The metabolism of [3-(13)C]lactate in the rat brain is specific of a pyruvate carboxylase-deprived compartment.
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 mM) or both glucose (750 mM) and [3-(13)C]lactate (534 mM). 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.
Bouzier
A K
AK
Laboratoire de Résonance Magnétique des Systèmes Biologiques, UMR 5536, Centre National de la Recherche Scientifique-Université Victor Segalen, Bordeaux, France.
Thiaudiere
E
E
Biran
M
M
Rouland
R
R
Canioni
P
P
Merle
M
M
D000818:Animals; D001253:Astrocytes / Q000378:metabolism*; D001786:Blood Glucose / Q000378:metabolism; D001921:Brain / Q000378:metabolism*; D002247:Carbon Isotopes; D005260:Female; D005943:Gluconeogenesis; D007700:Kinetics; D007773:Lactates / Q000097:blood / Q000378:metabolism*; D008099:Liver / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D009474:Neurons / Q000378:metabolism*; D011766:Pyruvate Carboxylase / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar
D001786:Blood Glucose; D002247:Carbon Isotopes; D007773:Lactates; D011766:Pyruvate Carboxylase