Determination of sickle hemoglobin polymer in SS and AS erythrocytes

Using 13C nuclear magnetic resonance techniques, we have studied the polymerization of hemoglobin S and intracellular polymerization in SS and AS erythrocytes. For SS erythrocytes, polymer could be detected at high oxygen saturations (greater than 90%) and increased with decreasing oxygen saturation to 70% of the total hemoglobin at complete deoxygenation. These results are consistent with the non-ideal behavior of hemoglobin S at the high intracellular concentration of 34 g/dl. The amount of polymer in AS erythrocytes was also measured as a function of oxygen saturation and is in agreement with the amount of polymer determined for homolysates using ultracentrifuge sedimentation. In general, these results on intracellular gelation are in good agreement with results predicted by cell-free studies extrapolated to the high intracellular hemoglobin concentration (34 g/dl). The significance of the detection of polymer at high oxygen saturation of SS erythrocytes is discussed in terms of morphologic deformation and erythrocyte transit through the circulation. We propose that intracellular polymerization is important in abnormal cell rheology and manifestation of disease.