1
|
Teixeira CS, Cabral MES, Carneiro RF, Brito SV, Nagano CS, Silva ALC, Garcia W, Almeida WO, Sampaio AH, Delatorre P, Carvalho JMS, Sousa EHS, Rocha BAM. Structural aspects and physiological implications of the hemoglobin of green iguana (Iguana iguana). Int J Biol Macromol 2018; 120:1275-1285. [PMID: 30171953 DOI: 10.1016/j.ijbiomac.2018.08.174] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2018] [Revised: 08/28/2018] [Accepted: 08/28/2018] [Indexed: 10/28/2022]
Affiliation(s)
- Claudener S Teixeira
- Centro de Ciências Agrárias e Ambientais, Universidade Federal do Maranhão, Chapadinha, Maranhão, Brazil
| | - Mario E S Cabral
- Departamento de Engenharia de Pesca, Universidade Federal do Ceará, Fortaleza, Ceará, Brazil
| | - Rômulo F Carneiro
- Departamento de Engenharia de Pesca, Universidade Federal do Ceará, Fortaleza, Ceará, Brazil
| | - Samuel V Brito
- Centro de Ciências Agrárias e Ambientais, Universidade Federal do Maranhão, Chapadinha, Maranhão, Brazil
| | - Celso S Nagano
- Departamento de Engenharia de Pesca, Universidade Federal do Ceará, Fortaleza, Ceará, Brazil
| | - André L C Silva
- Centro de Ciências Naturais e Humanas, Universidade Federal do ABC, Santo André, São Paulo, Brazil
| | - Wanius Garcia
- Departamento de Bioquímica e Biologia Molecular, Universidade Federal do Ceará, Fortaleza, Ceará, Brazil
| | - Waltécio O Almeida
- Departamento de Química Biológica, Universidade Regional do Cariri, Crato, Ceará, Brazil
| | - Alexandre H Sampaio
- Departamento de Engenharia de Pesca, Universidade Federal do Ceará, Fortaleza, Ceará, Brazil
| | - Plínio Delatorre
- Departamento de Biologia Molecular, Universidade Federal da Paraíba, João Pessoa, Paraíba, Brazil
| | - José M S Carvalho
- Departamento de Química Orgânica e Inorgânica, Universidade Federal do Ceará, Fortaleza, Ceará, Brazil
| | - Eduardo H S Sousa
- Departamento de Química Orgânica e Inorgânica, Universidade Federal do Ceará, Fortaleza, Ceará, Brazil
| | - Bruno A M Rocha
- Centro de Ciências Naturais e Humanas, Universidade Federal do ABC, Santo André, São Paulo, Brazil.
| |
Collapse
|
2
|
Petersen AG, Petersen SV, Frische S, Drakulic S, Golas MM, Sander B, Fago A. Hemoglobin polymerization via disulfide bond formation in the hypoxia-tolerant turtle Trachemys scripta: implications for antioxidant defense and O 2 transport. Am J Physiol Regul Integr Comp Physiol 2017; 314:R84-R93. [PMID: 28877869 DOI: 10.1152/ajpregu.00024.2017] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The ability of many reptilian hemoglobins (Hbs) to form high-molecular weight polymers, albeit known for decades, has not been investigated in detail. Given that turtle Hbs often contain a high number of cysteine (Cys), potentially contributing to the red blood cell defense against reactive oxygen species, we have examined whether polymerization of Hb could occur via intermolecular disulfide bonds in red blood cells of freshwater turtle Trachemys scripta, a species that is highly tolerant of hypoxia and oxidative stress. We find that one of the two Hb isoforms of the hemolysate HbA is prone to polymerization in vitro into linear flexible chains of different size that are visible by electron microscopy but not the HbD isoform. Polymerization of purified HbA is favored by hydrogen peroxide, a main cellular reactive oxygen species and a thiol oxidant, and inhibited by thiol reduction and alkylation, indicating that HbA polymerization is due to disulfide bonds. By using mass spectrometry, we identify Cys5 of the αA-subunit of HbA as specifically responsible for forming disulfide bonds between adjacent HbA tetramers. Polymerization of HbA does not affect oxygen affinity, cooperativity, and sensitivity to the allosteric cofactor ATP, indicating that HbA is still fully functional. Polymers also form in T. scripta blood after exposure to anoxia but not normoxia, indicating that they are of physiological relevance. Taken together, these results show that HbA polymers may form during oxidative stress and that Cys5αA of HbA is a key element of the antioxidant capacity of turtle red blood cells.
