RESUMO
We used mathematical modeling to investigate nitric oxide (NO)-dependent vasodilatory signaling in the arteriolar wall. Detailed continuum cellular models of calcium (Ca2+) dynamics and membrane electrophysiology in smooth muscle and endothelial cells (EC) were coupled with models of NO signaling and biotransport in an arteriole. We used this theoretical approach to examine the role of endothelial hemoglobin-α (Hbα) as a modulator of NO-mediated myoendothelial feedback, as previously suggested in Straub et al. (Nature 491: 473-477, 2012). The model considers enriched expression of inositol 1,4,5-triphosphate receptors (IP3Rs), endothelial nitric oxide synthase (eNOS) enzyme, Ca2+-activated potassium (KCa) channels and Hbα in myoendothelial projections (MPs) between the two cell layers. The model suggests that NO-mediated myoendothelial feedback is plausible if a significant percentage of eNOS is localized within or near the myoendothelial projection. Model results show that the ability of Hbα to regulate the myoendothelial feedback is conditional to its colocalization with eNOS near MPs at concentrations in the high nanomolar range (>0.2 µM or 24,000 molecules). Simulations also show that the effect of Hbα observed in in vitro experimental studies may overestimate its contribution in vivo, in the presence of blood perfusion. Thus, additional experimentation is required to quantify the presence and spatial distribution of Hbα in the EC, as well as to test that the strong effect of Hbα on NO signaling seen in vitro, translates also into a physiologically relevant response in vivo.NEW & NOTEWORTHY Mathematical modeling shows that although regulation of nitric oxide signaling by hemoglobin-α (Hbα) is plausible, it is conditional to its presence in significant concentrations colocalized with endothelial nitric oxide synthase in myoendothelial projections. Additional experimentation is required to test that the strong effect of Hbα seen in vitro translates into a physiologically relevant response in vivo.
Assuntos
Endotélio Vascular/fisiologia , Hemoglobina A/fisiologia , Óxido Nítrico/fisiologia , Transdução de Sinais/fisiologia , Vasodilatação/fisiologia , Algoritmos , Simulação por Computador , Eritrócitos/efeitos dos fármacos , Retroalimentação Fisiológica , Humanos , Receptores de Inositol 1,4,5-Trifosfato/efeitos dos fármacos , Modelos Teóricos , Óxido Nítrico Sintase Tipo III/biossíntese , Canais de Potássio Cálcio-Ativados/biossínteseAssuntos
Neoplasias da Mama , Hipóxia Celular/fisiologia , Hemoglobina A , Tolerância a Radiação , Neoplasias do Colo do Útero , Neoplasias da Mama/sangue , Neoplasias da Mama/irrigação sanguínea , Neoplasias da Mama/radioterapia , Feminino , Hemoglobina A/análise , Hemoglobina A/fisiologia , Humanos , Recidiva Local de Neoplasia/sangue , Recidiva Local de Neoplasia/irrigação sanguínea , Dosagem Radioterapêutica , Transplante Heterólogo , Resultado do Tratamento , Neoplasias do Colo do Útero/sangue , Neoplasias do Colo do Útero/irrigação sanguínea , Neoplasias do Colo do Útero/radioterapiaRESUMO
Hemoglobinopathies are diseases involving abnormalities of the structure or production of hemoglobin. Examples include sickle cell disease, the thalassemias, and rare hemoglobin variants producing cyanosis. Recent advances in the understanding of the consequences of hemoglobin dysfunction on nitric oxide signaling have led to a reassessment of the pathophysiology of sickle cell disease and thalassemia. Chronic vascular inflammation and damage is now recognized as playing an important role in disease expression. Hemoglobinopathies may present to the anesthesiologist as the primary cause of a surgical procedure, as an incidental complicating factor of a surgical patient, or with a problem arising from the disease itself. This article reviews the common types of hemoglobinopathies, presents a basic summary of the pathophysiology relevant to anesthesia, and outlines current perioperative management.
