Use of [2-14C]glucose and [5-14C]glucose for evaluating the mechanism and quantitative significance of the ‘liver-cell’ pentose cycle

Longenecker, John P.; Williams, John F.

doi:10.1042/bj1880847

Cited by 30 publications

(12 citation statements)

References 20 publications

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“…In all samples of liver cells from either control or hyperthyroid rats, the relative enrichment of label at C1 and C3 of glucose was approximately 2:l. This value measured in the whole respiring cell is exactly that predicted by the classic pentose cycle reaction scheme, which has evolved in large measure from the work of Horecker an his colleagues with the purified enzymes of this pathway. On the other hand, our 13C NMR measurements do not support the very different predictions of a new model proposed recently (26) for the operation of the pentose cycle in liver. In the oxidative segment of the pentose cycle pathway, hexose derived from glucose-6-P is decarboxylated, losing C1.…”

Section: Applications Of 13c Nmr Gluconeogenesis From Glycerol In Thecontrasting

confidence: 99%

Application of Nuclear Magnetic Resonance to the Study of Liver Physiology and Disease

Cohen

2007

Hepatology

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Technological advances in nuclear magnetic resonance (NMR) have occurred at a rapid pace in recent years. As a result of a series of significant innovations, NMR, which only a decade ago was considered to be largely a tool of the structural chemist, has assumed a place of growing importance as a noninvasive technique in biomedical research. As noted in previous reviews (1-4), it is now possible to make measurements on metabolites in intact cells, subcellular organelles, and isolated perfused organs and obtain the same sort of detailed information about structure, reaction rates, and binding sites that has been available from NMR studies of purified biomolecules in solution. Some phenomena, however, are observable only in the whole cell; these include intracellular pH, ApH across the plasma membrane, and ApH across the mitochondria1 membrane, which have all been measured in uiuo by phosphorus-31 ("P) NMR. The concentrations of phosphorylated metabolites, such as adenosine triphosphate (ATP) and inorganic phosphate (Pi), are measured simultaneously and repetitively; thus, their levels can be followed with time for correlation with changes in ApH or the onset of a period of ischemia or hypoxia. In the carbon-13 (13C) NMR experiments discussed here, in which 13C-enriched substrates are metabolized in isolated rat liver cells and perfused liver, signals from intermediates and endproducts are observed, and the distribution of the "C-label in these metabolites is used to elucidate pathways and kinetics. The NMR method has the advantage of simultaneously detecting all metabolites that have been adequately labeled. This property makes NMR especially useful in advancing our understanding of the complex responses of the cell to hormonal stimulation or to direct challenges from specific enzyme inhibitors. Since 13C and 31P nuclei frequently yield complementary data, the simultaneous observation of both 13C and 31P NMR spectra can supply a panoply of information on the regulation of metabolism in uiuo. In our latest study of hepatic metabolism (5) NMR studies of liver metabolism now include several 31P and 13C high-resolution NMR investigations of metabolism in respiring isolated rat liver cells (6-lo), isolated perfused mouse (9-12), and rat (5, 13) liver, and preliminary in uiuo 31P (14) and 13C (15) studies in rat liver.The most rapidly expanding medical application of NMR-clinical NMR imaging-will be mentioned only briefly because the instrumentation that NMR imaging methods require and the range of application of these methods differ greatly from those of the high-resolution NMR techniques which are the major focus of this review. Proton (lH)NMR imaging is currently being used to detect liver disease in humans (16-18) and in experimental animals (19,20). Before describing specific applications of NMR to liver physiology, it is useful to consider briefly the principles of the Fourier transform (FT) NMR technique, concentrating on the properties to be mentioned later; full, but quite readable, introductions to FT-NMR have ...

