scholarly journals Effect of 3,5-di-iodo-L-thyronine on the mitochondrial energy-transduction apparatus

1998 ◽  
Vol 330 (1) ◽  
pp. 521-526 ◽  
Author(s):  
Assonta LOMBARDI ◽  
Antonia LANNI ◽  
Maria MORENO ◽  
D. Martin BRAND ◽  
Fernando GOGLIA
Keyword(s):  
Cytochrome C ◽  
Mitochondrial Respiration ◽  
Atp Synthesis ◽  
Substrate Oxidation ◽  
Energy Transduction ◽  
Energy Utilization ◽  
Proton Leak ◽  
Elasticity Analysis ◽  
Top Down ◽  
Respiratory State

We examined the effect of a single injection of 3,5-di-iodo-l-thyronine (3,5-T2) (150 μg/100 g body weight) on the rat liver mitochondrial energy-transduction apparatus. We applied ‘top-down’ elasticity analysis, which allows identification of the site of action of an effector within a metabolic pathway. This kinetic approach considers oxidative phosphorylation as two blocks of reactions: those generating the mitochondrial inner-membrane potential (Δψ; ‘substrate oxidation’) and those ‘consuming’ it (‘proton leak’ and ‘phosphorylating system’). The results show that 1 h after the injection of 3,5-T2, state 4 (respiratory state in which there is no ATP synthesis and the exogenous ADP added has been exhausted) and state 3 (respiratory state in which ATP synthesis is at maximal rate) of mitochondrial respiration were significantly increased (by approx. 30%). ‘Top-down’ elasticity analysis revealed that these increases were due to the stimulation of reactions involved in substrate oxidation; neither ‘proton leak’ nor the ‘phosphorylating system’ was influenced by 3,5-T2. Using the same approach we divided the respiratory chain into two blocks of reactions: cytochrome c reducers and cytochrome c oxidizers. We found that both cytochrome c reducers and cytochrome c oxidizers are targets for 3,5-T2. The rapidity with which 3,5-T2 acts in stimulating the mitochondrial respiration rate suggests to us that di-iodo-L-thyronine may play an important role in the physiological conditions in which rapid energy utilization is required, such as cold exposure or overfeeding.

Top-down control analysis of the effect of temperature on ectotherm oxidative phosphorylation

2004 ◽  
Vol 287 (4) ◽  
pp. R794-R800 ◽  
Author(s):  
M. E. Chamberlin
Keyword(s):  
Oxygen Consumption ◽  
Membrane Potential ◽  
Oxidative Phosphorylation ◽  
Substrate Oxidation ◽  
The State ◽  
Proton Leak ◽  
Control Analysis ◽  
Top Down ◽  
Temperature Ranges ◽  
Oxidation System

Top-down control and elasticity analysis was conducted on mitochondria isolated from the midgut of the tobacco hornworm ( Manduca sexta) to assess how temperature affects oxidative phosphorylation in a eurythermic ectotherm. Oxygen consumption and protonmotive force (measured as membrane potential in the presence of nigericin) were monitored at 15, 25, and 35°C. State 4 respiration displayed a Q10 of 2.4–2.7 when measured over two temperature ranges (15–25°C and 25–35°C). In state 3, the Q10s for respiration were 2.0 and 1.7 for the lower and higher temperature ranges, respectively. The kinetic responses (oxygen consumption) of the substrate oxidation system, proton leak, and phosphorylation system increased as temperature rose, although the proton leak and substrate oxidation system showed the greatest thermal sensitivity. Whereas there were temperature-induced changes in the activities of the oxidative phosphorylation subsystems, there was no change in the state 4 membrane potential and little change in the state 3 membrane potential. Top-down control analysis revealed that control over respiration did not change with temperature. In state 4, control of respiration was shared nearly equally by the proton leak and the substrate oxidation system, whereas in state 3 the substrate oxidation system exerted over 90% of the control over respiration. The proton leak and phosphorylation system account for <10% of the temperature-induced change in the state 3 respiration rate. Therefore, when the temperature is changed, the state 3 respiration rate is altered primarily because of temperature's effect on the substrate oxidation system.

scholarly journals Uncoupling protein 2 mRNA expression and respiratory parameters in Kupffer cells isolated from euthyroid and hyperthyroid rat livers

2001 ◽  
Vol 145 (3) ◽  
pp. 317-322 ◽  
Author(s):  
A Voci ◽  
I Demori ◽  
AT Franzi ◽  
E Fugassa ◽  
F Goglia ◽  
...  
Keyword(s):  
Kupffer Cells ◽  
Mitochondrial Respiration ◽  
Uncoupling Protein ◽  
Liver Perfusion ◽  
Atp Synthesis ◽  
Proton Leak ◽  
Uncoupling Protein 2 ◽  
Mrna Levels ◽  
Respiratory Parameters ◽  
Ucp2 Mrna

