Skip to main content
SpringerLink
Log in

Metabolic Compartmentation in Cortical Synaptosomes: Influence of Glucose and Preferential Incorporation of Endogenous Glutamate into GABA

  • Published:
Neurochemical Research Aims and scope Submit manuscript

Abstract

Metabolism of glutamine was determined under a variety of conditions to study compartmentation in cortical synaptosomes. The combined intracellular and extracellular amounts of [U-13C]GABA, [U-13C]glutamate and [U-13C]glutamine were the same in synaptosomes incubated with [U-13C]glutamine in the presence and absence of glucose. However, the concentration of these amino acids was decreased in the latter group, demonstrating the requirement for glucose to maintain the size of neurotransmitter pools. In hypoglycemic synaptosomes more [U-13C]glutamine was converted to [U-13C]aspartate, and less glutamate was re-synthesized from the tricarboxylic acid (TCA) cycle, suggesting use of the partial TCA cycle from α-ketoglutarate to oxaloacetate for energy. Compartmentation was studied in synaptosomes incubated with glucose plus labeled and unlabeled glutamine and glutamate. Incubation with [U-13C]glutamine plus unlabeled glutamate gave rise to [U-13C]GABA but not labeled aspartate; however, incubation with [U-13C]glutamate plus unlabeled glutamine gave rise to [U-13C]aspartate, but not labeled GABA. Thus the endogenous glutamate formed via glutaminase in synaptic terminals is preferentially used for GABA synthesis, and is metabolized differently than glutamate taken up from the extracellular milieu.

This is a preview of subscription content, log in via an institution to check access.

Access this article

Log in via an institution

Price excludes VAT (USA)
Tax calculation will be finalised during checkout.

Instant access to the full article PDF.

Institutional subscriptions

Similar content being viewed by others

REFERENCES

  1. Battaglioli, G. and Martin, D. L. 1996. Glutamine stimulates gamma-aminobutyric acid synthesis in synaptosomes but other putative astrocyte-to-neuron shuttle substrates do not. Neurosci. Lett. 209:129–133.

    Google Scholar 

  2. Westergaard, N., Sonnewald, U., Petersen, S. B., and Schousboe, A. 1995. Glutamate and glutamine metabolism in cultured GABAergic neurons studied by 13C NMR spectroscopy may indicate compartmentation and mitochondrial heterogeneity. Neurosci. Lett. 185:24–28.

    Google Scholar 

  3. McKenna, M. C., Tildon, J. T., Stevenson, J. H., Jr., Boatright, R., and Huang, S. 1993. Regulation of energy metabolism in synaptic terminals and cultured rat brain astrocytes: Differences revealed using aminooxyacetate. Develop. Neurosci. 15:320–329.

    Google Scholar 

  4. Johnson, J. L. and Roberts, E. 1984. Proline, glutamate and glutamine metabolism in mouse brain synaptosomes. Brain Res. 323:247–256.

    Google Scholar 

  5. Erecinska, M., Zaleska, M. M., Nissim, I., Nelson, D., Dagani, F., and Yudkoff, M. 1988. Glucose and synaptosomal glutamate metabolism: studies with [15N]glutamate. J. Neurochem. 51:892–902.

    Google Scholar 

  6. Yudkoff, M., Zaleska, M. M., Nissim, I., Nelson, D., and Erecinska, M. 1989. Neuronal glutamine utilization: pathways of nitrogen transfer studied with [15N]glutamine. J. Neurochem. 53:632–640.

    Google Scholar 

  7. Yudkoff, M., Nelson, D., Daikhin, Y., and Erecinska, M. 1994. Tricarboxylic acid cycle in rat brain synaptosomes. Fluxes and interactions with aspartate aminotransferase and malate/aspartate shuttle. J. Biol. Chem. 269:27414–27420.

    Google Scholar 

  8. Fitzpatrick, S. M., Hetherington, H. P., Behar, K. L., and Shulman, R. G. 1990. The flux from glucose to glutamate in the rat brain in vivo as determined by 1H-observed, 13C-edited NMR spectroscopy. J. Cereb. Blood Flow Metab. 10:170–179.

    Google Scholar 

  9. Gruetter, R., Seaquist, E. R., Kim, S., and Ugurbil, K. 1998. Localized in vivo 13C-NMR of glutamate metabolism in the human brain: initial results at 4 tesla. Dev. Neurosci. 20:380–388.

    Google Scholar 

  10. McKenna, M. C., Tildon, J. T., Stevenson, J. H., and Hopkins, I. B. 1994. Energy metabolism in cortical synaptic terminals from weanling and mature rat brain: Evidence for multiple compartments of tricarboxylic acid (TCA) cycle activity. Develop. Neurosci. 16:291–300.

