Activity of the lactate-alanine shuttle is independent of glutamate-glutamine cycle activity in cerebellar neuronal-astrocytic cultures
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Activity of the lactate-alanine shuttle is independent of glutamate-glutamine cycle activity in cerebellar neuronal-astrocytic cultures. / Bak, Lasse K; Sickmann, Helle M; Schousboe, Arne; Waagepetersen, Helle S.
In: Journal of Neuroscience Research, Vol. 79, No. 1-2, 04.12.2004, p. 88-96.Research output: Contribution to journal › Journal article › Research › peer-review
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T1 - Activity of the lactate-alanine shuttle is independent of glutamate-glutamine cycle activity in cerebellar neuronal-astrocytic cultures
AU - Bak, Lasse K
AU - Sickmann, Helle M
AU - Schousboe, Arne
AU - Waagepetersen, Helle S
N1 - (c) 2004 Wiley-Liss, Inc.
PY - 2004/12/4
Y1 - 2004/12/4
N2 - The glutamate-glutamine cycle describes the neuronal release of glutamate into the synaptic cleft, astrocytic uptake, and conversion into glutamine, followed by release for use as a neuronal glutamate precursor. This only explains the fate of the carbon atoms, however, and not that of the ammonia. Recently, a role for alanine has been proposed in transfer of ammonia between glutamatergic neurons and astrocytes, denoted the lactate-alanine shuttle (Waagepetersen et al. [ 2000] J. Neurochem. 75:471-479). The role of alanine in this context has been studied further using cerebellar neuronal cultures and corresponding neuronal-astrocytic cocultures. A superfusion paradigm was used to induce repetitively vesicular glutamate release by N-methyl-D-aspartate (NMDA) in the neurons, allowing the relative activity dependency of the lactate-alanine shuttle to be assessed. [(15)N]Alanine (0.2 mM), [2-(15)N]/[5-(15)N]glutamine (0.25 mM), and [(15)N]ammonia (0.3 mM) were used as precursors and cell extracts were analyzed by mass spectrometry. Labeling from [(15)N]alanine in glutamine, aspartate, and glutamate in cerebellar cocultures was independent of depolarization of the neurons. Employing glutamine with the amino group labeled ([2-(15)N]glutamine) as the precursor, an activity-dependent increase in the labeling of both glutamate and aspartate (but not alanine) was observed in the cerebellar neurons. When the amide group of glutamine was labeled ([5-(15)N]glutamine), no labeling could be detected in the analyzed metabolites. Altogether, the results of this study support the existence of the lactate-alanine shuttle and the associated glutamate-glutamine cycle. No direct coupling of the two shuttles was observed, however, and only the glutamate-glutamine cycle seemed activity dependent.
AB - The glutamate-glutamine cycle describes the neuronal release of glutamate into the synaptic cleft, astrocytic uptake, and conversion into glutamine, followed by release for use as a neuronal glutamate precursor. This only explains the fate of the carbon atoms, however, and not that of the ammonia. Recently, a role for alanine has been proposed in transfer of ammonia between glutamatergic neurons and astrocytes, denoted the lactate-alanine shuttle (Waagepetersen et al. [ 2000] J. Neurochem. 75:471-479). The role of alanine in this context has been studied further using cerebellar neuronal cultures and corresponding neuronal-astrocytic cocultures. A superfusion paradigm was used to induce repetitively vesicular glutamate release by N-methyl-D-aspartate (NMDA) in the neurons, allowing the relative activity dependency of the lactate-alanine shuttle to be assessed. [(15)N]Alanine (0.2 mM), [2-(15)N]/[5-(15)N]glutamine (0.25 mM), and [(15)N]ammonia (0.3 mM) were used as precursors and cell extracts were analyzed by mass spectrometry. Labeling from [(15)N]alanine in glutamine, aspartate, and glutamate in cerebellar cocultures was independent of depolarization of the neurons. Employing glutamine with the amino group labeled ([2-(15)N]glutamine) as the precursor, an activity-dependent increase in the labeling of both glutamate and aspartate (but not alanine) was observed in the cerebellar neurons. When the amide group of glutamine was labeled ([5-(15)N]glutamine), no labeling could be detected in the analyzed metabolites. Altogether, the results of this study support the existence of the lactate-alanine shuttle and the associated glutamate-glutamine cycle. No direct coupling of the two shuttles was observed, however, and only the glutamate-glutamine cycle seemed activity dependent.
KW - Alanine
KW - Amino Acids
KW - Ammonia
KW - Animals
KW - Animals, Newborn
KW - Astrocytes
KW - Cells, Cultured
KW - Cerebellum
KW - Chromatography, High Pressure Liquid
KW - Citric Acid Cycle
KW - Coculture Techniques
KW - Extracellular Space
KW - Gas Chromatography-Mass Spectrometry
KW - Glutamic Acid
KW - Glutamine
KW - Lactic Acid
KW - Mice
KW - Neurons
KW - Tritium
U2 - 10.1002/jnr.20319
DO - 10.1002/jnr.20319
M3 - Journal article
C2 - 15578733
VL - 79
SP - 88
EP - 96
JO - Journal of Neuroscience Research
JF - Journal of Neuroscience Research
SN - 0360-4012
IS - 1-2
ER -
ID: 152061162