Participation of band 3 protein in hypotonic hemolysis of human erythrocytes.

The study was designed to show whether band 3, anion exchange protein in human erythrocytes, is responsible for hemolysis in hypotonic solution. From ESR spectra of the spin labeled erythrocytes, it was found that the change of the osmotic condition had no effect on membrane fluidity at pH 7.4. At pH 6.0, however, the fluidity at the central part of the lipid bilayer was dependent on osmotic stress. In this case, the fluidity change as a function of KCl concentration was similar to the hemolysis curve. From circular dichroism (CD) spectra of erythrocyte ghosts, it was found that the conformational and/or associative changes of the membrane proteins correlated with the hypotonic hemolysis. In contrast to the osmotic stress, sodium dodecyl sulfate (SDS) changed the fluidity of the membranes but not the conformation of the membrane proteins regardless of the medium pH. In this case, the changes in the fluidity corresponded to the hemolysis curves in SDS solutions. Further, by using anion transport inhibitors, 4,4'-diisothiocyanostilbene-2,2'-disulfonate, eosin 5-isothiocyanate and eosin-5-maleimide, a correlation between the effect on the hypotonic hemolysis and the conformational and/or associative change of band 3 was suggested. These results demonstrate that band 3 is responsible for the hypotonic hemolysis.