Osmotic fragility of the erythrocyte membrane: characterization by modeling of the transmittance curve as a function of the NaCl concentration.

The theoretical extinction of blood suspensions submitted to a slow dialysis is analyzed in terms of their NaCl concentration. The model involves two adjustable parameters, chi and K, related to swelling and hemolysis. During swelling, the erythrocyte volume is supposed to vary linearly with the saline concentration. During hemolysis, an exponential decay of the hemoglobin concentration in the erythrocyte is used. The theoretical transmittance curves are consistent with the measurements carried out at a wavelength of 0.808 microm on native and incubated blood samples. Chi and K are relevant parameters to characterize quantitatively the fragility of the erythrocyte membrane. The effect of a non ideal character of the hemoglobin solutions and of normal distributions of chi and K is also discussed.