title: 13C NMR spectroscopy study of cortical nerve cell cultures exposed to hypoxia.
abstract: Primary cultures of cerebral cortical GABA-ergic neurons growing on top of a preformed layer of astrocytes (co-cultures) were incubated with [1-13C]glucose and exposed to a low oxygen atmosphere (2% O2) for 17 hr. 13C, 1H, and 31P nuclear magnetic resonance (NMR) spectroscopy was performed on perchloric acid (PCA) extracts of cells and of media collected from these cultures. In the control groups incorporation of 13C label into glutamine, citrate, and lactate could be demonstrated in both cell extracts and culture media. Labeled GABA and glutamate were only observed in cell extracts. During hypoxia high energy phosphates decreased but lactate production and glucose consumption increased. There was a decreased amount of citrate and glutamine in cell extracts and media of the hypoxic co-cultures. There was a change in distribution of the 13C label within the GABA molecule, with an increase of labeling in the C-2 position. This change in 13C distribution was not found in glutamine present in the media where it is a precursor for GABA in neurons. Instead a decrease in the corresponding C-4 position was observed. These results suggest that energy depletion during hypoxia leads to reduced export from the astrocytic tricarboxylic acid (TCA) cycle as demonstrated by a decreased amount of citrate and changed distribution of 13C in glutamine. The change in the distribution of label in GABA from cell extracts as compared to glutamine in the medium may indicate that neurons are synthesizing GABA using precursors supplied from their own TCA cycle and not from precursors supplied by astrocytes.
authors.affiliation: Department of Neurosurgery, University Hospital of Trondheim, Norway.
authors.forename: T B
authors.initials: TB
authors.lastname: Müller
authors.forename: U
authors.initials: U
authors.lastname: Sonnewald
authors.forename: N
authors.initials: N
authors.lastname: Westergaard
authors.forename: A
authors.initials: A
authors.lastname: Schousboe
authors.forename: S B
authors.initials: SB
authors.lastname: Petersen
authors.forename: G
authors.initials: G
authors.lastname: Unsgård
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000737:chemistry* / Q000166:cytology; D002952:Citric Acid Cycle / Q000502:physiology; D003470:Culture Media; D018698:Glutamic Acid / Q000378:metabolism; D006019:Glycolysis; D002534:Hypoxia, Brain / Q000378:metabolism*; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy; D051379:Mice; D009474:Neurons / Q000378:metabolism; D018377:Neurotransmitter Agents / Q000096:biosynthesis; D005680:gamma-Aminobutyric Acid / Q000378:metabolism / Q000502:physiology
chemical_list: D003470:Culture Media; D018377:Neurotransmitter Agents; D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid; D007770:L-Lactate Dehydrogenase