Shape changes and deformability in human erythrocyte membranes.

To evaluate the membrane events that take place during red blood cell shape change, the deformability of resealed ghosts was studied in the ektacytometer while alterations in ghost shapes were produced. By studying ghosts in the ektacytometer it is possible to assess small changes in membrane dynamic rigidity free of the complicating factors that exist in intact red blood cells, such as concerns over the ratio of surface area to volume and the internal viscosity. Ghosts resealed in isotonic buffers are echinocytic, but addition of magnesium-adenosine triphosphate converts them to discocytes. This conversion to discocytosis was accompanied by an increase in membrane rigidity. Addition of vanadate along with magnesium-adenosine triphosphate blocked the conversion of echinocytic ghosts to discocytes, and in parallel blocked the accompanying increase in rigidity. Monospecific rabbit antispectrin antibody was resealed within ghosts and produced the anticipated increase in membrane rigidity. Morphologic evaluation revealed that such ghosts had changed from echinocytes to discocytes. Therefore two very different methods were used to convert normally echinocytic ghosts into discocytic ghosts, and in both cases the shape change was accompanied by an increase in ghost rigidity. These experiments indicate that in isotonically resealed ghosts, the discocytic shape is achieved as a consequence of membrane protein changes that produce an increase in membrane rigidity.