scholarly journals Activation of pyruvate dehydrogenase in perfused rat heart by dichloroacetate (Short Communication)

1973 ◽  
Vol 134 (2) ◽  
pp. 651-653 ◽  
Author(s):  
Sue Whitehouse ◽  
Philip J. Randle
Keyword(s):  
Pyruvate Dehydrogenase ◽  
Rat Heart ◽  
Short Communication ◽  
Perfused Rat Heart ◽  
Phosphorylated Form ◽  
Rat Hearts

The activity of pyruvate dehydrogenase was assayed in extracts of rat hearts perfused in vitro with media containing glucose and insulin±acetate±dichloroacetate. Dichloroacetate (100μm, 1mm or 10mm) increased the activity of pyruvate dehydrogenase in perfusions with glucose or glucose+acetate. Evidence is given that dichloroacetate may facilitate the conversion of pyruvate dehydrogenase from an inactive (phosphorylated) form into an active (dephosphorylated) form.

scholarly journals The activation of pyruvate dehydrogenase in the perfused rat heart by adrenaline and other inotropic agents

1981 ◽  
Vol 194 (2) ◽  
pp. 639-643 ◽  
Author(s):  
J G McCormack ◽  
R M Denton
Keyword(s):  
Pyruvate Dehydrogenase ◽  
Oxidative Metabolism ◽  
Rat Heart ◽  
Fold Increase ◽  
Diabetic Rats ◽  
Inotropic Agents ◽  
Perfusion Medium ◽  
Perfused Rat Heart ◽  
Phosphorylated Form

Adrenaline resulted in a reversible 4-fold increase in the amount of pyruvate dehydrogenase in its active non-phosphorylated form in the perfused rat heart within 1 min. The increase was less in extent in hearts from starved or diabetic rats or in hearts from control rats oxidizing acetate, unless pyruvate was added to the perfusion medium. Increases could also be induced by other inotropic agents, supporting the hypothesis that increases in cytoplasmic Ca2+ can be relayed into mitochondria and influence oxidative metabolism.

scholarly journals Conversion of inactive (phosphorylated) pyruvate dehydrogenase complex into active complex by the phosphate reaction in heart mitochondria is inhibited by alloxan-diabetes or starvation in the rat

1978 ◽  
Vol 173 (2) ◽  
pp. 669-680 ◽  
Author(s):  
N J Hutson ◽  
A L Kerbey ◽  
P J Randle ◽  
P H Sugden
Keyword(s):  
Pyruvate Dehydrogenase ◽  
Rat Heart ◽  
Pyruvate Dehydrogenase Complex ◽  
Diabetic Rats ◽  
Atp Depletion ◽  
Heart Mitochondria ◽  
Active Complex ◽  
Phosphate Complex ◽  
Rat Hearts ◽  
Dehydrogenase Complex

1. The conversion of inactive (phosphorylated) pyruvate dehydrogenase complex into active (dephosphorylated) complex by pyruvate dehydrogenase phosphate phosphatase is inhibited in heart mitochondria prepared from alloxan-diabetic or 48h-starved rats, in mitochondria prepared from acetate-perfused rat hearts and in mitochondria prepared from normal rat hearts incubated with respiratory substrates for 6 min (as compared with 1 min). 2. This conclusion is based on experiments with isolated intact mitochondria in which the pyruvate dehydrogenase kinase reaction was inhibited by pyruvate or ATP depletion (by using oligomycin and carbonyl cyanide m-chlorophenylhydrazone), and in experiments in which the rate of conversion of inactive complex into active complex by the phosphatase was measured in extracts of mitochondria. The inhibition of the phosphatase reaction was seen with constant concentrations of Ca2+ and Mg2+ (activators of the phosphatase). The phosphatase reaction in these mitochondrial extracts was not inhibited when an excess of exogenous pig heart pyruvate dehydrogenase phosphate was used as substrate. It is concluded that this inhibition is due to some factor(s) associated with the substrate (pyruvate dehydrogenase phosphate complex) and not to inhibition of the phosphatase as such. 3. This conclusion was verified by isolating pyruvate dehydrogenase phosphate complex, free of phosphatase, from hearts of control and diabetic rats an from heart mitochondria incubed for 1min (control) or 6min with respiratory substrates. The rates of re-activation of the inactive complexes were then measured with preparations of ox heart or rat heart phosphatase. The rates were lower (relative to controls) with inactive complex from hearts of diabetic rats or from heart mitochondria incubated for 6min with respiratory substrates. 4. The incorporation of 32Pi into inactive complex took 6min to complete in rat heart mitocondria. The extent of incorporation was consistent with three or four sites of phosphorylation in rat heart pyruvate dehydrogenase complex. 5. It is suggested that phosphorylation of sites additional to an inactivating site may inhibit the conversion of inactive complex into active complex by the phosphatase in heart mitochondria from alloxan-diabetic or 48h-starved rats or in mitochondria incubated for 6min with respiratory substrates.

