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Alilova GA, Tikhonova LA, Kosenko EA. NMDA Receptors and Indices of Energy Metabolism in Erythrocytes: Missing Link to the Assessment of Efficiency of Oxygen Transport in Hepatic Encephalopathy. BIOCHEMISTRY. BIOKHIMIIA 2024; 89:1490-1508. [PMID: 39245457 DOI: 10.1134/s000629792408008x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/13/2024] [Revised: 06/16/2024] [Accepted: 06/23/2024] [Indexed: 09/10/2024]
Abstract
Hepatic encephalopathy (HE) is a neuropsychiatric syndrome that develops in patients with severe liver dysfunction and/or portocaval shunting. Despite more than a century of research into the relationship between liver damage and development of encephalopathy, pathogenetic mechanisms of hepatic encephalopathy have not yet been fully elucidated. It is generally recognized, however, that the main trigger of neurologic complications in hepatic encephalopathy is the neurotoxin ammonia/ammonium, concentration of which in the blood increases to toxic levels (hyperammonemia), when detoxification function of the liver is impaired. Freely penetrating into brain cells and affecting NMDA-receptor-mediated signaling, ammonia triggers a pathological cascade leading to the sharp inhibition of aerobic glucose metabolism, oxidative stress, brain hypoperfusion, nerve cell damage, and formation of neurological deficits. Brain hypoperfusion, in turn, could be due to the impaired oxygen transport function of erythrocytes, because of the disturbed energy metabolism that occurs in the membranes and inside erythrocytes and controls affinity of hemoglobin for oxygen, which determines the degree of oxygenation of blood and tissues. In our recent study, this causal relationship was confirmed and novel ammonium-induced pro-oxidant effect mediated by excessive activation of NMDA receptors leading to impaired oxygen transport function of erythrocytes was revealed. For a more complete evaluation of "erythrocytic" factors that diminish brain oxygenation and lead to encephalopathy, in this study, activity of the enzymes and concentration of metabolites of glycolysis and Rapoport-Lubering shunt, as well as morphological characteristics of erythrocytes from the rats with acute hyperammoniemia were determined. To elucidate the role of NMDA receptors in the above processes, MK-801, a non-competitive receptor antagonist, was used. Based on the obtained results it can be concluded that it is necessary to consider ammonium-induced morphofunctional disorders of erythrocytes and hemoglobinemia which can occur as a result of alterations in highly integrated networks of metabolic pathways may act as an additional systemic "erythrocytic" pathogenetic factor to prevent the onset and progression of cerebral hypoperfusion in hepatic encephalopathy accompanied by hyperammonemia.
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Affiliation(s)
- Gubidat A Alilova
- Institute of Theoretical and Experimental Biophysics, Russian Academy of Sciences, Pushchino, Moscow Region, 142290, Russia
| | - Lyudmila A Tikhonova
- Institute of Theoretical and Experimental Biophysics, Russian Academy of Sciences, Pushchino, Moscow Region, 142290, Russia
| | - Elena A Kosenko
- Institute of Theoretical and Experimental Biophysics, Russian Academy of Sciences, Pushchino, Moscow Region, 142290, Russia.
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2
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Peluffo RD, Hernández JA. The Na +,K +-ATPase and its stoichiometric ratio: some thermodynamic speculations. Biophys Rev 2023; 15:539-552. [PMID: 37681108 PMCID: PMC10480117 DOI: 10.1007/s12551-023-01082-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2023] [Accepted: 06/18/2023] [Indexed: 09/09/2023] Open
Abstract
Almost seventy years after its discovery, the sodium-potassium adenosine triphosphatase (the sodium pump) located in the cell plasma membrane remains a source of novel mechanistic and physiologic findings. A noteworthy feature of this enzyme/transporter is its robust stoichiometric ratio under physiological conditions: it sequentially counter-transports three sodium ions and two potassium ions against their electrochemical potential gradients per each hydrolyzed ATP molecule. Here we summarize some present knowledge about the sodium pump and its physiological roles, and speculate whether energetic constraints may have played a role in the evolutionary selection of its characteristic stoichiometric ratio.
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Affiliation(s)
- R. Daniel Peluffo
- Group of Biophysical Chemistry, Department of Biological Sciences, CENUR Litoral Norte, Universidad de La República, Rivera 1350, CP: 50000 Salto, Uruguay
| | - Julio A. Hernández
- Biophysics and Systems Biology Section, Department of Cell and Molecular Biology, Facultad de Ciencias, Universidad de La República, Iguá 4225, CP: 11400 Montevideo, Uruguay
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3
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Meyer DJ, Díaz-García CM, Nathwani N, Rahman M, Yellen G. The Na +/K + pump dominates control of glycolysis in hippocampal dentate granule cells. eLife 2022; 11:e81645. [PMID: 36222651 PMCID: PMC9592084 DOI: 10.7554/elife.81645] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2022] [Accepted: 10/11/2022] [Indexed: 11/13/2022] Open
Abstract
Cellular ATP that is consumed to perform energetically expensive tasks must be replenished by new ATP through the activation of metabolism. Neuronal stimulation, an energetically demanding process, transiently activates aerobic glycolysis, but the precise mechanism underlying this glycolysis activation has not been determined. We previously showed that neuronal glycolysis is correlated with Ca2+ influx, but is not activated by feedforward Ca2+ signaling (Díaz-García et al., 2021a). Since ATP-powered Na+ and Ca2+ pumping activities are increased following stimulation to restore ion gradients and are estimated to consume most neuronal ATP, we aimed to determine if they are coupled to neuronal glycolysis activation. By using two-photon imaging of fluorescent biosensors and dyes in dentate granule cell somas of acute mouse hippocampal slices, we observed that production of cytoplasmic NADH, a byproduct of glycolysis, is strongly coupled to changes in intracellular Na+, while intracellular Ca2+ could only increase NADH production if both forward Na+/Ca2+ exchange and Na+/K+ pump activity were intact. Additionally, antidromic stimulation-induced intracellular [Na+] increases were reduced >50% by blocking Ca2+ entry. These results indicate that neuronal glycolysis activation is predominantly a response to an increase in activity of the Na+/K+ pump, which is strongly potentiated by Na+ influx through the Na+/Ca2+ exchanger during extrusion of Ca2+ following stimulation.
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Affiliation(s)
- Dylan J Meyer
- Department of Neurobiology, Harvard Medical SchoolBostonUnited States
| | | | - Nidhi Nathwani
- Department of Neurobiology, Harvard Medical SchoolBostonUnited States
| | - Mahia Rahman
- Department of Neurobiology, Harvard Medical SchoolBostonUnited States
| | - Gary Yellen
- Department of Neurobiology, Harvard Medical SchoolBostonUnited States
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4
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Pogglitsch H, Estelberger W, Petek W, Zitta S, Ziak E. Relationship between Generation and Plasma Concentration of Anorganic Phosphorus. in Vivo Studies on Dialysis Patients and in Vitro Studies on Erythrocytes. Int J Artif Organs 2018. [DOI: 10.1177/039139888901200808] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The plasma concentration of inorganic phosphorus (Pi) was determined before, during and after hemodialysis in 28 patients with chronic renal failure. Pi plasma concentration decreased rapidly when hemodialysis was started but did not fall below normal levels during continued dialysis. These changes of Pi concentration were fitted to a model of Pi kinetics in which Pi delivery to plasma is a nonlinear function of the extracellular Pi concentration. In separate in vitro studies, erythrocytes from six subjects with normal renal function and from 14 patients with chronic renal failure were incubated in homologous plasma with various amounts of Pi added. All other factors known to affect the Pi shift between intra - and extracellular fluid compartments (pH, calcium concentration) were kept constant. The relation between Pi concentration in plasma used for incubation and in red cells after 1h incubation suggested a mechanism in which a high plasma concentration results in movement of Pi into red cells where Pi is stored most probably in glucose esters. At low Pi plasma concentration Pi is delivered to plasma at a rate which cannot be explained solely by passive movement of intracellular Pi to plasma but requires additional generation from intracellular storage forms. The generation and delivery of Pi in patients and in their erythrocytes indicate a simple cell-mediated Pi homeostasis counter-acting abnormal fluctuations of plasma Pi.
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Affiliation(s)
- H. Pogglitsch
- Departments of Internal Medicine, Medical Chemistry and Medical Biochemistry, Karl-Franzens University, Graz-Austria
| | - W. Estelberger
- Departments of Internal Medicine, Medical Chemistry and Medical Biochemistry, Karl-Franzens University, Graz-Austria
| | - W. Petek
- Departments of Internal Medicine, Medical Chemistry and Medical Biochemistry, Karl-Franzens University, Graz-Austria
| | - S. Zitta
- Departments of Internal Medicine, Medical Chemistry and Medical Biochemistry, Karl-Franzens University, Graz-Austria
| | - E. Ziak
- Departments of Internal Medicine, Medical Chemistry and Medical Biochemistry, Karl-Franzens University, Graz-Austria
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5
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Cornelius F, Tsunekawa N, Toyoshima C. Distinct pH dependencies of Na +/K + selectivity at the two faces of Na,K-ATPase. J Biol Chem 2017; 293:2195-2205. [PMID: 29247005 DOI: 10.1074/jbc.ra117.000700] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2017] [Revised: 11/28/2017] [Indexed: 11/06/2022] Open
Abstract
The sodium pump (Na,K-ATPase) in animal cells is vital for actively maintaining ATP hydrolysis-powered Na+ and K+ electrochemical gradients across the cell membrane. These ion gradients drive co- and countertransport and are critical for establishing the membrane potential. It has been an enigma how Na,K-ATPase discriminates between Na+ and K+, despite the pumped ion on each side being at a lower concentration than the other ion. Recent crystal structures of analogs of the intermediate conformations E2·Pi·2K+ and Na+-bound E1∼P·ADP suggest that the dimensions of the respective binding sites in Na,K-ATPase are crucial in determining its selectivity. Here, we found that the selectivity at each membrane face is pH-dependent and that this dependence is unique for each face. Most notable was a strong increase in the specific affinity for K+ at the extracellular face (i.e. E2 conformation) as the pH is lowered from 7.5 to 5. We also observed a smaller increase in affinity for K+ on the cytoplasmic side (E1 conformation), which reduced the selectivity for Na+ Theoretical analysis of the pKa values of ion-coordinating acidic amino acid residues suggested that the face-specific pH dependences and Na+/K+ selectivities may arise from the protonation or ionization of key residues. The increase in K+ selectivity at low pH on the cytoplasmic face, for instance, appeared to be associated with Asp808 protonation. We conclude that changes in the ionization state of coordinating residues in Na,K-ATPase could contribute to altering face-specific ion selectivity.
