scholarly journals Regulation of pyruvate dehydrogenase by insulin and polyamines within electropermeabilized fat-cells and isolated mitochondria

1992 ◽  
Vol 285 (2) ◽  
pp. 435-439 ◽  
Author(s):  
G A Rutter ◽  
T A Diggle ◽  
R M Denton
Keyword(s):  
Adipose Tissue ◽  
Pyruvate Dehydrogenase ◽  
Rat Heart ◽  
Fat Cells ◽  
Permeabilized Cells ◽  
Isolated Mitochondria ◽  
Mitochondrial Fractions ◽  
Rat Heart Mitochondria ◽  
Rapid Stimulation ◽  
Stimulation Of

1. Regulation of the mammalian pyruvate dehydrogenase (PDH) complex by insulin and polyamines has been examined by using electropermeabilized rat epididymal fat-cells and isolated mitochondria. The complex could be regulated within the permeabilized cells not only by insulin, but also by certain low-M(r) species, including Ca2+ and the polyamine spermidine. 2. Both spermine and spermidine increased the level of active dephosphorylated PDH (PDHa) in isolated adipose-tissue mitochondria 2-3-fold, with half-maximal effects at 0.9 mM and 1.7 mM respectively. By contrast, PDH activity in rat heart mitochondria was essentially insensitive to the effects of these polyamines. 3. The effects on PDH activity of incubation of adipose-tissue mitochondria with spermine persisted through re-isolation and re-incubation of the mitochondria in the absence of the polyamine. 4. No evidence was found of any increase in the concentration of spermine associated with purified mitochondrial fractions prepared from insulin-treated tissue. 5. Overall, the data provide further evidence against a role for polyamines in the rapid stimulation of PDH by insulin, but suggest that polyamines may be important in mediating longer-term changes in the activity of the complex.

scholarly journals Effect of micromolar concentrations of free Ca2+ ions on pyruvate dehydrogenase interconversion in intact rat heart mitochondria

1981 ◽  
Vol 194 (3) ◽  
pp. 721-732 ◽  
Author(s):  
R G Hansford
Keyword(s):  
Pyruvate Dehydrogenase ◽  
Rat Heart ◽  
Inhibitory Effect ◽  
O2 Uptake ◽  
Mitochondrial Content ◽  
Bicarbonate Ions ◽  
Direct Inhibitory Effect ◽  
Na Ions ◽  
Rat Heart Mitochondria ◽  
Stimulation Of

1. The mitochondrial content of active (dephospho) pyruvate dehydrogenase (PDHA) was found to be severalfold higher at an extramitochondrial Ca2+ concentration of 2 microM (pCa6) than at pCa7. The nature of the respiratory substrate did not affect this finding. 2. This Ca2+-dependence was shown in state-4 and 50%-state-3 conditions [see Chance & Williams (1956) Adv. Enzymol. 17, 65-134], but was absent in the presence of excess ADP (state 3). 3. Na+ and Mg2+ ions shifted the pCa value required for a maximal PDHA content to lower values. This was attributed to a stimulation of mitochondrial Ca2+ egress and an inhibition of uptake, respectively. Na+ ions diminished pyruvate dehydrogenase phosphate phosphatase activity in mitochondria which had been extensively depleted of Ca2+ ions by incubation with EGTA, raising the possibility of a direct inhibitory effect of Na+ ions, unrelated to Ca2+ movements. 4. Mg2+ ions lowered the mitochondrial PDHA content at pCa 6.24 and 6.48, but had only minimal effects in the presence of EGTA. 5. The effects of P1 and bicarbonate ions on PDHA content were also studied, as possible effectors of mitochondrial Ca2+ transport. Bicarbonate ions abolished the response to Ca2+ ions, by generating maximal values of PDHA content, but such a response was still observed when physiological concentrations of both P1 and bicarbonate were used. 6. The pCa of the medium in the range 6.33 to over 7 affected PDHA content, with only very minor changes in state-4 rates of O2 uptake and no change in [ATP]/[ADP] ratio or in mitochondrial [NADH]/[NAD+] ratio, provided that Mg2+ ions were present. Thus the effect of Ca2+ ions on PDHA content is unlikely to be mediated by changes in [ATP]/[ADP] and [NADH]/[NAD+] ratio and is more likely to be direct. Equally, changes in the [acetyl-CoA]/[CoA] ratio in response to Ca2+ ions when the substrate was pyruvate were the converse of those required to mediate changes in interconversion, and are probably secondary to changes in PDHA content.

