Sickle cell vaso-occlusion in an animal model; intravital microscopy and radionuclide imaging of selective sequestration of dense cells.

The impaired deformability and heterogeneity of erythrocytes in sickle cell disease endows them with abnormal microvascular flow dynamics. In the sickle cell exchange-transfused rat model, sickle cells exhibit lower volumetric flux and shear rates compared to normal (HbAA) or autologous rat cells. A subpopulation of dense sickle cells and irreversibly sickled cells show a propensity to induce occlusion at precapillary arterioles, residing at such sites for several seconds and causing local rheological disequilibrium. Radionuclide studies with indium-111 demonstrate preferential uptake of labeled HbSS cells in pulmonary microcirculation. These data are relevant to the factors that are involved in the initiation and propagatin of vaso-occlusion resulting in derangement of homeostasis in certain microvascular beds and perhaps painful crisis and selective organ injury.