scholarly journals Systematic variations in the content of the purine nucleotides in the steady-state perfused rat heart. Evidence for the existence of controlled storage and release of adenine nucleotides

1978 ◽  
Vol 176 (2) ◽  
pp. 485-493 ◽  
Author(s):  
David J. Bates ◽  
David Perrett ◽  
John Mowbray
Keyword(s):  
Cyclic Amp ◽  
Rat Heart ◽  
Energy Demand ◽  
De Novo ◽  
Adenine Nucleotide ◽  
Adenine Nucleotides ◽  
Purine Nucleotide ◽  
Purine Nucleotides ◽  
Perfused Rat Heart ◽  
Adenine Nucleotide Pool

1. The contents of the major purine nucleotides in the isolated non-working perfused rat heart varied systematically during 80min of perfusion. In particular the amounts of ATP, ADP, GTP, cyclic AMP and cyclic GMP in the well-oxygenated myocardium showed changes ranging from 25 to 60% of the mean concentrations. The apparent periodicity was about 30min for some and about 60min for other nucleotides. 2. These data are in contrast with measurements of parameters reflecting heart performance, which remained constant over this period of perfusion. 3. The ATP/ADP ratio, the cyclic AMP content, the GTP content and the GTP/GDP ratio in the tissue bore a constant relationship to one another, and all showed the same temporal variation. 4. Increasing the energy demand on the heart by administration of bovine somatotropin (1μg/ml) tended to damp the variations, and generally lower the content of all the nucleotides. 5. The total extractable adenine nucleotide pool also showed systematic temporal variations of as much as 1.3μmol/g wet wt. of tissue within 10min. 6. These variations could not be accounted for as inter-conversion with adenosine, other purine nucleotides, nucleosides or purine-degradation products either in the tissue or in the perfusion medium. No evidence was found in this preparation of the purine nucleotide oscillations described by Lowenstein and his co-workers [see Tornheim & Lowenstein (1975) J. Biol. Chem.250, 6304–6314]. 7. Further, the pool size increases cannot be satisfactorily explained by either synthesis de novo or the breakdown of any purine macromolecular species in the cell. Thus it is suggested that an unsuspected substantial storage form of purine nucleotide may exist in heart.

scholarly journals Purine catabolism in isolated rat hepatocytes. Influence of coformycin

1980 ◽  
Vol 188 (3) ◽  
pp. 913-920 ◽  
Author(s):  
Georges Van Den Berghe ◽  
Françoise Bontemps ◽  
Henri-Géry Hers
Keyword(s):  
High Speed ◽  
Adenine Nucleotide ◽  
Adenine Nucleotides ◽  
Rat Hepatocytes ◽  
Amp Deaminase ◽  
Purine Nucleotides ◽  
Isolated Rat Hepatocytes ◽  
Adenine Nucleotide Pool ◽  
Isolated Rat

1. The catabolism of purine nucleotides was investigated by both chemical and radiochemical methods in isolated rat hepatocytes, previously incubated with [14C]adenine. The production of allantoin reached 32±5nmol/min per g of cells (mean±s.e.m.) and as much as 30% of the radioactivity incorporated in the adenine nucleotides was lost after 1h. This rate of degradation is severalfold in excess over values previously reported to occur in the liver in vivo. An explanation for this enhancement of catabolism may be the decrease in the concentration of GTP. 2. In a high-speed supernatant of rat liver, adenosine deaminase was maximally inhibited by 0.1μm-coformycin. The activity of AMP deaminase, measured in the presence of its stimulator ATP in the same preparation, as well as the activity of the partially purified enzyme, measured after addition of its physiological inhibitors GTP and Pi, required 50μm-coformycin for maximal inhibition. 3. The production of allantoin by isolated hepatocytes was not influenced by the addition of 0.1μm-coformycin, but was decreased by concentrations of coformycin that were inhibitory for AMP deaminase. With 50μm-coformycin the production of allantoin was decreased by 85% and the formation of radioactive allantoin from [14C]adenine nucleotides was completely suppressed. 4. In the presence of 0.1μm-coformycin or in its absence, the addition of fructose (1mg/ml) to the incubation medium caused a rapid degradation of ATP, without equivalent increase in ADP and AMP, followed by transient increases in IMP and in the rate of production of allantoin; adenosine was not detectable. In the presence of 50μm-coformycin, the fructose-induced breakdown of ATP was not modified, but the depletion of the adenine nucleotide pool proceeded much more slowly and the rate of production of allantoin increased only slightly. No rise in IMP concentration could be detected, but AMP increased manyfold and reached values at which a participation of soluble 5′-nucleotidase in the catabolism of adenine nucleotides is most likely. 5. These results are in agreement with the hypothesis that the formation of allantoin is controlled by AMP deaminase. They constitute further evidence that 5′-nucleotidase is inactive on AMP, unless the concentration of this nucleotide rises to unphysiological values.