Assuntos
Anemia Falciforme , Anestesia/métodos , Hemoglobina M , Talassemia , Anemia Falciforme/complicações , Anemia Falciforme/genética , Anemia Falciforme/terapia , Transfusão de Sangue , Hemoglobina A/química , Hemoglobina A/fisiologia , Humanos , Talassemia/complicações , Talassemia/genética , Talassemia/terapiaRESUMO
PURPOSE: The tumor oxygenation status is likely influenced by two major factors: local tumor blood supply (tumor perfusion) and its systemic oxygen carrier, hemoglobin (Hgb). Each has been independently shown to affect the radiotherapy (RT) outcome in cervical cancer. This study assessed the effect of local tumor perfusion, systemic Hgb levels, and their combination on the treatment outcome in cervical cancer. METHODS AND MATERIALS: A total of 88 patients with cervical cancer, Stage IB2-IVA, who were treated with RT/chemotherapy, underwent serial dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) before RT, at 20-22 Gy, and at 45-50 Gy. The DCE-MRI perfusion parameters, mean and lowest 10th percentile of the signal intensity distribution in the tumor pixels, and the Hgb levels, including pre-RT, nadir, and mean Hgb (average of weekly Hgb during RT), were correlated with local control and disease-specific survival. The median follow-up was 4.6 years. RESULTS: Local recurrence predominated in the group with both a low mean Hgb (<11.2 g/dL) and low perfusion (lowest 10th percentile of signal intensity <2.0 at 20-22 Gy), with a 5-year local control rate of 60% vs. 90% for all other groups (p = .001) and a disease-specific survival rate of 41% vs. 72% (p = .008), respectively. In the group with both high mean Hgb and high perfusion, the 5-year local control rate and disease-specific survival rate was 100% and 78%, respectively. CONCLUSION: These results suggest that the compounded effects of Hgb level and tumor perfusion during RT influence the radioresponsiveness and survival in cervical cancer patients. The outcome was worst when both were impaired. The management of Hgb may be particularly important in patients with low tumor perfusion.
Assuntos
Hemoglobina A/fisiologia , Neoplasias do Colo do Útero , Adenocarcinoma/sangue , Adenocarcinoma/irrigação sanguínea , Adenocarcinoma/mortalidade , Adenocarcinoma/radioterapia , Adulto , Idoso , Idoso de 80 Anos ou mais , Carcinoma de Células Escamosas/sangue , Carcinoma de Células Escamosas/irrigação sanguínea , Carcinoma de Células Escamosas/mortalidade , Carcinoma de Células Escamosas/radioterapia , Hipóxia Celular/fisiologia , Terapia Combinada/métodos , Intervalo Livre de Doença , Feminino , Seguimentos , Hemoglobina A/análise , Humanos , Imageamento por Ressonância Magnética/métodos , Pessoa de Meia-Idade , Recidiva Local de Neoplasia/sangue , Recidiva Local de Neoplasia/irrigação sanguínea , Recidiva Local de Neoplasia/mortalidade , Estudos Prospectivos , Dosagem Radioterapêutica , Taxa de Sobrevida , Resultado do Tratamento , Neoplasias do Colo do Útero/sangue , Neoplasias do Colo do Útero/irrigação sanguínea , Neoplasias do Colo do Útero/mortalidade , Neoplasias do Colo do Útero/radioterapiaRESUMO
Hemoglobin (Hb) plays an important role in oxygen transfer from lung to tissues. Possession of a Hb with high oxygen affinity helps highland animals to adapt to high altitude, has been studied profoundly. Plateau pika (Ochotona curzoniae), a native species living at 3,000-5,000 m above sea level on Qinghai-Tibet Plateau, is a typical hypoxia and low temperature tolerant mammal. To investigate the possible mechanisms of plateau pika Hb in adaptation to high altitude, the complete cDNA and amino acid sequences of plateau pika hemoglobin alpha and beta chains have been described. Compared with human Hb, alterations in important regions can be noted: alpha111 Ala-->Asn, beta35 Tyr-->Phe, beta112 Cys-->Val, beta115 Ala-->Ser, and beta125 Pro-->Gln. Phylogenetic analysis of alpha and beta chains shows that plateau pika is closer to rabbit than to other species. This study provides essential information for elucidating the possible roles of hemoglobin in adaptation to extremely high altitude in plateau pika.
