We have established that 2,3-diphosphoglycerate (2,3-DPG) content and intracellular pH exert separate, but interdependent, effects on the equilibrium solubility (csat) of deoxyhemoglobin S (deoxy-Hb S) that act in concert to modulate intraerythrocytic polymer formation. In a nonphysiologic csat assay system, a steep dependence of csat on pH in the physiologic range 7.0 to 7.6 was shown for both stripped (Hb) and DPG-saturated deoxy-Hb S (Hb-DPG). The solubility-pH profile for Hb under near-physiologic buffer conditions also showed that csat increased steeply in the same pH range (6.8 to 7.6). The effect of 2,3-DPG on csat under near-physiologic conditions was evaluated separately. At pH 7.20, the pH of the human red blood cell, csat values for Hb and Hb-DPG were 19.56 +/- 0.14 and 17.95 +/- 0.45 g/dL, respectively, indicating that the solubility of Hb-DPG is lower than that of Hb by 8.2% +/- 2.3%. Thus, binding of 2,3-DPG in the beta-cleft promotes the polymerization of deoxy-Hb S, the ultimate determinant of cell sickling. Furthermore, because of the abnormal Bohr effect of sickle blood (approximately double that of normal blood), the intracellular pH of deoxygenated sickle erythrocytes should be approximately 0.28 pH unit higher than that of oxygenated cells (ie, 7.41 v 7.13). At the higher pH, the corresponding csat for Hb-DPG is 20.22 g/dL, which is the best estimate of the intrinsic solubility of T-state Hb S under conditions that approximate closely those of pH, temperature, ionic strength, and 2,3-DPG saturation in the fully desaturated sickle erythrocyte.

译文

我们已经确定,2,3-二磷酸甘油酸 (2,3-dpg) 含量和细胞内pH对脱氧血红蛋白S (脱氧-Hb S) 的平衡溶解度 (csat) 产生独立但相互依存的影响,而脱氧血红蛋白S (脱氧-Hb S) 协同作用调节红细胞内聚合物的形成。在非生理性csat测定系统中,对于汽提 (Hb) 和DPG饱和脱氧-Hb S (hb-dpg),显示出csat对7.0至7.6的生理范围内的pH的急剧依赖性。Hb在近生理缓冲条件下的溶解度-pH曲线也表明,在相同的pH范围内 (6.8至7.6),csat急剧增加。分别评估了近生理条件下2,3-dpg对csat的影响。在pH 7.20时,人红细胞的pH、Hb和hb-dpg的csat值分别为19.56 +/- 0.14和17.95 +/- 0.45g/dL,表明hb-dpg的溶解度比Hb的溶解度低8.2% +/- 2.3%。因此,在 β-裂隙中结合2,3-dpg会促进脱氧-Hb S的聚合,脱氧-Hb S是细胞镰状的最终决定因素。此外,由于镰状血液的异常玻尔效应 (大约是正常血液的两倍),脱氧镰状红细胞的细胞内pH应该比氧合细胞的pH高约0.28 pH单位 (即7.41 v 7.13)。在较高的pH下,hb-dpg的相应csat为20.22g/dL,这是在非常接近pH、温度、离子强度和完全去饱和镰刀红细胞中2,3-DPG饱和度的条件下,T-态Hb S固有溶解度的最佳估计值。

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