A (13)C isotopomer kinetic analysis of cardiac metabolism: influence of altered cytosolic redox and [Ca(2+)](o).
Rat hearts were perfused with mixtures of [3-(13)C]pyruvate and [3-(13)C]lactate (to alter cytosolic redox) at low (0.5 mM) or high (2.5 mM) Ca(2+) concentrations to alter contractility. Hearts were frozen at various times after exposure to these substrates, were extracted, and were then analyzed by (13)C NMR spectroscopy. The time-dependent multiplets observed in the (13)C NMR resonances of glutamate in all hearts and in malate and aspartate in hearts perfused with high-pyruvate/low-lactate concentrations were analyzed using a kinetic model of the tricarboxylic acid (TCA) cycle. The analysis showed that TCA cycle flux (V(TCA)) and exchange flux (V(X)) that involved cycle intermediates were both sensitive to cell redox and altered Ca(2+) concentration, and the ratio of these fluxes (V(X)/V(TCA)) varied >10-fold.
Carvalho
Rui A
RA
Department of Biochemistry, Faculty of Sciences and Technology, University of Coimbra, Coimbra, Portugal.
Rodrigues
Tiago B
TB
Zhao
Piyu
P
Jeffrey
F Mark H
FM
Malloy
Craig R
CR
Sherry
A Dean
AD
D000818:Animals; D001224:Aspartic Acid / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D002247:Carbon Isotopes; D002952:Citric Acid Cycle / Q000502:physiology; D003600:Cytosol / Q000378:metabolism*; D018698:Glutamic Acid / Q000378:metabolism; D006339:Heart Rate; D007700:Kinetics; D019344:Lactic Acid / Q000008:administration & dosage; D009682:Magnetic Resonance Spectroscopy; D008293:Malates / Q000378:metabolism; D008297:Male; D009206:Myocardium / Q000378:metabolism*; D009994:Osmolar Concentration; D010084:Oxidation-Reduction; D010101:Oxygen Consumption; D011312:Pressure; D019289:Pyruvic Acid / Q000008:administration & dosage; D051381:Rats; D017207:Rats, Sprague-Dawley; D016277:Ventricular Function, Left
D002247:Carbon Isotopes; D008293:Malates; D001224:Aspartic Acid; D019344:Lactic Acid; D018698:Glutamic Acid; C030298:malic acid; D019289:Pyruvic Acid; D002118:Calcium