OBJECTIVE: The levels of uncoupling protein 2 (UCP2) mRNA and determinants of respiration (ATP synthesis, proton leak and non-mitochondrial respiration) were evaluated in Kupffer cells isolated from the livers of normal euthyroid, acute hyperthyroid and chronic hyperthyroid rats. METHODS: After liver perfusion, Kupffer cells were purified by density-gradient centrifugation followed by counterflow centrifugal elutriation. UCP2 mRNA levels were measured by Northern blot and respiratory parameters by polarographic method. RESULTS: In cells isolated from hyperthyroid (tri-iodothyronine (T(3))-treated) rats, the effect of T(3) treatment on the UCP2 mRNA level varied: it was more than doubled (P<0.05) in acutely T(3)-treated rats but, after chronic (3-week) T(3) treatment, it was only 30% (not statistically significant) above the control (euthyroid) level. In Kupffer cells from the livers of chronic hyperthyroid rats, we observed an increase in total respiration rate, with an increase in the percentage attributable to the proton leak and a corresponding decrease in the percentage attributable to ATP synthesis (no alteration was observed in the percentage attributable to non-mitochondrial respiration). In the acute hyperthyroid rats, no significant differences were observed in any of the respiratory parameters, although they all tended to increase. CONCLUSION: These data are indicative of a possible uncoupling effect of UCP2 in Kupffer cells. T(3), by enhancing the expression of UCP2, could play a role in the energy homeostasis of these cells.

Primary causes of decreased mitochondrial oxygen consumption during metabolic depression in snail cells

2002 ◽  
Vol 282 (2) ◽  
pp. R372-R382 ◽  
Author(s):  
Tammie Bishop ◽  
Julie St-Pierre ◽  
Martin D. Brand
Keyword(s):  
Membrane Potential ◽  
Mitochondrial Membrane Potential ◽  
Mitochondrial Respiration ◽  
Mitochondrial Membrane ◽  
Substrate Oxidation ◽  
Proton Leak ◽  
Mitochondrial Oxygen Consumption ◽  
Atp Turnover ◽  
Hypometabolic State ◽  
Kinetics Of

Cells isolated from the hepatopancreas of estivating snails ( Helix aspersa) have strongly depressed mitochondrial respiration compared with controls. Mitochondrial respiration was divided into substrate oxidation (which produces the mitochondrial membrane potential) and ATP turnover and proton leak (which consume it). The activity of substrate oxidation (and probably ATP turnover) decreased, whereas the activity of proton leak remained constant in estivation. These primary changes resulted in a lower mitochondrial membrane potential in hepatopancreas cells from estivating compared with active snails, leading to secondary decreases in respiration to drive ATP turnover and proton leak. The respiration to drive ATP turnover and proton leak decreased in proportion to the overall decrease in mitochondrial respiration, so that the amount of ATP turned over per O2 consumed remained relatively constant and aerobic efficiency was maintained in this hypometabolic state. At least 75% of the total response of mitochondrial respiration to estivation was caused by primary changes in the kinetics of substrate oxidation, with only 25% or less of the response occurring through primary effects on ATP turnover.

Hyperthyroidism stimulates mitochondrial proton leak and ATP turnover in rat hepatocytes but does not change the overall kinetics of substrate oxidation reactions

1994 ◽  
Vol 72 (8) ◽  
pp. 899-908 ◽  
Author(s):  
Mary-Ellen Harper ◽  
Martin D. Brand
Keyword(s):  
Oxygen Consumption ◽  
Oxidative Phosphorylation ◽  
Thyroid Hormones ◽  
Rat Hepatocytes ◽  
Substrate Oxidation ◽  
Proton Leak ◽  
Control Analysis ◽  
Top Down ◽  
Sites Of Action ◽  
Kinetics Of

Thyroid hormones have well-known effects on oxidative phosphorylation, but there is little quantitative information on their important sites of action. We have used top-down elasticity analysis, an extension of metabolic control analysis, to identify the sites of action of thyroid hormones on oxidative phosphorylation in rat hepatocytes. We divided the oxidative phosphorylation system into three blocks of reactions: the substrate oxidation subsystem, the phosphorylating subsystem, and the mitochondrial proton leak subsystem and have identified those blocks of reactions whose kinetics are significantly changed by hyperthyroidism. Our results show significant effects on the kinetics of the proton leak and the phosphorylating subsystems. Quantitative analyses revealed that 43% of the increase in resting respiration rate in hyperthyroid hepatocytes compared with euthyroid hepatocytes was due to differences in the proton leak and 59% was due to differences in the activity of the phosphorylating subsystem. There were no significant effects on the substrate oxidation subsystem. Changes in nonmitochondrial oxygen consumption accounted for −2% of the change in respiration rate. Top-down control analysis revealed that the distribution of control over the rates of mitochondrial oxygen consumption, ATP synthesis and consumption, and proton leak and over mitochondrial membrane potential (Δψm) was similar in hepatocytes from hyperthyroid and littermate-paired euthyroid controls. The results of this study include the first complete top-down elasticity and control analyses of oxidative phosphorylation in hepatocytes from hyperthyroid rats.Key words: thyroid hormones, oxidative phosphorylation, mitochondria, proton leak, thermogenesis.

