Ontogeny and Cellular Localization of the Pyruvate Recycling System in Rat Brain

• Published in: Journal of neurochemistry 1998-06, Vol.70 (6), p.2613-2619
• Main Authors: Cruz, Fátima, Scott, Steve R., Barroso, Isabel, Santisteban, Pilar, Cerdán, Sebastián
• Format: Article
• Language: English
• Subjects: 13C NMR; Animals; Animals, Newborn; Astrocytes - enzymology; Biochemistry and metabolism; Biological and medical sciences; Brain - enzymology; Brain - growth & development; Brain - metabolism; Brain - ultrastructure; Brain development; Brain gene expression; Cells, Cultured; Central nervous system; Cerebral pyruvate recycling; Fundamental and applied biological sciences. Psychology; Magnetic Resonance Spectroscopy; Malate Dehydrogenase - biosynthesis; Malate Dehydrogenase - metabolism; Malate Dehydrogenase - ultrastructure; Malic enzyme; Neurons - enzymology; Organ Specificity; Phosphoenolpyruvate carboxykinase; Phosphoenolpyruvate Carboxykinase (GTP) - biosynthesis; Phosphoenolpyruvate Carboxykinase (GTP) - metabolism; Phosphoenolpyruvate Carboxykinase (GTP) - ultrastructure; Pyruvic Acid - metabolism; Rats; Rats, Wistar; Synaptosomes - enzymology; Tumor Cells, Cultured; Vertebrates: nervous system and sense organs
• ISSN: 0022-3042; 1471-4159
• DOI: 10.1046/j.1471-4159.1998.70062613.x

: The ontogeny of the cerebral pyruvate recycling pathway and the cellular localization of associated enzymes, malic enzyme (ME) and phosphoenolpyruvate carboxykinase (PEPCK), have been investigated using a combination of 13C NMR spectroscopy, enzymatic analysis, and molecular biology approaches. Activity of the pathway, using [1,2‐13C2]acetate as a substrate, was detected by 13C NMR in brain extracts 3 weeks after birth, increasing progressively up to the third month of age. In whole‐brain homogenates, ME activity increased to adult levels with the same time course as the recycling pathway. PEPCK activity was low during the first 2 weeks of life and decreased further toward adulthood. ME and PEPCK activity were found in primary cultures of astrocytes and in synaptosomal fractions of adult brain. Primary cultures of cortical neurons showed PEPCK activity but no detectable ME activity. The cytosolic ME gene was expressed in primary cultures of neurons and in astrocytes as well as in the neonatal and adult brain. The PEPCK gene was expressed both in primary cultures of cortical neurons and in astrocytes, but the level of its expression in the neonatal and adult brain was undetectable.