Adenine nucleotide synthesis from inosine during normoxia and after ischaemia in the isolated perfused rat heart

1985 ◽  
Vol 63 (9) ◽  
pp. 1159-1164 ◽  
Author(s):  
J. Aussedat ◽  
M. Verdys ◽  
A. Rossi
Keyword(s):  
Rat Heart ◽  
Adenine Nucleotide ◽  
Adenine Nucleotides ◽  
Low Flow ◽  
Nucleotide Synthesis ◽  
Perfused Rat Heart ◽  
Isolated Perfused Rat Heart ◽  
Nucleotide Content ◽  
Glycogen Stores

[14C]inosine in a range of concentrations of 20 μM to 1 mM was administered-to the isolated perfused rat heart for 30 min. The incorporation of the nucleoside into myocardial adenine nucleotides increased for extracellular concentrations of the precursor up to 50 μM, reaching a plateau at 60 nmol∙g−1∙30 min−1 with concentrations ranging between 50 and 200 μM. The supply of 500 μM and 1 mM of inosine induced a further increase in cardiac adenine nucleotide synthesis to about 200 nmol∙g−1∙30 min−1. When supplied during low flow ischaemia (0.5 mL∙min−1, 30 min.), 1 mM of inosine protected the heart against ATP degradation, while 100 μM of inosine was inefficacious. In the presence of 1 mM of inosine on reperfusion the adenine nucleotide content of the heart was similar to that observed in the absence of the nucleoside. The incorporation of [14C]inosine into adenine nucleotides was, in this last condition, below the value measured before ischaemia. Inosine administration was effective in protecting the heart against ischaemic breakdown of glycogen and favoured postischaemic restoration of glycogen stores.

scholarly journals Changes of nucleotide content in human and rat heart during cardiac surgery and ischemia.

1993 ◽  
Vol 40 (4) ◽  
pp. 531-538 ◽  
Author(s):  
R T Smoleński ◽  
A C Składanowski ◽  
J Swierczyński ◽  
M Perko ◽  
M Narkiewicz ◽  
...  
Keyword(s):  
Cardiac Surgery ◽  
Rat Heart ◽  
Human Heart ◽  
Adenine Nucleotide ◽  
Heart Defects ◽  
Human Myocardium ◽  
Purine Nucleotide ◽  
Initial Value ◽  
Adenylate Pool ◽  
Adenine Nucleotide Pool

