Comparative hemorheology—Hematological implications of species differences in blood viscosity

Abstract

The rheological behavior of blood and red cell suspensions was studied in five mammalian (man, dog, elephant, sheep and goat) and four non-mammalian (turkey, box turtle, frog and amphiuma) species. Normal red cells from these species were suspended in Ringer solution, serum, plasma and fibrinogen solutions; aldehyde-hardened red cells were suspended in Ringer solution. Viscosity measurements were made at different temperatures and over wide ranges of shear rates and cell volume concentrations, and the findings were correlated with the data on cell passage through micropores in polycarbonate sieves and on centrifugal packing. Analyses of the results indicate that the shape (axial asymmetry or deviation from sphericity) of the suspended cells or aggregates exerts a greater influence than their size on the rheological behavior of blood. The cell shape can be changed by two shear-dependent phenomena: cell deformation and cell aggregation. Cell deformability is determined by membrane flexibility (area-to-volume ratio and tensile property of membrane) and the internal viscosity (physico-chemical state of internal fluid and MCHC). Cell aggregation depends on the aggregation tendency of RBC (deformability, etc.) and the aggregating effectiveness of plasma proteins (fibrinogen and α ₁- and β ₂-globulins). The shape change due to cell deformation and cell aggregation, together with the true cell volume concentration determine the effective cell volume concentration, which in turn is the final determinant of blood viscosity. Based upon the knowledge gained from such comparative studies, a systematic approach to analyze the hemorheological abnormalities in various hematological diseases has been proposed. Such studies promise to improve our understanding of the pathogenesis and the methods of management in these disorders.