GLUCOSE-METABOLISM IN THE DEVELOPING CEREBRAL-CORTEX AS DETECTED BY H-1(C-13) NUCLEAR-MAGNETIC-RESONANCE SPECTROSCOPY EX-VIVO

Metabolism of [1-C-13]glucose was monitored in superfused cerebral cor tex slice preparations from 1-, 2-, and 5-week-old rats using H-1-obse rved/C-13-edited (H-1{C-13}) NMR spectroscopy. The rate of label incor poration into glutamate C-4 did not differ among the three age groups: 0.52-0.67% of total H-1 NMR-detected glutamate/min. This was rather u nexpected, as oxygen uptake proceeded at 1.1 +/- 0.1, 1.9 +/- 0.1, and 2.0 +/- 0.1 mu mol/ min/g wet weight in brain slices prepared from 1- , 2-, and 5-week-old animals, respectively. Steady-state glutamate C-4 fractional enrichments in the slice preparations were similar to 23% in all age groups. In the acid extracts of slices glutamate C-4 enrich ments were smaller, however, in 1- and 2-week-old (17.8 +/- 1.7 and 16 .8 +/- 0.8%, respectively) than in 5-week-old rats (22.7 +/- 0.7%) aft er 75 min of incubation with 5 mM [1-C-13]glucose. We add a new assign ment to the H-1{C-13}. NMR spectroscopy, as acetate C-2 was detected i n slice preparations from 5-week-old animals. In the acid extracts of slice preparations acetate C-2 was labeled by similar to 30% in 5-week -old rats but by 15% in both 1- and 2-week-old animals, showing that t he turnover rate was increased in 5-week-old animals. In the extracts 3-4% of the C-6 of N-acetylaspartate (NAA; CH, of the acety[ group) co ntained label as determined by both NMR and mass spectrometry, which i ndicated that there was no significant labeling to other carbons in NA A. NAA accumulated label from [1-C-13]glucose but not from [2-C-13]ace tate, and the rate of label incorporation increased by threefold on ce rebral maturation.