Assuntos
Altitude , Clonagem Molecular , Hemoglobina A/genética , Hemoglobinas/genética , Lagomorpha/genética , Adaptação Fisiológica , Sequência de Aminoácidos , Substituição de Aminoácidos , Animais , Asparagina/metabolismo , Sequência de Bases , Códon de Iniciação , Códon de Terminação , Sequência Conservada , Primers do DNA , DNA Complementar , Glicina/metabolismo , Hemoglobina A/química , Hemoglobina A/fisiologia , Hemoglobinas/química , Hemoglobinas/fisiologia , Humanos , Lagomorpha/fisiologia , Dados de Sequência Molecular , Fenilalanina/metabolismo , Filogenia , Reação em Cadeia da Polimerase , Serina/metabolismo , Valina/metabolismoRESUMO
Many branchiopod crustaceans are endowed with extracellular, high-molecular-weight hemoglobins whose exact structural characteristics have remained a matter of conjecture. By using a broad spectrum of techniques, we provide precise and coherent information on the hemoglobin of one of the phylogenetically 'oldest' extant branchiopods, the tadpole shrimp Triops cancriformis. The hemoglobin dissociated under reducing conditions into two subunits, designated TcHbA and TcHbB, with masses of 35,775+/-4 and 36,055+/-4 Da, respectively, determined by ESI-MS. Nonreducing conditions showed only two disulfide-bridged dimers, a homodimer of TcHbA, designated D1 (71,548+/-5 Da), and the heterodimer D2 (71,828+/-5 Da). Carbamidomethylation of free SH groups revealed the presence of three cysteines per subunit and indicated one intrasubunit and one intersubunit disulfide bridge. Ultracentrifugation and light-scattering experiments under nondenaturating conditions yielded mass estimates that suggested an uneven number of 17 subunits forming the native hemoglobin. This unrealistic number resulted from the presence of two size classes (16-mer and 18-mer), which were recognized by native PAGE and Ferguson plot analysis. ESI-MS revealed three hemoglobin isoforms with masses of 588.1 kDa, 662.0 kDa, and 665.0 kDa. The 16-mer and the smaller 18-mer species are supposed to be composed of TcHbA only, given the dominance of this subunit type in SDS/PAGE. Transmission electron microscopy of negatively stained specimens showed a population of compact molecules with geometrical extensions of 14, 16 and 9 nm. The proposed stoichiometric model of quarternary structure provides the missing link to achieve a mechanistic understanding of the structure-function relationships among the multimeric arthropodan hemoglobins.
Assuntos
Crustáceos/química , Hemoglobinas/química , Subunidades Proteicas/química , Animais , Bovinos , Crustáceos/fisiologia , Hemoglobina A/química , Hemoglobina A/fisiologia , Hemoglobinas/fisiologia , Hemolinfa/química , Hemolinfa/fisiologia , Peso Molecular , Estrutura Quaternária de Proteína , Subunidades Proteicas/fisiologia , Relação Estrutura-AtividadeRESUMO
A long-standing puzzle with regard to protein structure/function relationships is the proton-dependent modification of haemoglobin (Hb) structure that causes oxygen to be unloaded from Root effect Hbs into the swim bladders and eyes of fish even against high oxygen pressure gradients. Although oxygen unloading in Root effect Hbs has generally been attributed to proton-dependent stabilization of the T-state, protonation of Root effect Hbs can alter their ligand affinities in both R- and T-state conformations and either stabilize the T-state or destabilize the R-state. The C-terminal residues that are so important in the Bohr effect of human Hb appear to be involved in the Root effects of some fish Hbs and not in others, indicating that several evolutionary pathways have resulted in expression of highly pH-dependent Hbs. New data are presented that show surprising similarities in the pH- and anion-dependence of sulfhydryl group reactivity and anaerobic oxidation of human and fish Hbs. The available evidence supports the concept that in both Bohr effect and Root effect Hbs a large steric component acts in addition to quaternary shifts between R and T conformations to regulate ligand affinity. Allosteric effectors moderate these steric effects within both R- and T-state conformations and allow for an elegant match between Hb function and the wide-ranging physiological needs of diverse organisms.
