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At least 19 recordsLinked to original sources
PubMed2005

Intense exercise induces the degradation of adenine nucleotide and purine nucleotide synthesis via de novo pathway in the rat liver.

The purpose of this study was to investigate the influence of intense exercise on the metabolism of adenine nucleotides in the liver. In the first experiment, to determine the degradation of adenine nucleotides, hepatic adenine nucleotides of rats were labeled by an intraperitoneal administration of 15N-labeled adenine the day before treadmill running to exhaustion. In the second experiment, to determine the de novo synthesis of purine nucleotides after intense exercise, 14C-glycine was intraperitoneally administered to rats performing intense running on a treadmill. In the first experiment, hepatic levels of ATP and total adenine nucleotides showed a reduction immediately after exercise. In contrast, hepatic levels of AMP, adenosine, hypoxanthine and uric acid showed an increase immediately after exercise. The hepatic 15N level continued to decline during the recovery period after exercise. Urinary excretion of 15N-urate was 40% higher in the exercised rats than in the control rats. In the second experiment, the radioactivity of 14C detected in the fraction of hepatic urate and allantoin was approximately 300% higher in the exercised rats than in the control rats. 14C-radioactivity that excreted into urine as urate and allantoin was approximately 200% higher in the exercised rats. Intense exercise led to the degradation of hepatic adenine nucleotides, which were not utilized for the re-synthesis of nucleotide and further degraded to hypoxanthine or uric acid. Intense exercise induced the synthesis of purine nucleotides in the liver via a de novo pathway and these synthesized nucleotides were also degraded to nucleosides and excreted into urine.

Adenine Nucleotides↗
PubMed1992

Concentrations of purine nucleotides and purine and pyrimidine bases in cerebrospinal fluid of neurologically healthy children.

The concentrations of the nucleotides AMP and IMP, the nucleosides adenosine, guanosine and inosine, the purine bases adenine, guanine, hypoxanthine and xanthine, urate, and the pyrimidine bases cytosine, thymine and uracil were determined by high performance liquid chromatography in the cerebrospinal fluid of 63 children aged between 1 month and 13 years who showed no sign of neurological disease. The results are compared with those of other authors, and used to establish reference ranges for the above metabolites in the cerebrospinal fluid of children.

Adolescent↗
PubMed1981

Metabolic basis for disorders of purine nucleotide degradation.

Purine nucleotide degradation refers to a regulated series of reactions by which human purine ribonucleotides and deoxyribonucleotides are degraded to uric acid in humans. Two major types of disorders occur in this pathway. A block of degradation occurs with syndromes involving immune deficiency, myopathy or renal calculi. Increased degradation of nucleotides occurs with syndromes characterized by hyperuricemia and gout, renal calculi, anemia or acute hypoxia. Management of disorders of purine nucleotide degradation is dependent upon modifying the specific molecular pathology underlying each disease state.

AMP Deaminase↗
PubMed1998

The role of gene duplication in the evolution of purine nucleotide salvage pathways.

Purine nucleotides are formed de novo by a widespread biochemical route that may be of monophyletic origin, or are synthesized from preformed purine bases and nucleosides through different salvage pathways. Three monophyletic sets of purine salvage enzymes, each of which catalyzes mechanistically similar reactions, can be identified: (a) adenine-, xanthine-, hypoxanthine- and guanine-phosphoribosyltransferases, which are all homologous among themselves, as well as to nucleoside phosphorylases; (b) adenine deaminase, adenosine deaminase, and adenosine monophophate deaminase; and (c) guanine reductase and inosine monophosphate dehydrogenase. These homologies support the idea that substrate specificity is the outcome of gene duplication, and that the purine nucleotide salvage pathways were assembled by a patchwork process that probably took place before the divergence of the three cell domains (Bacteria, Archaea, and Eucarya). Based on the ability of adenine PRTase to catalyze the condensation of PRPP with 4-aminoimidazole-5-carboxamide (AICA), a simpler scheme of purine nucleotide biosynthesis is presented. This hypothetical route requires the prior evolution of PRPP biosynthesis. Since it has been argued that PRPP, nucleosides, and nucleotides are susceptible to hydrolysis, they are very unlikely prebiotic compounds. If this is the case, it implies that many purine salvage pathways appeared only after the evolution of phosphorylated sugar biosynthetic pathways made ribosides available.

AMP Deaminase↗
PubMed1995

The influence of testosterone on purine nucleotide metabolism in rat liver.

Purine nucleotide metabolism was studied in rat liver by following the incorporation of 14C-formate into soluble nucleotides, uric acid and RNA ribonucleotides. After castration, GMP formation was less than that of AMP, and purine nucleotide catabolism and RNA synthesis decreased. Testosterone administration did not modify GMP or AMP synthesis, but restored purine nucleotide catabolism and RNA production to normal values. These results demonstrate the influence of testosterone on purine nucleotide metabolism in a non-reproductive organ.

Animals↗
PubMed1992

A defective purine nucleotide synthesis pathway in psoriatic patients.

