Direct intracellular measurement of deoxygenated hemoglobin S solubility

The solubility of deoxygenated hemoglobin S (HbS), which is the concentrati on of fully deoxygenated HbS in equilibrium with polymer (C-SAT), is a fact or that determines in vivo polymer formation. However, measurement of C-SAT is usually performed under conditions that are far from physiological. In solution studies of HbS by Benesch at al, it was demonstrated that p50, the point at which hemoglobin is half-saturated with oxygen, is proportional t o the amount of polymer formed and that it may be used to measure C-SAT. Th is method has been extended to measure C-SAT In Intact red cells by varying extracellular osmolarity, which, in turn, varies intracellular hemoglobin concentration. This method measures intracellular C-SAT under physiological conditions with intact red cell contents and can be applied to human and t ransgenic mouse red cells. The principle is demonstrated by measuring p50 a s a function of extracellular osmolarity for AA, SS, and AS red cells. (C) 2001 by The American Society of Hematology.