Reduced high-energy phosphate levels in rat hearts. I. Effects of alloxan diabetes

1976 ◽  
Vol 230 (6) ◽  
pp. 1744-1750 ◽  
Author(s):  
TB Allison ◽  
SP Bruttig ◽  
Crass MF ◽  
RS Eliot ◽  
JC Shipp
Keyword(s):  
Oxidative Metabolism ◽  
Oxygen Delivery ◽  
Rat Heart ◽  
High Energy ◽  
Diabetic Rat ◽  
High Energy Phosphate ◽  
Atp Production ◽  
Rat Hearts

Significant alterations in heart carbohydrate and lipid metabolism are present 48 h after intravenous injection of alloxan (60 mg/kg) in rats. It has been suggested that uncoupling of oxidative phosphorylation occurs in the alloxanized rat heart in vivo, whereas normal oxidative metabolism has been demonstrated in alloxan-diabetic rat hearts perfused in vitro under conditions of adequate oxygen delivery. We examined the hypothesis that high-energy phosphate metabolism might be adversely affected in the alloxan-diabetic rat heart in vivo. Phosphocreatine and ATP were reduced by 58 and 45%, respectively (P is less than 0.001). Also, oxygen-dissociation curves were shifted to the left by 4 mmHg, and the rate of oxygen release from blood was reduced by 21% (P is less than 0.01). Insulin administration normalized heart high-energy phosphate compounds. ATP production was accelerated in diabetic hearts perfused in vitro with a well-oxygenated buffer. These studies support the hypothesis that oxidative ATP production in the alloxan-diabetic rat heart is reduced and suggest that decreased oxygen delivery may have a regulatory role in the oxidative metabolism of the diabetic rat heart.

scholarly journals The discovery of a rapidly metabolized polymeric tetraphosphate derivative of adenosine in perfused rat heart

1984 ◽  
Vol 223 (3) ◽  
pp. 627-632 ◽  
Author(s):  
J Mowbray ◽  
W L Hutchinson ◽  
G R Tibbs ◽  
P G Morris
Keyword(s):  
Organic Acid ◽  
Rat Heart ◽  
Purine Nucleoside ◽  
Acid Phosphate ◽  
Perfused Rat Heart ◽  
Rat Hearts ◽  
Adenosine Phosphate ◽  
Perfused Rat Hearts ◽  
Radioactive Labelling

The predicted presence in perfused rat hearts of a rapidly metabolized but hitherto unrecognized form of adenosine phosphate has been confirmed by specific radioactive labelling. The properties of the purified compound suggest that it is a heteropolymer of a small organic acid, phosphate and purine nucleoside in the proportions 1:4:1.

scholarly journals The release of 3′:5′-cyclic monophosphate from the isolated perfused rat heart

1975 ◽  
Vol 152 (2) ◽  
pp. 429-432 ◽  
Author(s):  
John A. O'Brien ◽  
Richard C. Strange
Keyword(s):  
Cyclic Amp ◽  
Rat Heart ◽  
Perfused Rat Heart ◽  
Cyclic Monophosphate ◽  
Isolated Perfused Rat Heart ◽  
Rat Hearts ◽  
Basal Release ◽  
Perfused Rat Hearts ◽  
Isolated Perfused Rat Hearts

Although basal release of cyclic AMP from isolated perfused rat hearts was not measurable, isoprenaline induced substantial release of the nucleotide, suggesting that in vivo the myocardium can contribute to plasma cyclic AMP. Anoxia also increased the amount of cyclic AMP released, but insulin and nicotinate alone or in combination had no effect.

Computer simulation of metabolism in pyruvate-perfused rat heart. III. Pyruvate dehydrogenase

1979 ◽  
Vol 237 (3) ◽  
pp. R167-R173 ◽  
Author(s):  
M. C. Kohn ◽  
M. J. Achs ◽  
D. Garfinkel
Keyword(s):  
Pyruvate Dehydrogenase ◽  
Rat Heart ◽  
Pyruvate Dehydrogenase Complex ◽  
Active Form ◽  
Realistic Model ◽  
Specific Protein ◽  
Active Species ◽  
Perfused Rat Heart ◽  
Synergistic Activation ◽  
The Difference

A physiologically and biochemically realistic model of the regulation of pyruvate dehydrogenase complex (PDH) was constructed for the perfused rat heart. It includes conversion between inactive (phospho) and active (dephospho) forms by a specific protein kinase (PDHK) and phosphoprotein phosphatase (PDHP). The activity of the tightly bound PDHK is influenced by synergistic activation/inhibition by acetyl CoA/CoASH and NADH/NAD. PDHK in this simulation was more sensitive to the fraction of ADP that was Mg2+-chelated than to the ATP-to-ADP ratio. Ca2+ stimulates binding of Mg2+-dependent PDHP to the complex; the bound enzyme was considered to be the active species. The fraction of PDH in the active form, rather than substrate and inhibitor levels, determines PDH activity under these conditions. This fraction depends on the present value and recent history of the difference between PDHK and PDHP activities. Both of these are active continuously and continuously control PDH.