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Section: Applications Of 13c Nmr Gluconeogenesis From Glycerol In Thecontrasting

confidence: 99%

Application of Nuclear Magnetic Resonance to the Study of Liver Physiology and Disease

Cohen

2007

Hepatology

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“…It is difficult to conceive of a pathway, however, where such a loss would occur. The proposed L-type non-oxidative pathway does not provide a mechanism for separate loss of C-S and C-6 [18].…”

Section: Discussionmentioning

confidence: 84%

Measurement of pentose phosphate-pathway activity in a single incubation with [1,6-13C2,6,6-2H2]glucose

Ross

Kingsley

Ben-Yoseph

1994

Biochemical Journal

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The isotopically substituted molecule D-[1,6-13C2,6,6-2H2]glucose is introduced for measuring the relative activities of the pentose phosphate pathway (PPP) and glycolysis in a single incubation. PPP activity in cultured cells was determined by gas chromatography/mass spectrometric analysis of lactate produced by cells incubated with [1,6-13C2,6,6-2H2]glucose. Two other isotopes, [1,5,6-13C3]glucose and [6-13C,1,6,6-2H3]glucose, were not satisfactory for measurements of this activity. This method has four advantages over the traditional one in which 14CO2 production from [1-14C]glucose and [6-14C]glucose is compared: (1) repeated measurements can be made on a single set of cells, (2) only a single incubation is required, (3) extensive CO2 production by Krebs-cycle activity does not interfere with the measurements and (4) it is not necessary to measure the amount of glucose consumed in order to calculate relative activities of the PPP and glycolysis. Preliminary observation indicates that rat brain PPP activity may be measured in vivo with [1,6-13C2,6,6-2H2]glucose when combined with microdialysis techniques.

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“…where rH25 is the ratio C-2/C-5 (Longenecker & Williams, 1980). The C-2/C-5 ratio is (17.7-1.3)/ 70.8, or 0.23, and the resulting value of PC is 30%.…”

Section: Resultsmentioning

confidence: 99%

“…Recent work has shown that the reaction sequence for the non-oxidative segment of the pentose pathway is more extensive and complex than that of the classical pathway (Williams et al, 1978). Theoretical expressions for estimating the contribution of the L-type pentose cycle to the metabolism of glucose have been derived [see the preceding paper (Longenecker & Williams, 1980)]. In practice these methods involve the application of [5-"4C]and 2-"4Clglucose to the test tissue.…”

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confidence: 99%

Quantitative measurement of the L-type pentose phosphate cycle with [2-14C]glucose and [5-14C]glucose in isolated hepatocytes

Longenecker¹,

Williams²

1980

Biochemical Journal

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1. Investigations of the mechanism of the non-oxidative segment of the pentose phosphate cycle in isolatd hepatocytes by prediction-labelling studies following the metabolism of [2-14C]-, [5-14C]- and [4,5,6-14C]glucose are reported. The 14C distribution patterns in glucose 6-phosphate show that the reactions of the L-type pentose pathway in hepatocytes. 2. Estimates of the quantitative contribution of the L-type pentose cycle are the exclusive form of the pentose cycle to glucose metabolism have been made. The contribution of the L-type pentose cycle to the metabolism of glucose lies between 22 and 30% in isolated hepatocytes. 3. The distribution of 14C in the carbon atoms of glucose 6-phosphate following the metabolism of [4,5,6-14C]- and [2-14C]glucose indicate that gluconeogenesis from triose phosphate and non-oxidative formation of pentose 5-phosphate do not contribute significantly to randomization of 14C in isolated hepatocytes. The transaldolase exchange reaction between fructose 6-phosphate and glyceraldehyde 3-phosphate is very active in these cells.

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Use of [2-14C]glucose and [5-14C]glucose for evaluating the mechanism and quantitative significance of the ‘liver-cell’ pentose cycle

Cited by 30 publications

References 20 publications

Application of Nuclear Magnetic Resonance to the Study of Liver Physiology and Disease

Application of Nuclear Magnetic Resonance to the Study of Liver Physiology and Disease

Measurement of pentose phosphate-pathway activity in a single incubation with [1,6-13C2,6,6-2H2]glucose

Quantitative measurement of the L-type pentose phosphate cycle with [2-14C]glucose and [5-14C]glucose in isolated hepatocytes

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