Transgenic livers expressing mitochondrial and cytosolic CK: mitochondrial CK modulates free ADP levels

2002 ◽  
Vol 282 (2) ◽  
pp. C338-C346 ◽  
Author(s):  
Nadir Askenasy ◽  
Alan P. Koretsky
Keyword(s):  
Atp Synthesis ◽  
Fold Increase ◽  
High Energy ◽  
High Energy Phosphates ◽  
Saturation Transfer ◽  
Reaction Velocity ◽  
Total Enzyme Activity ◽  
Phosphorus Metabolites ◽  
Total Enzyme

The function of creatine kinase (CK) and its effect on phosphorus metabolites was studied in livers of transgenic mice expressing human ubiquitous mitochondrial CK (CK-Mit) and rat brain CK (CK-B) isoenzymes and their combination.31P NMR spectroscopy and saturation transfer were recorded in livers of anesthetized mice to measure high-energy phosphates and hepatic CK activity. CK reaction velocity was related to total enzyme activity irrespective of the isoenzyme expressed, and it increased with increasing concentrations of creatine (Cr). The fluxes mediated by both isoenzymes in both directions (phosphocreatine or ATP synthesis) were equal. Over a 20-fold increase in CK-Mit activity (28–560 μmol · g wet wt−1 · min−1), the fraction of phosphorylated Cr increased 1.6-fold. Hepatic free ADP concentrations calculated by assuming equilibrium of the CK-catalyzed reaction in vivo decreased from 84 ± 9 to 38 ± 4 nmol/g wet wt. Calculated free ADP levels in mice expressing high levels of CK-B (920–1,635 μmol · g wet wt−1 · min−1) were 52 ± 6 nmol/g wet wt. Mice expressing both isoenzymes had calculated free ADP levels of 36 ± 4 nmol/g wet wt. These findings indicate that CK-Mit catalyzes its reaction equally well in both directions and can lower hepatic apparent free ADP concentrations.

scholarly journals Efficiency of human skeletal muscle in vivo: comparison of isometric, concentric, and eccentric muscle action

1997 ◽  
Vol 83 (3) ◽  
pp. 867-874 ◽  
Author(s):  
T. W. Ryschon ◽  
M. D. Fowler ◽  
R. E. Wysong ◽  
A.-R. Anthony ◽  
R. S. Balaban
Keyword(s):  
Skeletal Muscle ◽  
Steady State ◽  
Production Rate ◽  
Human Skeletal Muscle ◽  
Atp Synthesis ◽  
High Energy ◽  
High Energy Phosphates ◽  
Muscle Action ◽  
Atp Production

Ryschon, T. W., Fowler, R. E. Wysong, A.-R. Anthony, and R. S. Balaban. Efficiency of human skeletal muscle in vivo: comparison of isometric, concentric, and eccentric muscle action. J. Appl. Physiol. 83(3): 867–874, 1997.—The purpose of this study was to estimate the efficiency of ATP utilization for concentric, eccentric, and isometric muscle action in the human tibialis anterior and extensor digitorum longus in vivo. A dynamometer was used to quantitate muscle work, or tension, while simultaneous 31P-nuclear magnetic resonance data were collected to monitor ATP, phosphocreatine, inorganic phosphate, and pH. The relative efficiency of the actions was estimated in two ways: steady-state effects on high-energy phosphates and a direct comparison of ATP synthesis rates with work. In the steady state, the cytosolic free energy dropped to the lowest value with concentric activity, followed by eccentric and isometric action for comparative muscle tensions. Estimates of ATP synthesis rates revealed a mechanochemical efficiency [i.e., ATP production rate/work (both in J/s)] of 15.0 ± 1.3% in concentric and 34.7 ± 6.1% in eccentric activity. The estimated maximum ATP production rate was highest in concentric action, suggesting an activation of energy metabolism under these conditions. By using direct measures of metabolic strain and ATP turnover, these data demonstrate a decreasing metabolic efficiency in human muscle action from isometric, to eccentric, to concentric action.

