scholarly journals The regulation of brain mitochondrial calcium-ion transport. The role of ATP in the discrimination between kinetic and membrane-potential-dependent calcium-ion efflux mechanisms

1980 ◽  
Vol 186 (3) ◽  
pp. 833-839 ◽  
Author(s):  
D G Nicholls ◽  
I D Scott
Keyword(s):  
Steady State ◽  
Membrane Potential ◽  
Calcium Ion ◽  
Adenine Nucleotide ◽  
Brain Mitochondria ◽  
The Matrix ◽  
High Membrane Potential ◽  
Calcium Ion Transport ◽  
Efflux Pathway

Mitochondria from guinea-pig cerebral cortex incubated in the presence of Pi or acetate are unable to regulate the extramitochondrial free Ca2+ at a steady-state which is independent of the Ca2+ accumulated in the matrix. This is due to the superimposition on kinetically regulated Ca2+ cycling of a membrane-potential-dependent reversal of the Ca2+ uniporter. The latter efflux is a consequence of a low membrane potential, which correlates with a loss of adenine nucleotide loss from the matrix, enable the mitochondria to maintain a high membrane potential and allow the mitochondria to buffer the extramitochondrial free Ca2+ precisely when up to 200 nmol of Ca2+/mg of protein is accumulated in the matrix. The steady-state extramitochondrial free Ca2+ is maintained as low as 0.3 microM. The Na+-activated efflux pathway is functional in the presence of ATP and oligomycin and accounts precisely for the change in steady-state free Ca2+ induced by Na+ addition. The need to distinguish carefully between kinetic and membrane-potential-dependent efflux pathways is emphasized and the competence of brain mitochondria to regulate cytosolic free Ca2+ concentrations in vivo is discussed.

scholarly journals Stimulation of mitochondrial proton conductance by hydroxynonenal requires a high membrane potential

2008 ◽  
Vol 28 (2) ◽  
pp. 83-88 ◽  
Author(s):  
Nadeene Parker ◽  
Antonio Vidal-Puig ◽  
Martin D. Brand
Keyword(s):  
Membrane Potential ◽  
Feedback Loop ◽  
Adenine Nucleotide ◽  
Proton Leak ◽  
Skeletal Muscle Mitochondria ◽  
Mitochondrial Ros ◽  
The Matrix ◽  
High Membrane Potential ◽  
Uncoupling Of Oxidative Phosphorylation ◽  
Mild Uncoupling

Mild uncoupling of oxidative phosphorylation, caused by a leak of protons back into the matrix, limits mitochondrial production of ROS (reactive oxygen species). This proton leak can be induced by the lipid peroxidation products of ROS, such as HNE (4-hydroxynonenal). HNE activates uncoupling proteins (UCP1, UCP2 and UCP3) and ANT (adenine nucleotide translocase), thereby providing a negative feedback loop. The mechanism of activation and the conditions necessary to induce uncoupling by HNE are unclear. We have found that activation of proton leak by HNE in rat and mouse skeletal muscle mitochondria is dependent on incubation with respiratory substrate. In the presence of HNE, mitochondria energized with succinate became progressively more leaky to protons over time compared with mitochondria in the absence of either HNE or succinate. Energized mitochondria must attain a high membrane potential to allow HNE to activate uncoupling: a drop of 10–20 mV from the resting value is sufficient to blunt induction of proton leak by HNE. Uncoupling occurs through UCP3 (11%), ANT (64%) and other pathways (25%). Our findings have shown that exogenous HNE only activates uncoupling at high membrane potential. These results suggest that both endogenous HNE production and high membrane potential are required before mild uncoupling will be triggered to attenuate mitochondrial ROS production.

scholarly journals Stable enhancement of calcium retention in mitochondria isolated from rat liver after the administration of glucagon to the intact animal

1978 ◽  
Vol 176 (3) ◽  
pp. 705-714 ◽  
Author(s):  
Veronica Prpić ◽  
Terry L. Spencer ◽  
Fyfe L. Bygrave
Keyword(s):  
Rat Liver ◽  
Molecular Mechanisms ◽  
Adenine Nucleotide ◽  
Adenine Nucleotides ◽  
Mitochondrial Protein ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Matrix Space ◽  
The Matrix