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Affiliation(s)
- Flemming Cornelius
- From the Department of Biomedicine, University of Aarhus, Ole Worms Allé 6, 8000 Aarhus C, Denmark and
| | - Naoki Tsunekawa
- the Institute of Molecular and Cellular Biosciences, University of Tokyo, Bunkyo-ku, Tokyo 113-0032
| | - Chikashi Toyoshima
- the Institute of Molecular and Cellular Biosciences, University of Tokyo, Bunkyo-ku, Tokyo 113-0032
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6
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Kumar P, Chaudhary N, Sharma NK, Maurya PK. Detection of oxidative stress biomarkers in myricetin treated red blood cells. RSC Adv 2016. [DOI: 10.1039/c6ra15213a] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Effect of myricetin on RBC membrane enzymes (Na+, K+-ATPase and Ca2+-ATPase) and Na+, H+exchanger.
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Affiliation(s)
- Prabhanshu Kumar
- Amity Institute of Biotechnology
- Amity University Uttar Pradesh
- Noida
- India
| | - Nidhee Chaudhary
- Amity Institute of Biotechnology
- Amity University Uttar Pradesh
- Noida
- India
| | - Narendra Kumar Sharma
- Division of Infectious Disease
- Department of Medicine
- Universidade Federal de Sao Paulo – UNIFESP
- Brazil
| | - Pawan Kumar Maurya
- Amity Institute of Biotechnology
- Amity University Uttar Pradesh
- Noida
- India
- Interdisciplinary Laboratory for Clinical Neuroscience (LiNC)
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7
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Glynn IM, Karlish SJ. ATP hydrolysis associated with an uncoupled sodium flux through the sodium pump: evidence for allosteric effects of intracellular ATP and extracellular sodium. J Physiol 2015; 256:465-96. [PMID: 16992511 PMCID: PMC1309316 DOI: 10.1113/jphysiol.1976.sp011333] [Citation(s) in RCA: 181] [Impact Index Per Article: 20.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
1. A method has been developed for regenerating [gamma(32)P]ATP of constant specific activity within resealed red cell ghosts, and for measuring its hydrolysis. The method may be used to follow the hydrolysis of ATP at concentrations down to 1 muM, and for periods long enough for the ATP at these very low concentrations to turn over several hundred times.2. Using this method we have been able to show that the ;uncoupled' efflux of Na caused by the Na pump when resealed red cell ghosts are incubated in (Na + K)-free media is associated with a hydrolysis of ATP. The stoicheiometry is roughly 2-3 Na ions expelled per molecule of ATP hydrolysed.3. Measurements of ATP hydrolysis and Na efflux as functions of intracellular ATP concentration have shown that uncoupled Na efflux, and its associated ATP hydrolysis, are saturated at intracellular ATP concentrations in the region of 1 muM.4. Measurement of ATP hydrolysis as a function of ATP concentration in resealed ghosts incubated in a K-containing medium gave a complicated activation curve suggesting the involvement of high-affinity (K(m)ca. 1 muM) and low-affinity (K(m)ca. 100 muM) sites.5. When resealed ghosts containing about 1 muM-ATP were incubated in a Na-free or in a high-Na medium, the addition of K to the medium reduced the rate of ouabain-sensitive ATP hydrolysis.6. Ouabain-sensitive ATP hydrolysis in resealed ghosts incubated in K-free choline media was inhibited by external Na at low concentrations (K(i) < 1 mM), but this inhibition was reversed as the external Na concentration was further increased.7. The results show that uncoupled Na efflux may be thought of as the transport mode associated with Na-ATPase activity, just as Na-K exchange is the transport mode associated with (Na + K)-ATPase activity. The significance of the differences between uncoupled Na efflux and Na-ATPase activity, on the one hand, and Na-K exchange and (Na + K)-ATPase activity, on the other, is discussed.
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Affiliation(s)
- I M Glynn
- Physiological Laboratory, University of Cambridge, Cambridge CB2 3EG
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8
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Sousa L, Garcia IJP, Costa TGF, Silva LND, Renó CO, Oliveira ES, Tilelli CQ, Santos LL, Cortes VF, Santos HL, Barbosa LA. Effects of Iron Overload on the Activity of Na,K-ATPase and Lipid Profile of the Human Erythrocyte Membrane. PLoS One 2015. [PMID: 26197432 PMCID: PMC4510300 DOI: 10.1371/journal.pone.0132852] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Iron is an essential chemical element for human life. However, in some pathological conditions, such as hereditary hemochromatosis type 1 (HH1), iron overload induces the production of reactive oxygen species that may lead to lipid peroxidation and a change in the plasma-membrane lipid profile. In this study, we investigated whether iron overload interferes with the Na,K-ATPase activity of the plasma membrane by studying erythrocytes that were obtained from the whole blood of patients suffering from iron overload. Additionally, we treated erythrocytes of normal subjects with 0.8 mM H2O2 and 1 μM FeCl3 for 24 h. We then analyzed the lipid profile, lipid peroxidation and Na,K-ATPase activity of plasma membranes derived from these cells. Iron overload was more frequent in men (87.5%) than in women and was associated with an increase (446%) in lipid peroxidation, as indicated by the amount of the thiobarbituric acid reactive substances (TBARS) and an increase (327%) in the Na,K-ATPase activity in the plasma membrane of erythrocytes. Erythrocytes treated with 1 μM FeCl3 for 24 h showed an increase (132%) in the Na,K-ATPase activity but no change in the TBARS levels. Iron treatment also decreased the cholesterol and phospholipid content of the erythrocyte membranes and similar decreases were observed in iron overload patients. In contrast, erythrocytes treated with 0.8 mM H2O2 for 24 h showed no change in the measured parameters. These results indicate that erythrocytes from patients with iron overload exhibit higher Na,K-ATPase activity compared with normal subjects and that this effect is specifically associated with altered iron levels.
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Affiliation(s)
- Leilismara Sousa
- Laboratório de Bioquímica Celular, Universidade Federal de São João del Rei, Campus Centro-Oeste Dona Lindú, Av Sebastião Gonçalves Coelho 400, 35501–296, Divinópolis, Brazil
| | - Israel J. P. Garcia
- Laboratório de Bioquímica Celular, Universidade Federal de São João del Rei, Campus Centro-Oeste Dona Lindú, Av Sebastião Gonçalves Coelho 400, 35501–296, Divinópolis, Brazil
| | - Tamara G. F. Costa
- Laboratório de Bioquímica Celular, Universidade Federal de São João del Rei, Campus Centro-Oeste Dona Lindú, Av Sebastião Gonçalves Coelho 400, 35501–296, Divinópolis, Brazil
| | - Lilian N. D. Silva
- Laboratório de Bioquímica Celular, Universidade Federal de São João del Rei, Campus Centro-Oeste Dona Lindú, Av Sebastião Gonçalves Coelho 400, 35501–296, Divinópolis, Brazil
| | - Cristiane O. Renó
- Laboratório de Bioquímica Celular, Universidade Federal de São João del Rei, Campus Centro-Oeste Dona Lindú, Av Sebastião Gonçalves Coelho 400, 35501–296, Divinópolis, Brazil
| | - Eneida S. Oliveira
- Laboratório de Biologia Molecular, Universidade Federal de São João del Rei, Campus Centro-Oeste Dona Lindú, Av Sebastião Gonçalves Coelho 400, 35501–296, Divinópolis, Brazil
| | - Cristiane Q. Tilelli
- Laboratório de Estudos em Neurociências das Epilepsias e Comorbidades, Universidade Federal de São João del Rei, Campus Centro-Oeste Dona Lindú, Av Sebastião Gonçalves Coelho 400, 35501–296, Divinópolis, Brazil
| | - Luciana L. Santos
- Laboratório de Biologia Molecular, Universidade Federal de São João del Rei, Campus Centro-Oeste Dona Lindú, Av Sebastião Gonçalves Coelho 400, 35501–296, Divinópolis, Brazil
| | - Vanessa F. Cortes
- Laboratório de Bioquímica Celular, Universidade Federal de São João del Rei, Campus Centro-Oeste Dona Lindú, Av Sebastião Gonçalves Coelho 400, 35501–296, Divinópolis, Brazil
| | - Herica L. Santos
- Laboratório de Bioquímica Celular, Universidade Federal de São João del Rei, Campus Centro-Oeste Dona Lindú, Av Sebastião Gonçalves Coelho 400, 35501–296, Divinópolis, Brazil
| | - Leandro A. Barbosa
- Laboratório de Bioquímica Celular, Universidade Federal de São João del Rei, Campus Centro-Oeste Dona Lindú, Av Sebastião Gonçalves Coelho 400, 35501–296, Divinópolis, Brazil
- * E-mail:
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9
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Baker PF, Connelly CM. Some properties of the external activation site of the sodium pump in crab nerve. J Physiol 2010; 185:270-97. [PMID: 16992223 PMCID: PMC1395814 DOI: 10.1113/jphysiol.1966.sp007987] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
1. Methods are described for using the changes in respiration of intact Libinia nerve to follow the rate of energy utilization by the sodium pump in this tissue.2. Short tetani in 10 K(Na)ASW (artificial sea water in which Na is the major cation and the potassium concentration is 10 mM) increased the oxygen uptake which then declined exponentially. From the net influx of Na during the tetanus and the associated oxygen uptake, values between 1.9 and 3.4 were calculated for the Na: approximately P ratio. After longer tetani, the recovery curve was S-shaped.3. The pump was activated by potassium ions in the external medium and this activation was competitively inhibited by external sodium ions. The data are consistent with a Michaelis constant (K(m)) for external potassium of 1 mM and an inhibitor constant (K(i)) for external sodium of 60 mM.4. In activating the pump, K could be replaced by Tl(+), Rb, NH(4) and Cs ions; but, of the monovalent ions tested, sodium seemed to be unique in its inhibitory action.5. In sea waters containing 460 mM-Na, ouabain behaved like a mixed inhibitor of the pump, reducing both the maximum velocity and the apparent affinity for external potassium. At a given ouabain concentration, reducing the sodium content of the medium was without effect on the maximum rate of pumping; but the apparent affinity for potassium increased more steeply than in a ouabain-free solution.6. The rate of energy utilization associated with pumping was unaffected by inclusion of quite high concentrations of sulphydryl-blocking agents in the external medium.
