Critical hemolytic volume, surface area, and red cell hemoglobin concentration of reticulocytes and red cells.

(A) Quantitation of surface area of reticulocytes and red cells in a blood sample. The whole blood sample was diluted 1 to 1000 in a series of 16 solutions with osmolality ranging from 290 to 110 mosm/kg, and the volume of red cells and reticulocytes was measured using an automated hematology analyzer (Bayer Diagnostics, Puteaux, France). As the suspending medium osmolality decreased, cell volume increased until the cells attained their critical hemolytic volume (indicated by the arrows) just prior to cell lysis. The surface area of reticulocytes and mature red cells was derived from their respective critical hemolytic volumes, Vc retic and Vc RBC as outlined in “Patients, materials, and methods.” (B) Surface area (diamonds) and mean cell hemoglobin concentration (CHCM) (squares) as a function of red cell density. As the cell density increased, the surface area decreased and CHCM increased.