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- Title
<sup>15</sup>N-NMR Spectroscopy Studies of Ammonia Transport and Glutamine Synthesis in the Hyperammonemic Rat Brain.
- Authors
Shen, Jun; Sibson, Nicola R.; Cline, Gary; Behar, Kevin L.; Rothman, Douglas L.; Shulman, Robert G.
- Abstract
Ammonia transport and glutamine synthesis were studied in the hyperammonaemic rat brain in vivo using 15N-NMR spectroscopy at a plasma ammonia level of approximately 0.39 mM raised via an intravenous [15N]-ammonium acetate infusion. The initial slope of the time course of the summed cerebral 15N-labelled metabolites was used to determine the rate of ammonia net transport during hyperammonemia as 0.13 ± 0.02 µmol/min/g (mean ± SD; n = 5). Based on the total accumulation of glutamine and the 1:2 stoichiometric relationship between fluxes of four-carbon skeletons and nitrogen atoms, the rate of de novo glutamine synthesis through anaplerosis and subsequent glutamate dehydrogenase action was calculated to be 0.065 ± 0.01 µmol/min/g. The rate of total glutamine synthesis was estimated to be 0.20 ± 0.06 µmol/min/g (n = 5) by fitting the [5-15N]glutamine time course to a previously described model of glutamate-glutamine cycling between astrocytes and neurones. A large dilution was also observed in [2-15N]glutamine, which supports the glutamate-glutamine cycle as being an important pathway for neuronal glutamate repletion in vivo.
- Publication
Developmental Neuroscience, 1998, Vol 20, Issue 4/5, p434
- ISSN
0378-5866
- Publication type
Article
- DOI
10.1159/000017341