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10
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Bernstein J, Videla L, Israel Y. Metabolic alterations produced in the liver by chronic ethanol administration. Changes related to energetic parameters of the cell. Biochem J 2010; 134:515-21. [PMID: 16742812 PMCID: PMC1177838 DOI: 10.1042/bj1340515] [Citation(s) in RCA: 146] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
1. Chronic ethanol administration to rats for 21-27 days increases the rate of O(2) consumption as measured in liver slices. The extra respiration can be abolished by inhibition of the active transport of Na(+) and K(+). Dinitrophenol activates the respiratory rate in the liver of the treated animals only in the presence of ouabain. 2. Active (ouabain-sensitive) transport of (86)Rb and (Na(+)+K(+))-stimulated adenosine triphosphatase activity were increased in the livers of the ethanol-treated animals. 3. Chronic ethanol administration also led to a decrease in the phosphorylation potential ([ATP]/[ADP][P(i)]) in the liver cell owing to a decrease in [ATP] and an increase in [P(i)]. 4. It is suggested that an increased sodium pump activity is responsible for the increased oxidative capacity and for the insensitivity to dinitrophenol observed in the livers of ethanol-treated animals.
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Affiliation(s)
- J Bernstein
- Department of Pharmacology, University of Toronto, Toronto 181, Ont., Canada
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11
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Gruener N, Avi-Dor Y. Temperature-dependence of activation and inhibition of rat-brain adenosine triphosphatase activated by sodium and potassium ions. Biochem J 2010; 100:762-7. [PMID: 16742417 PMCID: PMC1265212 DOI: 10.1042/bj1000762] [Citation(s) in RCA: 96] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
1. The adenosine-triphosphatase activity of rat-brain microsomes was measured between 0 degrees and 37 degrees . The stimulatory effect of Na(+) plus K(+) on the Mg(2+)-dependent adenosine-triphosphatase activity decreased sharply with decreasing temperature and became negligible at 0 degrees . An Arrhenius plot drawn from the experimental data showed two discontinuities: one at about 6 degrees and the other at about 20 degrees . 2. The increment in activity induced by Na(+) plus K(+) was more sensitive to oligomycin at lower than at higher temperatures, but the opposite was observed for ouabain. The action of oligomycin showed a biphasic character, since below a certain concentration it caused slight activation of Na(+)-plus-K(+)-activated adenosine triphosphatase. 3. Where oligomycin increased the activity of the enzyme, it also enhanced the accumulation of an acid-precipitable phosphorylated compound formed through the transfer of the gamma-phosphate group of [(32)P]ATP to the enzyme system. Stimulatory concentrations of oligomycin did not interfere with K(+)-mediated dephosphorylation of the intermediate, though high concentrations of oligomycin counteracted the effect of K(+). 4. The temperature profile of K(+)-stimulated microsomal phosphatase qualitatively resembled that of microsomal adenosine triphosphatase.
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Affiliation(s)
- N Gruener
- Department of Chemistry, Israel Institute of Technology, Haifa, Israel
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12
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Glynn IM, Karlish SJ. Different approaches to the mechanism of the sodium pump. CIBA FOUNDATION SYMPOSIUM 2008:205-23. [PMID: 125188 DOI: 10.1002/9780470720134.ch12] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The way in which the sodium pump uses energy from the hydrolysis of ATP to perform osmotic and electrical work is not yet understood. We attempt to bring together the results of a number of different approaches to this problem. One approach has been to correlate biochemical changes and ionic fluxes, both when the pump operates normally and when it operates in various abnormal 'modes' in particular unphysiological conditions. A second approach has been to expose fragments of cell membrane to (gamma-32P)ATP and to study the properties of components of the membrane that become labelled. It is now clear that 32P can be transferred to the beta-carboxy group of an aspartyl residue in a pump polypeptide, but there is controversy about the interrelations of different forms of this polypeptide and its role, if any, in the normal functioning of the pump. A third approach has been to attempt to purify the pump and to determine the properties of the pure enzyme. It seems that the pump contains a polypeptide (molecular weight about 100,000), which bears the phosphorylation site, and a smaller glycopeptide, but there is disagreement about the molecular ratios. The results of these and other approaches cannot yet be fitted into a satisfactory model for the sodium pump, but we shall consider some of the problems involved in this task.
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13
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CONNER ROBERTL, CLINE SYLVIAG. Some Factors Governing Respiration, Glucose Metabolism and Iodoacetate Sensitivity in Tetrahymena pyriformis*. ACTA ACUST UNITED AC 2007. [DOI: 10.1111/j.1550-7408.1967.tb01441.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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14
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Ljungberg I, Waldenström A, Ronquist G. Rubidium-86 uptake and energy metabolism in suspended human erythrocytes monitored by microdialysis. J Int Med Res 2004; 32:384-91. [PMID: 15303769 DOI: 10.1177/147323000403200406] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
We aimed to develop a model for studying membrane leakiness. A microdialysis technique was used to investigate rubidium-86 (86Rb) uptake in suspended human erythrocytes in vitro, with the aim of later applying the technique to in vivo studies. Suspensions were prepared from washed erythrocytes and 86Rb administered directly or via the microdialysis probe. The effects on 86Rb uptake of varying the haematocrit were measured. Erythrocytes were also treated with the K+ ionophore valinomycin or the Na+/K+-ATPase inhibitor ouabain. The effects on 86Rb uptake, microdialysate content of lactate and pyruvate, and erythrocyte content of 2,3-bisphosphoglycerate (2,3-BPG) were measured. Valinomycin dissipates the potassium gradient and activates Na+/K+-ATPase, demonstrated by decreased erythrocyte 86Rb uptake with increasing concentrations of valinomycin. This increased ion pump activity enhanced glycolysis, which was demonstrated by accumulation of pyruvate and lactate due to enhanced consumption of 2,3-BPG. The microdialysis technique is appropriate for in vitro studies of ion fluxes across cellular membranes.
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Affiliation(s)
- I Ljungberg
- Department of Public Health and Clinical Medicine, Umeå University, Umeå, Sweden.
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15
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Lo A, Fuglevand AJ, Secomb TW. Theoretical simulation of K+-based mechanisms for regulation of capillary perfusion in skeletal muscle. Am J Physiol Heart Circ Physiol 2004; 287:H833-40. [PMID: 15277205 DOI: 10.1152/ajpheart.00139.2004] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Muscle fibers release K(+) into the interstitial space upon recruitment. Increased local interstitial K(+) concentration ([K(+)]) can cause dilation of terminal arterioles, leading to perfusion of downstream capillaries. The possibility that capillary perfusion can be regulated by vascular responses to [K(+)] was examined using a theoretical model. The model takes into account the spatial relationship between functional units of muscle fiber recruitment and capillary perfusion. Diffusion of K(+) in the interstitial space was simulated. Two hypothetical mechanisms for vascular sensing of interstitial [K(+)] were considered: direct sensing by arterioles and sensing by capillaries with stimulation of feeding arterioles via conducted responses. Control by arteriolar sensing led to poor tissue oxygenation at high levels of muscle activation. With control by capillary sensing, increases in perfusion matched increases in oxygen demand. The time course of perfusion after sudden muscle activation was considered. Predicted capillary perfusion increased rapidly within the first 5 s of muscle fiber activation. The reuptake of K(+) by muscle fibers had a minor effect on the increase of interstitial [K(+)]. Uptake by perfused capillaries was primarily responsible for limiting the increase in [K(+)] in the interstitial space at the onset of fiber activation. Vascular responses to increasing interstitial [K(+)] may contribute to the rapid increase in blood flow that is observed to occur after the onset of muscle contraction.
