Affiliations: Institute of Transfusion Medicine, Medical Faculty Charité, Humboldt University of Berlin, D‐10098 Berlin, Germany | Department of Physiology and Biophysics, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033, USA
Note: [] Address for correspondence: Dr. Hans Bäumler, Institute of Transfusion Medicine, Charité, D‐10098 Berlin, Germany. Fax: +49 30 2802 5167; E‐mail: hans.baeumler@charite.de.
Abstract: The electrophoretic mobility of native and glutaraldehyde‐fixed bovine, human, and horse red blood cells (RBC) was investigated as a function of ionic strength (5–150 mM) and concentration of 464 kDa dextran (2 and 3 g/dl); RBC aggregation in autologous plasma and in dextran solutions was also measured. In agreement with previous observations, human and horse RBC form stable rouleaux whereas bovine RBC do not aggregate in either plasma or in dextran 464 kDa solutions. Electrophoretic measurements showed a species‐dependent adsorption and depletion of dextran that can be theoretically evaluated. Adsorption of polymer is not a prerequisite for RBC aggregation (bovine RBC show the highest amount of adsorbed dextran yet do not aggregate). Aggregate formation thus occurs as long as the Gibbs free energy difference, given by the osmotic pressure difference between the bulk phase and the polymer‐depleted region between two RBC, is larger than the steric and electrostatic repulsive energy contributed by the macromolecules present on the RBC surface. With increasing bulk‐phase polymer concentration the depletion layer thickness decreases and the amount of adsorbed macromolecules increases, thereby resulting in an increase of the repulsive component of the interaction energy and decreased aggregation. We thus view electrophoretic measurements of RBC in various media as an important tool for understanding polymer behavior near the red cell surface and hence the mechanisms involved in RBC aggregation.
