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Identification of metabolic fluxes in hepatic cells from transient 13 C‐labeling experiments: Part I. Experimental observations
Author(s) -
Hofmann Ute,
Maier Klaus,
Niebel Anja,
Vacun Gabriele,
Reuss Matthias,
Mauch Klaus
Publication year - 2007
Publication title -
biotechnology and bioengineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.136
H-Index - 189
eISSN - 1097-0290
pISSN - 0006-3592
DOI - 10.1002/bit.21747
Subject(s) - isotopomers , metabolite , intracellular , chemistry , biochemistry , metabolism , citric acid cycle , pentose phosphate pathway , metabolic pathway , glycolysis , metabolic flux analysis , extracellular , metabolic intermediate , tricarboxylic acid , chromatography , organic chemistry , molecule
An experimental set‐up for acquiring metabolite and transient 13 C‐labeling data in mammalian cells is presented. An efficient sampling procedure was established for hepatic cells cultured in six‐well plates as a monolayer attached to collagen, which allowed simultaneous quenching of metabolism and extraction of the intracellular intermediates of interest. Extracellular concentrations of glucose, amino acids, lactate, pyruvate, and urea were determined by GC–MS procedures and were used for estimation of metabolic uptake and excretion rates. Sensitive LC–MS and GC–MS methods were used to quantify the intracellular intermediates of tricarboxylic acid cycle, glycolysis, and pentose phosphate pathway and for the determination of isotopomer fractions of the respective metabolites. Mass isotopomer fractions were determined in a transient 13 C‐labeling experiment using 13 C‐labeled glucose as substrate. The absolute amounts of intracellular metabolites were obtained from a non‐labeled experiment carried out in exactly the same way as the 13 C‐labeling experiment, except that the media contained naturally labeled glucose only. Estimation of intracellular metabolic fluxes from the presented data is addressed in part II of this contribution. Biotechnol. Bioeng. 2008;100: 344–354. © 2007 Wiley Periodicals, Inc.