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Red Cells with High Oxygen Affinity Hemoglobins
Published in Ronald L. Nagel, Genetically Abnormal Red Cells, 2019
In terms of the diagnosis of high-affinity hemoglobin variants the following points need to be remembered: Routine Hb electrophoresis is capable of detecting only a fraction of high-affinity mutants. More sophisticated methods such as agar electrophoresis or isoelectric focusing can improve detection, but a group of abnormal hemoglobins with high affinity and neutral to neutral substitutions cannot be detected by any electrophoretic methods. Recently it can become apparent that some of these cases can be detected by HPLC. Nevertheless it should always be remembered that a normal electrophoresis does not exclude the diagnosis of high-affinity hemoglobin.A p50 useful for the diagnosis of high-affinity hemoglobin cannot be a “calculated” p50 from PO2 data. The machine has to be able to measure saturation of hemoglobin and PO2 in order to render a useful p50. The Hem-o-scan type of apparatus are perfectly adequate for this purpose, but the state-of-the art equipment is the Imai cell as an attachment to a good recording spectrophotometer.
The HbS Containing Cell
Published in Ronald L. Nagel, Genetically Abnormal Red Cells, 2019
Ronald L. Nagel, Mary E. Fabry
Metabolic status, oxygen affinity, and HbS polymer formation — Seakins and coworkers77 studied p50, 2,3-DPG, and intracellular pH of the top, middle, and bottom layers of centrifuged cells. They found that p50 and intracellular pH (pHi) were increased in the bottom (ISC enriched) layer and that the 2,3-DPG content was decreased. Cells which are separated on Percoll-Stractan gradients exhibit a monotonic decrease in the cell age dependent enzyme glucose-6-phosphate dehydrogenase (G-6-PDase) which varies from patient to patient. Since other evidence suggests that the ISCs are not the oldest cells, it is possible that the same conditions which contribute to ISC formation also affect the activity of G-6-PDase. The intracellular 2,3-DPG content decreases with increasing MCHC as does the oxygen affinity (Table 1). Since low DPG should be associated with a high oxygen affinity, it is clear that the decreased oxygen affinity of high MCHC SS cells is determined by the low oxygen affinity of the hemoglobin S polymer. Noguchi et al.95 demonstrated that the extent of polymer formation is correlated with the MCHC. This implies that, in a whole blood sample which contains a heterogeneous population of cells, at any given pO2, not all cells will be deoxygenated to the same extent. The densest cells will be preferentially deoxygenated, and since the percent of dense cells varies from patient to patient, the percent deoxy hemoglobin as a function of pO2 will vary from patient to patient.
Determination of oxygen status in human blood
Published in John Edward Boland, David W. M. Muller, Interventional Cardiology and Cardiac Catheterisation, 2019
When peripheral factors such as vascular disease, anaemia, heavy exercise and cardiac output are the main limitations to oxygen transport, the p50 increases to facilitate oxygen unloading. When the limitation to oxygen transport is due to poor oxygen diffusion in the lungs, the p50 decreases to reduce oxygen unloading. Chemoreceptor control of ventilation, allosteric control of p50 and the diffusing capacities of the lungs and tissues regulate loading and unloading so that the resultant p50 provides the best level of oxygen transport for all conditions.6
Protective effect and mechanism of low P50 haemoglobin oxygen carrier on isolated rat heart
Published in Artificial Cells, Nanomedicine, and Biotechnology, 2022
Wentao Zhou, Shen Li, Shasha Hao, Honghui Zhang, Tao Li, Wanjing Li, Jiaxin Liu, Hong Wang, Chengmin Yang
However, due to the different structure and quality standards of HBOCs, the effects of these products on MI are not completely understood. Natason [7] and Silverman [8] reported 3,711 and 3,489 clinical research reports in the United States, the five HBOCs products were used to rescue patients with traumatic blood loss, and the survival rates were 91.6% and 91.7% respectively. However, the MI in the HBOCs group was higher than that in the control group, the main cause of MI is oxidative stress caused by excessive oxygen loading. Thus, any imbalance between oxygen supply and metabolic demand leads to functional, metabolic, morphologic, and electrophysiologic alterations, causing cell death. Substantial evidence suggests that controlled reoxygenation may ameliorate postischemic organ dysfunction. We hypothesized that changing the oxygen affinity of HBOCs can relieve MI caused by excessive oxygen loading. P50 (refers to the partial pressure of blood oxygen when the haemoglobin oxygen saturation is 50%) is an important indicator for evaluating oxygen affinity. Theoretically, MI can effectively be lessened with the right dose of oxygen supply caused by oxidative stress. To evaluate this hypothesis, the rat Langendorff isolated heart perfusion model was used to study the protective effect for myocardial on cardioprotective solution without or with different oxygen supply. Theoretically, an ideal cardioprotective solution can not only effectively prolong the preservation time of the isolated heart by right oxygen, but also will not cause new MI due to excessive oxygen.