Collapse
Affiliation(s)
| | | | | | - Srdja Drakulic
- Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | - Monika M Golas
- Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | - Bjoern Sander
- Centre for Stochastic Geometry and Advanced Bioimaging, Aarhus University , Aarhus , Denmark
| | - Angela Fago
- Department of Bioscience, Aarhus University , Aarhus , Denmark
| |
Collapse
|
3
|
Damsgaard C, Storz JF, Hoffmann FG, Fago A. Hemoglobin isoform differentiation and allosteric regulation of oxygen binding in the turtle, Trachemys scripta. Am J Physiol Regul Integr Comp Physiol 2013; 305:R961-7. [PMID: 23986362 PMCID: PMC3798770 DOI: 10.1152/ajpregu.00284.2013] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2013] [Accepted: 08/20/2013] [Indexed: 01/09/2023]
Abstract
When freshwater turtles acclimatize to winter hibernation, there is a gradual transition from aerobic to anaerobic metabolism, which may require adjustments of blood O2 transport before turtles become anoxic. Here, we report the effects of protons, anionic cofactors, and temperature on the O2-binding properties of isolated hemoglobin (Hb) isoforms, HbA and HbD, in the turtle Trachemys scripta. We determined the primary structures of the constituent subunits of the two Hb isoforms, and we related the measured functional properties to differences in O2 affinity between untreated hemolysates from turtles that were acclimated to normoxia and anoxia. Our data show that HbD has a consistently higher O2 affinity compared with HbA, whereas Bohr and temperature effects, as well as thiol reactivity, are similar. Although sequence data show amino acid substitutions at two known β-chain ATP-binding site positions, we find high ATP affinities for both Hb isoforms, suggesting an alternative and stronger binding site for ATP. The high ATP affinities indicate that, although ATP levels decrease in red blood cells of turtles acclimating to anoxia, the O2 affinity would remain largely unchanged, as confirmed by O2-binding measurements of untreated hemolysates from normoxic and anoxic turtles. Thus, the increase in blood-O2 affinity that accompanies winter acclimation is mainly attributable to a decrease in temperature rather than in concentrations of organic phosphates. This is the first extensive study on freshwater turtle Hb isoforms, providing molecular evidence for adaptive changes in O2 transport associated with acclimation to severe hypoxia.
Collapse
|
4
|
Frische S, Bruno S, Fago A, Weber RE, Mozzarelli A. Oxygen binding by single red blood cells from the red-eared turtle Trachemys scripta. J Appl Physiol (1985) 2001; 90:1679-84. [PMID: 11299255 DOI: 10.1152/jappl.2001.90.5.1679] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Oxygen-binding properties of single red blood cells from the red-eared turtle Trachemys scripta were measured by microspectrophotometry to describe the variation in oxygen affinity of red blood cells and to gain insight into the distribution of functionally different hemoglobins among red blood cells. Methodologically, this study represents the first report on the cell-to-cell variation in oxygen-binding properties based on oxygen-binding curves of single vertebrate red blood cells. The cells differed significantly with respect to oxygen affinity. Mean oxygen pressure at half saturation of the cells in a blood sample was found to be 20.1 +/- 3.3 (SD) Torr. The distribution of oxygen affinities among red blood cells is unimodal, indicating that the two hemoglobins found in turtle blood are not segregated in distinct cells. Therefore, the functional interaction shown by these hemoglobins in vitro is likely to take place in vivo. The considerable variation in oxygen affinity between individual red blood cells calls for its incorporation in models of tissue oxygenation.