Assuntos
Peixes/fisiologia , Hemoglobinas/fisiologia , Oxigênio/fisiologia , Prótons , Sequência de Aminoácidos , Animais , Hemoglobina A/fisiologia , Humanos , Concentração de Íons de Hidrogênio , Oxirredução , Conformação Proteica , Relação Estrutura-Atividade , Compostos de Sulfidrila/fisiologia , Atum/fisiologiaRESUMO
The water-filled central cavity of human adult hemoglobin (Hb A) is the binding or interaction site for many different allosteric effectors. Oxygen binding titrations reveal that pyrenetetrasulfonate (PyTS), a fluorescent analogue of 2,3-diphosphoglycerate, behaves like an allosteric effector. The ligation state, pH, and concentrations of other effectors (IHP, L35, and chloride) alter PyTS fluorescence for both solution-phase and sol-gel-encapsulated Hb samples. These conditions also alter the resonance Raman spectra and rates of geminate recombination of CO-ligated Hb. Together, these results demonstrate that there are conformational and functional consequences resulting from interactions between specific domains of the central cavity and individual effectors as well as from long-range synergistic effects that are mediated through the central cavity.
Assuntos
Hemoglobina A/química , Hemoglobina A/fisiologia , Adulto , Regulação Alostérica , Sítio Alostérico , Monóxido de Carbono/química , Corantes Fluorescentes/química , Géis , Hemoglobina A/metabolismo , Humanos , Concentração de Íons de Hidrogênio , Ligantes , Oxigênio/metabolismo , Compostos de Fenilureia/química , Compostos de Fenilureia/metabolismo , Conformação Proteica , Estrutura Quaternária de Proteína , Estrutura Terciária de Proteína , Pirenos/química , Soluções , Espectrometria de Fluorescência , Análise Espectral RamanRESUMO
A stabilized hemoglobin as oxygen-carrying macromolecules was developed. It had approximately 90,000 dalton molecular weights and its intravascular half life was 36 hours. Its molecular size was less than 0.1 micron. Its hemoglobin concentration was 6% and P50 value was 24 mmHg. The oxygen carried inside the plasma performs differently than the oxygen carried inside the red cells. Only less than 0.3 ml of oxygen in 100 ml of blood is available inside the plasma while 14-19 ml of oxygen is carried inside the red cells. Thus, less than 5 ml of oxygen is available inside the plasma of the entire body. When a patient develops hypovolemic shock, the red cells are bypassed and are not perfused directly inside the tissues. However, the plasma should reach such hypoxic tissues. Thus, infusion of oxygen-carrying macromolecules in the plasma should be therapeutically effective even if less than 100 ml of stabilized hemoglobin solution were infused under shock conditions. The basic physiology of oxygen-carrying macromolecules is described in detail, which is different from the oxygen carried inside the red cells.
Assuntos
Hemoglobina A/fisiologia , Oxigênio/sangue , Transporte Biológico , Hemoglobina A/metabolismo , Humanos , Peso MolecularRESUMO
K-Cl cotransport is abnormally active in erythrocytes containing positively charged hemoglobins such as Hb S (SS: beta6 Glu --> Val) or Hb C (CC: beta6 Glu --> Lys). The relatively younger age of erythrocytes in these diseases cannot completely account for the increased K-Cl cotransport activity. It has been suggested that these positively charged Hb may interact with the K-Cl cotransport system or one of its regulators and induce changes in its functional activity. We report here data on the volume- and pH-dependence of K-Cl cotransport in ghosts obtained from normal and sickle erythrocytes, and on the effect of addition of either Hb A or Hb S before resealing. In erythrocyte ghosts prepared with the gel column method to contain minimal amounts of Hb, (white ghosts, WG), K-Cl cotransport has similar magnitude in normal and sickle erythrocytes, is not inhibited by alkaline pH and it is volume-independent. Addition of low concentrations of Hb A to WG from normal erythrocytes decreases the magnitude of K-Cl cotransport and restores its volume dependency, but not its pH sensitivity. Addition of Hb S to WG from either normal or sickle erythrocytes restores the volume-dependent component of K-Cl cotransport and increases the magnitude of flux mediated by this transporter. Thus, Hb A and Hb S seem to affect in different manners the functional properties of K-Cl cotransport.
