Erythrocyte deformability in diabetes and erythrocyte membrane lipid composition.

Erythrocyte deformability was assessed in 40 diabetic patients, 24 insulin-dependent (IDD) and 16 non-insulin-dependent (NIDD), by measuring the initial filtration flow rate of whole blood, isolated red blood cells (RBC), and isolated RBC membranes with the Hanss hemorheometer, and its relationship to the plasma and ghost membrane lipid composition was investigated. RBC deformability was significantly reduced, whereas the deformability of the isolated RBC membranes did not differ significantly from the controls. In the plasma, the triglycerides were high, the high-density lipoprotein (HDL) cholesterol was reduced, and the ratio of total cholesterol over HDL cholesterol was high as compared with the controls. The RBC lipid composition expressed in mumol lipids/10(10) RBC showed significantly lower levels of free cholesterol, sphingomyelines, and phosphatidylcholine, which are the lipids principally located on the outer layer of the RBC membranes. These data suggest that in both IDD and NIDD patients, there may be a relation between these modifications in the RBC lipid composition and rheological impairment of the RBC.

Physico-chemical factors of erythrocyte deformability.

The aim of this study is to assess the role of different physico-chemical factors on the deformability measurements by using the initial filtration flow rate method, and to differentiate between the membrane or internal origin of some rigidity changes. The deformability is maximum for the physiological pH value and it decreases sharply for hypotonic and hypertonic buffer. For normal RBC, the deformability is independent of the pO2 level and a small decrease is observed for increasing pCO2 values (with constant pH). A theoretical model of filtration for the "Hemorheometre" will be also developed.