Loss of the mitochondrial phosphate carrier SLC25A3 induces remodeling of the cardiac mitochondrial protein acylome

2021 ◽  
Author(s):  
Jessica N. Peoples ◽  
Nasab Ghazal ◽  
Duc M. Duong ◽  
Katherine R. Hardin ◽  
Janet R. Manning ◽  
...  
Keyword(s):  
Energy Production ◽  
Mitochondrial Protein ◽  
Atp Synthesis ◽  
High Energy ◽  
Mitochondrial Proteins ◽  
Isocitrate Dehydrogenase 2 ◽  
Signaling Organelles ◽  
Specific Pathway ◽  
Phosphate Carrier

Mitochondria are recognized as signaling organelles because, under stress, mitochondria can trigger various signaling pathways to coordinate the cell's response. The specific pathway(s) engaged by mitochondria in response to mitochondrial energy defects in vivo and in high-energy tissues like the heart are not fully understood. Here, we investigated cardiac pathways activated in response to mitochondrial energy dysfunction by studying mice with cardiomyocyte-specific loss of the mitochondrial phosphate carrier (SLC25A3), an established model that develops cardiomyopathy as a result of defective mitochondrial ATP synthesis. Mitochondrial energy dysfunction induced a striking pattern of acylome remodeling, with significantly increased post-translational acetylation and malonylation. Mass spectrometry-based proteomics further revealed that energy dysfunction-induced remodeling of the acetylome and malonylome preferentially impacts mitochondrial proteins. Acetylation and malonylation modified a highly interconnected interactome of mitochondrial proteins, and both modifications were present on the enzyme isocitrate dehydrogenase 2 (IDH2). Intriguingly, IDH2 activity was enhanced in SLC25A3-deleted mitochondria, and further study of IDH2 sites targeted by both acetylation and malonylation revealed that these modifications can have site-specific and distinct functional effects. Finally, we uncovered a novel crosstalk between the two modifications, whereby mitochondrial energy dysfunction-induced acetylation of sirtuin 5 (SIRT5), inhibited its function. Because SIRT5 is a mitochondrial deacylase with demalonylase activity, this finding suggests that acetylation can modulate the malonylome. Together, our results position acylations as an arm of the mitochondrial response to energy dysfunction and suggest a mechanism by which focal disruption to the energy production machinery can have an expanded impact on global mitochondrial function.

Metabolic and energy correlates of intracellular pH in progressive fatigue of squid (L. brevis) mantle muscle

1996 ◽  
Vol 271 (5) ◽  
pp. R1403-R1414 ◽  
Author(s):  
H. O. Portner ◽  
E. Finke ◽  
P. G. Lee
Keyword(s):  
Free Energy ◽  
Critical Velocity ◽  
Energy Levels ◽  
High Energy ◽  
Swimming Velocity ◽  
High Energy Phosphates ◽  
Energy Status ◽  
Intracellular Acidosis ◽  
Model Calculations

Squid (Lolliguncula brevis) were exercised at increasing swimming speeds to allow us to analyze the correlated changes in intracellular metabolic, acid-base, and energy status of the mantle musculature. Beyond a critical swimming velocity of 1.5 mantle lengths/s, an intracellular acidosis developed that was caused by an initial base loss from the cells, the onset of respiratory acidification, and, predominantly, octopine formation. The acidosis was correlated with decreasing levels of phospho-L-arginine and, thus, supported ATP buffering at the expense of the phosphagen. Monohydrogenphosphate, the actual substrate of glycogen phosphorylase accumulated, enabling glycogen degradation, despite progressive acidosis. In addition to octopine, succinate, and glycerophosphate accumulation, the onset of acidosis characterizes the critical velocity and indicates the transition to a non-steady-state time-limited situation. Accordingly, swimming above the critical velocity caused cellular energy levels (in vivo Gibbs free energy change of ATP hydrolysis) to fall. A minimal value was reached at about -45 kJ/mol. Model calculations demonstrate that changes in free Mg2+ levels only minimally affect ATP free energy, but minimum levels are relevant in maintaining functional concentrations of Mg(2+)-complexed adenylates. Model calculations also reveal that phosphagen breakdown enabled L. brevis to reach swimming speeds about three times higher than the critical velocity. Comparison of two offshore squid species (Loligo pealei and Illex illecebrosus) with the estuarine squid L.brevis indicates that the latter uses a strategy to delay the exploitation of high-energy phosphates and protect energy levels at higher than the minimum levels (-42 kJ/mol) characterizing fatigue in the other species. A more economical use of anaerobic resources and an early reduction in performance may enable L. brevis to tolerate more extreme environmental conditions in shallow estuarine waters and even hypoxic environments and to prevent a fatal depletion of energy stores.

