THE ASSOCIATION BETWEEN ERYTHROCYTE INTERNAL VISCOSITY, PROTEIN NONENZYMATIC GLYCOSYLATION AND ERYTHROCYTE-MEMBRANE DYNAMIC PROPERTIES IN JUVENILE DIABETES-MELLITUS

The association of intracellular viscosity of red blood cells and the dynamic properties of erythrocyte membranes in children suffering from diabetes has been investigated by means of ESR spectroscopy. It has been revealed that the slight decrease in the ratio h(w)/h(s) of maleimide bound to membrane protein -SH groups of erythrocytes in diabetes may ensue from the enhanced membrane protein immobilization in the plane of lipid bilayer. These alterations were accompanied by a corresponding increase in the relative rotational correlation time (tau(c)) of iodoacetamide spin label, thus suggesting that the conformational changes in membrane proteins may occur at both the intrinsic and more exposed thiol groups. The membranes of diabetic red blood cells were more glycosylated than those of relevant controls, and the extent of glycosylation was found to correlate significantly with h+1/h0 and tau(c) (r = - 0.6 52, P < 0.0 1 and r = 0. 609, P < 0.0 1). Further, the conformational alterations in erythrocyte membranes from diabetic subjects were accompanied by a significant increase in the mobility parameter (h+1/h0) of haemoglobin molecules in diabetic erythrocytes. The latter changes correlated well with the enhanced intracellular viscosity of diabetic red blood cells and the level of glycosylated haemoglobin. We conclude that the alterations in membrane lipid-protein interactions together with the increased glycosylation-derived internal viscosity may consequently imply altered viscoelastic properties of erythrocyte membranes and, underlying the impaired deformability of red blood cells in the diabetic state, contribute to the development of late diabetic sequelae.