The single erythrocyte rigidometer (SER) as a reference for RBC deformability.

The SER allows the "deformability" of individual red blood cells to be quantitated by determining their passage time through a pore (d = 5.8 microns, 1 = 50 microns) under the shear stresses of 1.5 Pa-4 Pa. Using this system, we examined the influence of: 1. cytoplasmic viscosity, 2. membrane viscoelastic properties, 3. area to volume relationship. To change these determinants of RBC-deformability, the cells have been altered with 1. Acetylphenylhydrazine (0.016 mol/l), 2. diamide (0.5 mmol/l), 3. osmotic swelling (200 mosm/l) and osmotic shrinking (480 mosm/l) by suspending the cells in hypo- and hypertonic saline. The passage time has been found to be primarily influenced by changes in cytoplasmic viscosity. The same cells when tested in 4 other systems considered to measure RBC-deformability (filtrometer, packed cell viscometry, rheoscope and ektacytometry) behaved differently.