Intrinsic material properties of the erythrocyte membrane indicated by
mechanical analysis of deformation
EA Evans and PL La Celle
Department of Biomedical Engineering, Duke University, Durham, N.C. 27706.
Deformation of the erythrocyte membrane by the micropipette technique
permits analysis of intrinsic material characteristics of the membrane and
provides a means to differentiate purely membrane factors from such
extrinsic factors as surface area-to-volume ratio. Using small
micropipettes (less than 0.5 microns radius) to deform cells, it is evident
that the red cell membrane behaves like a solid for periods of time up to
5-10 min of sustained deformation; for long periods of strain, permanent
deformations occur, indicative of the semi-solid structural character. In
the time range in which the membrane behaves like a solid, the material is
linearly elastic up to strains of 400%, implying a loose network structure
in the membrane plane, and evaluation of the elastic parameter mu (mu for
normal discocytes equals 7 x 10(-3) dynes/cm) suggests that the elements
comprising the network may have a molecular weight of approximately that of
the water-soluble membrane protein spectrin. Whether the network system is
cross-linked or simply a polymer solution remains unanswered. Experimental
data indicate that plastic flow of the membrane under conditions of
protracted strain may lead to permanent deformation of the membrane,
whereas uniform dilation of the membrane, requiring over 1000 times more
energy than for plastic flow, results in membrane failure and lysis.
Analyses of the data from larger micropipettes of limiting mean cylindrical
diameter show their utility in evaluating extrinsic factors, e.g., surface
area-to-volume relationships, which are related to the capability of the
whole cell to form a new configuration with implicit resistance to total
surface area change, as the cell enters narrow channels of the
microcirculation. Thus, micropipettes with diameters in the 2.7-3.0-microns
range can provide sensitive comparisons of cellular deformability of
erythrocytes.
Volume 45,
Issue 1,
pp. 29-43,
01/01/1975
Copyright © 1975 by The American Society of Hematology