Carbofuran-induced alterations (in vivo) in high-energy phosphates, creatine kinase (CK) and CK isoenzymes

1991 ◽  
Vol 65 (4) ◽  
pp. 304-310 ◽  
Author(s):  
Ramesh C. Gupta ◽  
John T. Goad ◽  
Wade L. Kadel
Keyword(s):  
Creatine Kinase ◽  
High Energy ◽  
High Energy Phosphates

Function and bioenergetics in isolated perfused trained rat hearts

1997 ◽  
Vol 272 (1) ◽  
pp. H409-H417 ◽  
Author(s):  
R. G. Spencer ◽  
P. M. Buttrick ◽  
J. S. Ingwall
Keyword(s):  
Diastolic Function ◽  
Citrate Synthase ◽  
Recovery Of Function ◽  
Complete Recovery ◽  
High Energy ◽  
Left Ventricular ◽  
Female Rats ◽  
Saturation Transfer

To evaluate the resistance of physiologically hypertrophied hearts to hypoxic insult, we quantified the development of functional deficits during hypoxia and reoxygenation in hypertrophied hearts from swim-trained female rats and we correlated this with assessment of high-energy phosphate (HEP) metabolites from simultaneous 31P nuclear magnetic resonance (NMR) measurements. Furthermore, in vivo enzymatic studies were carried out with saturation transfer NMR under well-oxygenated perfusion conditions for both beating and KCl-arrested hearts. Finally, in vitro enzymatic assays were performed. During hypoxia, the trained hearts exhibited improved systolic and diastolic function compared with hearts from sedentary animals. After 16 min of hypoxia, left ventricular (LV) developed pressure fell to 9% of baseline in control hearts but to only 21% of baseline in trained hearts (P < 0.01). LV diastolic function was also improved by training, increasing during hypoxia from a baseline of 10 to 71.0 +/- 3.3 mmHg in control hearts and to 55.3 +/- 4.8 mmHg in trained hearts (P < 0.05). Trained hearts also showed more rapid and complete recovery of function during reoxygenation and greater coronary flow per gram of heart throughout the entire protocol. Functional differences were not accompanied by differences in HEP at baseline; moreover, ATP and phosphocreatine (PCr) loss during hypoxia was similar between control and trained hearts, as was the recovery of PCr during reoxygenation. Saturation transfer experiments showed an increase in the forward creatine kinase (CrK) rate constant in trained hearts of 18% while beating, whereas in vitro enzymatic analysis revealed a 16% increase in the ratio of mitochondrial CrK to citrate synthase activity in LV tissue. Thus the relative preservation of function in hearts from trained rats could not be accounted for by overall HEP levels but may reflect adaptations in the CrK system.

The effect of an adenosine and lidocaine intravenous infusion on myocardial high-energy phosphates and pH during regional ischemia in the rat model in vivo

2006 ◽  
Vol 84 (8-9) ◽  
pp. 903-912 ◽  
Author(s):  
Sarah J. Canyon ◽  
Geoffrey P. Dobson
Keyword(s):  
Body Mass ◽  
Rat Model ◽  
Intravenous Infusion ◽  
High Energy ◽  
Coronary Artery Ligation ◽  
Ischemia And Reperfusion ◽  
High Energy Phosphates ◽  
Regional Ischemia ◽  
Significant Difference