scholarly journals Actions of the creatine analogue β-guanidinopropionic acid on rat heart mitochondria

1994 ◽  
Vol 300 (1) ◽  
pp. 211-216 ◽  
Author(s):  
J F Clark ◽  
Z Khuchua ◽  
A V Kuznetsov ◽  
E Vassil'eva ◽  
E Boehm ◽  
...  
Keyword(s):  
Creatine Kinase ◽  
Rat Heart ◽  
Heart Mitochondria ◽  
Isolated Cardiomyocytes ◽  
Isolated Mitochondria ◽  
Significant Stimulation ◽  
Ionic Detergent ◽  
Rat Heart Mitochondria ◽  
Kinetics Of ◽  
Stimulation Of

The action of the creatine analogue beta-guanidinopropionic acid (beta-GPA) was examined in rat heart mitochondria and in isolated cardiomyocytes or fibres which were permeabilized with the non-ionic detergent saponin to determine the kinetics of mitochondrial creatine kinase for beta-GPA. Fibres and myocytes were subjected to increasing [ADP] in the presence and absence of beta-GPA or creatine, whereas isolated mitochondria received a similar protocol with increasing [ATP]. In isolated mitochondria given ATP, there was a stimulation of respiration by creatine, but no significant stimulation of respiration by beta-GPA. Further studies on fibres from control and beta-GPA-fed rats also found that beta-GPA is not utilized by the mitochondria, as evidenced by a lack of beta-GPA-stimulated respiration (Km for ADP = 142 +/- 23 microM) compared with control (Km for ADP from 161 +/- 23 microM), but no significant change in Vmax. Therefore the rat heart mitochondria are not responsive to beta-GPA as compared with creatine. Interestingly, the fibres from beta-GPA-fed rats had no creatine- or beta-GPA-stimulated respiration (Km for ADP = 57.3 +/- 7.2 microM for control, 54.2 +/- 7.2 microM with creatine, and 53.5 +/- 7.8 microM with beta-GPA). The mitochondria prepared from the hearts of rats exposed for 10 weeks to 1% beta-GPA in their diet had a significant decrease in Vmax. and a significant decrease in Km for ADP. Thus the hearts from beta-GPA-fed animals may be pathologic, due to a disruption of the creatine kinase energy circuit.

Studies on the rapid stimulation of mitochondrial respiration by thyroid hormones

1992 ◽  
Vol 127 (6) ◽  
pp. 542-546 ◽  
Author(s):  
Ian O'Reilly ◽  
Michael P Murphy
Keyword(s):  
Pyruvate Dehydrogenase ◽  
Mitochondrial Respiration ◽  
Liver Mitochondria ◽  
Respiration Rates ◽  
Iodothyronine Deiodinases ◽  
Rapid Stimulation ◽  
Isolated Liver ◽  
Cytoplasmic Ribosomes ◽  
Stimulation Of

Injection of L-3,5-diiodothyronine (T2) into rats made hypothyroid by 6-n-propyl-2-thiouracil (PTU) increased the respiration rates of subsequently isolated liver mitochondria; this stimulation of respiration by T2 occurred in the presence of cycloheximide and is therefore independent of protein synthesis on cytoplasmic ribosomes. Injection of T3 into PTU-treated rats had a lesser effect than T2 on the respiration rates of subsequently isolated mitochondria; as PTU is an inhibitor of 5′-iodothyronine deiodinases, which convert T3 into T2 in vivo, the rapid stimulation of mitochondrial respiration by T3, which has been shown in a range of systems, may not be due directly to T3 itself, but may be mediated by its deiodination product T2. Injection of T2, or T3, into hypothyroid or euthyroid rats had no effect on the percentage activity of mitochondrial pyruvate hydrogenase assayed 30 min later. The amount of active pyruvate dehydrogenase is regulated by changes in mitochondrial calcium concentration and matrix ATP/ADP ratio; therefore these parameters are not persistently affected by treatment with T3 or T2. In addition, the total amount of pyruvate dehydrogenase present was the same in euthyroid and hypothyroid rats, indicating that the expression of this enzyme is not stringently controlled by thyroid hormone status.