Assuntos
Anemia Falciforme/metabolismo , Cloretos/metabolismo , Membrana Eritrocítica/metabolismo , Hemoglobina A/fisiologia , Hemoglobina Falciforme/fisiologia , Potássio/metabolismo , Simportadores , Proteínas de Transporte/metabolismo , Tamanho Celular/efeitos dos fármacos , Tamanho Celular/fisiologia , Centrifugação com Gradiente de Concentração , Membrana Eritrocítica/efeitos dos fármacos , Etilmaleimida/farmacologia , Humanos , Concentração de Íons de Hidrogênio , Transporte de Íons/efeitos dos fármacos , Transporte de Íons/fisiologia , Cotransportadores de K e Cl-RESUMO
Many micronutrients play key roles in energy metabolism and, during strenuous physical activity, the rate of energy turnover in skeletal muscle may be increased up to 20-100 times the resting rate. Although an adequate vitamin and mineral status is essential for normal health, marginal deficiency states may only be apparent when the metabolic rate is high. Prolonged strenuous exercise performed on a regular basis may also result in increased losses from the body or in an increased rate of turnover, resulting in the need for an increased dietary intake. An increased food intake to meet energy requirements will increase dietary micronutrient intake, but athletes in hard training may need to pay particular attention to their intake of iron, calcium and the antioxidant vitamins.
Assuntos
Metabolismo Energético/fisiologia , Micronutrientes/metabolismo , Esportes/fisiologia , Cálcio/administração & dosagem , Cálcio/fisiologia , Dieta , Carboidratos da Dieta/administração & dosagem , Feminino , Hemoglobina A/fisiologia , Humanos , Ferro/fisiologia , Masculino , Oxigênio/sangue , Aptidão Física , Oligoelementos/fisiologiaRESUMO
Determinamos la acción de los cambios hormonales, progesterona y estrogeno sobre la hematopoyesis, hemostasia, coagulacion y fibrinolisis, en mujeres nativas de la altura. Se estudio 50 casos, con se respectiva ficha clinica, antes y despues de ciclo menstrual. Se correlacionaron factores geneticos (Grupos, sanguineos: A, B, O). Los sujetos del grupo O y AB, mostraron disminucion significativa de sus reticulocitos (p<0.001). En cambio, los del grupo A y B, aumentaron el numero de estas celulas (p<0.001). Ademas en el grupo sanguineo O, se observo que hacen uso de las reservas de Fe (Protoporfirina), a diferencia de los otros grupos. Referente a la hemostasia, el estudio cuantitativo y cualitativo (numeracion, agragacion y fragilidad capilar), mostraron una disminucion significativa (p<0.05 - p<0.001). En la coagulacion se observo una disminucion significativa en cuanto a la actividad protrombinica y del tiempo de tromboplastina parcial, (p<0.005 y 0.0001). Esto expliacria los sangrados menstruales prolongados y abundantes. Finalmente, la fibrinolisis tuvo valores superiores a 3 horas, en relacion a os valores normales (12 hrs. 30 min). De este trabajo concluimos, que los factores geneticos influyen en la Eritropoyesis, la Hemostasia, Coagulación y Fribrinolisis, en los sujetos de la altura, lo que nos permitira continuar estos estudios, referentes a la Eritrocitosis de nuestro medio.
