Diabetes mellitus: evaluation of erythrocyte and polymorphonuclear leukocyte rheology

Aim: To explore red blood cells (RBC) and leukocyte rheology, that may be relevant in the pathophysiology of diabetes mellitus. Methods and Results: Significant alterations have been observed in RBC behaviour using several filtration techniques, but the exploration of RBC deformability by laser diffractometry did not show any abnormality. We have also employed microrheological methods based on fluorescence spectroscopy: membrane microviscosity was evaluated in ghosts, while in intact RBC we explored the membrane polarity gradient using fluorescent fatty acids, the phospholipid and protein lateral mobility using respectively pyrene and pyrene-3-maleimide. Alterations emerged only using the latter methods. We also investigated the filterability of polymorphonuclear leukocytes (PMN), their membrane fluidity and cytosolic Ca2+ concentration, both at baseline and after in vitro activation. At baseline no difference was evident in PMN filtration parameters or in cytosolic calcium content between normals and diabetics; a difference was noted in membrane fluidity. In normals, activation only induced a decrease in filterability, whereas in diabetics of both types we also observed an increase in cytosolic Ca2+ content and, only in type 1 diabetics, a decrease in membrane fluidity. Moreover, PMNs showed an altered integrin pattern in diabetes. Conclusions: The functional impairment observed in blood cells of diabetic subjects can play a role in the development of vascular complications.