The rate of osmotic influx of water by flexible and inflexible erythrocytes.

1. The rate of osmotic influx of water into flexible and hardened erythrocytes has been studied using a stopped-flow rapid-reaction method, and diluting the cells 1:20 in hypotonic media.2. Neither the initial rate of swelling nor the time to the onset of haemolysis were changed after making the erythrocytes inflexible by adding formaldehyde or by heating at 48 degrees C for 30 min.3. From a plot of the initial rate of uptake with hypotonicity, the permeability coefficient k can be calculated as 0.098 mu(3)/mu(2). sec atm (+/- 10%) at 20.5 degrees C.4. The value of k calculated from the time to the onset of haemolysis is 0.28 mu(3)/mu(2) sec atm. This suggests individual cells may differ over a wide range of permeability.5. The results are consistent with the pores being at fixed sites in the membrane and unaffected by flexing of the cell.