Parallel Decrease of Erythrocyte Membrane Deformability and Spectrin Solubility at Low pH

Reduction of pH over the range 6.0-4.5 rereduced elasticity occurred at calculated suits in a decrease of erythrocyte deformaintracellular pH values at which solubility bility in parallel with the induced progresin vitro of extracted erythrocyte spectrin is sive sphericity of cells. At low deformation also markedly reduced. The parallel derates employed, increase of hemoglobin crease of deformability and spectrin soluviscosity was not significant. A decrease of bility supports the hypothesis that spectrin membrane elasticity was detected in cells aggregation may contribute to regulation when sphering, the major determinant of of erythrocyte deformability through efcellular deformability, was prevented at fects on shape and membrane elastic charpH 5.0 by hyperosmotic medium. The proacteristics. nounced change of deformability and the R EDUCTION of pH induces increase in bulk viscosity of blood’’ and causes reduction of cellular deformability of individual erythrocytes.34 Fragmentation of cells with loss of membrane area increases sphericity and results in decrease of cell deformability,4 as does sphericity resulting from metabolic depletion.5 Modification of the intrinsic membrane structure by protein crosslinking agents6 and heating to 50#{176}C7alters the erythrocyte membrane’s viscoelastic properties, and the heat affects the resistance of the membrane to areal expansion.8 The present study was designed to examine the relative effect of reduced pH on membrane elasticity as one determinant of overall cellular deformability and to correlate elastic behavior with known pH-modulated properties of the membrane protein spectrin. The results indicate that there is an increase in sphericity, and a detectable reduction in membrane elasticity with reduced pH, in parallel with pH-induced aggregation of spectrin. No effect on cellular deformability as a result of increase of hemoglobin viscosity was observed, but a major influence of pH-induced sphericity on deformability was confirmed.