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Affiliation(s)
- Arthur Lo
- Program in Applied Mathematics, University of Arizona, Tucson, AZ 85724-5051, USA
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16
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Ronquist G, Waldenström A. Imbalance of plasma membrane ion leak and pump relationship as a new aetiological basis of certain disease states. J Intern Med 2003; 254:517-26. [PMID: 14641792 DOI: 10.1111/j.1365-2796.2003.01235.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The basis for life is the ability of the cell to maintain ion gradients across biological membranes. Such gradients are created by specific membrane-bound ion pumps [adenosine triphosphatases (ATPases)]. According to physicochemical rules passive forces equilibrate (dissipate) ion gradients. The cholesterol/phospholipid ratio of the membrane and the degree of saturation of phospholipid fatty acids are important factors for membrane molecular order and herewith a determinant of the degree of non-specific membrane leakiness. Other operative principles, i.e. specific ion channels can be opened and closed according to mechanisms that are specific to the cell. Certain compounds called ionophores can be integrated in the plasma membrane and permit specific inorganic ions to pass. Irrespective of which mechanism ions leak across the plasma membrane the homeostasis may be kept by increasing ion pumping (ATPase activity) in an attempt to restore the physiological ion gradient. The energy source for this work seems to be glycolytically derived ATP formation. Thus an increase in ion pumping is reflected by increased ATP hydrolysis and rate of glycolysis. This can be measured as an accumulation of breakdown products of ATP and end-products of anaerobic glycolysis (lactate). In certain disease entities, the balance between ATP formation and ion pumping may be disordered resulting in a decrease in inter alia (i.a.) cellular energy charge, and an increase in lactate formation and catabolites of adenylates. Cardiac syndrome X is proposed to be due to an excessive leakage of potassium ions, leading to electrocardiographic (ECG) changes, abnormal Tl-scintigraphy of the heart and anginal pain (induced by adenosine). Cocksackie B3 infections, a common agent in myocarditis might also induce an ionophore-like effect. Moreover, Alzheimer's disease is characterized by the formation of extracellular amyloid deposits in the brain of patients. Perturbation of cellular membranes by the amyloid peptide during the development of Alzheimer's disease is one of several mechanisms proposed to account for the toxicity of this peptide on neuronal membranes. We have studied the effects of the peptide and fragments thereof on 45Ca2+-uptake in human erythrocytes and the energetic consequences. Treatment of erythrocytes with the beta 1-40 peptide, results in qualitatively similar nucleotide pattern and decrease of energy charge as the treatment with Ca2+-ionophore A23187. Finally, in recent studies we have revealed and published in this journal that a rare condition, Tarui's disease or glycogenosis type VII, primarily associated with a defect M-subunit of phosphofructokinase, demonstrates as a cophenomenon an increased leak of Ca2+ into erythrocytes.
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Affiliation(s)
- G Ronquist
- Department of Clinical Chemistry, University Hospital, Uppsala, Sweden.
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Myers AC, Bochner BS, Tomaselli GF, Fedarko N, Hudson SA, Rohde H, Huang SK, Xu KY. Cell surface expression of a specific antigenic site on the catalytic subunit of (Na(+) + K(+))-ATPase. Biochem Biophys Res Commun 2002; 291:111-5. [PMID: 11829469 DOI: 10.1006/bbrc.2002.6419] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Structural localization of a peptide region, KRQPRNPKTDKLVNE, in the catalytic subunit of (Na(+) + K(+))-ATPase was investigated using a specific antibody directed against this peptide in cultured African green monkey kidney CV-1 cells. Immunofluorescence staining of frozen cell sections shows that an anti-KRQPRNPKTDKLVNE antibody (SSA95) interacts with its antigenic site and binds to the extracellular side of the cell membrane. Indirect immunofluorescence and flow cytometric analyses confirmed the presence of this epitope on intact cell surfaces. These results suggest that the KRQPRNPKTDKLVNE region of the (Na(+) + K(+))-ATPase is expressed on the cellular membrane surface.
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Affiliation(s)
- Allen C Myers
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland 21224, USA
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18
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Ronquist G, Rudolphi O, Engström I, Waldenström A. Familial phosphofructokinase deficiency is associated with a disturbed calcium homeostasis in erythrocytes. J Intern Med 2001; 249:85-95. [PMID: 11168788 DOI: 10.1046/j.1365-2796.2001.00780.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
OBJECTIVES To critically evaluate whether an altered calcium homeostasis in erythrocytes could be contributing to the symptomatology of the Tarui's disease, which is an inherited phosphofructokinase (PFK) deficiency of the muscle isoenzyme. PFK is a tetrameric enzyme with three different isoenzymes, muscle (M), liver (L), and platelet (P). Erythrocytes contain a 50 : 50 hybrid of M and L type. The deficiency of the muscle isoenzyme displays a symptomatology which is mainly characterized by myopathy, and a compensated haemolytic anaemia. DESIGN Erythrocyte deformability was assessed before and after autoincubation. Energy related metabolites and energy charge was determined in erythrocytes under various experimental conditions. SETTING The clinical part of the study was performed at the Departments of Cardiology and Clinical Chemistry, Umeå University Hospital, and the experimental investigation was carried out at the Department of Clinical Chemistry of the University Hospital of Uppsala, Sweden. SUBJECTS Four family members with Tarui's disease participated in the study: the proband (patient 1), a 39-year-old male and two siblings, patient 2 (male, aged 46 years) and patient 3 (female, 30 years). Patient 4 (male, 16 years) was the son of the patient 2. Five healthy persons served as controls (controls 1-5). INTERVENTIONS None. MAIN OUTCOME MEASURES Cell-physiological variables were determined after autoincubation of erythrocytes (i.e. incubation in their own plasma at 37 degrees C) and after incubation in a composite buffered medium. RESULTS Erythrocyte deformability as assessed by the erythrocyte fluidity was substantially decreased in patients compared to the moderate decrease in the control after 24 h of autoincubation, in presence of endogenous Ca2+ (heparin plasma). Moreover, autoincubation of erythrocytes shows that the patient's erythrocytes, although being moderately deficient in PFK activity, exhibit a normal (or slightly increased) lactate production compared to controls. Despite this, we show an increased ATP turnover with an Ca2+-induced AMP deaminase (and 5'-nucleotidase) activation leading to an increase in hypoxanthine content in patients' erythrocytes of about 100% after 24 h of autoincubation in heparin plasma, when compared to controls. A loss of volume in patient's erythrocytes after 24 h of autoincubation (in presence of Ca2+), as revealed by a diminished MCV, was consistent with an increased metabolic pool of intracellular calcium ions with a selective loss of K+ due to the activation of the K+ channel by intracellular Ca2+ (Gardos-effect). CONCLUSION We conclude that the different calcium ion-induced effects on energy metabolism, structure and function of patients' erythrocytes are due to an augmented membrane leakage of Ca2+ and therefore an accumulated intracellular Ca2+ pool. This will result in an increased energy demand by the Ca2+-stimulated ATPase (calcium pump) to compensate for the dissipated Ca2+ gradient across the plasma membrane. The concomitant haemolysis may be explained by a diminished erythrocyte deformability due to Ca2+ overload.
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Affiliation(s)
- G Ronquist
- Department of Clinical Chemistry, University Hospital, S-751 85 Uppsala, Sweden
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19
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James JH, Wagner KR, King JK, Leffler RE, Upputuri RK, Balasubramaniam A, Friend LA, Shelly DA, Paul RJ, Fischer JE. Stimulation of both aerobic glycolysis and Na(+)-K(+)-ATPase activity in skeletal muscle by epinephrine or amylin. THE AMERICAN JOURNAL OF PHYSIOLOGY 1999; 277:E176-86. [PMID: 10409142 DOI: 10.1152/ajpendo.1999.277.1.e176] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Epinephrine and amylin stimulate glycogenolysis, glycolysis, and Na(+)-K(+)-ATPase activity in skeletal muscle. However, it is not known whether these hormones stimulate glycolytic ATP production that is specifically coupled to ATP consumption by the Na(+)-K(+) pump. These studies correlated glycolysis with Na(+)-K(+)-ATPase activity in resting rat extensor digitorum longus and soleus muscles incubated at 30 degrees C in well-oxygenated medium. Lactate production rose three- to fourfold, and the intracellular Na(+)-to-K(+) ratio (Na(+)/K(+)) fell with increasing concentrations of epinephrine or amylin. In muscles exposed to epinephrine at high concentrations (5 x 10(-7) and 5 x 10(-6) M), ouabain significantly inhibited glycolysis by approximately 70% in either muscle and inhibited glycogenolysis by approximately 40 and approximately 75% in extensor digitorum longus and soleus, respectively. In the absence of ouabain, but not in its presence, statistically significant inverse correlations were observed between lactate production and intracellular Na(+)/K(+) for each hormone. Epinephrine had no significant effect on oxygen consumption or ATP content in either muscle. These results suggest for the first time that stimulation of glycolysis and glycogenolysis in resting skeletal muscle by epinephrine or amylin is closely linked to stimulation of active Na(+)-K(+) transport.
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Affiliation(s)
- J H James
- Departments of Surgery, University of Cincinnati, Cincinnati, Ohio 45267, USA.
