Techniques to evaluate erythrocyte deformability in diabetes mellitus.

Using several rheological techniques, we examined erythrocyte deformability in different groups of diabetic subjects. The macrorheological techniques used for this evaluation were respectively whole-blood filtration, filtration of erythrocyte suspensions, polyviscosimetry and diffractometry. Whole-blood filterability, at a negative pressure of 20 cm water, was decreased in type 2 diabetics; no difference was evident at a negative pressure of 10 cm water. The filtration of erythrocyte suspensions at low haematocrit (5%) did not show differences between normal and diabetic subjects. Polyviscosimetry, which explores the filterability of erythrocyte suspensions at high haematocrit (80%) through wide pores, demonstrated an impaired behaviour especially in type 2 diabetics. Diffractometry, which measures erythrocyte elongation induced by a defined shear stress through the diffraction pattern of a laser beam, showed an alteration in type 1 diabetic subjects. The microrheological methods employed for this evaluation were those based on fluorescence spectroscopy. Labeling intact red blood cells with fluorescent probes, we determined the membrane dynamic properties and using these techniques we found a reduction of erythrocyte membrane fluidity and a decrease of red cell membrane protein lateral mobility.