Effect of lanthanum on red blood cell deformability

Prior reports describing the effects of lanthanum (La³⁺) on red blood cells (RBC) have focused on the effects of this lanthanide on cell fusion or on membrane characteristics (e.g., ion movement across membrane, membrane protein aggregation); the present study explores its rheological and biophysical effects. Normal human RBC were exposed to La³⁺ levels up to 200 μM then tested for: (1) cellular deformability using a laser-based ektacytometer and an optical-based rheoscope; (2) membrane viscoelastic behavior via micropipettes; (3) surface charge via micro electrophoresis. La ³⁺ concentrations of 12.5 to 200 μM caused dose-dependent decreases of deformability that were greatest at low stresses: these rheological changes were completely reversible upon removing La³⁺ from the media either by washing with La³⁺-free buffer or by suspending La ³⁺-exposed cells in La³⁺-free media (i.e., viscous dextran solution). Both membrane shear elastic modulus and membrane surface viscosity were increased by 25-30% at 100 or 200 μM. As expected, La³⁺ decreased RBC electrophoretic mobility (EPM), with EPM inversely but not linearly associated with deformability; changes of EPM were also completely reversible. These results thus indicate novel aspects of RBC cellular and membrane rheological behavior yet raise questions regarding specific mechanisms responsible for La³⁺-induced alterations.