Relationship between morphologic characteristics of sickle cells and method of deoxygenation

The relationship between the morphologic characteristics of sickle erythrocytes and the method of deoxygenation was studied using rectangular glass capillary tubes (0.05 X 0.5 X 50 mm). Deoxygenated blood samples were anaerobically collected into the tubes and directly observed under a microscope. A high yield (90%) of sickled red blood cells was observed if the sample was deoxygenated slowly with nitrogen gas. However, rapid deoxygenation by sodium dithionite resulted in low percentages of sickling and high percentages of irregularly shaped cells (mosaic cells). Mosaic cells were also formed upon rapid deoxygenation with nitrogen gas and thus appear to result from the precipitation of intracellular deoxygenated hemoglobin S. Only 20% of the mosaic cells converted to sickle cells with prolonged incubation at 37 degrees C. However, if the mosaic cells were cooled, desickled, and deoxygenated again slowly by nitrogen gas, most could be converted to typical sickle-shaped cells. Further studies on the comparison of sodium dithionite and sodium metabisulfite as reducing agents showed that sodium dithionite reduced intracellular hemoglobin rapidly, and sodium metabisulfite reduced it slowly. This difference explains the high yield of sickling with sodium metabisulfite compared with sodium dithionite.