Glial glutamine release and neuronal reuptake by SAT1 studied in vivo by N-15 NMR and microdialysis
Kanamori K, Ross B
Huntington Medical Research Institutes
Kinetics and mechanism of transport of glutamine from glia to the neuron in vivo - a key step in the glutamine/glutamate cycle - are unknown. The time-course of extracellular glutamine (GLN) and its N-15 enrichment was determined, in the presence and absence of transport inhibitors, by a combination of N-15 NMR and microdialysis/gradient heteronuclear single-quantum correlation NMR. The rate of glial glutamine release to the extracellular fluid (ECF) was 2.8 micromol/g/h in mildly hyperammonemic rat brain at steady-state brain glutamine concentration of 8.5 micromol/g. Transporter SAT1 mediates at least 85% of neuronal uptake of extracellular GLN.