Assuntos
Humanos , Feminino , Adolescente , Adulto , Tempo de Tromboplastina Parcial , Plaquetas/citologia , Plaquetas/fisiologia , Tromboplastina/fisiologia , Hormônios/biossíntese , Hormônios/metabolismo , Valores de Referência , Hemoglobina A/fisiologia , Ciclo Menstrual/fisiologia , Fatores de Coagulação Sanguínea/fisiologia , Antígenos de Grupos Sanguíneos/fisiologia , Hematócrito/tendências , Coleta de Dados/tendênciasRESUMO
In order to clarify the functional and structural role of intra- and intersubunit hydrogen bonds in human hemoglobin (Hb A), we prepared two artificial beta chain mutant hemoglobins by site-directed mutagenesis. The mutant Hb Phe-37 beta, in which Trp-37 beta is replaced by Phe to remove the intersubunit hydrogen bond between Asp-94 alpha and Trp-37 beta at the alpha 1-beta 2 interface in deoxy Hb A, showed a markedly increased oxygen affinity and almost completely diminished Bohr effect and cooperativity. However, 1H-NMR data indicated that the structure of deoxy Hb Phe-37 beta is rather similar to that of deoxy Hb A. The enhanced tetramer-to-dimer dissociation previously observed in Hb Hirose (Trp-37 beta----Ser) together with our observation of the effects of organic phosphate on the structure and function of Hb Phe-37 beta suggested that a large part of the abnormal properties of Hb Phe-37 beta observed for dilute solutions appears to result from partial dissociation into alpha beta dimers rather than direct destabilization of the T-quaternary structure in the deoxygenated state. Thus, the primary and direct role of the hydrogen bond between Asp-94 alpha and Trp-37 beta is to stabilize the tetrameric assembly, and thereby this hydrogen bond indirectly contributes to stabilization of the T-quaternary structure. The other mutant Hb Phe-145 beta has a Phe residue at the 145 beta site and lacks the intrasubunit hydrogen bond formed between Tyr-145 beta and the carbonyl group of Val-98 beta in deoxy Hb A.(ABSTRACT TRUNCATED AT 250 WORDS)
Assuntos
Hemoglobina A/genética , Ligação de Hidrogênio , Mutagênese Sítio-Dirigida , Mutação , Sequência de Aminoácidos , Ácido Aspártico/genética , Hemoglobina A/química , Hemoglobina A/fisiologia , Humanos , Espectroscopia de Ressonância Magnética , Oxigênio/química , Conformação Proteica , Espectrofotometria , Análise Espectral Raman , Relação Estrutura-Atividade , Triptofano/genéticaRESUMO
With the help of diverse factors, definitive erythropoiesis is induced by the junction of a pluripotential stem-cell with a specialized macrophage. In the normal adult marrow the latter becomes the reticular cell forming the core of an 'erythroblastic island'. It stays in close contact with all the erythroid cells descending from the stem-cell until their full maturation. While this contact lasts, only alpha and beta (delta) globin chains are produced. The production of gamma chains is inhibited. Stress forces the reticular cell to let the erythroid cells go. The stronger the stress, the earlier the separation. When free from the reticular cell, the erythroid cells stop producing beta chains and switch to form gamma ones. Increase in the volume of blood circulation is a potent stress. Since it is relatively enormous in the embryo and the fetus, most hemoglobin produced at these periods will be fatal. The important quality of fetal hemoglobin is its high oxidizability. It permits the senescent fetal red cell to be hemolysed intravascularly before any membrane alterations appear. The heme is dealt with by the placenta. Since no erythrophagocytosis has occurred, no bilirubin is formed. This process prevents bilirubin, which is toxic to the fetal liver, to reach it.
