TCA cycle kinetics in the rat heart by analysis of (13)C isotopomers using indirect (1)H.
This study was designed to test the hypothesis that indirect (1)H[(13)C] detection of tricarboxylic acid (TCA) cycle intermediates using heteronuclear multiple quantum correlation-total correlation spectroscopy (HMQC-TOCSY) nuclear magnetic resonance (NMR) spectroscopy provides additional (13)C isotopomer information that better describes the kinetic exchanges that occur between intracellular compartments than direct (13)C NMR detection. NMR data were collected on extracts of rat hearts perfused at various times with combinations of [2-(13)C]acetate, propionate, the transaminase inhibitor aminooxyacetate, and (13)C multiplet areas derived from spectra of tissue glutamate were fit to a standard kinetic model of the TCA cycle. Although the two NMR methods detect different populations of (13)C isotopomers, similar values were found for TCA cycle and exchange fluxes by analyzing the two data sets. Perfusion of hearts with unlabeled propionate in addition to [2-(13)C]acetate resulted in an increase in the pool size of all four-carbon TCA cycle intermediates. This allowed the addition of isotopomer data from aspartate and malate in addition to the more abundant glutamate. This study illustrates that metabolic inhibitors can provide new insights into metabolic transport processes in intact tissues.
Carvalho
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RA
Mary Nell and Ralph B. Rogers Magnetic Resonance Center, Department of Radiology, University of Texas Southwestern Medical Center, Dallas 75390-9085, USA.
Zhao
P
P
Wiegers
C B
CB
Jeffrey
F M
FM
Malloy
C R
CR
Sherry
A D
AD
D019342:Acetic Acid / Q000378:metabolism / Q000493:pharmacokinetics; D000625:Aminooxyacetic Acid / Q000494:pharmacology; D000818:Animals; D001224:Aspartic Acid / Q000378:metabolism; D002247:Carbon Isotopes / Q000032:analysis; D002952:Citric Acid Cycle / Q000502:physiology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D018698:Glutamic Acid / Q000378:metabolism; D006321:Heart / Q000187:drug effects; D066298:In Vitro Techniques; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008293:Malates / Q000378:metabolism; D008954:Models, Biological; D009206:Myocardium / Q000378:metabolism*; D010477:Perfusion; D011422:Propionates / Q000378:metabolism / Q000493:pharmacokinetics; D051381:Rats; D000637:Transaminases / Q000037:antagonists & inhibitors
D002247:Carbon Isotopes; D004791:Enzyme Inhibitors; D008293:Malates; D011422:Propionates; D000625:Aminooxyacetic Acid; D001224:Aspartic Acid; D018698:Glutamic Acid; C030298:malic acid; D000637:Transaminases; C029658:propionic acid; D019342:Acetic Acid