1. Mitochondria isolated from rat liver by centrifugation of the homogenate in buffered iso-osmotic sucrose at between 4000 and 8000g-min, 1h after the administration in vivo of 30μg of glucagon/100g body wt., retain Ca2+ for over 45min after its addition at 100nmol/mg of mitochondrial protein in the presence of 2mm-Pi. In similar experiments, but after the administration of saline (0.9% NaCl) in place of glucagon, Ca2+ is retained for 6–8min. The ability of glucagon to enhance Ca2+ retention is completely prevented by co-administration of 4.2mg of puromycin/100g body wt. 2. The resting rate of respiration after Ca2+ accumulation by mitochondria from glucagon-treated rats remains low by contrast with that from saline-treated rats. Respiration in the latter mitochondria increased markedly after the Ca2+ accumulation, reflecting the uncoupling action of the ion. 3. Concomitant with the enhanced retention of Ca2+ and low rates of resting respiration by mitochondria from glucagon-treated rats was an increased ability to retain endogenous adenine nucleotides. 4. An investigation of properties of mitochondria known to influence Ca2+ transport revealed a significantly higher concentration of adenine nucleotides but not of Pi in those from glucagon-treated rats. The membrane potential remained unchanged, but the transmembrane pH gradient increased by approx. 10mV, indicating increased alkalinity of the matrix space. 5. Depletion of endogenous adenine nucleotides by Pi treatment in mitochondria from both glucagon-treated and saline-treated rats led to a marked diminution in ability to retain Ca2+. The activity of the adenine nucleotide translocase was unaffected by glucagon treatment of rats in vivo. 6. Although the data are consistent with the argument that the Ca2+-translocation cycle in rat liver mitochondria is a target for glucagon action in vivo, they do not permit conclusions to be drawn about the molecular mechanisms involved in the glucagon-induced alteration to this cycle.

scholarly journals The regulation of extramitochondrial free calcium ion concentration by rat liver mitochondria

1978 ◽  
Vol 176 (2) ◽  
pp. 463-474 ◽  
Author(s):  
David G. Nicholls
Keyword(s):  
Steady State ◽  
Membrane Potential ◽  
Rat Liver ◽  
Liver Mitochondria ◽  
Weak Acid ◽  
Ion Concentration ◽  
Rat Liver Mitochondria ◽  
Free Calcium ◽  
Electrochemical Gradient

The mechanism whereby rat liver mitochondria regulate the extramitochondrial concentration of free Ca2+ was investigated. At 30°C and pH7.0, mitochondria can maintain a steady-state pCa2+0 (the negative logarithm of the free extramitochondrial Ca2+ concentration) of 6.1 (0.8μm). This represents a true steady state, as slight displacements in pCa2+0 away from 6.1 result in net Ca2+ uptake or efflux in order to restore pCa2+0 to its original value. In the absence of added permeant weak acid, the steady-state pCa2+0 is virtually independent of the Ca2+ accumulated in the matrix until 60nmol of Ca2+/mg of protein has been taken up. The steady-state pCa2+0 is also independent of the membrane potential, as long as the latter parameter is above a critical value. When the membrane potential is below this value, pCa2+0 is variable and appears to be governed by thermodynamic equilibration of Ca2+ across a Ca2+ uniport. Permeant weak acids increase, and N-ethylmaleimide decreases, the capacity of mitochondria to buffer pCa2+0 in the region of 6 (1μm-free Ca2+) while accumulating Ca2+. Permeant acids delay the build-up of the transmembrane pH gradient as Ca2+ is accumulated, and consequently delay the fall in membrane potential to values insufficient to maintain a pCa2+0 of 6. The steady-state pCa2+0 is affected by temperature, incubation pH and Mg2+. The activity of the Ca2+ uniport, rather than that of the respiratory chain, is rate-limiting when pCa2+0 is greater than 5.3 (free Ca2+ less than 5μm). When the Ca2+ electrochemical gradient is in excess, the activity of the uniport decreases by 2-fold for every 0.12 increase in pCa2+0 (fall in free Ca2+). At pCa2+0 6.1, the activity of the Ca2+ uniport is kinetically limited to 5nmol of Ca2+/min per mg of protein, even when the Ca2+ electrochemical gradient is large. A steady-state cycling of Ca2+ through independent influx and efflux pathways provides a model which is kinetically and thermodynamically consistent with the present observations, and which predicts an extremely precise regulation of pCa2+0 by liver mitochondria in vivo.

