Journal
JOURNAL OF NEUROCHEMISTRY
Volume 75, Issue 2, Pages 480-486Publisher
LIPPINCOTT WILLIAMS & WILKINS
DOI: 10.1046/j.1471-4159.2000.0750480.x
Keywords
C-13-NMR; lactate; brain metabolism; neurons; astrocytes
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Lactate metabolism in the adult rat brain was investigated in relation with the concept of lactate trafficking between astrocytes and neurons. Wistar rats were infused intravenously with a solution containing either [3-C-13]lactate (534 mM) or both glucose (750 mM) and [3-C-13]lactate (534 mM). The time courses of both the concentration and C-13 enrichment of blood glucose and lactate were determined. The data indicated the occurrence of [3-C-13]actate recycling through liver gluconeogenesis. The yield of glucose labeling was, however, reduced when using the glucose-containing infusate. After a 20-min or 1-h infusion, perchloric acid extracts of the brain tissue were prepared and subsequently analyzed by C-13- and H-1-observed/C-13-edited NMR spectroscopy. The C-13 labeling of amino acids indicated that [3-C-13]lactate was metabolized in the brain. Based on the alanine C3 enrichment, lactate contribution to brain metabolism amounted to 35% under the most favorable conditions used. By contrast with what happens with [1-C-13]glucose metabolism, no difference in glutamine C2 and C3 labeling was evidenced, indicating that lactate was metabolized in a compartment deprived of pyruvate carboxylase activity. This result confirms, for the first time from an in vivo study, that lactate is more specifically a neuronal substrate.
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