Functional Effects of the Coexistence of Hb-A with High Oxygen Affinity Hemoglobins
https://doi.org/10.4081/jbr.2003.10560
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In carriers of abnormal haemoglobins with increased oxygen affinity, polyglobulia is the only possible functional compensation for tissue hypoxia.However, this adaptation is reduced if some Hb-A is used to synthesize hybrid haemoglobins of the type a2bAbX (heterotetramers). In fact, they display increased oxygen affinity. Four patients of this kind were studied: two carriers of Hb-Kempsey: b 99Asp-Asn, one of Hb-Gàmbara: b 82Lys-Glu, and one of Hb- Trento, a new variant with elongated b chains. Moreover, there are some cases, like that of Hb- Tak, also with elongated b chains, and Hb-Casper: b 106Leu-Pro, in which the abnormal Hb does not interact with Hb-A to form hybrids and the patient presents good functional compensation. This is demonstrated by at least three signs: the absence of polyglobulia, the good reactivity of Hb-A towards 2,3-DPG, and the absence of left- shifting of the upper half of the dissociation curve,which is commonly considered the expression of Hb-A oxygenation.
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