Red Cell Membrane Deformability: an Examination of Two Apparently Disparate Methods of Measurement

Abstract

Two techniques for measuring the deformability of the red blood cell membrane give divergent results. The folded cell traction technique indicates that an exponential stiffening occurs with increasing deformation, a response highly characteristic of most biological materials. Up till now, when membrane has been analyzed by the micropipette aspiration technique, no change in membrane characteristics has been elicited even at large deformations.

The assumptions underlying both techniques were critically examined. The mathematical analysis underlying the interpretation of the micropipette data proved to be crucially sensitive to a priori assumptions about how the membrane would respond.

Additional data were secured by a new membrane aspiration technique using polycarbonate sieves instead of micropipettes. These new data strongly support the picture of cell membrane characteristics derived from the folded cell traction technique. The RBC membrane responds to shear stress in a non-linear manner which tends to be exponential at deformations of more than 50%.