Top-down control analysis of the cadmium effects on molluscan mitochondria and the mechanisms of cadmium-induced mitochondrial dysfunction

2011 ◽  
Vol 300 (1) ◽  
pp. R21-R31 ◽  
Author(s):  
Ilya O. Kurochkin ◽  
Markus Etzkorn ◽  
David Buchwalter ◽  
Larry Leamy ◽  
Inna M. Sokolova
Keyword(s):  
Mitochondrial Function ◽  
Adenine Nucleotide ◽  
Eastern Oyster ◽  
Substrate Oxidation ◽  
Proton Leak ◽  
Control Analysis ◽  
Proton Conductance ◽  
Inner Mitochondrial Membrane ◽  
Top Down ◽  
Atp Production

Cadmium (Cd) is a toxic metal and an important environmental pollutant that can strongly affect mitochondrial function and bioenergetics in animals. We investigated the mechanisms of Cd action on mitochondrial function of a marine mollusk (the eastern oyster Crassostrea virginica ) by performing a top-down control analysis of the three major mitochondrial subsystems (substrate oxidation, proton leak, and phosphorylation). Our results showed that the substrate oxidation and proton leak subsystems are the main targets for Cd toxicity in oyster mitochondria. Exposure to 12.5 μM Cd strongly inhibited the substrate oxidation subsystem and stimulated the proton conductance across the inner mitochondrial membrane. Proton conductance was also elevated and substrate oxidation inhibited by Cd in the presence of a mitochondrially targeted antioxidant, MitoVitE, indicating that Cd effects on these subsystems were to a large extent ROS independent. Cd did not affect the kinetics of the phosphorylation system, indicating that it has negligible effects on F1, FO ATP synthase and/or the adenine nucleotide transporter in oyster mitochondria. Cd exposure altered the patterns of control over mitochondrial respiration, increasing the degree of control conferred by the substrate oxidation subsystem, especially in resting (state 4) mitochondria. Taken together, these data suggest that Cd-induced decrease of mitochondrial efficiency and ATP production are predominantly driven by the high sensitivity of substrate oxidation and proton leak subsystems to this metal.

scholarly journals Mitochondrial Respiration in KRAS and BRAF Mutated Colorectal Tumors and Polyps

Cancers ◽  
2020 ◽  
Vol 12 (4) ◽  
pp. 815 ◽  
Author(s):  
Egle Rebane-Klemm ◽  
Laura Truu ◽  
Leenu Reinsalu ◽  
Marju Puurand ◽  
Igor Shevchuk ◽  
...  
Keyword(s):  
Mitochondrial Respiration ◽  
Atp Synthesis ◽  
Colorectal Polyps ◽  
Metabolic Phenotype ◽  
Mitochondrial Outer Membrane ◽  
Control Group ◽  
Colon Polyps ◽  
Wild Type ◽  
Tissue Samples ◽  
Potential Component

This study aimed to characterize the ATP-synthesis by oxidative phosphorylation in colorectal cancer (CRC) and premalignant colon polyps in relation to molecular biomarkers KRAS and BRAF. This prospective study included 48 patients. Resected colorectal polyps and postoperative CRC tissue with adjacent normal tissue (control) were collected. Patients with polyps and CRC were divided into three molecular groups: KRAS mutated, BRAF mutated and KRAS/BRAF wild-type. Mitochondrial respiration in permeabilized tissue samples was observed using high resolution respirometry. ADP-activated respiration rate (Vmax) and an apparent affinity of mitochondria to ADP, which is related to mitochondrial outer membrane (MOM) permeability, were determined. Clear differences were present between molecular groups. KRAS mutated CRC group had lower Vmax values compared to wild-type; however, the Vmax value was higher than in the control group, while MOM permeability did not change. This suggests that KRAS mutation status might be involved in acquiring oxidative phenotype. KRAS mutated polyps had higher Vmax values and elevated MOM permeability as compared to the control. BRAF mutated CRC and polyps had reduced respiration and altered MOM permeability, indicating a glycolytic phenotype. To conclude, prognostic biomarkers KRAS and BRAF are likely related to the metabolic phenotype in CRC and polyps. Assessment of the tumor mitochondrial ATP synthesis could be a potential component of patient risk stratification.

