Erythrocyte and ghost cytoplasmic resistivity and voltage-dependent apparent size

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Particle resistivity is explicitly included in the equations relating volume to voltage pulse, in electronic cell sizing or resistive pulse spectroscopy (RPS). It has long been known that in high electric fields cell resistivity decreases as the membrane undergoes dielectric breakdown. At sufficiently high electric field strengths, well past dielectric breakdown, the red cell membrane becomes electrically transparent, or nearly so, and apparent cell size becomes essentially a function of the cytoplasmic resistivity. Electronic cell sizing is traditionally carried out at low electric field strengths, and corrections made for the influence of cell shape by use of the Laplace equation. We find the Laplace solution to be still applicable at very high electric field strengths for purposes of calculating specific cytoplasmic resistivity from RPS measurements. Our value for discocytes, 220 omega X cm, is in good agreement with published results obtained by other researchers using other techniques. We have also applied these same procedures to determine the time course of voltage-dependent resistivity changes in ghosts and intact spherocytes, during the first 5 min after suspension in hypotonic medium. We believe these to be the first explicit calculations of particle specific resistivity from post-dielectric-breakdown apparent size, using traditional electronic sizing techniques.