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20
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Martinka E, Galajada P, Ochodnicky M, Lichardus B, Straka S, Mokan M. Endogenous digoxin-like immunoactivity and diabetes mellitus: facts and hypotheses. Med Hypotheses 1997; 49:271-5. [PMID: 9293472 DOI: 10.1016/s0306-9877(97)90212-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Substances with digoxin- and ouabain-like immunoactivity (DLIA) are specific inhibitors of Na(+)-K(+)-ATPase which increase the total amount of intracellular stored calcium (Ca2+i). In diabetic patients, DLIA levels have been reported to be increased. Although this increase is probably secondary to sodium retention and volume expansion (included in diabetic subjects by hyperinsulinemia and/or diabetic nephropathy), the question arises of whether it has pathophysiological consequences: namely, whether substances with DLIA, via their effect on Na(+)-K(+)-ATPase activity and Ca2+i stores, could in diabetic subjects facilitate development of hypertension and/or modulate insulin sensitivity or insulin secretion. Clinical findings of correlations of DLIA to blood pressure, insulin levels and to degree of insulin resistance, together with experimental findings of decreased Na(+)-K(+)-ATPase activity, increased Ca2+i and decreased Mg2+i in both diabetic and hypertensive subjects, support these hypotheses. However, the issue of whether or not these relations are causative and whether or not defects in intracellular milieu are primary or secondary to non-insulin-dependent diabetes mellitus has not been resolved yet. Moreover, pathogenesis of both diabetes mellitus and hypertension is multifactorial and includes many other factors. Therefore, further efforts should be made to elucidate the exact role of substances with DLIA in diabetes mellitus.
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Affiliation(s)
- E Martinka
- Department of Internal Medicine I, Jesenius Medical School, Martin, Slovakia
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Waldenström A, Martinussen HJ, Kock J, Ronquist G, Hultman J. Parasympathetic muscarinic stimulation limits noradrenaline induced myocardial creatine kinase release: a study in the isolated perfused working rat heart. Scand J Clin Lab Invest 1994; 54:615-21. [PMID: 7709164 DOI: 10.3109/00365519409087541] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
It has long been known that high concentrations of catecholamines may induce myocardial damage, and aggravate ischaemic injury. It has also been shown that beta-blockade may protect the myocardium from ischaemic damage. Stimulation of muscarinic receptors modulates beta-adrenergic receptor affinity for isoproterenol and attenuates isoproterenol induced adenylyl cyclase activation. Effects of muscarinic receptor stimulation were therefore investigated in isolated anterogradely perfused rat hearts under different experimental conditions. One group of hearts was perfused with noradrenaline, 10(-6) mol l-1 for 45 min, and another group was perfused with different carbachol concentrations (3 x 10(-7)-10(-5) mol l-1) with or without noradrenaline 10(-6) mol l-1, for 45 min. Release of creatine kinase to the perfusion buffer was taken as a sign of cell damage. Heart rate, left ventricular maxdP/dt and left ventricular pressure were measured throughout the perfusion time by insertion of a 20 gauge cannula through the left ventricular wall near the base. Carbachol (3 x 10(-7) mol l-1) alone induced a decrease of heart rate by 25% and maxdP/dt by 13%. Noradrenaline produced a 20% increase in heart rate, whereas the combination of noradrenaline plus carbachol induced a minor decrease in heart rate. Muscarinic receptor stimulation alone decreased myocardial contractility. However, when combined with noradrenaline no decrease in contractility was seen. Also, the release of creatine kinase to the perfusion buffer containing the combination of carbachol plus noradrenaline was reduced. Thus, muscarinic receptor stimulation protected the myocardium from catecholamine induced damage at concentrations where no change in contractility was seen.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- A Waldenström
- Department of Cardiology, University Hospital, University of Uppsala, Sweden
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22
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Kaul S, Krishnakanth TP. Effect of retinol deficiency and curcumin or turmeric feeding on brain Na(+)-K+ adenosine triphosphatase activity. Mol Cell Biochem 1994; 137:101-7. [PMID: 7845384 DOI: 10.1007/bf00944071] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The effect of retinol deficiency and curcumin and turmeric feeding on brain microsomal Na(+)-K(+)ATPase activity was investigated. The brain Na(+)-K(+)ATPase activity registered an increase of 148.5% as compared to the control group. Upon treating retinol deficient rats with curcumin or turmeric, the abnormally elevated activity showed a decrease of 36.9 and 47.1%, respectively, when compared to the retinol deficient group. An increase in Vmax by 67% and Km by 66% for ATP was observed in the retinol deficient group. Curcumin or turmeric fed retinol-deficient groups reduced the Vmax by 25 and 33%, while Km was reduced by 25 and 31%, respectively, compared to the retinol deficient group. Arrhenius plot of Na(+)-K(+) ATPase showed a typical bi-phasic pattern in all the groups. Cholesterol:Phospholipid ratio showed a decrease in the retinol-deficient group by 67.8%, which showed a marked increase in curcumin or turmeric treated groups. Detergents could increase the Na(+)-K(+) ATPase activity more in the control group than in the retinol deficient groups. Curcumin or turmeric improved the detergent action on the enzyme. Subsequent freezing and thawing over a period of 30 min decreased the enzyme activity by 22.8% in the retinol deficient group compared to 15.9% decrease in the control group. Curcumin or turmeric treated groups showed a decrease in the enzyme activity by 22.0 and 19.2%, respectively, when compared to the zero time in each group. In the presence of concanavalin-A (Con-A) there was only 52.4% stimulation in the enzyme activity in retinol deficient groups, compared to 108.0% in the control group.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- S Kaul
- Department of Biochemistry and Nutrition, Central Food Technological Research Institute, Mysore, India
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23
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Kaloyianni M, Moutou K. Substrate utilization by Rana ridibunda erythrocytes. COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY. BIOCHEMISTRY AND MOLECULAR BIOLOGY 1994; 108:357-66. [PMID: 8081659 DOI: 10.1016/0305-0491(94)90087-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Various monosaccharides, including ribose, mannose, galactose, and urea, in combination with glucose, were studied to determine their efficacy in supporting the formation of pyruvate, lactate, 2,3-diphosphoglycerate and ATP in Rana ridibunda erythrocytes. Lactate formation was found to increase during the course of incubation in the presence of all the substrates. None of the studied substrates maintained cellular ATP levels. About 0.36 mumole of lactic acid per hour was produced for each mumol of ribose that was metabolized. The presence of 1 mM Na-iodoacetate accelerated the loss of ATP and lactate in the presence of either glucose or ribose. Additionally, ouabain suppressed lactate formation from ribose alone, as well as in combination with glucose. From the metabolic substrates studied, ribose was shown to be the most efficient substrate to support Rana ridibunda erythrocyte metabolism. Mannose, galactose and urea may also be used as alternative metabolic substrates by Rana ridibunda erythrocytes.
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Affiliation(s)
- M Kaloyianni
- Zoology Department, Science School, Aristotle University of Thessaloniki, Greece
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24
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Saumon G, Martet G. Effect of metabolic inhibitors on Na+ transport in isolated perfused rat lungs. Am J Respir Cell Mol Biol 1993; 9:157-65. [PMID: 7687851 DOI: 10.1165/ajrcmb/9.2.157] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Alveolar fluid absorption is a process driven by transepithelial alveolar Na+ transport. Since lungs produce significant amounts of lactate under anaerobic but also under aerobic conditions, glycolysis may conceivably contribute to producing the energy needed for transepithelial Na+ transport and fluid absorption. The effects of inhibition of oxidative phosphorylation or glycolysis on alveolar Na+ transport, fluid absorption, and preservation of alveolar epithelial barrier properties were examined using isolated, fluid-filled rat lungs. Basal lung lactate production was 65 +/- 1.0 mumol/h/g dry wt in the presence of 10 mmol/liter glucose. When oxidative phosphorylation was inhibited with rotenone, cyanide, or the uncoupler carbonyl cyanide m-chlorophenylhydrazone (CCCP), lung lactate production increased 5- to 7-fold within 30 min (P < 0.001). No significant decrease in alveolar Na+ transport was observed over 1 h, whereas a 3-fold increase in passive epithelial permeability was observed. With rotenone and CCCP, but not cyanide, fluid absorption from airspaces was decreased but never abolished. Inhibition of aerobic glycolysis with iodoacetate did not significantly affect alveolar Na+ transport or fluid absorption. In the presence of isoproterenol or dibutyryl cyclic adenosine monophosphate (cAMP) + isobutylmethylxanthine, which have previously been shown to stimulate alveolar Na+ transport, lung lactate production increased 2-fold (P < 0.001). Inhibition of glycolysis depressed stimulated alveolar Na+ and fluid transports (P < 0.001). Inhibition of ion transport by ouabain or amiloride decreased lung lactate production (P < 0.001) under stimulated but not under unstimulated conditions. These observations suggest that glycolysis does not significantly contribute to energy provision for alveolar epithelial Na+ transport in lungs under basal, aerobic conditions.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- G Saumon
- INSERM U82, Faculté Xavier Bichat, Paris, France
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25
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Engström I, Waldenström A, Ronquist G. Effects of the ionophore gramicidin D on energy metabolism in human erythrocytes. Scand J Clin Lab Invest 1993; 53:247-52. [PMID: 7686299 DOI: 10.3109/00365519309088416] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Washed human erythrocytes were incubated in phosphate-buffered saline at 37 degrees C with different concentrations (2-80 mg l-1) of the monovalent cationophore gramicidin D. The ionophore induced a decrease of ATP content and energy charge (EC) and a concomitant increase in ADP and AMP contents. At a concentration of 10 mg l-1 of the ionophore the reduction of EC and ATP concentration was about 50%. Increasing the concentration of the ionophore resulted in a substantial haemolysis with no further effect on the nucleotide levels. Lowering the concentration of the ionophore to 5 mg l-1 (to avoid haemolysis) lead to a similar effect on the energy status. Ouabain at 0.5 mmol l-1 in incubation medium distinctly blunted the ionophoric effect on EC and adenine nucleotides. Addition of glucose on the contrary reversed these effects by about 80%. Hence, the glucose-induced increase in glycolytic flux as evidenced by an increase in lactate production was not sufficient to restore energy state.