scholarly journals Pyruvate Dehydrogenase Activity in the Liver, Brain and Adipose-Tissue of Lipid-Deprived Developing Rats. Effect of Minute Amounts of Polyunsaturated Fatty Acids

1982 ◽  
Vol 9 (2) ◽  
pp. 221-229 ◽  
Author(s):  
C. Loriette ◽  
M. Launay ◽  
D. Lapous ◽  
J. Raulin
Keyword(s):  
Fatty Acids ◽  
Adipose Tissue ◽  
Pyruvate Dehydrogenase ◽  
Tetraenoic Acid ◽  
Female Progeny ◽  
Adipose Tissues ◽  
Minute Amount ◽  
Acid Ratio ◽  
The Brain ◽  
Stimulation Of

ABSTRACT:The present experiment was carried out using the following diets:FF, fat-free, andLPthe same diet with 0.7% sunflower oil - given to the progeny of females kept on theFFdiet since the mating. After 10 mM Mg2+ activation of the PDH phosphatase, the rate of [1-14C] pyruvate decarboxylation into acetyl-CoA ester units was determined in the liver, brain and adipose-tissue of the pair-fed developing rats.Results: In the male progeny, pyruvate dehydrogenase (PDH) activity was higher (61%) in theLPgroup livers than in theFFgroup livers, at the end of the 13 week experiment. Such a difference was not observed in the two group brains up to the 91 days postweaning, but was even larger (94%) between adipose-tissues of theLPandFFgroups. In the female progeny kept 12 weeks on the diets, PDH activity in theLPgroup tissues was also higher than in theFFgroup tissues: 63% in the liver, 43% in adipose-tissues, and less than 10% in the brain. Therefore, a minute amount of lipids high in linoleic acid appeared to increase PDH activity, and especially in the liver and adipose-tissues of animals kept on a strictly fat-free diet. This stimulation of the PDH activity seems closely related to the phospholipid rehabilitation in the tissues (decrease in the trienoic: tetraenoic acid ratio values).

scholarly journals Role of calcium ions in the regulation of intramitochondrial metabolism. Effects of Na+, Mg2+ and ruthenium red on the Ca2+-stimulated oxidation of oxoglutarate and on pyruvate dehydrogenase activity in intact rat heart mitochondria

1980 ◽  
Vol 190 (1) ◽  
pp. 107-117 ◽  
Author(s):  
R M Denton ◽  
J G McCormack ◽  
N J Edgell
Keyword(s):  
Dehydrogenase Activity ◽  
Pyruvate Dehydrogenase ◽  
Rat Heart ◽  
Ruthenium Red ◽  
Heart Mitochondria ◽  
Heart Cells ◽  
Maximal Effect ◽  
Rat Heart Mitochondria ◽  
20 Nm

1. In uncoupled rat heart mitochondria, the kinetic parameters for oxoglutarate oxidation were very close to those found for oxoglutarate dehydrogenase activity in extracts of the mitochondria. In particular, Ca2+ greatly diminished the Km for oxoglutarate and the k0.5 value (concentration required for half-maximal effect) for this effect of Ca2+ was close to 1 microM. 2. In coupled rat heart mitochondria incubated with ADP, increases in the extramitochondrial concentration of Ca2+ greatly stimulated oxoglutarate oxidation at low concentrations of oxoglutarate, but not at saturating concentrations of oxoglutarate. The k0.5 value for the activation by extramitochondrial Ca2+ was about 20 nM. In the presence of either Mg2+ or Na+ this value was increased to about 90 nM, and in the presence of both to about 325 nM. 3. In coupled rat heart mitochondria incubated without ADP, increases in the extramitochondrial concentration of Ca2+ resulted in increases in the proportion of pyruvate dehydrogenase in its active non-phosphorylated form. The sensitivity to Ca2+ closely matched that found to affect oxoglutarate oxidation, and Mg2+ and Na+ gave similar effects. 4. Studies of others have indicated that the distribution of Ca2+ across the inner membrane of heart mitochondria is determined by a Ca2+-transporting system which is composed of a separate uptake component (inhibited by Mg2+ and Ruthenium Red) and an efflux component (stimulated by Na+). The present studies are entirely consistent with this view. They also indicate that the intramitochondrial concentration of Ca2+ within heart cells is probably about 2–3 times that in the cytoplasm, and thus the regulation of these intramitochondrial enzymes by Ca2+ is of likely physiological significance. It is suggested that the Ca2+-transporting system in heart mitochondria may be primarily concerned with the regulation of mitochondrial Ca2+ rather than cytoplasmic Ca2+; the possible role of Ca2+ as a mediator of the effects of hormones and neurotransmitters on mammalian mitochondrial oxidative metabolism is discussed.