    Google Scholar 

  11. Shurr, A., West, C. A., and Rigor, B. M. 1988. Lactate supported synaptic function in rat hippocampal slice preparation. Science 240:1326–1328.

    Google Scholar 

  12. Waagepetersen, H. S., Bakken, I. J., Larsson, O. M., Sonnewald, U., and Schousboe, A. 1998. Comparison of lactate and glucose metabolism in cultured neocortical neurons and astrocytes using 13C-NMR spectroscopy. Dev. Neurosci. 20:310–320.

    Google Scholar 

  13. Ransom, B. R. and Fern, R. 1997. Does astrocytic glycogen benefit axon function and survival in CNS white matter during glucose deprivation? Glia 21:134–141.

    Google Scholar 

  14. Gundersen, V., Fonnum, F., Ottersen, O. P., and Storm-Mathisen, J. 2001. Redistribution of neuroactive amino acids in hippocampus and striatum during hypoglycemia: a quantitative immunogold study. J. Cereb. Blood Flow Metab. 21:41–51.

    Google Scholar 

  15. Kauppinen, R. A. and Nicholls, D. G. 1986. Synaptosomal bioenergetics. The role of glycolysis, pyruvate oxidation and responses to hypoglycaemia. Eur. J. Biochem. 158:159–165.

    Google Scholar 

  16. Petroff, O. A., Burlina, A. P., Black, J., and Prichard, J. W. 1991. Metabolism of [1–13C]glucose in a synaptosomally enriched fraction of rat cerebrum studied by 1H/13C magnetic resonance spectroscopy. Neurochem. Res. 16:1245–1251.

    Google Scholar 

  17. Lai, J. C. and Clark, J. B. 1976. Preparation and properties of mitochondria derived from synaptosomes. Biochem. J. 154:423–432.

    Google Scholar 

  18. Smith, P. K., Khron, R. I., Hermanson, G. T., Mallia, A. K., Artner, F. H., Provenzano, M. D., Fujimoto, E. K., Goeke, N. M., Olson, B. J., and Klenck, D. C. 1985. Measurement of protein using bicinchoninic acid. Anal. Biochem. 150:76–85.

    Google Scholar 

  19. Geddes, J. W. and Wood, J. D. 1984. Changes in the amino acid content of nerve endings (synaptosomes) induced by drugs that alter the metabolism of glutamate and 4–aminobutyric acid. J. Neurochem. 42:16–24.

    Google Scholar 

  20. Snedecor, G. W. and Cochran, W. G. 1967. Statistical Methods, 6th edit., Iowa State University Press, Ames.

    Google Scholar 

  21. Kvamme, E., Torgner, I. A., and Svenneby, G. 1985. Glutaminase from mammalian tissues. Methods Enzymol. 113:241–256.

    Google Scholar 

  22. McKenna, M. C., Stevenson, J. H., Huang, X., Tildon, J. T., Zielke, C. L., and Hopkins, I. B. 2000. Mitochondrial malic enzyme activity is much higher in mitochondria from cortical synaptic terminals compared with mitochondria from primary cultures of cortical neurons or cerebellar granule cells. Neurochem. Int. 36:451–459.

    Google Scholar 

  23. Engelsen, B. and Fonnum, F. 1983. Effects of hypoglycemia on the transmitter pool and the metabolic pool of glutamate in rat brain. Neurosci. Lett. 42:317–322.

    Google Scholar 

  24. Akasu, T., Tsurusaki, M., and Shoji, S. 1996. Depletion of glucose causes presynaptic inhibition of neuronal transmission in the rat dorsolateral septal nucleus. Synapse 24:125–134.

    Google Scholar 

  25. McKenna, M. C., Tildon, J. T., Stevenson, J. H., Hopkins, I. B., Huang, X., and Couto, R. 1998. Lactate transport by cortical synaptosomes from adult rat brain: Characterization of kinetics and inhibitor specificity. Develop. Neurosci. 20:300–309.

    Google Scholar 

  26. Wender, R., Brown, A. M., Fern, R., Swanson, R. A., Farrell, K., and Ransom, B. R. 2000. Astrocytic glycogen influences axon function and survival during glucose deprivation in central white matter. J. Neurosci. 20:6804–6810.

    Google Scholar 

  27. Hertz, L., Peng, L., Westergaard, N., Yudkoff, M., and Schousboe, A. 1991. Neuronal-astrocytic interactions in metabolism of transmitter amino acids of the glutamate family. Pages 30–48, in Schousboe, A., Diemer, N. H., and Kofod, H. (eds.), Drug research related to neuroactive amino acids. Munksgaard, Copenhagen, DK.

    Google Scholar 

  28. Bakken, I. J., White, L. R., Unsgard, G., Aasly, J., and Sonnewald, U. 1998. [U-13C]glutamate metabolism in astrocytes during hypoglycemia and hypoxia. J. Neurosci. Res. 51:636–645.