Mitochondrial Inhibition Prior to Oxygen-Withdrawal Facilitates the Occurrence of Hypoxia-Induced Spreading Depression in Rat Hippocampal Slices

2006 ◽  
Vol 96 (1) ◽  
pp. 492-504 ◽  
Author(s):  
Florian J. Gerich ◽  
Sebastian Hepp ◽  
Irmelin Probst ◽  
Michael Müller
Keyword(s):  
Mitochondrial Respiration ◽  
Spreading Depression ◽  
Hippocampal Slices ◽  
Atp Synthesis ◽  
Atp Depletion ◽  
Mitochondrial Uncoupling ◽  
Ca1 Neurons ◽  
Optical Signals ◽  
Nitropropionic Acid ◽  
Carbonyl Cyanide

Oxygen withdrawal blocks mitochondrial respiration. In rat hippocampal slices, this triggers a massive depolarization of CA1 neurons and a negative shift of the extracellular DC potential, the characteristic sign of hypoxia-induced spreading depression (HSD). To unveil the contribution of mitochondria to the sensing of hypoxia and the ignition of HSD, we modified mitochondrial function. Mitochondrial uncoupling by carbonyl cyanide 4-(trifluoromethoxy) phenylhydrazone (FCCP, 1 μM) prior to hypoxia hastened the onset and shortened the duration of HSD. Blocking mitochondrial ATP synthesis by oligomycin (10 μg/ml) was without effect. Inhibition of mitochondrial respiration by rotenone (20 μM), diphenyleneiodonium (25 μM), or antimycin A (20 μM) also hastened HSD onset and shortened HSD duration. 3-nitropropionic acid (1 mM) increased HSD duration. Cyanide (100 μM) hastened HSD onset and increased HSD duration. At higher concentrations, cyanide (1 mM), azide (2 mM), and FCCP (10 μM) triggered SD episodes on their own. Compared with control HSD, the spatial extent of the intrinsic optical signals of cyanide- and azide-induced SDs was more pronounced. Monitoring NADH (nicotinamide adenine dinucleotide) and FAD (flavin adenine dinucleotide) autofluorescence and mitochondrial membrane potential verified the mitochondrial targeting by the drugs used. Except 1 mM cyanide, no treatment reduced cellular ATP levels severely and no correlation was found between ATP, NADH, or FAD levels and the time to HSD onset. Therefore ATP depletion or a cytosolic reducing shift due to NADH/FADH2 accumulation cannot serve as a general explanation for the hastening of HSD onset on mitochondrial inhibition. Additional redox couples (glutathione) or events downstream of the mitochondrial depolarization need to be considered.

ConA induced changes in energy metabolism of rat thymocytes

1992 ◽  
Vol 12 (5) ◽  
pp. 381-386 ◽  
Author(s):  
F. Buttgereit ◽  
M. D. Brand ◽  
M. Müller
Keyword(s):  
Protein Synthesis ◽  
Oxygen Consumption ◽  
Energy Metabolism ◽  
Dna Synthesis ◽  
Atp Synthesis ◽  
Proton Leak ◽  
Ehrlich Ascites ◽  
Activated State ◽  
Ehrlich Ascites Tumour ◽  
Induced Changes

The influence of ConA on the energy metabolism of quiescent rat thymocytes was investigated by measuring the effects of inhibitors of protein synthesis, proteolysis, RNA/DNA synthesis, Na+K+-ATPase, Ca2+-ATPase and mitochondrial ATP synthesis on respiration. Only about 50% of the coupled oxygen consumption of quiescent thymocytes could be assigned to specific processes using two different media. Under these conditions the oxygen is mainly used to drive mitochondrial proton leak and to provide ATP for protein synthesis and cation transport, whereas oxygen consumption to provide ATP for RNA/DNA synthesis and ATP-dependent proteolysis was not measurable. The mitogen ConA produced a persistent increase in oxygen consumption by about 30% within seconds. After stimulation more than 80% of respiration could be assigned to specific processes. The major oxygen consuming processes of ConA-stimulated thymocytes are mitochondrial proton leak, protein synthesis and Na+K+-ATPase with about 20% each of total oxygen consumption, while Ca2+-ATPase and RNA/DNA synthesis contribute about 10% each. Quiescent thymocytes resemble resting hepatocytes in that most of the oxygen consumption remains unexplained. In constrast, the pattern of energy metabolism in stimulated thymocytes is similar to that described for Ehrlich Ascites tumour cells and splenocytes, which may also be in an activated state. Most of the oxygen consumption is accounted for, so the unexplained process(es) in unstimulated cells shut(s) off on stimulation.

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