Erythrocyte membrane microviscosity in diabetes.

Decreased erythrocyte membrane fluidity was revealed by analyses with fluorescence depolarization using 1,6-diphenyl-1,3,5-hexatriene (DPH) and with electron paramagnetic resonance using spin-labelled stearates (EPR). The decreased membrane fluidity measured by DPH appeared to be related to the increase in membrane or plasam free cholesterol to phospholipid (C/PL) mol ratios. The decreased membrane fluidity observed by EPR appeared to be located, at least in part, in a deeper portion of membrane lipid core and the change may not be derived principally from the effect of cholesterol. Increases of membrane sphingomyelin (+ lysophosphatidylcholine) and decreases of phosphatidylethanolamine were found in erythrocytes of diabetic patients. The contributing factors to the decreased erythrocyte membrane fluidity in diabetic patients were suggested to be not only an increase in membrane C/PL mol ratios but also multifactorial changes involving membrane phospholipid fractions and other complex factors. It is considered that the determinant factors of membrane fluidity are so complex that the decreased membrane fluidity observed with diabetic erythrocytes cannot be closely correlated with any single constituent measured. The decreased membrane fluidity observed in this study appears to be related to poor metabolic control and is often associated with diabetic microangiopathy.