Membrane instability during erythrocyte maturation

The morphology and mechanical properties of the red blood cell change dramatically during maturation of the cell from the nucleated normoblast stage to the mature biconcave cell. The report examines changes in the stability of the membrane as the cells reach maturity. Surface stability was assessed by measuring forces required to form tethers (thin, tubular, lipid strands) from the cell surface. Cells obtained from fresh human marrow samples were brought into adhesive contact with a glass microcantilever. The cell was withdrawn using a micropipette mounted on a motorized micromanipulator to pull a tether from the cell surface. The force needed to form the tether was determined from the deflection of the glass cantilever. The mean force required to form tethers from marrow reticulocytes and normoblasts was 27/spl plusmn/9 pN, compared to 54/spl plusmn/14 pN for mature cells. These lower values of tethering force show that the membranes of immature cells are unstable, and may explain the difficulty to grow red cells to maturity in culture.