Electric fields induce reversible changes in the surface to volume ratio of micropipette-aspirated erythrocytes

Micropipette-aspirated erythrocytes exhibit reversible changes in sphericity (surface-to-volume ratio) in response to applied electric fields. The potentials were applied between the shaft of the pipette and the bathing medium using Ag-AgCl electrodes and current clamping electronics. The change in surface-to-volume ratio is evidenced as a reversible change in the length of the cell projection in the pipette at constant aspiration pressure and changing voltage. The magnitude of the changes decreased in proportion to the inverse of the solute concentration indicating that the change in sphericity was due to a change in cell volume. Reversible changes in projection length equivalent to a 10% change in cell volume were observed to occur over times on the order of 10 s. The magnitude and time course of the effect were not affected by the removal of intracellular hemoglobin or inhibition of anion exchange. The effect was reduced by the presence of lanthanum and other multivalent cations in the suspending solution, suggesting that surface charge may play a role in mediating the effect.