University of Texas System

Piyu Zhao

A Dean Sherry

Craig R Malloy

Entry of .sup.13 C-enriched acetyl-CoA into the citric acid cycle results in scrambling of .sup.13 C into the various carbon positions of all intermediate pools. The eventual result is that the .sup.13 C resonances of all detectable intermediates or molecules exchanging with those intermediates appear as multiplets due to nearest neighbor spin-spin couplings. Isotopomer analysis of the glutamate .sup.13 C multiplets provides a history of .sup.13 C flow through the cycle pools. Relative substrate utilization and relative anaplerotic flux can be quantitated. A major limitation of the method for in vivo applications is spectral resolution of multi-line resonances required for a complete isotopomer analysis. It is now shown that (.sup.13 C)homonuclear decoupling of the glutamate C3 resonance collapses nine-line C4 and C2 resonances into three line multiplets. These three-line .sup.13 C multiplets are well resolved in isolated, perfused rat hearts and present steady-state equations which allow an isotopomer analysis from data obtained in intact tissue. This advancement shows for the first time that .sup.13 C isotopomer methods may be extended to complex metabolic conditions for resolution of carbon-carbon coupling, and particularly to in vivo measurements.

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Dallas, TX, United States of America

Piyu Zhao