Investigations of artificial aggregation of washed human erythrocytes caused by decreased pH and reduced ionic strength

Aggregation measurements of washed human erythrocytes were carried out in a NaCl-PBS solution under laminar shear conditions. An artificial aggregation was caused by decreased pH and reduced ionic strength, and characterized by the collision efficiency, e.m., the probability of a permanent aggregate formation. It was found that the aggregation increases reducing the ionic strength and decreasing the pH of the medium. Pretreatment with Amphothericin B did not change the aggregation. The results cannot be explained neither by the usual D.L.O.V. theory (force balance between electrostatic repulsion and attraction due to dispersion forces) nor by direct influence of the changed transmembrane potential. It is supposed that this type of aggregation involves reversible changes of the membrane and/or the surface structure.