Metabolic inhibition in the perfused rat heart: evidence for glycolytic requirement for normal sodium homeostasis

1998 ◽  
Vol 274 (4) ◽  
pp. H1082-H1089 ◽  
Author(s):  
José Dizon ◽  
Daniel Burkhoff ◽  
Joseph Tauskela ◽  
John Whang ◽  
Paul Cannon ◽  
...  
Keyword(s):  
Oxidative Metabolism ◽  
Rat Heart ◽  
High Energy ◽  
Shift Reagent ◽  
Resonance Spectroscopy ◽  
High Energy Phosphate ◽  
Perfused Rat Heart ◽  
Rat Hearts ◽  
Rapid Pacing ◽  
Subcellular Compartmentalization

Subcellular compartmentalization of energy stores to support different myocardial processes has been exemplified by the glycolytic control of the ATP-sensitive K+ channel. Recent data suggest that the control of intracellular sodium (Nai) may also rely on glycolytically derived ATP; however, the degree of this dependence is unclear. To examine this question, isolated, perfused rat hearts were exposed to hypoxia, to selectively inhibit oxidative metabolism, or iodoacetate (IAA, 100 μmol/l), to selectively inhibit glycolysis. Nai and myocardial high-energy phosphate levels were monitored using triple-quantum-filtered (TQF)23Na and31P magnetic resonance spectroscopy, respectively. The effects of ion exchange mechanisms (Na+/Ca2+, Na+/H+) on Nai were examined by pharmacological manipulation of these channels. Nai, as monitored by shift reagent-aided TQF 23Na spectral amplitudes, increased by ∼220% relative to baseline after 45 min of perfusion with IAA, with or without rapid pacing. During hypoxia, Nai increased by ∼200% during rapid pacing but did not increase in unpaced hearts or when the Na+/H+exchange blocker ethylisopropylamiloride (EIPA, 10 μmol/l) was used. Neither EIPA nor a low-Ca2+perfusate (50 μmol/l) could prevent the rise in Nai during perfusion with IAA. Myocardial function and high-energy phosphate stores were preserved during inhibition of glycolysis with IAA and continued oxidative metabolism. These results suggest that glycolysis is required for normal Na+ homeostasis in the perfused rat heart, possibly because of preferential fueling of Na-K-adenosinetriphosphatase by glycolytically derived ATP.

scholarly journals The effects of glucose, acetate, lactate and insulin on protein degradation in the perfused rat heart

1982 ◽  
Vol 206 (3) ◽  
pp. 467-472 ◽  
Author(s):  
P H Sugden ◽  
D M Smith
Keyword(s):  
Protein Degradation ◽  
Rat Heart ◽  
Plasma Concentrations ◽  
Normal Range ◽  
Perfused Rat Heart ◽  
Rat Hearts ◽  
Insulin Inhibition

Rat hearts were perfused as working preparations by the method of Taegtmeyer, Hems & Krebs [(1980 Biochem. J. 186, 701-711]. In the presence of glucose, insulin significantly inhibited protein degradation at concentrations as low as 50 mu units/ml. Acetate or lactate, when present either as sole fuel for contraction or in combination with glucose, did not inhibit protein degradation. Insulin inhibition or protein degradation was decreased with either lactate as sole fuel. We suggest that the inhibition of protein degradation occurs over the normal range of plasma concentrations of insulin present in vivo and that the presence of glucose may be at least in part necessary for this effect of insulin.

scholarly journals Measurement of oxidized glutathione and total glutathione in the perfused rat heart

1970 ◽  
Vol 117 (4) ◽  
pp. 661-665 ◽  
Author(s):  
P. L. Wendell
Keyword(s):  
Glutathione Reductase ◽  
Rat Heart ◽  
Enzyme Reaction ◽  
Heart Tissue ◽  
Oxidized Glutathione ◽  
Total Glutathione ◽  
Perfused Rat Heart ◽  
Rat Hearts

1. A method was developed for the assay of GSSG in heart tissue. 2. GSSG and total glutathione were measured in rat hearts perfused under a variety of conditions. About 2% of the total glutathione is present as GSSG. The concentrations of GSSG and GSH remained constant under all the conditions tested. 3. These results are discussed with reference to the equilibrium and rate of the glutathione reductase reaction in the cell. It is concluded that the enzyme reaction does not lie near equilibrium.

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