ELECTROSTATIC REPULSION AMONG ERYTHROCYTES IN TUBE FLOW, DEMONSTRATEDBY THE THICKNESS OF MARGINAL CELL-FREE LAYER

Electrostatic repulsion among erythrocytes in flow was evaluated throu gh measurement of the thickness of the marginal cell-free layer in nar row glass tubes of 20-50 mu m in inner diameter. To reduce the electro static repulsive force, due mainly to sialic acid of the membrane glyc oproteins, human erythrocytes were treated with neuraminidase. The sur face negative charge of the erythrocytes, as determined from the elect rophoretic mobility using free-flow electrophoresis, was found to be p roportional to the sialic acid content. When erythrocytes with decreas ed sialic acid content flowed through narrow tubes, the thickness of c ell-free layer determined using an image processor increased even in t he absence of erythrocyte aggregation in the suspension. The effect wa s more pronounced at acidic pH. The addition of Dextran T-70 (70,400 M el. Wt.) further increased the cell-free layer thickness due to erythr ocyte aggregation. Thus, reducing the negative charge density on the e rythrocyte surface by itself accelerates the axial accumulation of ery throcytes in flow due to the decreased electrostatic repulsive force b etween the cells, even in the absence of erythrocyte aggregation.