Stabilization of erythrocyte shape by a chemical increase in membrane shear stiffness

Treatment of human erythrocytes with the SH oxidant, diamide, suppresses shape transformations of biconcave erythrocytes into echinocytes or stomatocytes by shape-transforming agents assumed to exert their action via the lipid phase as well as via membrane proteins. The effect of diamide on shape changes is due to a formation of inter- and intramolecular disulfide bonds in membrane proteins, and can be reversed by reduction of these disulfide bonds. A monofunctional SH reagent, N-ethylmaleimide, also stabilizes the shape of the cell. Moreover, echinocytes produced by salicylate, and stomatocytes produced by Triton X-100, can be stabilized by diamide and do not return to the biconcave shape upon removal of the shape-transforming agents. The stabilizing effect of the SH reagents is paralleled by a loss of shear-induced deformability of the erythrocytes. A model is discussed that describes the possible mechanism by which SH reagents may stabilize the shape of the cell due to an increase of membrane shear stiffness.