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Affiliation(s)
- I Engström
- Department of Clinical Chemistry, University Hospital, University of Uppsala, Sweden
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26
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Engström I, Waldenström A, Ronquist G. Ionophore A23187 reduces energy charge by enhanced ion pumping in suspended human erythrocytes. Scand J Clin Lab Invest 1993; 53:239-46. [PMID: 8391160 DOI: 10.3109/00365519309088415] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Washed human erythrocytes were basically incubated in phosphate-buffered saline at 37 degrees C with different concentrations (1-5 mumol l-1) of the divalent cationophore A23187. This ionophore induced a decrease by about 75% of ATP content and energy charge (EC) and a concomitant increase in ADP and AMP contents in a dose-dependent fashion such that an inverse ATP/ADP relationship developed. EGTA at 1 mumol l-1 annihilated the effect of A23187 on energy status. When glucose was added to the basic incubation medium A23187 inclusion resulted in an elevated lactate production concomitantly with a partial restoration of EC. Introduction of Mg2+ to basic incubation medium containing glucose and the ionophore resulted in a sharp increase in lactate production with an energy state that was maintained at a control level. It is concluded that the low EC of erythrocytes obtained by this ionophore is the result of runaway ATPases dissociated from glycolysis. Since human erythrocytes are devoid of organelles other than the plasma membrane it is concluded that the ionophoric effect is exerted in the plasma membrane.
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Affiliation(s)
- I Engström
- Department of Clinical Chemistry, University Hospital, University of Uppsala, Sweden
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Martinussen HJ, Waldenström A, Ronquist G. Functional and biochemical effects of a K(+)-ionophore on the isolated perfused rat heart. ACTA PHYSIOLOGICA SCANDINAVICA 1993; 147:221-5. [PMID: 8475749 DOI: 10.1111/j.1748-1716.1993.tb09492.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Valinomycin, a K(+)-specific ionophore, influenced function and metabolism of isolated perfused rat hearts in a dose-dependent fashion. At a concentration of 0.05 micrograms ml-1 in perfusion fluid a 50% reduction of heart rate (HR) and a 90% reduction in max dP/dt were observed. These effects were paralleled by a substantial decrease of myocardial energy charge from about 0.80 to 0.20. A 2.5 fold increase in tissue lactate concentration indicated an increased rate of glycolytic activity. Low ATP combined with high ADP and AMP levels as found in these valinomycin-treated hearts is known to promote phosphofructokinase activity and may explain the elevated lactate levels. A significant increase in the concentrations of adenosine, IMP and inosine was observed as well.
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Affiliation(s)
- H J Martinussen
- Department of Anaesthesiology, University Hospital, Uppsala, Sweden
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Miwa I, Duan YJ, Murase S, Fukatsu H, Tamura A, Okuda J. Stimulatory effect of phospholipase A2 treatment on glucose utilization in human erythrocytes. BIOCHIMICA ET BIOPHYSICA ACTA 1993; 1175:174-80. [PMID: 8418896 DOI: 10.1016/0167-4889(93)90020-p] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
We examined whether modification of membrane phospholipids of human erythrocytes by hydrolysis with phospholipase A2 (PLA2 from bee venom) would affect glucose utilization, chosen as a typical model of intracellular metabolism, and, if so, intended to clarify the mechanism of the alteration of glycolysis. Treatment of erythrocytes with PLA2 induced a marked shape change (i.e., crenation) and significantly increased the rate of lactate production from glucose. Available evidence indicated that there is no relevance of this cell-shape change to the alteration of glycolysis. The lack of a detectable effect of papain treatment on glycolysis in PLA2-treated cells suggested that the increase in glycolysis by PLA2 treatment might not be caused by the conformational change of band-3 protein through modulation of membrane phospholipids. The result of the measurement of lactate production in the presence and absence of ouabain did not support the idea that hydrolysis of phospholipids by PLA2 treatment makes plasma membranes leaky to Na+ and consequently enhances glycolysis through activation of Na+/K(+)-ATPase. The action of PLA2 on glycolysis was abolished by extraction of free fatty acids in the cell membrane with bovine serum albumin. Loading erythrocytes with free fatty acid (oleic acid, linoleic acid, or arachidonic acid) caused a significant increase in glycolysis. Analysis of glycolytic intermediates suggested that the enhancement of glycolysis was induced by activation of 6-phosphofructokinase. The data, thus, indicate that treatment of human erythrocytes with PLA2 significantly accelerates glucose utilization and suggest that the stimulation of glycolysis is caused by activation of 6-phosphofructokinase through liberation of free fatty acids of membrane phospholipids by PLA2.
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Affiliation(s)
- I Miwa
- Department of Clinical Biochemistry, Faculty of Pharmacy, Meijo University, Nagoya, Japan
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Glitsch HG, Tappe A. The Na+/K+ pump of cardiac Purkinje cells is preferentially fuelled by glycolytic ATP production. Pflugers Arch 1993; 422:380-5. [PMID: 8382364 DOI: 10.1007/bf00374294] [Citation(s) in RCA: 51] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The role of glycolysis and oxidative phosphorylation in providing the ATP for the cardiac Na+/K+ pump was studied in cardioballs from sheep Purkinje fibres. As an indicator of the pump activity, the pump current Ip was measured at -20 mV and 30-33 degrees C by means of whole-cell recording. During intracellular perfusion with a pipette solution containing 5 mM ATP and 15 mM glucose Ip reached a maximum within 8 min and declined to 50% of this value within 27 min after gaining access to the cell interior. Perfusion with an ATP- and glucose-free medium barely enhanced the Ip decline. Inhibition of the oxidative phosphorylation by carbonylcyanide m-chlorophenylhydrazone (CCCP, 2 microM or 20 microM) moderately accelerated the effect of the ATP- and glucose-free pipette solution. Addition of 2 mM iodoacetic acid (an inhibitor of glycolysis) to the latter medium further enhanced the Ip decrease with time. Inhibition of the glycolytic ATP synthesis by 2-deoxy-D-glucose (5 mM) caused a dramatic decline of Ip to half of its maximum within 7.3 min. Pyruvate (5 mM) and inorganic phosphate (2 mM) did not affect the fast Ip decline evoked by the ATP- and glucose-free, 2-deoxyglucose-containing medium, whereas 2 microM CCCP still hastened the fast Ip decrease slightly. This effect of complete metabolic inhibition was reversed by switching to an inhibitor-free pipette solution containing 15 mM ATP. It is concluded that the Na+/K+ pump of cardiac Purkinje cells is preferentially fuelled by glycolytic ATP synthesis.
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Affiliation(s)
- H G Glitsch
- Department of Cell Physiology, Ruhr-University Bochum, Federal Republic of Germany
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30
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Owicki JC, Parce JW. Biosensors based on the energy metabolism of living cells: the physical chemistry and cell biology of extracellular acidification. Biosens Bioelectron 1992; 7:255-72. [PMID: 1622600 DOI: 10.1016/0956-5663(92)87004-9] [Citation(s) in RCA: 215] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The silicon microphysiometer is a biosensor-based instrument that detects changes in the physiological state of cultured living cells by monitoring the rate at which the cells excrete acidic products of metabolism. This paper discusses the chemical and biological factors that determine the performance and applications of such a system. Under typical culture conditions, extracellular acidification is dominated by the excretion of lactic and carbonic acids formed during the energy metabolism, using glucose and glutamine as carbon sources. The maintenance of transmembrane ionic gradients is an important use of energy, as is cell growth. The activation of cellular receptors usually causes transient or sustained increases in acidification rate. The energetic cost of generating second messengers is probably too small to account for either change, so events more distal to the receptor-activation process must be responsible. The opening of ion channels may cause the increases in some cases. In others, changes in intracellular pH and loose coupling between ATP hydrolysis and synthesis may be involved; models for these processes are presented.
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Affiliation(s)
- J C Owicki
- Molecular Devices Corporation, Menlo Park, CA 94025
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31
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Cornelius F. Functional reconstitution of the sodium pump. Kinetics of exchange reactions performed by reconstituted Na/K-ATPase. BIOCHIMICA ET BIOPHYSICA ACTA 1991; 1071:19-66. [PMID: 1848452 DOI: 10.1016/0304-4157(91)90011-k] [Citation(s) in RCA: 102] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Affiliation(s)
- F Cornelius
- Institute of Biophysics, University of Aarhus, Denmark
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32
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Schneider W, Siems W, Grune T. Balancing of energy-consuming processes of rat hepatocytes. Cell Biochem Funct 1990; 8:227-32. [PMID: 1703050 DOI: 10.1002/cbf.290080407] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
A method for the quantification of energy consuming processes described by Siems et al. for reticulocytes and by Müller et al. for ascites tumour cells was applied to balance the ATP-consumption of isolated rat hepatocytes. On the basis of decreased coupled respiration rates following the specific inhibition of energy-requiring reactions, the energy demands of protein turnover, nucleic acid synthesis, Na+/K(+)-ATPase and Ca2(+)-transport of hepatocytes in different incubation media were assessed. These processes together with urea synthesis account for about 60 per cent of the total energy consumption in a glucose and amino acid-enriched Eagle/Borsook medium. The metabolic flux rates of total ATP-consumption and ATP-consumption of single energy-requiring processes in hepatocytes are compared with those in reticulocytes and different tumour cell types.