Collapse
Affiliation(s)
- S Frische
- Danish Centre for Respiratory Adaptation, Department of Zoophysiology, University of Aarhus, 8000 Aarhus C, Denmark.
| | | | | | | | | |
Collapse
|
5
|
Abstract
Following the discovery of inositol-1,4,5-trisphosphate as a second messenger, many other inositol phosphates were discovered in quick succession, with some understanding of their synthesis pathways and a few guesses at their possible functions. But then it all seemed to go comparatively quiet, with an explosion of interest in the inositol lipids. Now the water-soluble phase is once again becoming a focus of interest. Old and new data point to a new vista of inositol phosphates, with functions in many diverse aspects of cell biology, such as ion-channel physiology, membrane dynamics and nuclear signalling.
Collapse
Affiliation(s)
- R F Irvine
- Department of Pharmacology, Tennis Court Road, Cambridge CB2 1QJ, UK.
| | | |
Collapse
|
6
|
Wang T, Brauner CJ, Milsom WK. The effect of isovolemic anaemia on blood O2 affinity and red cell triphosphate concentrations in the painted turtle (Chrysemys picta). Comp Biochem Physiol A Mol Integr Physiol 1999; 122:341-5. [PMID: 10356763 DOI: 10.1016/s1095-6433(99)00016-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
The blood oxygen affinity of vertebrates is regulated, in part, through changes in red cell phosphate levels and increased oxygen affinity during reductions in inspired oxygen and is a well-described and common feature. However, during anaemia, when oxygen delivery is compromised by a reduction in blood oxygen carrying capacity, a lowering of blood oxygen affinity will facilitate oxygen unloading in the tissues, while oxygen loading at the gas exchange organ is not impaired. The present study investigated the effects of artificially induced anaemia in vivo on the blood oxygen affinity and red cell nucleoside triphosphate (NTP) concentrations in the turtle, Chrysemys picta. Blood was obtained from conscious animals through an arterial catheter and oxygen equilibrium curves were determined using the Tucker method while NTP concentrations were analyzed spectrophotometrically. Before induction of anaemia haematocrit averaged 23% and P50 was 18.5 +/- 0.7 with a NTP/Hb of 0.20 +/- 0.01 (mmol/mmol). After the haematocrit had been reduced to approximately 10% by bleeding (48-96 h) (blood volume was maintained by re-infusion of plasma and Ringer) there were no effects on P50 or red cell NTP concentrations. Thus, in contrast to fish and mammals, turtles do not exhibit a change in blood oxygen affinity during anaemia.
Collapse
Affiliation(s)
- T Wang
- Department of Zoology, University of British Columbia, Vancouver, Canada.
| | | | | |
Collapse
|
7
|
Ragsdale FR, Herman JK, Ingermann RL. Nucleoside triphosphate levels versus oxygen affinity of rattlesnake red cells. RESPIRATION PHYSIOLOGY 1995; 102:63-9. [PMID: 8610209 DOI: 10.1016/0034-5687(95)00053-g] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Squamate hemoglobins are responsive to modulation by nucleoside triphosphates (NTP, generally ATP), and bind NTP with a 1-to-1 molar stoichiometry. However, red cells of nonpregnant rattlesnakes contain NTP-to-hemoglobin molar ratios of approximately 2.5 suggesting most NTP is supersaturating and should not influence the oxygen affinity directly. To test this hypothesis, we metabolically depleted red cells of NTP and determined the oxygen affinity. There was a significant linear relationship between red cell NTP concentrations and oxygen affinity over the NTP/Hb range examined. In contrast, intracellular pH, Mg2+ and C1- changed slightly, or not all, during depletion. These data indicate NTP concentrations represent the primary control of hemoglobin function within these cells. Purified hemoglobin was functionally sensitive to 5 mM GTP or inositol hexaphosphate but not sensitive to 5 mM ATP or pH. Together, these findings indicate rattlesnake hemoglobin, within red cells, is functionally controlled by NTP, but the binding affinity is low such that NTP is not saturating at NTP/Hb ratios below 3.5.
