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Abstract #3297

Fast 13C Label Exchange Between Mitochondria and Cytosol in Brain Revealed by Saturation Transfer Spectroscopy

Jehoon Yang1,2, Su Xu1, Jun Shen3

1NIMH, USA; 2Samsung Biomedical Research Institute, Korea; 3NIMH, Bethesda, MD, USA

13C MRS has been applied to studying brain metabolism by measuring 13C label incorporation into cytosolic pools. The rate of 13C label exchange between mitochondria and cytosolic glutamate and aspartate (Vx) has been controversial. Because brain fumarase is exclusively located in the mitochondria it is possible to directly measure Vx from the four-carbon side of the tricarboxylic acid cycle (TCA) by saturation transfer. In rat brain a 13C saturation transfer effect on aspartate C2 was detected after extensive signal averaging with fumarate C2 irradiated using radiofrequency pulses. Quantitative analysis found that Vx >> the TCA cycle rate.