The influence of ischemia on purine nucleotide and their catabolite concentration in human myocardium was investigated during surgery of acquired and congenital heart defects. This was compared with the influence of ischemia on rat heart. Concentrations of adenine and guanine nucleotides and their catabolites were measured in the extracts of heart biopsies taken at the onset of ischemia and at the time of reperfusion. The content of myocardial ATP in human heart decreased from the initial value of 22.3 +/- 1.1 to 14.6 +/- 1.5 nmol/mg protein and total adenine nucleotide pool decreased from 34.2 +/- 1.8 to 27.6 +/- 1.5 nmol/mg protein during the operation. Significant increases in myocardial concentrations of purine catabolites were also observed with the most prominent rise in inosine from below 0.5 at the onset of the ischemia to 3.0 +/- 0.5 nmol/mg protein at the time of reperfusion. A positive correlation was demonstrated between the concentration of purine catabolites in the heart at the end of ischemia with the decrease of both ATP and the total nucleotide pool. An interesting metabolic specificity of the ischemic human heart appeared to be only a small accumulation of inosine monophosphate (IMP). The increase of IMP in the rat heart after ischemia was several-fold higher. Thus, cardiac surgery of congenital and acquired heart defects was associated with a significant decrease in myocardial adenylate pool and a single biopsy collected at the end of ischemia seems to be sufficient to evaluate the extent of this metabolic and possibly functional impairment of the heart.

scholarly journals Adenine nucleotide metabolism in isolated chicken hepatocytes

1987 ◽  
Vol 242 (2) ◽  
pp. 551-558 ◽  
Author(s):  
J Spychała ◽  
G Van den Berghe
Keyword(s):  
Uric Acid ◽  
Metabolic Flux ◽  
De Novo ◽  
Adenine Nucleotide ◽  
Adenine Nucleotides ◽  
Total Concentration ◽  
Nucleotide Metabolism ◽  
Adenosine Kinase ◽  
Adenine Nucleotide Metabolism ◽  
Adenine Nucleotide Pool

The turnover of the adenine nucleotide pool, the pathway of the degradation of AMP and the occurrence of recycling of adenosine were investigated in isolated chicken hepatocytes, in which the adenylates had been labelled by prior incubation with [14C]adenine. Under physiological conditions, 85% of the IMP synthesized by the ‘de novo’ pathway (approx. 37 nmol/min per g of cells) was catabolized directly via inosine into uric acid, and 14% was converted into adenine nucleotides. The latter were found to turn over at the rate of approx. 5 nmol/min per g of tissue. Inhibition of adenosine deaminase by 1 microM-coformycin had no effect on the formation of labelled uric acid, indicating that the initial degradation of AMP proceeds by way of deamination rather than dephosphorylation. Inhibition of adenosine kinase by 100 microM-5-iodotubercidin resulted in a loss of labelled ATP, demonstrating that adenosine is normally formed from AMP but is recycled. Unexpectedly, 5-iodotubercidin did not decrease the total concentration of ATP, indicating that the loss of adenylates caused by inhibition of adenosine kinase was nearly completely compensated by formation of AMP de novo. Anoxia induced a greatly increased catabolism of the adenine nucleotide pool, which proceeded in part by dephosphorylation of AMP. On reoxygenation, the formation of AMP de novo was increased 8-fold as compared with normoxic conditions. The latter results indicate the existence of adaptive mechanisms in chick liver allowing, when required, channelling of the metabolic flux through the ‘de novo’ pathway, away from the uricotelic catabolic route, into the synthesis of adenine nucleotides.

scholarly journals The role of glutamine oxidation and the purine nucleotide cycle for adaptation of tumour energetics to the transition from the anaerobic to the aerobic state

1988 ◽  
Vol 252 (2) ◽  
pp. 381-386 ◽  
Author(s):  
Z Kovacević ◽  
D Jerance ◽  
O Brkljac
Keyword(s):  
Adenine Nucleotide ◽  
The Other ◽  
Purine Nucleotide ◽  
Purine Nucleotide Cycle ◽  
Adenine Nucleotide Pool

It is proposed that the purine nucleotide cycle and glutamine oxidation play a key role in the adaptation of tumour energetics to the transition from the anaerobic to the aerobic state. In support of this proposal, it was found that glutamine and inosine markedly increase total adenylates in the presence of oxygen, whereas the addition of hadacidin abolishes this effect. Transition of the cells from the anaerobic to the aerobic state, and vice versa, in the presence of glutamine plus inosine revealed that there are two components of the adenine nucleotide pool, one which is stable and the other which is variable and responds to the aerobic-anaerobic transition. This part of the pool undergoes degradation or resynthesis owing to activation of the enzymes of the purine nucleotide cycle. Resynthesis of the pool is accompanied by substantial net utilization of aspartate, which is produced by glutamine oxidation. This is supported by the experiments in which the cells were alternately incubated with nitrogen or oxygen, demonstrating that hadacidin significantly decreased utilization of aspartate and regeneration of ATP owing to inhibition of adenylosuccinate synthase.