Purine nucleotide concentrations in skin- and blood-cells of psoriatic patients are abnormal: The increase in the steady state level of cGMP and the decrease in the cAMP concentrations are associated with an enhanced rate of cellular proliferation. Concomitantly we found in the present study decreased ADP and ATP concentrations in blood cells (p less than 0.0001). The change in nucleotide concentrations suggests a defective purine nucleotide synthesis pathway. Stimulation of the Krebs cycle with fumaric acid raises ATP (p less than 0.0001) and most probably cAMP levels and at the same time slows down the purine nucleotide synthesis through end-product inhibition. Both effects can inhibit DNA and protein synthesis activity, which results in inhibition of cellular proliferation. Fumaric acid seems therefore a useful treatment for psoriatic lesions if liver and kidney functions (purine nucleotide and urea cycle) are controlled during treatment.

Adenosine Diphosphate↗
PubMed1990

Evidence for two separate vasoconstriction-mediating nucleotide receptors, both distinct from the P2x-receptor, in rabbit basilar artery: a receptor for pyrimidine nucleotides and a receptor for purine nucleotides.

Uridine 5'-triphosphate- (UTP-) and adenosine 5'-triphosphate- (ATP) induced vasoconstriction was studied in the rabbit basilar artery. The arteries were incubated and perfused at a constant rate of flow. Vasoconstriction was measured as an increase in perfusion pressure. Serotonin, histamine and noradrenaline caused concentration-dependent vasoconstriction, with potency decreasing in that order. Of the nucleotides tested, UTP, UDP, UMP, CTP, ATP, ADP, adenosine 5'-O-(3-thio)-triphosphate (ATP gamma S), and beta,gamma-imido adenosine 5'-triphosphate (AMP-PNP) elicited concentration-dependent vasoconstriction, whereas AMP, 2-methylthio-ATP, alpha,beta-methylene-ATP and beta,gamma-methylene-ATP up to 10(-3) mol/l caused no or only a very small increase in perfusion pressure. The order of potency of the pyrimidine nucleotides was: UTP = UDP much greater than UMP = CTP; that of the purine nucleotides was: ATP gamma S greater than AMP-PNP greater than ATP greater than ADP greater than 2-methylthio-ATP = alpha,beta-methylene-ATP = beta,gamma-methylene-ATP. The vasoconstrictor effects of UTP and ATP were not or only to a minor degree influenced by: phentolamine; a mixture of atropine, diphenhydramine and methysergide; indomethacin; nordihydroguaiaretic acid; denervation by 6-hydroxydopamine; or mechanical removal of endothelium. Prolonged exposure to alpha,beta-methylene-ATP elicited only a very small vasoconstriction and did not change the constrictor effects of UTP or ATP. Prolonged exposure to ATP gamma S elicited marked vasoconstriction; subsequently, responses to ATP were reduced whereas those to UTP were, if anything, slightly enhanced. Reactive blue 2 reduced neither the UTP- nor the ATP-induced vasoconstriction.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Regulation of purine synthesis de novo in human fibroblasts by purine nucleotides and phosphoribosylpyrophosphate.

Previous studies of purine nucleotide synthesis de novo have suggested that major regulation of the rate of the pathway is affected at either the phosphoribosylpyrophosphate (PP-Rib-P) synthetase reaction or the amidophosphoribosyltransferase (amido PRT) reaction, or both. We studied control of purine synthesis de novo in cultured normal, hypoxanthine-guanine phosphoribosyltransferase (HGPRT)-deficient, and PP-Rib-P synthetase-superactive human fibroblasts by measuring concentrations and rates of synthesis of PP-Rib-P and purine nucleotide end products, proposed effectors of regulation, during inhibition of the pathway. Incubation of cells for 90 min with 0.1 mM azaserine, a glutamine antagonist which specifically blocked the pathway at the level of conversion of formylglycinamide ribotide, resulted in a 5-16% decrease in purine nucleoside triphosphate concentrations but no consistent alteration in generation of PP-Rib-P. During this treatment, however, rates of the early steps of the pathway were increased slightly (9-15%) in normal and HGPRT-deficient strains, more markedly (32-60%) in cells with catalytically superactive PP-Rib-P synthetases, and not at all in fibroblasts with purine nucleotide feedback-resistant PP-Rib-P synthetases. In contrast, glutamine deprivation, which inhibited the pathway at the amido PRT reaction, resulted in time-dependent nucleoside triphosphate pool depletion (26-43% decrease at 24 h) accompanied by increased rates of PP-Rib-P generation and, upon readdition of glutamine, substantial increments in rates of purine synthesis de novo. Enhanced PP-Rib-P generation during glutamine deprivation was greatest in cells with regulatory defects in PP-Rib-P synthetase (2-fold), but purine synthesis in these cells was stimulated only 1.4-fold control rates by glutamine readdition. Stimulation of these processes in normal and HGPRT-deficient cells and in cells with PP-Rib-P synthetase catalytic defects was, respectively: 1.5 and 2.0-fold; 1.5 and 1.7-fold; and 1.6 and 4.1-fold. These studies support the following concepts. 1) Rates of purine synthesis de novo are regulated at both the PP-Rib-P synthetase and amido PRT reactions by end products, with the latter reaction more sensitive to small changes in purine nucleotide inhibitor concentrations. 2) PP-Rib-P exerts its role as a major regulator of purine synthetic rate by virtue of its interaction with nucleotide inhibitors to determine the activity of amido PRT. 3) Activation of amido PRT by PP-Rib-P is nearly maximal at base line in fibroblasts with regulatory defects in PP-Rib-P synthetase.

Azaserine↗
PubMed1978

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.

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 (1mug/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 1.3mumol/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.

Adenine Nucleotides↗