Letters to the Editor

1998 ◽  
Vol 275 (2) ◽  
pp. H726-H729
Author(s):  
J. A. L. Jeneson ◽  
M. J. Kushmerick ◽  
H. V. Westerhoff
Keyword(s):  
Oxygen Consumption ◽  
Steady State ◽  
Western Blot ◽  
Northern Blot ◽  
Adenine Nucleotide ◽  
Respiratory Control ◽  
High Energy ◽  
High Energy Phosphates ◽  
Adenine Nucleotide Translocator

The following is the abstract of the article discussed in the subsequent letter: Portman, Michael A., Yun Xiao, Ying Song, and Xue-Han Ning. Expression of adenine nucleotide translocator parallels maturation of respiratory control in heart in vivo. Am. J. Physiol. 273 ( Heart Circ. Physiol. 42): H1977–H1983, 1997.—Changes in the relationship between myocardial high-energy phosphates and oxygen consumption in vivo occur during development, implying that the mode of respiratory control undergoes maturation. We hypothesized that these maturational changes in sheep heart are paralleled by alterations in the adenine nucleotide translocator (ANT), which are in turn related to changes in the expression of this gene. Increases in myocardial oxygen consumption (MV˙o 2) were induced by epinephrine infusion in newborn (0–32 h, n = 6) and mature sheep (30–32 days, n = 6), and high-energy phosphates were monitored with 31P nuclear magnetic resonance. Western blot analyses for the ANT1 and the β-subunit of F1-adenosinetriphosphatase (ATPase) were performed in these hearts and additional ( n = 9 total per group) as well as in fetal hearts (130–132 days of gestation, n = 5). Northern blot analyses were performed to assess for changes in steady-state RNA transcripts for these two genes. Kinetic analyses for the31P spectra data revealed that the ADP-MV˙o 2 relationship for the newborns conformed to a Michaelis-Menten model but that the mature data did not conform to first- or second-order kinetic control of respiration through ANT. Maturation from fetal to mature was accompanied by a 2.5-fold increase in ANT protein (by Western blot), with no detectable change in β-F1-ATPase. Northern blot data show that steady-state mRNA levels for ANT and β-F1-ATPase increased ∼2.5-fold from fetal to mature. These data indicate that 1) respiratory control pattern in the newborn is consistent with a kinetic type regulation through ANT, 2) maturational decreases in control through ANT are paralleled by specific increases in ANT content, and 3) regulation of these changes in ANT may be related to increases in steady-state transcript levels for its gene.

Expression of adenine nucleotide translocator parallels maturation of respiratory control in heart in vivo

1997 ◽  
Vol 273 (4) ◽  
pp. H1977-H1983 ◽  
Author(s):  
Michael A. Portman ◽  
Yun Xiao ◽  
Ying Song ◽  
Xue-Han Ning
Keyword(s):  
Oxygen Consumption ◽  
Steady State ◽  
Western Blot ◽  
Northern Blot ◽  
Adenine Nucleotide ◽  
Respiratory Control ◽  
High Energy ◽  
High Energy Phosphates ◽  
Adenine Nucleotide Translocator

Changes in the relationship between myocardial high-energy phosphates and oxygen consumption in vivo occur during development, implying that the mode of respiratory control undergoes maturation. We hypothesized that these maturational changes in sheep heart are paralleled by alterations in the adenine nucleotide translocator (ANT), which are in turn related to changes in the expression of this gene. Increases in myocardial oxygen consumption (MV˙o 2) were induced by epinephrine infusion in newborn (0–32 h, n = 6) and mature sheep (30–32 days, n = 6), and high-energy phosphates were monitored with 31P nuclear magnetic resonance. Western blot analyses for the ANT1 and the β-subunit of F1-adenosinetriphosphatase (ATPase) were performed in these hearts and additional ( n = 9 total per group) as well as in fetal hearts (130–132 days of gestation, n = 5). Northern blot analyses were performed to assess for changes in steady-state RNA transcripts for these two genes. Kinetic analyses for the31P spectra data revealed that the ADP-MV˙o 2 relationship for the newborns conformed to a Michaelis-Menten model but that the mature data did not conform to first- or second-order kinetic control of respiration through ANT. Maturation from fetal to mature was accompanied by a 2.5-fold increase in ANT protein (by Western blot), with no detectable change in β-F1-ATPase. Northern blot data show that steady-state mRNA levels for ANT and β-F1-ATPase increased ∼2.5-fold from fetal to mature. These data indicate that 1) respiratory control pattern in the newborn is consistent with a kinetic type regulation through ANT, 2) maturational decreases in control through ANT are paralleled by specific increases in ANT content, and 3) regulation of these changes in ANT may be related to increases in steady-state transcript levels for its gene.

scholarly journals MODELING AND SIMULATION OF SKELETAL MUSCLE BASED ON METABOLISM PHYSIOLOGY