scholarly journals Evidence for the presence of oligophosphoglyceroyl-ATP in rat offney

1986 ◽  
Vol 240 (2) ◽  
pp. 597-599 ◽  
Author(s):  
W L Hutchinson ◽  
P J Ratcliffe ◽  
J Mowbray
Keyword(s):  
Trichloroacetic Acid ◽  
Adenine Nucleotides ◽  
Purine Nucleotide ◽  
Purine Nucleotides ◽  
Nucleotide Content ◽  
Rat Hearts ◽  
Perfused Rat Hearts ◽  
Rapid Equilibrium

The inability to account for large systematic variations in total purine nucleotide content of perfused rat hearts led to the demonstration that the soluble adenine nucleotides are in rapid equilibrium with a highly phosphorylated hetero-oligomeric derivative whose structure appears to be 3-phospho[glyceroyl-gamma-triphospho-5′-adenosine-3′-3-phosp ho]4glyceroyl- gamma-triphospho-5′-adenosine [Hutchinson, Morris & Mowbray (1986) Biochem. J. 234, 623-627]. Analogous techniques to those used with hearts for specifically labelling tissue purine nucleotides followed by extration and purification of nucleotides from the trichloroacetic acid-precipitable fraction show the existence of a corresponding rapid equilibrium between ATP and an oligomeric tetraphosphoadenosine derivative in perfused kidneys.

scholarly journals Nucleotide and Serotonin Metabolism in Platelets With Defective Secondary Aggregation

Blood ◽  
1974 ◽  
Vol 44 (6) ◽  
pp. 789-800 ◽  
Author(s):  
F. I. Pareti ◽  
H. J. Day ◽  
D. C. B. Mills
Keyword(s):  
Platelet Aggregation ◽  
Adenine Nucleotide ◽  
Platelet Rich Plasma ◽  
Adenine Nucleotides ◽  
Rapid Rate ◽  
Serotonin Metabolism ◽  
Release Reaction ◽  
Atp Breakdown ◽  
Platelet Defects ◽  
Adenine Nucleotide Pool

Abstract Ten patients with qualitative platelet defects have been investigated. All of the patients had impairment of secondary platelet aggregation induced by ADP, epinephrine, and collagen, and a defective release reaction. In seven patients from four families, the abnormality was consistent with the lack of a metabolically inert adenine nucleotide pool. Four of these patients, from two families, were albinos. Platelets from all of these patients had lower than normal amounts of adenine nucleotides and 5HT; the ability of these platelets to incorporate the amine was reduced and 5HT was metabolized at an abnormally rapid rate in platelet-rich plasma. It was not possible to distinguish the defect present in the albinos from that in the normally pigmented patients. Three other patients had normal amounts of platelet adenine nucleotides and 5HT; platelet aggregation and the release of adenine nucleotides induced by collagen were impaired. Metabolic ATP breakdown, during collagen aggregation, was also decreased. This defect is similar to that induced in normal platelets by aspirin. Studies on intracellular synthesis of cyclic 3'5' AMP in both groups of patients showed that the platelets were normally responsive to PGE1 and the antagonism of PGE1 by ADP and by epinephrine was also normal.

scholarly journals Labeling of the releasable adenine nucleotides of washed human platelets

Blood ◽  
1977 ◽  
Vol 49 (1) ◽  
pp. 89-99 ◽  
Author(s):  
HJ Reimers ◽  
MA Packham ◽  
JF Mustard
Keyword(s):  
Adenine Nucleotide ◽  
Adenine Nucleotides ◽  
Energy Charge ◽  
Human Platelets ◽  
Transport Processes ◽  
Adenylate Energy Charge ◽  
Prolonged Incubation ◽  
Atp Pool ◽  
Adenine Nucleotide Pool

