In vivo dynamic turnover of cerebral 13C isotopomers from [U-13C]glucose.
An INEPT-based (13)C MRS method and a cost-effective and widely available 11.7 Tesla 89-mm bore vertical magnet were used to detect dynamic (13)C isotopomer turnover from intravenously infused [U-(13)C]glucose in a 211 microL voxel located in the adult rat brain. The INEPT-based (1)H-->(13)C polarization transfer method is mostly adiabatic and therefore minimizes signal loss due to B(1) inhomogeneity of the surface coils used. High quality and reproducible data were acquired as a result of combined use of outer volume suppression, ISIS, and the single-shot three-dimensional localization scheme built in the INEPT pulse sequence. Isotopomer patterns of both glutamate C4 at 34.00 ppm and glutamine C4 at 31.38 ppm are dominated first by a doublet originated from labeling at C4 and C5 but not at C3 (with (1)J(C4C5) = 51 Hz) and then by a quartet originated from labeling at C3, C4, and C5 (with (1)J(C3C4) = 35 Hz). A lag in the transition of glutamine C4 pattern from doublet-dominance to quartet dominance as compared to glutamate C4 was observed, which provides an independent verification of the precursor-product relationship between neuronal glutamate and glial glutamine and a significant intercompartmental cerebral glutamate-glutamine cycle between neurons and glial cells.
Xu
Su
S
Molecular Imaging Branch, National Institute of Mental Health, Bethesda, MD 20892, USA.
Shen
Jun
J
D000818:Animals; D001921:Brain / Q000378:metabolism*; D002247:Carbon Isotopes / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism*; D005973:Glutamine / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy / Q000295:instrumentation / Q000379:methods*; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D015203:Reproducibility of Results
D002247:Carbon Isotopes; D005973:Glutamine; D005947:Glucose