Effect of low molecular weight dextrans on erythrocyte aggregation

Red blood cells (RBCs) can form aggregates of which shape is similar to stack-of-coin-like rouleaux. RBC aggregation is reversible and shear-dependent, thus it becomes a major determinant of shear-dependent nonlinear behavior of blood. It is generally known that high molecular weight polymers such as Dextran 70 and Dextran 500 can induce RBC aggregation, thus they have been widely used to adjust the degree of aggregation. Reversely, low molecular weight polymers (Dextran 10 and Dextran 40) have been reported to have an inhibitory effect on RBC aggregation. Maeda et al. found that the extent of RBC aggregation induced by Dextran 70 was decreased markedly by increasing concentrations of small dextrans (Dextran 10 and Dextran 40). Similarly, Chien and coworkers observed a reduction in the aggregation level when Dextran 40 was added to a suspension of human RBCs in Dextran 70-saline solution, which was attributed to augmentation of the RBC surface potential. Recently, our previous study with horse blood also reported that Dextran 40 might have an inhibitory effect on RBC aggregation induced by Dextran 500. However, it still remains relatively unclear how a neutral macromolecule like dextrans is capable of altering the surface potential of RBCs. Furthermore, no information has been available on whether or not even smaller dextrans (molecular weight <10 kDa) can provide such an inhibitory effect on aggregation. Thus, the present study utilized Dextran 1 to examine its potential inhibition effect on RBC aggregation induced by Dextran 500. Experimental