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Affiliation(s)
- W Schneider
- Institute of Biochemistry, Medical Faculty Charité, Berlin, G.D.R
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33
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Johnson JH, Crider BP. Increases in Na+,K+-ATPase activity of erythrocytes and skeletal muscle after chronic ethanol consumption: evidence for reduced efficiency of the enzyme. Proc Natl Acad Sci U S A 1989; 86:7857-60. [PMID: 2554292 PMCID: PMC298170 DOI: 10.1073/pnas.86.20.7857] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Increased Na+,K+-ATPase activity observed after chronic ethanol consumption has been examined to determine whether the increase is due to changes in the kinetic properties of the enzyme or increases in the amount of enzyme in the membranes examined. In skeletal muscle and erythrocyte ghosts from rat, as well as from humans, increased Na+,K+-ATPase activity in ethanol-consuming individuals was not accompanied by an increase in the number of ouabain binding sites. In studies with intact human erythrocytes, similar ouabain-sensitive 22Na+ and 86Rb+ pumping rates were observed between normal and ethanol-consuming individuals and the Na+ to Rb+ pumping ratio was found to be 1.5 in all cases. However, ouabain-sensitive lactate plus Pi formation was increased in cells from alcoholic individuals. Thus these data suggest that increased enzyme activity may be due to a kinetic alteration of the Na+,K+-ATPase and that the enzyme may be less efficient in coupling ion pumping to ATP hydrolysis than the enzyme in normal cells.
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Affiliation(s)
- J H Johnson
- Veterans Administration Medical Center, Dallas, TX 75216
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34
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Clarke RJ, Apell HJ, Läuger P. Pump current and Na+/K+ coupling ratio of Na+/K+-ATPase in reconstituted lipid vesicles. BIOCHIMICA ET BIOPHYSICA ACTA 1989; 981:326-36. [PMID: 2543461 DOI: 10.1016/0005-2736(89)90044-8] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
A method is described for studying the coupling ratio of the Na+/K+ pump, i.e., the ratio of pump-mediated fluxes of Na+ and K+, in a reconstituted system. The method is based on the comparison of the pump-generated current with the rate of K+ transport. Na+/K+-ATPase from kidney is incorporated into the membrane of artificial lipid vesicles; ATPase molecules with outward-oriented ATP-binding site are activated by addition of ATP to the medium. Using oxonol VI as a potential-sensitive dye for measuring transmembrane voltage, the pump current is determined from the change of voltage with time t. In a second set of experiments, the membrane is made selectively K+-permeable by addition of valinomycin, so that the membrane voltage U is equal to the Nernst potential of K+. Under this condition, dU/dt reflects the change of intravesicular K+ concentration and thus the flux of K+. Values of the Na+/K+ coupling ratio determined in this way are close to 1.5 in the experimental range (10-75 mM) of extravesicular (cytoplasmic) Na+ concentrations.
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Affiliation(s)
- R J Clarke
- Department of Biology, University of Konstanz, F.R.G
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35
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Marunaka Y. Effects of internal Na and external K concentrations on Na/K coupling of Na,K-pump in frog skeletal muscle. J Membr Biol 1988; 101:19-31. [PMID: 2835486 DOI: 10.1007/bf01872816] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
To clarify the dependency of the Na/K coupling of the Na,K-pump on internal Na and external K concentrations in skeletal muscle, the ouabain-induced change in membrane potential, the ouabain-induced change in Na efflux and the membrane resistance were measured at various internal Na and external K concentrations in bullfrog sartorius muscle. Upon raising the internal Na concentration from 6 mmol/kg muscle water to 20 mmol/kg muscle water, the magnitude of the ouabain-induced change in membrane potential increased about eightfold and the magnitude of the ouabain-induced change in Na efflux increased about fivefold while the membrane resistance was not significantly changed. As the external K concentration increased from 1 to 10 mM, the magnitude of the ouabain-induced change in membrane potential decreased (1/5.5 fold), while the magnitude of the ouabain-induced change in Na efflux increased (about 1.5-fold). The membrane resistance decreased upon raising the external K concentration from 1 to 10 mM (1/2-fold). These observations imply that the values of the Na/K coupling of the Na,K-pump increases upon raising the internal Na concentration and decreases upon raising the external K concentration.
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Affiliation(s)
- Y Marunaka
- Department of Physiology, Shiga University of Medical Science, Ohtsu, Japan
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36
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Hammerstedt RH, Volonté C, Racker E. Motility, heat, and lactate production in ejaculated bovine sperm. Arch Biochem Biophys 1988; 266:111-23. [PMID: 2972256 DOI: 10.1016/0003-9861(88)90241-x] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Effects of various inhibitors on motility, heat, and lactate production of ejaculated bovine sperm were determined in the presence of antimycin A and rotenone. erythro-9-[3-(2-Hydroxynonyl)]adenine (EHNA) and polyvinylpyrrolidone (PVP-360) stopped motility and reduced heat or lactate production by 30-50%. Carbodiimides resulted in loss of motility and a reduction of metabolism by 60-75%. Quercetin treatment, which enhanced rather than inhibited motility, depressed heat and lactate production by 50-60%. Since mechanical immobilization reduced heat production by only 30%, the question arises as to what other cellular processes are major contributors to the energy budget. Inhibitors of ion flux had little-to-no effect on heat or lactate production, suggesting that neither mitochondrial nor Na+/K+ ATPases were major ATP-requiring processes. Calcium flux at the plasma membrane also was minimal and previous reports eliminated glycolytic substrate cycling as major consuming processes for ATP. Although quercetin inhibited lactate production in intact cells, no effect of quercetin on cell-free glycolysis and the ATPase activities of isolated dynein was detected. Quercetin did, however, inhibit ATPase activity of plasma membrane, suggesting that this unidentified ATPase may contribute to the formation of ADP and Pi required for lactate production by the intact cell. We propose (a) that the bioenergetic costs of motility are divided between regulatory events and dynein-microtubule interaction (dynein ATPase), (b) that some of the membrane-related processes may be "inefficient," and (c) that quercetin may render these steps more "efficient," in a manner analogous to its action on the Na+/K+ pump of Ehrlich ascites tumor cells.
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Affiliation(s)
- R H Hammerstedt
- Program in Biochemistry, Pennsylvania State University, University Park 16802
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37
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Marunaka Y. Relationship between ionic surroundings and insulin actions on glucose transport and Na,K-pump in muscles. COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY. A, COMPARATIVE PHYSIOLOGY 1988; 89:103-12. [PMID: 2452047 DOI: 10.1016/0300-9629(88)91065-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
1. It is well known that insulin has various effects on glucose transport and the Na,K-pump in muscles. It is also known to have some effects on the membrane potential--in general, insulin induces a hyperpolarization of the membrane in muscles. Furthermore, it is suggested that the actions of insulin are modified by changes in ionic surroundings. 2. In this review article, the actions of ionic surroundings and insulin on glucose transport in muscles are discussed; in particular, the effects of changes in extracellular and/or intracellular concentrations of Na, K, Ca and H ions will be mentioned. 3. The actions of ionic surroundings and insulin on the Na,K-pump in muscles are discussed; in particular, the effects of changes in extracellular an/or intracellular concentrations of Na, K, Ca and H ions will be examined. 4. The relationship between the actions of ionic surroundings and insulin are discussed. 5. In particular, the effects of changes in ionic surroundings on the insulin-induced hyperpolarization of the membrane are discussed by relating it to the Na,K-pump function. The relationship between the insulin-induced change in membrane potential and glucose transport will be also mentioned.
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Affiliation(s)
- Y Marunaka
- Department of Physiology, Shiga University of Medical Science, Ohtsu, Japan
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38
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Mărgineanu DG. Equilibrium and non-equilibrium approaches in biomembrane thermodynamics. ARCHIVES INTERNATIONALES DE PHYSIOLOGIE ET DE BIOCHIMIE 1987; 95:381-422. [PMID: 2452614 DOI: 10.3109/13813458709075033] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Affiliation(s)
- D G Mărgineanu
- Laboratory of Biophysics, Faculty of Biology, University of Bucharest, Romania
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39
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Akanle OA, Spyrou NM, Damyanova AA, Shaw DM, Ali L. Investigation of elemental models in senile dementia and depressives using neutron activation analysis. J Radioanal Nucl Chem 1987. [DOI: 10.1007/bf02050514] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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40
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Marunaka Y. The effect of the internal Na concentration on the electrogenicity of the insulin-stimulated Na,K-pump in frog skeletal muscles. COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY. A, COMPARATIVE PHYSIOLOGY 1987; 86:133-6. [PMID: 2881643 DOI: 10.1016/0300-9629(87)90289-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Insulin induced a hyperpolarization of the membrane by stimulating the Na,K-pump in frog skeletal muscles. The Na,K-pump activity was dependent on the internal Na concentration. As the internal Na concentration was raised from 5 mmol/kg muscle water to 18 mmol/kg muscle water, the magnitude of the insulin-induced increase in the ouabain-sensitive Na efflux (an index of the Na,K-pump activity) rose by 5-fold and the magnitude of the insulin-induced hyperpolarization rose by 8.5-fold. On the other hand, the specific membrane resistance was not significantly changed by a rise in the internal Na concentration. The Na/K coupling of the Na,K-pump was calculated at low, normal or high internal Na concentration by using the values of the insulin-induced changes in the ouabain-sensitive Na efflux and the membrane potential. As a result of the calculation, it was suggested that in frog skeletal muscles the Na/K coupling would increase with a rise of the internal Na concentration.
