title: Doublet formation of diabetic erythrocytes as a model of impaired membrane viscous deformation.
abstract: Erythrocyte deformation involves both viscous dissipation in the cell interior and viscoelastic motion of the cell membrane. Reports that describe reduced filterability of diabetic erythrocytes, altered response to oscillatory motion in a capillary-sized pipet, and impaired packing during centrifugation indicate a disturbance of red cell rheology in diabetes. We have selected conditions that minimize the macromolecule-mediated energy of attraction between erythrocytes and studied erythrocyte motion during doublet formation. Under such conditions, doublet formation frequency is strikingly reduced in diabetes. For nondiabetic erythrocytes the formation rate is 0.73 doublets per minute, whereas for diabetic erythrocytes the rate is 0.23 doublets per minute. In addition, mean velocity of doublet formation was found to be decreased to half of normal in diabetes. Completeness of doublet formation, regularly diminished when cell size of the two component cells was similar, was the same for diabetic and nondiabetic erythrocytes. Observation of several features of doublet formation gave a picture of the mechanical process. The initial cell making contact with the glass microscope slide was observed to remain fixed in position. The late arriving cell's ability to form a doublet was seen to decrease rapidly, apparently because it came to adhere to the glass surface. The attractive force between the cells overcomes the force of gravity, but cell deformation resistance slows doublet formation by balancing the tendency for cell-cell contact area to increase. An integral equation combining strain energy and viscous dissipation was applied to the doublet formation process. Slowing of doublet formation in diabetes appears to be produced by a doubling of resistance to rate of change of curvature of diabetic erythrocytes.
mesh_terms: D003920:Diabetes Mellitus / Q000097:blood*; D004903:Erythrocyte Aggregation; D004910:Erythrocyte Membrane / Q000502:physiology; D004912:Erythrocytes / Q000502:physiology*; D006801:Humans; D012212:Rheology