Collapse
Affiliation(s)
- F R Ragsdale
- Biology Department, Winona State University, MN 55987, USA
| | | | | |
Collapse
|
8
|
Vorger P. Oxygen binding properties of blood and hemoglobin from the pigeon Columba livia. ACTA ACUST UNITED AC 1994. [DOI: 10.1016/0305-0491(94)90022-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
|
9
|
|
10
|
Calomenopoulou M, Kaloyianni M, Beis ID. Purification and regulatory properties of pigeon erythrocyte pyruvate kinase. COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY. B, COMPARATIVE BIOCHEMISTRY 1989; 93:697-706. [PMID: 2758802 DOI: 10.1016/0305-0491(89)90397-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
1. Pigeon erythrocyte pyruvate kinase (PK) was purified 22,000 fold by successive column chromatography on Sephadex DEAE A-50 and Red Agarose. The resulting enzyme preparation had a specific activity of 815.3 U/mg protein and an overall yield of 18.5%. 2. The molecular weight, as determined by gel filtration on Sephadex G-200 was 152,000. 3. Isoelectric focusing in the pH range of 3-10 showed that pigeon erythrocyte contained at least 3 PK isozymes with isoelectric points of 5, 5.7 and 6. 4. The variation of activity of PK at various ADP and phosphoenolpyruvate (PEP) concentrations was studied. The Km values for ADP and PEP were 0.40 and 0.46 mM respectively. 5. The enzyme was activated by FDP, and inhibited by ATP, highly phosphorylated inositol derivatives and 2,3-DPG: 6. It was activated by K+ and Mg2+ ions. 7. Phosphorylated hexoses and Pi stimulated the activity of PK. 8. The regulatory role of PK of pigeon erythrocytes, which lack the typical 2,3-DPG bypass, is discussed.
Collapse
Affiliation(s)
- M Calomenopoulou
- Department of Zoology, Science School, University of Thessaloniki, Greece
| | | | | |
Collapse
|
11
|
Werner A, Siems W, Gerber G. Purine and pyridine nucleotides in rabbit red blood cells of different maturity. Cell Biochem Funct 1988; 6:251-6. [PMID: 3191584 DOI: 10.1002/cbf.290060406] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Using reversed-phase high-performance liquid chromatography purine nucleotides, nucleosides and nucleobases as well as pyridine nucleotides were determined in extracts of reticulocytes and mature red blood cells of rabbits. The concentrations of almost all compounds measured decrease during the last phase of red blood cell maturation. These changes were interpreted with respect to the loss of mitochondria, accompanied by shifting the energy production from the preferentially oxidative mode to the exclusively glycolytic one and variations in the concentrations of purine compounds in blood plasma during reticulocytosis.
Collapse
Affiliation(s)
- A Werner
- Institut für Biochemie, Bereich Medizin (Charité) der Humboldt-Universität zu Berlin, DDR
| | | | | |
Collapse
|
12
|
|
13
|
Maginniss LA. Red cell organic phosphates and Bohr effects in house sparrow blood. RESPIRATION PHYSIOLOGY 1985; 59:93-103. [PMID: 3919436 DOI: 10.1016/0034-5687(85)90021-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
CO2 and fixed acid Bohr effects (d log PO2/d pH) were determined for fresh whole blood of adult house sparrow (Passer domesticus) at 35, 41 and 45 degrees C. At each temperature, the effects of titrating blood with CO2 at constant base excess (CO2 Bohr effect) were similar at P50 (35 degrees, -0.48; 41 degrees, -0.49; 45 degrees, -0.49). The CO2 Bohr slopes were also reasonably saturation independent between 10 and 90% S. Fixed acid Bohr values, determined by titrating sparrow blood with HCl and NaHCO3 at 4% CO2, were significantly less than the corresponding CO2 coefficients at half saturation (35 degrees, -0.43; 41 degrees, -0.39; 45 degrees, -0.41). The difference between CO2 and H+ Bohr effects, assumed here to represent carbamino CO2 binding to hemoglobin, decreased in magnitude with increasing saturation at each temperature. Inositol pentaphosphate (IPP, 3.1 mumol/ml RBC) and ATP (7.7 mumol/ml RBC) were the major organic phosphates present in Passer erythrocytes. CO2 and organic phosphates are known to complete for common binding sites on the Hb molecule. Because of IPP's strong binding affinity and high concentration in most avian red cells, carbamate formation is generally suppressed in bird blood. The presence of a small but significant specific CO2 effect in Passer blood may indicate that one or both sparrow isohemoglobins has reduced affinity for IPP and/or ATP, permitting CO2 to compete more effectively in Hb-carbamate formation.