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41
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Marunaka Y. Effects of external K concentration on the electrogenicity of the insulin-stimulated Na,K-pump in frog skeletal muscle. J Membr Biol 1986; 91:165-72. [PMID: 2427722 DOI: 10.1007/bf01925793] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Insulin hyperpolarized the membrane of frog skeletal muscle by stimulating the electrogenic Na,K-pump. At external K concentrations of 1,2,5 and 10 mM, both the insulin-induced hyperpolarization and the insulin-stimulated ouabain-sensitive Na efflux (an index of Na,K-pump activity) were observed. By increasing the external K concentration, the insulin-stimulated Na efflux increased, but the magnitude of the insulin-induced hyperpolarization decreased; i.e., although the activity of the insulin-stimulated Na,K-pump increased, on the contrary, the magnitude of the hyperpolarization decreased. To clarify the causes of this phenomenon, the specific membrane resistance was measured and found to decrease upon increasing the external K concentration. One of the reasons for the decrease in magnitude of the hyperpolarization is the decrease in the specific membrane resistance. However, the decrease in magnitude of the hyperpolarization with a rise of the external K concentration, which increased the insulin-stimulated Na,K-pump activity, cannot be explained only by the decrease in the specific membrane resistance. It is suggested that the decrease in magnitude of the hyperpolarization is mainly caused by a decrease in the electrogenicity of the insulin-stimulated Na,K-pump upon an increase in the external K concentration. The conclusion of the present study is that the electrogenicity of the insulin-stimulated Na,K-pump in muscles is variable and decreases with increasing the external K concentration.
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42
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Lichtstein D, Kachalsky S, Deutsch J. Identification of a ouabain-like compound in toad skin and plasma as a bufodienolide derivative. Life Sci 1986; 38:1261-70. [PMID: 3007907 DOI: 10.1016/0024-3205(86)90418-2] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
An ouabain-like compound (OLC) was purified from toad skin. The purification procedure consisted of three sequential separations on HPLC using amino and reverse phase chromatography. Using UV, NMR and Mass spectroscopy the structure of the purified material is suggested to be mono-hydroxy-14,15-epoxy-20,22-dienolide glycoside (resibufogenin). Evidence is presented that this compound is also present in the toad plasma. It is suggested that the endogenous bufodienolide derivative participates in the physiological regulation of the Na+,K+-ATPase activity.
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43
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Adorante JS, Macey RI. Calcium-induced transient potassium efflux in human red blood cells. THE AMERICAN JOURNAL OF PHYSIOLOGY 1986; 250:C55-64. [PMID: 3079961 DOI: 10.1152/ajpcell.1986.250.1.c55] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Human red blood cells pretreated with low-ionic-strength solutions and resuspended in saline respond biphasically to extracellular Ca. At first, addition of Ca causes a large transient K efflux of as much as 600 mM . liter cell H2O-1 . h-1; this is followed by a decrease in K flux below control levels. The first phase (phase I) resembles the Gardos effect in several respects. It is inhibited by oligomycin, by external K, and by increased exposure time to Ca. Further, the K permeability of phase I is similar to that of the Gardos effect (5 X 10(-8)-9 X 10(-8) cm/s), and the cells hyperpolarize in a low-K medium when Ca2+ is added. However, phase I is not identical to the Gardos phenomenon. For example, La, which prevents the Gardos response, is ineffective on phase I. Moreover, external Ba prevents the development of phase I but not the Gardos response, whereas internal Ba prevents the Gardos response. Attempts to demonstrate a Ca leak or pump failure during phase I have failed; passive Ca movements of both treated and normal cells are similar. The results suggest that low-ionic-strength solution exposes Ca-sensitive sites to the external medium; these sites are maintained when the cells are returned to saline.
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44
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45
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Morgan K, Lewis MD, Spurlock G, Collins PA, Foord SM, Southgate K, Scanlon MF, Mir MA. Characterization and partial purification of the sodium-potassium-ATPase inhibitor released from cultured rat hypothalamic cells. J Biol Chem 1985. [DOI: 10.1016/s0021-9258(17)38766-5] [Citation(s) in RCA: 31] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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46
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Racker E, Riegler C. On the mechanism of glycolysis stimulation by neutral detergents in 3T3 and Ehrlich ascites tumor cells. Arch Biochem Biophys 1985; 240:836-42. [PMID: 2992384 DOI: 10.1016/0003-9861(85)90093-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Glycolysis of 3T3 and Ehrlich ascites tumor cells was greatly enhanced by Nonidet P-40 or Triton X-100 at about 100 micrograms/mg cell protein. This enhanced glycolysis was partly sensitive to rutamycin and partly sensitive to ouabain, suggesting that the detergent released the control of the ATPase of the mitochondria and of the plasma membrane Na+K+-ATPase. Nonidet P-40 had no effect on glycolysis in cell-free extracts from Ehrlich ascites tumor cells to which soluble mitochondrial ATPase was added. Measuring ouabain-sensitive 22Na efflux and using ouabain-sensitive lactate production as a measure of ATP hydrolysis by the Na+K+ pump, it was shown that Nonidet P-40 greatly decreased the efficiency of the Na+K+ pump. Quercetin increased the efficiency of pumping in EAT cells both in the absence and presence of the detergent.
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47
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Abstract
ATPase activities were determined in haemolysed and dialysed erythrocytes and in haemoglobin-free membranes of twenty patients with essential hypertension and twenty normotensive controls. Ouabain-sensitive ATPase (Na-K-ATPase) activity of haemolysate but not that of membranes was decreased in hypertensives whereas ouabain-insensitive ATPase (Mg-ATPase + some residual Ca-ATPase) activity was increased in both enzyme preparations when measurements were preformed in the absence of Ca2+-chelating substances. In haemolysed erythrocytes ouabain-sensitivity as a percentage of total ATPase activity was a good discriminator between both groups and may be a possible marker for essential hypertension. The decreased activity of Na-K-ATPase in haemolysate is apparently due to a non dialysable inhibitor of Na-K-ATPase which is either tightly bound to the erythrocyte membrane or dissolved in the cytoplasm. Following haemolysis with subsequent centrifugation the Na-K-ATPase inhibitor is removed, at least in part, and thus differences in Na-K-ATPase activity demonstrable in haemolysed and dialysed erythrocytes are no longer apparent in haemoglobin-free membranes.
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48
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Brand SC, Whittam R. The activation of the sodium pump in pig red blood cells by internal and external cations. BIOCHIMICA ET BIOPHYSICA ACTA 1985; 845:139-50. [PMID: 2581622 DOI: 10.1016/0167-4889(85)90170-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
A study has been made with pig red blood cells of the activation of the sodium pump by internal and external cations. Cell Na and K concentrations were altered using a PCMBS cation loading procedure. The procedure was characterised for resultant ionic conditions, maintenance of ATP levels and fragility. The activation of the sodium pump by external K was measured in cells suspended in choline (Na-free) solutions. External Cs was used as a substitute for K and elicited lower rates of pump activity. Both the Vmax and apparent Km for 42K influx and 134Cs influx increased as internal Na concentration was raised (within the non-saturating range). Vmax/apparent Km ratios for cation influx were constant. Raising external Cs concentration exerted a similar influence on pump activation by internal Na: both the maximum pump velocity and the apparent Na-site dissociation constant (K'Na) increased. The results provide evidence for a transmembrane connection between cation binding sites on opposite faces of the membrane and are consistent with a consecutive model for the sodium pump in pig red blood cells.
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49
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Doonan B. Model of anion and monovalent cation transport as neutral ion pairs through lipophilic water channels of the Na,K ATPase complex. Med Hypotheses 1985; 16:265-77. [PMID: 2582229 DOI: 10.1016/0306-9877(85)90009-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
A model of anion and monovalent cation transport through a lipophilic water channel of the Na,K ATPase complex is presented. Literature data for the Na,K ATPase cation binding sites are combined with data for the anion binding sites of Band 3 to obtain adjacent cation and anion combining sites at the inner and outer channel mouths. Cations and anions form neutral ion pairs or undissociated acids at these sites and then partition much more favorably into lipophilic channel water, passing through the channel in diffusive fashion. Cation movements in an "uphill" direction occur without an enzyme translocating moiety and its specific energetic requirement. The pertinent factors are the exclusion of unpaired cations by the tight channel and the site selectivity or pickup ratios for Na/K at each side which dominate over bulk and transmembrane concentration ratios. ATP hydrolysis provides phosphate for ion pairing.
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50
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Monti M, Ikomi-Kumm J. Erythrocyte heat production in human obesity: microcalorimetric investigation of sodium-potassium pump and cell metabolism. Metabolism 1985; 34:183-7. [PMID: 3969017 DOI: 10.1016/0026-0495(85)90130-1] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Changes in overall cellular metabolism, induced by specific inhibition of the Na-K-pump, were determined in erythrocytes from 33 normal and 25 obese subjects. Cellular metabolism was determined by measurement of heat production rates in erythrocytes suspended in plasma with and without the cardioactive glycoside, ouabain. Specific inhibition with ouabain induced the same decrease of the heat production rate in the two groups (14 +/- 5 mW/L for normal subjects and 13 +/- 5 mW/L for obese subjects). In neither group was there a correlation between the ouabain-inhibitable rate of metabolism and body weight. The present study results do not give support to the suggestion that a defect in the Na-K-pump activity would exist in the erythrocyte of human obese subjects and could not therefore be of importance in the pathogenesis of the disease.
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