Elastic Area Compressibility Modulus Research Articles

Membrane mechanical properties of ATP-depleted human erythrocytes

Although the relations between the metabolic state and the mechanical properties of human red blood cells (RBC) continue to be of current interest, literature reports in this area are not in agreement. The present investigation was designed to determine several intrinsic mechanical properties of human RBC membranes before and after metabolic depletion via incubation at 37 degrees C for 24 hr. Using micropipette and flow channel techniques, three properties were measured: (1) mu, surface shear modulus of elasticity; (2) K, elastic area compressibility modulus; (3) etap, shear viscosity in the plastic domain. Our results indicate no significant differences in these parameters between fresh and ATP-depleted human RBC membranes. These present data are thus in disagreement with other literature reports indicating large changes in membrane mechanical properties consequent to metabolic depletion. A brief discussion of the possible reasons for this disagreement is presented.

Membrane Mechanical Properties of ATP-depleted Human Erythrocytes

Although the relations between the metabolic state and the mechanical properties of human red blood cells (RBC) continue to be of current interest, literature reports in this area are not in agreement. The present investigation was designed to determine several intrinsic mechanical properties of human RBC membranes before and after metabolic depletion via incubation at 37 degrees C for 24 hr. Using micropipette and flow channel techniques, three properties were measured: (1) mu, surface shear modulus of elasticity; (2) K, elastic area compressibility modulus; (3) etap, shear viscosity in the plastic domain. Our results indicate no significant differences in these parameters between fresh and ATP-depleted human RBC membranes. These present data are thus in disagreement with other literature reports indicating large changes in membrane mechanical properties consequent to metabolic depletion. A brief discussion of the possible reasons for this disagreement is presented.

Osmotic correction to elastic area compressibility measurements on red cell membrane

In a recent article (Biophys. J. 16:585, 1976), we reported measurements of the elastic area compressibility modulus or red cell membranes using micropipette aspiration on osmotically preswollen red cells. Subsequently, we have analyzed the effects of osmotic and hydrostatic pressure driving forces across the cell membrane in conjuction with the mass conservation equation; we find that the change in cell volume due to the reversible movement of water out of the cell can produce one-third of the movement of the cell projection in the pipette tip. Since the actual volume changes is too small to measure directly (about 1% of the total cell volume), we have used an indirect experimental method to provide critical evaluation of the analysis of cell volume change versus applied pressure; this is based on the model that the change in cell volume is inversely proportional to the cellular osmotic strength. We have increased the cellular cation concentration with a drug, nystatin, and measured the elastic area compressibility modulus corrected for osmotic volume changes as a function of cellular osmotic strength. We find that the corrected elastic are compressibility modulus is independent of cellular osmotic strength, which supports the model and calculated correction for the osmotic effect. The elastic area compressibility modulus is 450 dyn/cm at 25 degrees C instead of 300 dyn/cm, determined previously.