Assuntos
Eritropoese , Hemoglobina Fetal/fisiologia , Hemoglobina A/fisiologia , Adulto , Medula Óssea/fisiologia , Eritroblastos/fisiologia , Feminino , Feto/fisiologia , Humanos , Recém-Nascido , Doenças do Recém-Nascido/sangue , GravidezRESUMO
The blood of the adult swift contains one major (HbA = alpha 2A beta 2) and two minor components (HbD = alpha 2D beta 2 and HbD'). The components were separated by FPLC with a TSK SP-5 PW-column in phosphate buffers, and were eluted with a linear NaCl gradient. HbD' could be detected only in freshly prepared hemolysates with the sensitive FPLC separation method. The globin chains were separated on a cation exchanger (CM-cellulose), the tryptic peptides by HPLC with a RP-2 LiChrosorb column. Their amino-acid sequences were determined by automatic Edman degradation with the film- or gas-phase method. For the alpha A-, alpha D- and beta-chains, peptide alignment was achieved by homologous comparison with the corresponding chains of the greylag goose (Anser anser). The structural significance of the substitutions was examined with the aid of molecular graphics. The oxygen-binding properties of the stripped hemolysate and of HbA and HbD and their dependence on pH, temperature and inositol polyphosphate are presented and discussed with reference to molecular structures and hypothermy that occurs during torpidity.
Assuntos
Aves/sangue , Hemoglobina A/análise , Hemoglobinas Anormais/análise , Sequência de Aminoácidos , Animais , Aves/fisiologia , Hemoglobina A/isolamento & purificação , Hemoglobina A/fisiologia , Hemoglobinas Anormais/isolamento & purificação , Hemoglobinas Anormais/fisiologia , Hibernação/fisiologia , Humanos , Dados de Sequência Molecular , Fragmentos de Peptídeos/análise , Conformação Proteica , Relação Estrutura-Atividade , TripsinaRESUMO
Differences in the local structure of the heme in the isolated alpha-, beta- and gamma-chains of the adult and fetal human hemoglobin are detected by XANES (X-ray absorption near-edge structure) spectroscopy. The ligand bonding angle to the iron ion in the ligated forms and the displacement of the Fe respect to the porphyrin plane in the deoxy forms are found to be different for each chain.
Assuntos
Hemoglobina Fetal/análise , Hemoglobina A/análise , Monóxido de Carbono , Hemoglobina Fetal/fisiologia , Hemoglobina A/fisiologia , Humanos , Estrutura Molecular , Oxigênio , Análise Espectral/métodos , Relação Estrutura-Atividade , Raios XRESUMO
We have reported that circulating CC erythrocytes containing HbO2 C crystals exhibit little or no Hb F suggesting that Hb F may inhibit the crystallization of Hb C. We report now that Hb F inhibits in vitro crystallization of HbO2 and HbCO C when compared to the effect of Hb A in a wide range of mixture proportions. For example, while HbCO C solutions form tetragonal C crystals within 25 min, no crystals form within 2 h with 30% Hb F, whereas 550 crystals/mm3 form with 30% Hb A. Furthermore, an increase in the percent of Hb A is correlated with a greater number of orthorhombic crystal formation rather than the tetragonal morphology observed with 100% Hb C. We also report that Hb A2 (containing delta chains that exhibit 10 sequence differences with beta chains) and Hb Lepore Boston-Washington (a fusion mutant of delta and beta chains that contains only six of these differences) both inhibit Hb C crystallization. By comparing the sequences of the three inhibitory hemoglobins, we conclude that position Gln-87 in the gamma chains is, at least partially, the cause of the inhibitory effect of Hb F on the crystallization of Hb C.
Assuntos
Hemoglobina Fetal/fisiologia , Hemoglobina C , Sequência de Aminoácidos , Cristalização , Hemoglobina A/fisiologia , Hemoglobina A2/fisiologia , Hemoglobinas Anormais , Humanos , Cinética , Relação Estrutura-AtividadeRESUMO
Oxygen affinity of haemoglobin is modulated by several parameters such as the allosteric effector 2-3 DPG for most mammalians. Inositol hexaphosphate (I.H.P.) exerts the same effect on haemoglobin. A previously developed new methodology for the entrapment of drugs into erythrocytes has been adapted to I.H.P.; it is based on a reversible osmotic shock. I.H.P. loaded red blood cells have characteristics very similar to those of native cells. The decrease in oxygen affinity is related to the dose of encapsulated I.H.P. In piglets, transfusion of such cells has led to an increase of oxygen extraction from haemoglobin. Normal anesthetized animals regulate their oxygen consumption by reduction of cardiac output.