2020 ◽  
Vol 20 (09) ◽  
pp. 2040018
Author(s):  
MONAN WANG ◽  
JIALIN HAN ◽  
QIYOU YANG
Keyword(s):  
Skeletal Muscle ◽  
Energy Metabolism ◽  
Calcium Ion ◽  
Energy Systems ◽  
Metabolic Energy ◽  
Ion Concentration ◽  
Whole Body ◽  
Muscle Energy Metabolism ◽  
Calcium Ion Transport

Skeletal muscle energy metabolism plays a very important role in controlling movement of the whole body and has important theoretical guidance for making exercise training plans and losing weight. In this paper, we developed a mathematical model of skeletal muscle excitation–contraction pathway based on the energy metabolism that links excitation to contraction to explore the effects of different metabolic energy systems on calcium ion changes and the force during skeletal muscle contraction. In this paper, a membrane potential model, a calcium cycle model, a cross-bridge dynamics model and an energy metabolism model were established. Finally, the physiological phenomenon of calcium ion transport and calcium ion concentration change of the sarcoplasm was simulated. The results show that the phosphagen system has the fastest metabolic rate and the phosphagen system has the largest impact on the explosive power of skeletal muscle exercise. The specific characteristics of the three metabolic energy systems supporting skeletal muscle movement in vivo were also analyzed in detail.

scholarly journals Calcium-ion transport by intact synaptosomes. Intrasynaptosomal compartmentation and the role of the mitochondrial membrane potential

1980 ◽  
Vol 192 (3) ◽  
pp. 873-880 ◽  
Author(s):  
I D Scott ◽  
K E Akerman ◽  
D G Nicholls
Keyword(s):  
Plasma Membrane ◽  
Membrane Potential ◽  
Mitochondrial Membrane Potential ◽  
Calcium Ion ◽  
Mitochondrial Membrane ◽  
Mitochondrial Matrix ◽  
Free Medium ◽  
Rapid Phase ◽  
Calcium Ion Transport

The association of Ca2+ with isolated nerve endings (synaptosomes) is investigated and resolved into two components, that bound to the outer surface of the plasma membrane and that transported across the plasma membrane. When synaptosomes are added directly to a Ca2+-containing medium, there is an initial rapid uptake of Ca2+ across the plasma membrane, followed by a slow uptake that proceeds for 20 min. The rapid phase is not observed if the synaptosomes are initially pre-incubated in a Ca2+-free medium. Rapid disruption of synaptosomes reveals that less than 3 nmol of transported Ca2+ per mg of synaptosomal protein can be ascribed to non-mitochondrial components, whereas the remainder, up to 79% of the total, is further transported into the mitochondrial matrix. Abolition of oxidative phosphorylation while the mitochondrial membrane potential is retained leads to a time-dependent increase in transported Ca2+, whereas abolition of the mitochondrial membrane potential decreases both plasma-membrane transport and accumulation of Ca2+ in the mitochondrial matrix. It is concluded that intrasynaptosomal mitochondria are major regulators of synaptosomal Ca2+.

scholarly journals High membrane potential promotes alkenal-induced mitochondrial uncoupling and influences adenine nucleotide translocase conformation

2008 ◽  
Vol 413 (2) ◽  
pp. 323-332 ◽  
Author(s):  
Vian Azzu ◽  
Nadeene Parker ◽  
Martin D. Brand
Keyword(s):  
Membrane Potential ◽  
Adenine Nucleotide ◽  
Uncoupling Proteins ◽  
Adenine Nucleotide Translocase ◽  
Oxygen Species ◽  
Proton Conductance ◽  
Mitochondrial Uncoupling ◽  
Mitochondrial Inner Membrane ◽  
High Membrane Potential ◽  
Uncoupling Of Oxidative Phosphorylation

Mitochondria generate reactive oxygen species, whose downstream lipid peroxidation products, such as 4-hydroxynonenal, induce uncoupling of oxidative phosphorylation by increasing proton leak through mitochondrial inner membrane proteins such as the uncoupling proteins and adenine nucleotide translocase. Using mitochondria from rat liver, which lack uncoupling proteins, in the present study we show that energization (specifically, high membrane potential) is required for 4-hydroxynonenal to activate proton conductance mediated by adenine nucleotide translocase. Prolonging the time at high membrane potential promotes greater uncoupling. 4-Hydroxynonenal-induced uncoupling via adenine nucleotide translocase is prevented but not readily reversed by addition of carboxyatractylate, suggesting a permanent change (such as adduct formation) that renders the translocase leaky to protons. In contrast with the irreversibility of proton conductance, carboxyatractylate added after 4-hydroxynonenal still inhibits nucleotide translocation, implying that the proton conductance and nucleotide translocation pathways are different. We propose a model to relate adenine nucleotide translocase conformation to proton conductance in the presence or absence of 4-hydroxynonenal and/or carboxyatractylate.

