C6 cells were used to establish a
glioma-bearing rat model by stereotaxic injection in the left caudate nucleus. The
tumor status was evaluated by magnetic resonance imaging and conventional histology. The
glioma-bearing rats were infused for 1 h with a [1-(13)C]
glucose solution.
Perchloric acid extracts of the
tumor and the ipsilateral and contralateral hemispheres were analyzed by 13C-NMR spectroscopy. The 13C-labeling patterns in compounds, mainly
amino acids, indicated no drastic modification of
carbon metabolism in both ipsilateral and contralateral hemispheres, as compared with control rats, whereas profound metabolic differences between brain tissue and
tumor were observed.
Glutamine C4 enrichment was lower in the
glioma than in the brain [mean +/- SD values, 5.4 +/- 2.3 (n = 5) and 15.0 +/- 0.8% (n = 10), respectively] and also lower than the
glutamate C4 enrichment in the
glioma (mean +/- SD value, 22.6 +/- 4.2%; n = 5), indicating that
tumor glutamine was neither synthesized inside the
glioma nor taken up from the surrounding brain. The
glutamine C4 enrichment in the serum (6.7 +/- 0.5%; n = 10) suggested that the
glioma imported
glutamine from the blood, a process probably connected with angiogenesis.