SELECTIVE, IN-VIVO OBSERVATION OF [5-N-15]GLUTAMINE AMIDE PROTONS IN RAT-BRAIN BY H-1-N-15 HETERONUCLEAR MULTIPLE-QUANTUM-COHERENCE TRANSFER NMR

The amide protons of [5-N-15]glutamine were selectively observed in vivo in the brains of anesthetized, spontaneously breathing rats after intravenous (NH4+)-N-15 infusion by H-1-N-15 heteronuclear multiple-quantum-coherence (HMQC) transfer NMR at 200 MHz for H-1, The peak intensity of the upheld amide proton was proportional to brain [5-N-15] glut amine concentration, The N-15-decoupled amide-proton signal was observed in vivo in 2 min of acquisition at a brain [5-N-15] glutamine concentration of 7.7 +/- 0.4 mu mol/g, in <8 min at 4.35 +/- 0.15 mu mol/g, and in 17-34 min at 2.0 +/- 0.1 mu mol/g, H-1 signals not coupled to N-15 were suppressed by phase cycling, The result suggests that H-1-N-15 HMQC will be useful for kinetic study of glutamine synthesis in rat brain in vivo at physiological concentrations of brain ammonia. (C) 1995 Academic Press, Inc.