Glucose metabolism in the developing cerebral cortex as detected by 1H(13C) nuclear magnetic resonance spectroscopy ex vivo.

Metabolism of [1-13C]glucose was monitored in superfused cerebral cortex slice preparations from 1-, 2-, and 5-week-old rats using 1H-observed/13C-edited (1H(13C)) NMR spectroscopy. The rate of label incorporation into glutamate C-4 did not differ among the three age groups: 0.52-0.67% of total 1H NMR-detected glutamate/min. This was rather unexpected, as oxygen uptake proceeded at 1.1 +/- 0.1, 1.9 +/- 0.1, and 2.0 +/- 0.1 mumol/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 approximately 23% in all age groups. In the acid extracts of slices glutamate C-4 enrichments 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%) after 75 min of incubation with 5 mM [1-13C]glucose. We add a new assignment to the 1H(13C) NMR spectroscopy, as acetate C-2 was detected in slice preparations from 5-week-old animals. In the acid extracts of slice preparations acetate C-2 was labeled by approximately 30% in 5-week-old rats but by 15% in both 1- and 2-week-old animals, showing that the turnover rate was increased in 5-week-old animals. In the extracts 3-4% of the C-6 of N-acetyl-aspartate (NAA; CH3 of the acetyl group) contained label as determined by both NMR and mass spectrometry, which indicated that there was no significant labeling to other carbons in NAA.(ABSTRACT TRUNCATED AT 250 WORDS)