Abstract
Diabetic erythrocytes have recently been reported to have reduced deformability. This conclusion is based on studies using 5 micron polycarbonate filters or 4 micron glass pipets. The diabetic erythrocytes interact with the artificial surfaces during passage making it possible that the increased drag observed is an artifact not pertinent to capillary flow. In order to eliminate this possibility we have suspended diabetic and nondiabetic erythrocytes in nonaggregating physiologic media and studied their viscosity in a Couette viscometer with guard ring, an instrument in which red cell-artificial surface interactions are not of consequence. Shear rates ranged from .025 to 125 hertz. Two studies were done. In the first study cells of eight diabetic and eight nondiabetic subjects were compared in phosphate-buffered saline without added dextran. Viscosity elevation, seen only at low shear rate, did not achieve statistical significance. The second study compared cells from nine diabetic and nine nondiabetic subjects. Addition of 0.5% dextran (100,000–200,000 daltons) to the suspending medium more than doubled low shear rate viscosity and allowed demonstration of a statistically significant viscosity elevation limited to shear rates below 1.3 hertz. Limitation of increased flow resistance to this low shear rate range suggests that each diabetic erythrocyte’s ability to bend during flow is impaired, burdening its passage through the microcirculation.
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