
elliptical deformation induced by application of shear stress under
physiologic conditions (290 mOsm/L, 37 degrees C, pH 7.40) in the presence
of ouabain and furosemide. Measurement of resulting net passive K efflux
("K leak") demonstrated that shear-induced RBC deformation causes K leak in
a dose-dependent fashion at shear stresses far below the hemolytic
threshold, an effect shown to be due to deformation per se. To model the
specific hypothesis that oxidatively perturbed RBC membranes would be
abnormally susceptible to this potentially adverse effect of deformation,
we treated normal RBC with the lipid peroxidant t-butylhydroperoxide. Under
conditions inducing only minimal K leak due to either oxidation alone or
deformation alone, deformation of peroxidant-pretreated RBC showed a
markedly enhanced K leak (P less than .001). This highly synergistic
oxidation-plus- deformation leak pathway is less active at low pH, is
neither chloride- dependent nor calcium-dependent, and allows K efflux to
be balanced by Na influx so there is no change in total monovalent cation
content or cell density. Moreover, it is fully reversible since
deformation- induced K leak terminates on cessation of shear stress (even
for oxidant-treated RBC). Control experiments showed that our results are
not explained simply by hemolysis, RBC vesiculation, or development of
prelytic pores. We conclude that oxidation and deformation individually
promote passive leak of monovalent cation through RBC membranes and that a
markedly synergistic effect is exerted when the two stresses are combined.
We hypothesize that these findings may help explain the abnormal monovalent
cation leak stimulated by deoxygenation of sickle RBC.
Volume 75,
Issue 5,
pp. 1192-1198,
03/01/1990
Copyright © 1990 by The American Society of Hematology
