Mechanism of erythrocyte aggregation and sedimentation
TL Fabry
Department of Medicine, Mount Sinai School of Medicine, New York, NY 10029.
Unstirred suspensions of erythrocytes form stable spherical aggregates of
uniform size. The radius of the spheres depends upon the suspending medium
and the hematocrit. Erythrocyte suspensions will undergo sedimentation only
after these aggregates are formed. Aggregation is a two-step process:
first, erythrocytes associate in long chains (rouleau formation). Next,
these chains form spheres of uniform size. The requirements for this
well-defined process are an electrolyte and a neutral or negatively charged
macromolecule in the solution and a metabolically active red cell. If these
conditions are not met, red cells either will not aggregate at all or will
form amorphous aggregates. Rouleau formation and sedimentation are
inhibited by 4,4'- diisothiocyanatostilbene-2,2'-disulfonic acid, an
inhibitor of anion transport, but not by ouabain, a cation transport
inhibitor. The kinetics of erythrocyte sedimentation reflects the
aforementioned mechanism: no sedimentation occurs during rouleau formation.
Once the spheres of uniform size are formed, they will settle according to
the Einstein-Stokes equation. In this model, parameters of sedimentation
kinetics are the delay before sedimentation starts, the rate of
sedimentation in the steady state, and the radius of the sedimenting
aggregate. The radius can be calculated from the rate of fall of the
aggregates and agrees well with the microscopically observed radius. It is
inversely proportional to the hematocrit, which explains the elevated
sedimentation rates in anemia.
Volume 70,
Issue 5,
pp. 1572-1576,
11/01/1987
Copyright © 1987 by The American Society of Hematology