Physiological and oxidative stress responses to intermittent hypoxia training in Sprague Dawley rats
Published in Experimental Lung Research, 2020
Megha A. Nimje, Himadri Patir, Rajesh Kumar Tirpude, Prasanna K. Reddy, Bhuvnesh Kumar
The 2, 3-bisphosphoglycerate (2, 3-BPG) is a glycolytic intermediate and an important modifier of oxygen delivery by red blood cells during hypoxic condition. The enzyme bisphosphoglycerate mutase (BPGM) converts 1, 3-BPG to 2, 3-BPG.49 Increased in 2, 3-BPG levels, as seen in hypoxic condition,50,51 facilitate oxygen unloading to peripheral tissues. At high altitude where arterial oxygen tension is low, a low p50 (the arterial oxygen tension at which 50% of hemoglobin is saturated with oxygen) would load more oxygen onto hemoglobin in the lung with a higher concentration of 2, 3-BPG as a result of higher BPGM in the erythrocyte to bind to deoxyhemoglobin. Normally 2, 3-BPG is present at high concentrations (∼5 mM) in red blood cells and binds the deoxy form of hemoglobin to reduce its affinity for oxygen.52 In this study, there was a marked up regulated expression of BPGM in all the hypoxia exposed groups of animals. This could be due to an early adaptive mechanism to hypoxia, where BPGM makes more of the availability of 2, 3-BPG, which further binds with deoxy form of hemoglobin, thereby releasing oxygen molecules for tissue oxygenation as a part of cellular adaptation to tissue hypoxia. Similarly, previous studies showed that there exists a parallel relationship in between the increase in erythrocyte 2, 3-BPG level and the decrease in affinity of hemoglobin to bind to oxygen, thereby releasing more numbers of oxygen available to the tissues for its oxygenation,53 as a physiologic process to hypoxic adjustment.
Novel High Oxygen Affinity Hemoglobin Variant in a Patient with Polycythemia: Hb Kennisis [β85(F1)Phe→Leu (TTT>TTG); HBB: c.258T>G]
Published in Hemoglobin, 2020
Ibrahim Al Nabhani, John C. Aneke, Madeleine Verhovsek, Barry Eng, Kevin H.M. Kuo, Leona C. Rudinskas, John S. Waye
We describe a patient with longstanding polycythemia due to a previously unreported Hb variant, Hb Kennisis [β85(F1)Phe→Leu]. He had the classical presentation of polycythemia and was clinically asymptomatic. In patients with high affinity Hbs, the degree of enhanced oxygen affinity predicts the severity of erythrocytosis and the clinical presentation [5–7]. The presentation can vary from asymptomatic erythrocytosis to severe polycythemia with hyperviscosity. Serum erythropoietin is typically high or normal; our patient had a normal erythropoietin level at baseline. While some high oxygen affinity Hb variants can be detected using routine methods such as capillary electrophoresis (CE) or high performance liquid chromatography (HPLC), many are indistinguishable from normal Hb A. In such cases, measurement of p50, which is the partial pressure of oxygen at which 50.0% Hb is saturated, is critical for diagnosis. A low p50 value indicates the presence of high affinity Hb or low 2,3-bisphosphoglyceric acid (2,3-BPG) level in the erythrocyte, or mutations in the 2,3-BPG binding site [5–7].