Anant Bahadur Patel1, Henk De Feyter2, Douglas L. Rothman2, Kevin L. Behar3, Puneet Bagga1
1NMR Microimaging and Spectroscopy, Centre for Cellular and Molecular Biology, Hyderabad, Andhra Pradesh, India; 2Diagnostic Radiolgy, Magnetic Resonance Research Center, Yale University, New Haven, CT, United States; 3Psychiatry, , Magnetic Resonance Research Center, Yale University, New Haven, CT, United States
The steady state 13C enrichment of cortical glutamine (Gln) during intravenous infusion of [1-13C]/[1,6-13C2]glucose is ~25-30% lower than the corresponding glutamate enrichment. The source of this Gln dilution is unknown. The contribution of plasma Gln to the cortical Gln dilution was assessed in anesthetized mice after intravenous [U-13C5]glutamine infusion. Cortical Gln 13C enrichment increased with time while total cortical metabolite levels were unaltered over a range of plasma Gln. The steady state labeling of cortical Gln-C4 appeared to be independent of plasma glutamine level. Basal plasma Gln could account for ~30-35% of glutamine dilution.