DEFORMABILITY AND IN VITRO FLOW PROPERTIES OF IRON DEFICIENT RED CELLS

Abstract

Previous studies have shown that iron deficient red blood cells (RBC) are less deformable than normal cells (Yip et al. Blood 62:99, 1983). RBC from 20 children with severe iron deficiency and from 20 healthy adults were used to study deformability (rheoscope), geometry (micropipette), membrane viscoelasticity (micropipette) and the Fahraeus-Lindqvist effect (decrease in blood viscosity as tube diameters decrease from 500 to 50μm). RBC deformability decreased as the MCV decreased (p<0.05). The excess surface area of iron-deficient RBC was up to 20% larger than that of normal RBC (p<0.05). The membrane elastic shear modulus of iron-deficient RBC was by 20% increased (i.e., elasticity was impaired) whereas the time constant for recovery from extensional deformation was shortened by about 20% when compared to normal RBC. Membrane viscosity (computed as product of the elastic shear modulus and the time constant) was similar for both cell types. Viscosity of normal blood decreased by 31% when the tube diameter was decreased from 500 to 50μm, whereas the decrease in blood viscosity was only 25% for iron deficient cells (p<0.05). Thus,the Fahraeus-Lindqvist effect was less for iron-deficiency. We conclude that iron-deficient RBC show several peculiar properties which may impair blood flow particularly when the hematocrit is increased (e.g., in patients with chronic hypoxemia or primary polycythemia).