Cristina Cudalbu1, Bernard Lanz1, Florence D. Morgenthaler1, Yves Pilloud1, Vladimir Mlynrik1, Rolf Gruetter1,2
1Laboratory for Functional and Metabolic Imaging (LIFMET), Ecole Polytechnique Fdrale de Lausanne (EPFL), Lausanne, Switzerland; 2Departments of Radiology, Universities of Lausanne and Geneva, Switzerland
A complementary approach to 13C MRS for studying glutamate and glutamine metabolism is 15N MRS during infusion of 15N labeled ammonia. The goal of this study was to use in vivo localized 15N MRS interleaved with in vivo 1H MRS to measure the glutamine synthesis rate under ammonia infusion in the rat brain. We obtained a net synthesis flux of 0.0210.006mol/min/g. By fitting the in vivo 5-15N Gln time course the apparent glutamine synthesis rate and the plasma FE of NH3 were 0.290.1mol/min/g and 716%, respectively. Finally, the apparent neurotransmission rate was 0.260.1mol/min/g.
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