Collapse
|
14
|
Lee JW, Vidaver GA. Transport and control of Ca2+ by pigeon erythrocytes. I. Survey of some cell responses to a range of A23187 doses in the presence of Ca2+. Cell Calcium 1984; 5:501-24. [PMID: 6098373 DOI: 10.1016/0143-4160(84)90028-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Cells were subjected to a range of 45Ca2+ influx loads with A23187. We measured cell 45Ca2+ with time and A23187 dose, and the apparent 45Ca2+ influxes (identical to "J(in,app)") at Ca2+ steady state. We also measured endogeneous exchangeable and total cell Ca2+, which were 50 and 17-220 microM respectively. The effects of A23187 and Ca2+ on cell ATP, swelling, net Cl- permeability, and cell morphology were measured. These were modest and do not affect our conclusions. J(in,app) congruent to 3 X 10(-4) [A23187]2.9 X [Ca2+(o)]mumoles/l X min with 92-552 microM [Ca2+(o)] (identical to external Ca2+ concentration) and 0-7 microM A23187. J(in,app) was increased an order of magnitude by vanadate and is probably much less than the true influx. The least unlikely explanation found for the high [A23187] exponent, 2.9, was that most of the Ca2+ crossing the membrane is expelled by the pump before it can move deeper into the cell. Calcium pumping increased rapidly in response to increased influx, but the steady state cell 45Ca2+ was approximately proportional to J(in,app) rather than approximately constant between 10 and 120 mumoles/l X min with 184 microM [Ca2+(o)]. This is not the result expected from a simple feedback mechanism. At high A23187 doses the pump appears fully activated resulting in a linear relation between cell/medium 45Ca2+ and [A23187]-2. From the plot we calculated alpha identical to free/total exchangeable Ca2+ = 0.38 +/- 0.08 (n = 3) and a maximum pump rate, "Pmax" = 78 mumole/l X min. Pmax is underestimated insofar as J(in,app) is less than the true influx.
Collapse
|
15
|
Wideman RF. Organic phosphate probes of the avian renal phosphate secretory mechanism. COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY. B, COMPARATIVE BIOCHEMISTRY 1984; 78:315-319. [PMID: 6467898 DOI: 10.1016/0305-0491(84)90036-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Parathyroid hormone (PTH) stimulates net renal inorganic phosphate (Pi) secretion in domestic fowl (Gallus domesticus). Recent evidence indicates that secreted Pi is derived from a highly sequestered, presumably organic, phosphate pool. A modified Sperber technique was used to survey the response of domestic fowl to unilateral renal portal infusions of organic phosphate compounds that had been implicated in previous studies of Pi secretion. None of the organic phosphate compounds produced a significant unilateral Pi secretory effect. It is concluded that these compounds neither directly stimulate Pi secretion in normal or parathyroidectomized birds, nor are they rate-limiting for the Pi secretory mechanism in birds infused with PTH.