    Google Scholar 

  29. McKenna, M. C., Stevenson, J. H., Huang, X., and Hopkins, I. B. 2000. Differential distribution of the enzymes glutamate dehydrogenase and aspartate aminotransferase in cortical synaptic mitochondria contributes to metabolic compartmentation in cortical synaptic terminals. Neurochem. Int. 37:229–241.

    Google Scholar 

  30. Palaiologos, G., Hertz, L., and Schousboe, A. 1989. Role of aspartate aminotransferase and mitochondrial dicarboxylate transport for release of endogenously and exogenously supplied neurotransmitter in glutamatergic neurons. Neurochem. Res. 14:359–366.

    Google Scholar 

  31. Madl, J. E. and Royer, S. M. 1999. Glutamate in synaptic terminals is reduced by lack of glucose but not hypoxia in rat hippocampal slices. Neuroscience 94:417–430.

    Google Scholar 

  32. Waagepetersen, H. S., Sonnewald, U., Larsson, O. M., and Schousboe, A. 2000. A possible role of alanine for ammonia transfer between astrocytes and glutamatergic neurons. J. Neurochem. 75:471–479.

    Google Scholar 

  33. Zwingmann, C., Richter-Landsberg, C., Brand, A., and Leibfritz, D. 2000. NMR spectroscopic study on the metabolic fate of [3–13C]alanine in astrocytes, neurons, and cultures: implications for glia-neuron interactions in neurotransmitter metabolism. Glia 32:286–303.

    Google Scholar 

  34. Berl, S. and Clarke, D. D. 1969. Metabolic compartmentalization of glutamate in the CNS. Vol 1, pages 447–472, in Lajtha, A. (editor), Handbook of Neurochemistry, Plenum Press, New York.

    Google Scholar 

  35. Norenberg, M. D. and Martinez-Hernandez, A. 1979. Fine structural localization of glutamine synthetase in astrocytes of rat brain. Brain Res. 161:303–310.

    Google Scholar 

  36. Sonnewald, U., Westergaard, N., Petersen, S. B., Unsgård, G., and Schousboe, A. 1993. Metabolism of [U-13C]glutamate in astrocytes studied by 13C NMR spectroscopy: Incorporation of more label into lactate than into glutamine demonstrates the importance of the TCA cycle. J. Neurochem. 61:1179–1182.

    Google Scholar 

  37. Sonnewald, U., Hertz, L., and Schousboe, A. 1998. Mitochondrial heterogeneity in the brain at the cellular level. J. Cereb. Blood Flow Metab. 18:231–237.

    Google Scholar 

  38. Qu, H., Færø, E., Jørgensen, P., Dale, O., Gisvold, S. E., Unsgård, G., and Sonnewald, U. 1999. Decreased glutamate metabolism in cultured astrocytes in the presence of thiopental. Biochem. Pharmacol. 58:1075–1080.

    Google Scholar 

  39. Choi, I. Y., Tkac, I., Ugurbil, K., and Gruetter, R. 1999. Noninvasive measurements of [1–13C]glycogen concentrations and metabolism in rat brain in vivo. J. Neurochem. 73:1300–1308.

    Google Scholar 

  40. Brand, M. D. and Chappell, J. B. 1974. Glutamate and aspartate transport in rat brain mitochondria. Biochem. J. 140:205–210.

    Google Scholar 

  41. Martin, D. L. and Rimvall, K. 1993. Regulation of gamma-aminobutyric acid synthesis in the brain. J. Neurochem. 60:395–407.

    Google Scholar 

  42. Waagepetersen, H. S., Sonnewald, U., Gegelashvili, G., Larsson, O. M., and Schousboe, A. 2001. Metabolic distinction between vesicular and cytosolic GABA in cultured GABAergic neurons using 13C magnetic resonance spectroscopy. J. Neurosci. Res. 63:347–355.

    Google Scholar 

Download references

Author information

Authors and Affiliations

  1. Department of Clinical Neuroscience, Medical Faculty, Norwegian University of Science and Technology (NTNU), Trondheim, Norway

    Ursula Sonnewald

  2. Department of Pediatrics, University of Maryland School of Medicine, Baltimore, Maryland

    Mary McKenna

Authors
  1. Ursula Sonnewald
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. Mary McKenna
    View author publications

    You can also search for this author in PubMed Google Scholar

Rights and permissions

Reprints and permissions

About this article

Cite this article

Sonnewald, U., McKenna, M. Metabolic Compartmentation in Cortical Synaptosomes: Influence of Glucose and Preferential Incorporation of Endogenous Glutamate into GABA. Neurochem Res 27, 43–50 (2002). https://doi.org/10.1023/A:1014846404492

Download citation

  • Issue Date:

  • DOI: https://doi.org/10.1023/A:1014846404492

Search

Navigation