David O, Ivaldi G, Rabino-Massa E, Ricco G
Laboratorio di Ematologia, Ospedale Infantile Regina Margherita, Genova, Italia.
Acta Haematol. 2002;108(3):132-8. doi: 10.1159/000064702.
Nine carriers of beta-abnormal haemoglobins with increased oxygen affinity (Hb X) were examined. Their oxygen dissociation curves from whole blood were more or less left-shifted, with six of nine also characterized by biphasism. This refers to an 'inflection point' usually positioned at about 50-60% of Hb O(2) saturation, commonly believed to be a limit between oxygenation of the normal and abnormal components. In effect, the inflection does not always correspond to the Hb X level, which sometimes is much lower than 50% of the total Hb. Moreover, the upper half segment of the dissociation curve could not only be an expression of Hb A oxygenation, since it is always left-shifted. However, a high Hb A level is commonly believed to be the main compensatory factor of these subjects, but many indications suggest that often they have at least three, and not only two, main haemoglobin species: Hb A, Hb X plus hybrids of the type alpha(2)beta(A)beta(X). These would oxygenate after Hb X, but before Hb A. Finally, the interaction of 2,3-diphosphoglycerate with Hb X and/or hybrid tetramers must be altered, and the releasing of oxygen from both is more or less reduced. Unfortunately, it is difficult to demonstrate the presence of hybrids directly, i.e. with amino acid analysis of the abnormal beta-globin.
对九名携带具有增加氧亲和力的β异常血红蛋白（Hb X）的携带者进行了检查。他们全血的氧解离曲线或多或少向左移位，九名中有六名还具有双相性特征。这指的是一个“拐点”，通常位于Hb O₂饱和度的约50 - 60%处，通常被认为是正常和异常成分氧合之间的界限。实际上，该拐点并不总是与Hb X水平相对应，Hb X水平有时远低于总Hb的50%。此外，解离曲线的上半段不仅可能是Hb A氧合的表现，因为它总是向左移位。然而，通常认为高Hb A水平是这些受试者的主要代偿因素，但许多迹象表明，他们通常至少有三种而非仅两种主要血红蛋白类型：Hb A、Hb X以及α₂β(A)β(X)类型的杂合体。这些会在Hb X之后但在Hb A之前发生氧合。最后，2,3 - 二磷酸甘油酸与Hb X和/或杂合四聚体的相互作用必定发生了改变，并且两者释放氧的能力或多或少有所降低。不幸的是，很难直接证明杂合体的存在，即通过对异常β珠蛋白进行氨基酸分析来证明。