Collapse
|
16
|
Ogo SH, Matsuura MSA, Focesi A. Content of organic polyphosphates and their allosteric effects on haemoglobins from the water-snakes Helicops modestus and Liophis miliaris. ACTA ACUST UNITED AC 1984. [DOI: 10.1016/0300-9629(84)90601-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
|
17
|
Palacios L, Palomeque J, Riera M, Pagés T, Viscor G, Planas J. Oxygen transport properties in the starling, Sturnus vulgaris L. ACTA ACUST UNITED AC 1984. [DOI: 10.1016/0300-9629(84)90057-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
|
18
|
Hutchison VH, Hazard ES. Erythrocytic organic phosphates: diel and seasonal cycles in the frog, Rana berlandieri. COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY. A, COMPARATIVE PHYSIOLOGY 1984; 79:533-8. [PMID: 6150789 DOI: 10.1016/0300-9629(84)90443-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Hemoglobin (Hb) concentration, hematocrit (Hct), total organic phosphates (Ptot), nucleoside triphosphates (NTP), 2,3-diphosphoglycerate (DPG), and "inositol polyphosphates" (IPP) were measured in the erythrocytes of adult frogs at different times of day in winter and summer after acclimatization to 15 degrees C and an LD 12:12 photoperiod. The same measurements were also made on animals acclimated to LD 16:8 in summer. All of the measured parameters varied significantly at different times of the day and between seasons in animals acclimated to an LD 12:12 photoperiod. Summer animals acclimated to LD 16:8 showed significant diel cycles only in Hct and Hb.
Collapse
|
19
|
Wells RM, Tetens V, Brittain T. Absence of cooperative haemoglobin-oxygen binding in Sphenodon, a reptilian relict from the Triassic. Nature 1983; 306:500-2. [PMID: 6646231 DOI: 10.1038/306500a0] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
It is generally accepted that the sigmoidal nature of the haemoglobin-oxygen dissociation curve (ODC) is necessary for efficient oxygen transport in terrestrial vertebrates because it allows large volumes of oxygen to be bound or released for relatively small changes in the partial pressure of oxygen (PO2) in the blood. Furthermore, the amount of oxygen to tissues is increased by hydrogen ions produced from the dissociation of carbon dioxide in solution. The generality of these key features of cooperative oxygen binding and the Bohr effect holds for reptiles, birds and mammals, including representatives with special respiratory requirements for diving, burrowing and living at high altitude. Sphenodon punctatus is the sole surviving representative of the ancient order of 'beakhead' reptiles (order Rhynchocephalia) which were once widely distributed during the Triassic period before the spectacular radiation of dinosaur faunas. We have now investigated the oxygen transporting properties of blood from Sphenodon and find that the ODC is hyperbolic, with a high affinity for oxygen and very small Bohr effect. This combination of characteristics is unique among terrestrial vertebrates and accords with a low demand for oxygen and limited scope for aerobic activity.
Collapse
|
20
|
Coulson RA, Hernandez T. Alligator Metabolism. Studies On Chemical Reactions In Vivo. COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY. B, COMPARATIVE BIOCHEMISTRY 1983; 74:1-182. [PMID: 6831860 DOI: 10.1016/0305-0491(83)90418-2] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
|
21
|
|
22
|
Bartlett GR. Phosphate compounds in red cells of two dogfish sharks: Squalus acanthias and Mustelus canis. ACTA ACUST UNITED AC 1982. [DOI: 10.1016/0300-9629(82)90104-9] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
|
23
|
|
24
|
Seymour RS, Dobson GP, Baldwin J. Respiratory and cardiovascular physiology of the aquatic snake,Acrochordus arafurae. J Comp Physiol B 1981. [DOI: 10.1007/bf00802760] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
|
25
|
Abstract
Most cells are thought to contain trace amounts of 2,3-diphosphoglycerate (DPG), as it acts as a cofactor in the interconversion of 2-phosphoglycerate and 3-phosphoglycerate by the glycolytic enzyme phosphoglyceromutase. DPG is synthesized from 1,3-diphosphoglycerate by the action of diphosphoglycerate mutase. Lowry et al. reported levels of 29 mumol DPG per kg wet weight brain tissue which is approximately 3 pmol per 10(8) cells, assuming that 1 g of brain tissue contains 10(9) cells. In contrast, erythroid cells contain 50-100 nmol DPG per 10(8) cells, depending on the species and the stage of development. This is of the order of a 1,000-fold more DPG compared with non-erythroid cells. In red cells DPG concentration modulates the binding of oxygen to haemoglobin. I show here that erythroid precurser cells also contain markedly raised levels of DPG.
Collapse
|