The Single Erythrocyte Rigidometer (SER) has been applied to measure various extrinsic and intrinsic factors involved in red blood cell (RBC) passage time through a single pore membrane. The SER allows to measure the mean passage time (MPT in ms) of 250 single RBC’s each under a relevant and low constant pressure gradient of 70 Pa (τ = 3 Pa) through single pores of defined geometry (SEM measurements). Furthermore a computer program provides us with a list of every single RBC passage time, a flow distribution curve and the MPT of the 10, 5, 2.5, and 1% slowest RBC’s (“subpopulation”). In the course of the present investigation extrinsic factors like pressure gradient and pore geometry have been examined. MPT correlates directly with pore diameter, RBC shape, and volume. Also the influence of leucocyte removal by cotton wool filtration has been examined. Even the filtration of control RBC increased the MPT by 9% (n = 47). Furthermore we evaluated the influence of different intrinsic factors on RBC deformability. To simulate the imbalanced metabolic situation under pathophysiological conditions we have changed in vitro different parameters. Buffers of different stress degree have been composed and applied to pharmacological characterisation of compounds. Additionally all RBC preparations have been checked for possible subpopulations of rigid cells. The detection of rigid subpopulations was dependent of the pore diameter and they were even detectable in control blood.
