CELL POKING - DETERMINATION OF THE ELASTIC AREA COMPRESSIBILITY MODULUS OF THE ERYTHROCYTE-MEMBRANE

Cell poking, a new method for measuring mechanical properties of single cells was used to determine the elastic area compressibility modulus of osmotically swollen human erythrocytes. With this method, the force required to indent cell attached to a glass coverslip was determined. Forces on the order of 1 mdyn and indentations on the order of 1 .mu.m were detected. An analysis of these data in terms of a simplified mechanical model yielded the elastic area compressibility modulus. This analysis used a variational approach to minimize the isothermal elastic potential energy density function given by Evans and Skalak (1980). Measurements on swollen erythrocytes gave a range of values, depending in part on the osmotic conditions, of 17.9 .+-. 8.2 to 34.8 .+-. 12.0 mdyn/.mu.m for the elastic area compressibility modulus at 25.degree. C. Fractional area expansion > 2.6 .+-. 0.8% produced rapid cell lysis. These values were not corrected for the reversible movement of water across the cell membrane in response to hydrostatic pressure gradients. Results agree reasonably with those obtained by Evans et al. (1976) using micropipette aspiration under similar conditions.