Mathematical modeling of the osmotic fragility of rabbit red blood cells

The osmotic fragility (OF) test is used to determine the extent of red blood cell hemolysis (RBCH) produced by osmotic stress. RBCH is dependent upon cell volume, surface area, and functional integrity of cell membranes. The variation of cell lysis with stress reflects underlying cell subpopulations and their membranes' cytoskeletal functionality. OF was determined on blood from New Zealand white rabbits. The dependence of RBCH on NaCl concentration ([NaCl]) was determined spectrophotometrically by measuring absorbance (Abs) from hemoglobin release at 545 nm. Abs data were fitted to the equation Abs = p3 erfc(([NaCl]--p1)/p2) where p3 reflects maximum RBCH, p1 measures the [NaCl] at 50% RBCH, and p2 shows the dispersion in [NaCl] producing the RBCH. Parameter values for control blood were p1 = 0.4489 +/- 0.0016; p2 = 0.0486 +/- 0.0016; and p3 = 0.4366 +/- 0.0022. Addition of indomethacin (9.6 micrograms/mL) produced an increased fragility in the RBC's characterized by increased values of p1 and p2. Normalization of the data to p3 did not change the values of p1 or p2. Our equation satisfactorily describes the variation in RBCH as a function of [NaCl]. The parameters of the equation can be used to quantitatively characterize Abs/[NaCl] data and compare pharmacological, toxicological, and pathological effects on the OF of RBC's.