[A new technic for the study of the physiology of erythrocytes: measurement of their deformability as a function of osmolarity. Results obtained by an automatized Ektacytometer in normal blood and in various hemolytic anemias].

A system has been added to the Ektacytometer to allow continuous variation and measurement of the osmolarity of the suspension medium from 50 to 500 mosm kg-1 permitting the analysis of erythrocyte deformability over a range varying from hypo- to hypertonicity. The curves are obtained automatically in 7 min. from a blood sample of 150 microliters. The "minimum index" observed in hypotonicity indicates that the cells are non-deformable at this point just preceding hemolysis. The osmolarity at which this index occurs provides a measure of the osmotic fragility of the sample. In hypertonicity there is a zero index, corresponding to non-deformable cells, which occurs at an osmolarity dependent on the original internal viscosity of the cells. This "null index" introduces the notion of erythrocyte resistance to deformation in hypertonicity. This new technique permits the evaluation of the erythrocyte response to various factors affecting their shape, internal viscosity or membrane flexibility. We present and discuss examples of curves obtained with normal blood before and after fractionation by density and after treatment with cystamine, as well as pathological bloods from two hemolytic anemias (hereditary spherocytosis and sickle cell anemia).