IN-VIVO INVESTIGATION OF GLUTAMATE-GLUTAMINE METABOLISM IN HYPERAMMONEMIC MONKEY BRAIN USING C-13-MAGNETIC RESONANCE SPECTROSCOPY

To investigate the metabolism of glutamate and glutamine in living mon key brain, a system of in vivo C-13 magnetic resonance spectroscopy (M RS) using H-1-decoupled C-13 spectroscopy combined with monitoring tem perature changes in the brain by MR phase mapping was developed. Seria l C-13-NMR spectra of the amino acids glutamate and glutamine were acq uired non-invasively over 4 h from anesthetized monkey brain after the intravenous administration of [1-C-13]glucose (0.5-1.0 g/kg). In the acute hyperammonemic state induced by the administration of ammonium a cetate (77 mg/kg bolus), it was observed that C-13 incorporation into glutamine-4 was clearly accelerated, without changes of C-13 incorpora tion into glutamate-4. During hyperammonemia, it was shown directly by [2-C-13]glucose administration that the anaplerotic pathway for the T CA cycle was also augmented, contributing to the formation of glutamin e in the astroglia.