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The Metabolism of [3‐ 13 C]Lactate in the Rat Brain Is Specific of a Pyruvate Carboxylase‐Deprived Compartment
Author(s) -
Bouzier AnneKarine,
Thiaudiere Eric,
Biran Marc,
Rouland Richard,
Canioni Paul,
Merle Michel
Publication year - 2000
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1046/j.1471-4159.2000.0750480.x
Subject(s) - gluconeogenesis , metabolism , lactic acid , glutamine , pyruvate carboxylase , carbohydrate metabolism , biochemistry , compartment (ship) , chemistry , pyruvic acid , glycogen , in vivo , alanine , medicine , endocrinology , phosphocreatine , biology , amino acid , enzyme , energy metabolism , bacteria , oceanography , microbiology and biotechnology , genetics , geology
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‐ 13 C]lactate (534 m M ) or both glucose (750 m M ) and [3‐ 13 C]lactate (534 m M ). The time courses of both the concentration and 13 C enrichment of blood glucose and lactate were determined. The data indicated the occurrence of [3‐ 13 C]lactate 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 13 C‐ and 1 H‐observed/ 13 C‐edited NMR spectroscopy. The 13 C labeling of amino acids indicated that [3‐ 13 C]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‐ 13 C]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.