A basis for the increased thixotropy of diabetic blood

Abstract

Increased low shear rate blood viscosity in diabetes, linked in previous studies to elevated blood thixotropy, has been further examined by comparing erythrocytes from diabetic subjects with those from age- and sex-matched nondiabetic subjects. The red cells were resuspended at 0.60 hematocrit in phosphate-buffered saline containing sufficient 100–200,000 Dalton dextran to produce minimal erythrocyte aggregation. Diabetic erythrocytes were found to sediment at a rate not significantly higher than nondiabetic erythrocytes in this medium. Diabetic erythrocyte suspensions were 16% more viscous than those of nondiabetic erythrocytes at low shear rate, but their viscosity averaged only 3–4% higher at high shear rate. The increased viscosity was found to be related to current fasting glucose level but not to erythrocyte glycosylated hemoglobin content. Flow onset and cessation shear stress patterns were examined to assess RBC suspension viscoelasticity and thixotropy at shear rates below 30 inverse seconds. The apparent elastic modulus of diabetic erythrocyte suspensions was found to be elevated at shear onset but did not differ at cessation. Flow onset thixotropy was found to parallel steady shear stress in diabetic and nondiabetic suspensions. Thixotropic (flow initiation) work increased more rapidly than shear rate for both diabetic and nondiabetic erythrocytes. When examined in relation to published studies of diabetic blood flow properties, these observations support the conclusion that diabetic erythrocyte deformation as flow begins consumes more energy than that of nondiabetic erythrocytes.