We have previously shown that an intravenous infusion of adenosine and lidocaine (AL) solution protects against death and severe arrhythmias and reduces infarct size in the in vivo rat model of regional ischemia. The aim of this study was to examine the relative changes of myocardial high-energy phosphates (ATP and PCr) and pH in the left ventricle during ischemia–reperfusion using 31P NMR in AL-treated rats (n = 7) and controls (n = 6). The AL solution (A: 305 μg·(kg body mass)–1·min–1; L: 608 μg·(kg body mass)–1·min–1) was administered intravenously 5 min before and during 30 min coronary artery ligation. Two controls died from ventricular fibrillation; no deaths were recorded in AL-treated rats. In controls that survived, ATP fell to 73% ± 29% of baseline by 30 min ischemia and decreased further to 68% ± 28% during reperfusion followed by a sharp recovery at the end of the reperfusion period. AL-treated rats maintained relatively constant ATP throughout ischemia and reperfusion ranging from 95% ± 6% to 121% ± 10% of baseline. Owing to increased variability in controls, these results were not found to be significant. In contrast, control [PCr] was significantly reduced in controls compared with AL-treated rats during ischemia at 10 min (68% ± 7% vs. 99% ± 6%), at 15 min (68% ± 10% vs. 93% ± 2%), and at 20 min (67% ± 15% vs. 103% ± 5%) and during reperfusion at 10 min (56% ± 22% vs. 99% ± 7%), at 15 min (60% ± 10% vs. 98% ± 7%), and at 35 min (63% ± 14% vs. 120% ± 11%) (p < 0.05). Interestingly, changes in intramyocardial pH between each group were not significantly different during ischemia and fell by about 1 pH unit to 6.6. During reperfusion, pH in AL-treated rats recovered to baseline in 5 min but not in controls, which recovered to only around pH 7.1. There was no significant difference in the heart rate, mean arterial pressure, and rate-pressure product between the controls and AL treatment during ischemia and reperfusion. We conclude that AL cardioprotection appears to be associated with the preservation of myocardial high-energy phosphates, downregulation of the heart at the expense of a high acid-load during ischemia, and with a rapid recovery of myocardial pH during reperfusion.

Ketone bodies maintain normal cardiac function and myocardial high energy phosphates during insulin-induced hypoglycemia in vivo

1989 ◽  
Vol 84 (5) ◽  
pp. 510-523 ◽  
Author(s):  
J. Breuer ◽  
K. J. Chung ◽  
E. Pesonen ◽  
R. H. Haas ◽  
B. D. Guth ◽  
...  
Keyword(s):  
Cardiac Function ◽  
Ketone Bodies ◽  
High Energy ◽  
High Energy Phosphates ◽  
Normal Cardiac Function

Efficacy of recombinant human Hb by31P-NMR during isovolemic total exchange transfusion

1999 ◽  
Vol 86 (3) ◽  
pp. 887-894 ◽  
Author(s):  
Laurel O. Sillerud ◽  
Arvind Caprihan ◽  
Nancy Berton ◽  
Gary J. Rosenthal
Keyword(s):  
Exchange Transfusion ◽  
High Energy ◽  
Surface Coil ◽  
High Energy Phosphates ◽  
Significant Drop ◽  
Tissue Ph ◽  
Hb Concentration ◽  
Menten Constant ◽  
Total Exchange

The ability of recombinant human Hb (rHb1.1), which is being developed as an oxygen therapeutic, to support metabolism was measured by in vivo31P-NMR surface coil spectroscopy of the rat abdomen in control animals and in animals subjected to isovolemic exchange transfusion to hematocrit of <3% with human serum albumin or 5 g/dl rHb1.1. No significant changes in metabolite levels were observed in control animals for up to 6 h. The albumin-exchange experiments, however, resulted in a more than eightfold increase in Pi and a 50% drop in phosphocreatine and ATP within 40 min. The tissue pH dropped from 7.4 to 6.8. The decrease in high-energy phosphates obeyed Michaelis-Menten kinetics, with a Michaelis-Menten constant of 3% as the hematocrit at which a 50% drop in high-energy phosphates was observed. Exchange transfusion with rHb1.1 resulted in no significant drop in high-energy phosphates, no rise in Pi, and no change in tissue pH from 7.35 ± 0.15 for up to 5 h after exchange. By these criteria, rHb1.1 at a plasma Hb concentration of ∼5 g/dl after total exchange transfusion was able to sustain energy metabolism of gut tissue at levels indistinguishable from control rats with a threefold higher total Hb level in erythrocytes.

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