The mechanism of the dextran-induced red blood cell aggregation

Abstract

In order to clarify the mechanism of dextran-induced aggregation, the effect of the ionic strength (I) on the minimal shear stress (tau(c)) required to rupture RBC doublets was studied for suspensions with the external media containing 76 and 298 kDa dextrans. At low and high ionic strengths, tau(c) increases with increasing I, whereas at intermediate I values, tau(c) versus I dependencies reveal a plateau step. The non-monotonous shape of these curves disagrees with the depletion model of RBC aggregation and is consistent with the predictions of the bridging mechanism. Literature reports point out that elastic behavior of dextran molecules in low and high I regions is fairly typical of Hookean springs and hence predict an increase in tau(c) with increasing I. A plateau step is accounted for by the enthalpic component of the dextran elasticity due to the shear-induced chair-boat transition of the dextran's glucopyranose rings. A longer plateau step for suspensions with a higher molecular weight dextran is explained by a larger contribution of the enthalpic component to the dextran elasticity. Thus, the results reported in this study provide evidence that RBC aggregation is caused by the formation of dextran bridges between the cells.

Experimental evaluation of mechanical and electrical properties of RBC suspensions under flow. Role of RBC aggregating agent

“…The formation is changing from RBC aggregates of smaller size to aggregates with increased size and branched aggregates as it was observed from images, received by the optical shearing system consisted of a Lincam CSS-450 glass plate-plate shearing system, combined with an Olympus BX51 microscope and a CCD integrated camera (JVC TK-C1380 colour) in our previous work [13]. The enhanced RBC aggregation in RBC suspensions in dextrans and PEG found in the present study is in the line with data, obtained by low shear viscometry [7,23,24] and techniques based on phenomena of light scattering [4,5,12,13,25], electrical properties measurement [1,5,17,18] or direct microscopic observations [8]. Our results confirm the results of Reinhart et al [22,23] who observed that an increase of erythrocyte aggregation by addition of dextran 70 led to the expected increase of viscosity in the Couette viscometer.…”

Effect of Cell-Free Layer Variation on Arteriolar Wall Shear Stress

“…Thus, the WSS ( τ ) could be estimated with the plasma viscosity and slope of the linear velocity profile as follows:where μ is the plasma viscosity and W is the cell-free layer width. The dextran treatment increases plasma viscosity as well as level of red blood cell aggregation 20,28,39. However, in our in vivo study, the plasma viscosity effect on the WSS was isolated by using the same plasma viscosity value (1.3 cP)37 in determination of the WSS for all conditions.…”

Computational Biorheology of Human Blood Flow in Health and Disease

“…RBC aggregation interactions strongly depend on the nature and concentration of available proteins or polymers 24,107 and can be triggered by adding them to non-aggregating RBC suspensions. 107,126,144 Whole blood is also known to exhibit a yield stress 27,29,106 defined as a threshold stress that must be exceeded for flow to begin.…”