Abstract In rabbit platelets, the metabolically active ATP pool equilibrates with the releasable ATP pool within 1 day. The studies showing this have now been extended to human platelets. Human platelets labeled with 14C-adenosine or 14C-adenine were incubated for up to 10 hr in vitro at 37 degrees C. After 10 hr, about 12% of the total platelet 14C-ATP and 14C-ADP had become releasable with thrombin (4.2 units/ml). Lysis of platelets did not occur, since less than 1% of the platelet-bound 51Cr from platelets labeled with this radioisotope appeared in the ambient fluid upon thrombin treatment. The 14C-ATP/14C-ADP ratio of the released adenine nucleotides (7.6) was similar to the 14C-ATP/14C-ADP ratio of the nonreleasable adenine nucleotides (7.1) 2 hr after the labeling with 14C-adenosine. However, upon prolonged incubation (10 hr) in vitro, the 14C-ATP/14C-ADP ratio of the releasable adenine nucleotides decreased to 2.7. The adenylate energy charge and the 14C- ATP/14C-ADP ratio of the metabolic adenine nucleotide pool did not change significantly during the time of observation. The 14C-ATP content of the platelets decreased by less than 1% hr of incubation at 37 degrees C. These observations are interpreted to mean that the 14C is transferred from the metabolically active, nonreleasable adenine nucleotide pool of human platelets into the releasable adenine nucleotide pool as ATP and is partially hydrolyzed there to yield ADP. The transfer of ATP across the storage organelle membrane of platelets may be similar to transport processes in the chromaffin cells of the adrenal medulla and may represent a general phenomenon in cells that possess storage organelles containing adenine nucleotides.

Post-ischaemic synchronous purine nucleotide oscillations in perfused rat heart

1984 ◽  
Vol 16 (8) ◽  
pp. 889-894 ◽  
Author(s):  
John Mowbray ◽  
David Perrett ◽  
David J. Bates
Keyword(s):  
Rat Heart ◽  
Purine Nucleotide ◽  
Perfused Rat Heart

Computer simulation of ischemic rat heart purine metabolism. I. Model construction

1977 ◽  
Vol 232 (4) ◽  
pp. H386-H393
Author(s):  
M. C. Kohn ◽  
D. Garfinkel
Keyword(s):  
Adenylate Cyclase ◽  
Rat Heart ◽  
Adenine Nucleotide ◽  
Extracellular Fluid ◽  
Adenosine Kinase ◽  
Inorganic Pyrophosphatase ◽  
Rate Laws ◽  
Fitting Procedure ◽  
Tissue Po2 ◽  
Adenine Nucleotide Pool

A model is proposed for the partial depletion of the adenine nucleotide pool in the ischemic perfused rat heart which involves seven enzymes: adenylate cyclase, 3',5'-cyclic AMP phosphodiesterase, 5'-nucleotidase, adenosine kinase, adenosine deaminase, purine nucleoside phosphorylase, and inorganic pyrophosphatase. The computer implementation of this model is in terms of rate laws, several of which were obtained by a systematic least-squares fitting procedure. Depletion of the adenine nucleotide pool is initiated by the release of endogenous noradrenaline into the interstitial fluid, which results from a fall in tissue PO2, and the subsequent activation of adenylate cyclase. In this model the substrate for 5'-nucleotidase is a membrane-bound AMP pool formed by hydrolysis of extracellular fluid and functions as a vasodilator; excess adenosine is incorporated into the tissue by a "permease" with Michaelis-Menten kinetics and converted to AMP, inosine, and hypoxanthine. Alternative mechanisms, such as the deamination of AMP by adenylate deaminase and conversion of AMP to adenine by AMP pyrophosphorylase, were rejected primarily on qualitative biochemical grounds.

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