Photometric determination of phenomenological correlation between osmotic behavior and hemolysis of red blood cells.

The osmotic behavior of red blood cells from a human and from several other mammalian species was studied by photometric measurements. When red blood cells were suspended in sodium chloride solutions with various osmotic concentrations, the optical density at 620 nm was reciprocally related to the relative volume of the red cells. Thus, we evaluated the osmotic volume changes in the red cells from optical density measurements. The Boyle-van't Hoff relation was applicable to the osmotic behavior of red cells which responded as a complete osmometer in hypertonic and slightly hypotonic (lower than about 240 mOsm) solutions. Also, we examined the rheological correlation between osmotic volume changes and hemolysis. Osmotic hemolysis occurred corresponding to breakdown of the Boyle-van't Hoff relation in hypotonic solutions. The critical osmotic concentration for the breakdown of the Boyle-van't Hoff relation was that for osmotic hemolysis. In Na2SO4 solutions, although the critical osmotic concentration shifted towards a smaller value, the critical volume for the breakdown of the Boyle-van't Hoff relation and for osmotic hemolysis was maintained at a constant value, indicating that the onset of osmotic hemolysis depends exclusively upon the critical volume. In the samples from a human, the critical volume for the onset of hemolysis was estimated to be 1.25 +/- 0.05 in the ratio to the normal volume in iso-osmotic solution. From these obtained results, it is suggested that the red cell behaves in hypotonic solutions as a viscoelastic body of the type represented by the Voigt model, and the viscoelastic breakdown of the membrane results in osmotic hemolysis in hypotonic solution.