scholarly journals Celecoxib Decreases Mitochondrial Complex IV Activity and Induces Oxidative Stress in Isolated Rat Heart Mitochondria: An Analysis for its Cardiotoxic Adverse Effect

2020 ◽  
Author(s):  
Saman Atashbar ◽  
Elham Mohammad Khanlou ◽  
Saleh Khezri ◽  
Peyman Kurdpour ◽  
Ahmad Salimi
Keyword(s):  
Lipid Peroxidation ◽  
Rat Heart ◽  
Isolated Rat Heart ◽  
Mitochondrial Swelling ◽  
Heart Mitochondria ◽  
Isolated Mitochondria ◽  
Biochemical Assays ◽  
Ros Formation ◽  
Rat Heart Mitochondria ◽  
Isolated Rat

Abstract Background In spite of the cardiotoxic effect of selective cyclooxygenase-2 inhibitors, they are most widely used as anti-inflammatory and analgesic drugs. Today, valdecoxib and rofecoxib have been withdrawn on the market but celecoxib remains. In this study, we focused on an analysis of celecoxib toxic effects on isolated mitochondrial. Methods isolated rat heart mitochondria were obtained using differential centrifugation. Using flowcytometry and biochemical assays we searched succinate dehydrogenases (SDH), mitochondrial membrane potential (MMP), reactive oxygen species (ROS) formation, mitochondrial swelling, lipid peroxidation and mitochondrial complexes activity in rat heart isolated mitochondria. Results In here our results indicated a significant decrease in activity of complexes IV after exposure with celecoxib (16 µg/ml). This decrease in activity of complexes IV is paralleled by the MMP collapse, ROS formation, mitochondrial swelling and lipid peroxidation. Conclusion For the first time, this introductory study has showed a significant decrease in activity of complexes IV and mitochondrial dysfunction after exposure with celecoxib in rat heart isolated mitochondria.

STUDIES ON THE INHIBITION OF THE MITOCHONDRIAL ATP-ase BY REDUCTION OF THE RESPIRATORY CHAIN

1960 ◽  
Vol 38 (1) ◽  
pp. 1195-1214 ◽  
Author(s):  
W. Chefurka
Keyword(s):  
Electron Transport ◽  
Oxidative Phosphorylation ◽  
Respiratory Chain ◽  
Transport System ◽  
Heart Muscle ◽  
Rat Heart ◽  
Complete Inhibition ◽  
Muscle Preparation ◽  
Rat Heart Mitochondria ◽  
Stimulation Of

The effects of inhibition of the electron transport system on the stimulation of the ATP-ase reaction in liver and rat-heart mitochondria by dinitrophenol were studied. Cyanide at concentrations 10−3M and higher effectively reduced the stimulation of ATP-ase by dinitrophenol. A similar but less striking inhibition was observed for rat-heart sarcosomes. This ATP-ase reaction was also inhibited in the presence of 10−4M cyanide with glutamate, β-hydroxybutyrate, DPNH, and succinate as reductants of the respiratory chain. Anaerobiosis also caused a substantial decrease in the ATP-ase reaction. In all instances, complete inhibition of the ATP-ase reaction could not be achieved when the respiratory chain was reduced. The magnesium-stimulated ATP-ase of rat-heart sarcosomes, of aged mitochondria, and of the Keilin–Hartree heart-muscle preparation was insensitive to reduction of the carriers suggesting that this reaction may constitute only part of the total ATP-ase reaction. The compatability of the various mechanisms of oxidative phosphorylation with these results is discussed.

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