Research Information System
SANG THROMBOSE VAISSEAUX, vol.22, no.3, pp.137-143, 2010 (SCI-Expanded)
Red blood cell (RBC] aggregation is a process in which single cells form face-to-face linear aggregates then combine to form three-dimensional structures. This process is reversible : increased shear forces disperse aggregates while they reform at low shear or stasis and hence blood is a non-Newtonian fluid whose viscosity increases with decreasing shear. The in vivo effects of enhanced aggregation are yet to be fully defined, but include : 1] increased flow resistance in larger (i.e., > 1 mm] venous blood vessels; 2] abnormal RBC flux in microcirculation resulting in decreased tissue hematocrit; 3] more-pronounced cell-poor zone at vessel wall and hence decreased near-wall blood viscosity; 4] lower wall shear stress and thus impaired endothelial cell function. It is important to note that the influence of RBC aggregation on endothelial function should depend on the mechanism by which aggregation is increased : enhanced aggregation as the result of changes of RBC properties without altering plasma characteristics or as a result of modified plasma composition and hence higher plasma viscosity without altering RBC characteristics. The effects of enhanced RBC aggregation on wall shear stress may thus be partially or totally offset by increased plasma viscosity, and it is possible that discrepancies between studies investigating relations between RBC aggregation and vascular pathophysiology may be due to the manner by which higher red cell aggregation is achieved.