Morphologic and internal viscosity aspects of RBC rheologic behavior

Abstract

The influence of cellular morphology on the rheologic behavior of human red blood cells (RBC) was examined for both fresh and ATP-depleted erythrocytes. Rheologic measurements included cone-plate viscometry, cell deformation by high-speed centrifugation and direct microscopic observation via a counter-rotating Rheoscope. Evaluation of the experimental observations indicated the importance of RBC shape as a determinant of RBC deformability such that either echinocytic or stomatocytic shape alterations resulted in decreased deformability. the influences of both intracellular viscosity and the ratio of intracellular to suspending medium viscosity on age-separated RBC rheologic behavior were also investigated via the rheoscope. Deformation at a given stress level increased with increasing media viscosity; at constant media viscosity and shear stress, young cells deformed more than old. However, identical cellular deformation could be achieved by comparing RBC at equal ratios of internal to external viscosity. The above mentioned results appear relevant to measurements of SS RBC mechanical behavior when dealing with either non-biconcave cells (e.g., ISC or low oxygen tension) or with cells having altered internal viscosity (e.g., ISC, increased MCHC, gel formation). The relative importance of these effects is, however, as yet unknown.