AN IMPORTANT FACTOR IN THE LOW OXYGEN AFFINITY OF BLOOD IN SICKLE CELL ANEMIA

Abstract

of 2,3-DPG in top fractions could not account for the degree of right shift of P50, and in the middle and bottom fractions the even greater right shifts were associated with lower levels of 2,3-DPG. Top fraction cells depleted of 2,3-DPG had a higher, but still abnormally low, oxygen affinity. A strong relationship was found between oxygen affinity and MCHC. The fractions with the greatest right shift in Pw0 had the highest MCHC (top 32.4-+-2.0; middle 36.2±3.1; bottom 44.6±3.2 g/ 100 ml, respectively) and the plot of Pw vs. MCHC showed a positive correlation (r= 0.90, P < 0.001). The red cell population in sickle cell anemia is not homogeneous but contains cells of widely varying Hb F content, 2,3-DPG, and hemoglobin concentration. Paradoxically, the cells with the lowest 02 affinity have the lowest 2,3-DPG, but they also have the highest concentration of Hb S. The dense, deformed cell called the ISC is but the end stage in a process of membrane loss and consequent increase in hemoglobin concentration. The P50 of Hb SS blood is, to a large extent, determined by the presence of these cells (r = 0.85, P <0.001). Increased concentration of Hb S in the cell favors deoxygenation and crystallization even at relatively high Po,. Lowered affinity for oxygen appears to be closely associated with Hb S concentration and not with 2,3DPG content.