The membrane permeability transition in liver mitochondria of the great green goby Zosterisessor ophiocephalus (Pallas)

2000 ◽  
Vol 203 (22) ◽  
pp. 3425-3434 ◽  
Author(s):  
A. Toninello ◽  
M. Salvi ◽  
L. Colombo
Keyword(s):  
Membrane Potential ◽  
Rat Liver ◽  
Adenine Nucleotide ◽  
Respiratory Control ◽  
Permeability Transition ◽  
Liver Mitochondria ◽  
Transport Systems ◽  
Rat Liver Mitochondria ◽  
The Matrix ◽  
Zosterisessor Ophiocephalus

Liver mitochondria from the great green goby Zosterisessor ophiocephalus (Pallas) normally exhibit bioenergetic variables (membrane potential 165+/−7 mV; respiratory control ratio 6.6+/−0.4; ADP/O ratio 1.85+/−0.8; means +/− s.e.m., N=6) and activities of physiological transport systems (phosphate/proton symporter, adenine nucleotide antiporter, Ca(2+) electrophoretic uniporter) comparable with those of rat liver mitochondria. When incubated in the presence of Ca(2+) and an inducer agent such as phosphate, these mitochondria undergo a complete collapse of membrane potential accompanied by a large-amplitude swelling of the matrix, influx of sucrose from the incubation medium, release of endogenous Mg(2+) and K(+) (approximately 90% of the total) and of preaccumulated Ca(2+) and oxidation of endogenous pyridine nucleotides. All these phenomena, which are completely eliminated by cyclosporin A and inhibited with different efficacies by Mg(2+) and spermine, demonstrate that the induction of the permeability transition in this type of mitochondria has characteristics similar to those described in rat liver mitochondria. In contrast, the requirement for very high Ca(2+) concentrations (greater than 100 micromol l(−1) for the induction of the permeability transition represents a very important difference that distinguishes this phenomenon in fish and mammalian mitochondria.

scholarly journals Formation of an Energized Inner Membrane in Mitochondria with a γ-Deficient F1-ATPase

2005 ◽  
Vol 4 (12) ◽  
pp. 2078-2086 ◽  
Author(s):  
Christopher P. Smith ◽  
Peter E. Thorsness
Keyword(s):  
Mitochondrial Dna ◽  
Membrane Potential ◽  
Atp Hydrolysis ◽  
Adenine Nucleotide ◽  
Polyacrylamide Gel Electrophoresis ◽  
Electrical Potential ◽  
Inner Membrane ◽  
Γ Subunit ◽  
Native Polyacrylamide Gel Electrophoresis

ABSTRACT Eukaryotic cells require mitochondrial compartments for viability. However, the budding yeast Saccharomyces cerevisiae is able to survive when mitochondrial DNA suffers substantial deletions or is completely absent, so long as a sufficient mitochondrial inner membrane potential is generated. In the absence of functional mitochondrial DNA, and consequently a functional electron transport chain and F1Fo-ATPase, the essential electrical potential is maintained by the electrogenic exchange of ATP4− for ADP3− through the adenine nucleotide translocator. An essential aspect of this electrogenic process is the conversion of ATP4− to ADP3− in the mitochondrial matrix, and the nuclear-encoded subunits of F1-ATPase are hypothesized to be required for this process in vivo. Deletion of ATP3, the structural gene for the γ subunit of the F1-ATPase, causes yeast to quantitatively lose mitochondrial DNA and grow extremely slowly, presumably by interfering with the generation of an energized inner membrane. A spontaneous suppressor of this slow-growth phenotype was found to convert a conserved glycine to serine in the β subunit of F1-ATPase (atp2-227). This mutation allowed substantial ATP hydrolysis by the F1-ATPase even in the absence of the γ subunit, enabling yeast to generate a twofold greater inner membrane potential in response to ATP compared to mitochondria isolated from yeast lacking the γ subunit and containing wild-type β subunits. Analysis of the suppressing mutation by blue native polyacrylamide gel electrophoresis also revealed that the α3β3 heterohexamer can form in the absence of the γ subunit.

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