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Abstract #2256

Direct Assessment of Increased Pyruvate Carboxylase in the Hyperammonemic Brain using 13C MRS

Bernard Lanz1, Cristina Cudalbu1, Joo Miguel Duarte1, Rolf Gruetter1,2

1Laboratory for Functional & Metabolic Imaging, Ecole Polytechnique Fdrale de Lausanne, Lausanne, Switzerland; 2Department of Radiology, Universities of Lausanne & Geneva, Lausanne & Geneva, Switzerland

Dynamic 13C MRS using [1,6-13C2] glucose allows non-invasive measurement of the neuroglial metabolism in vivo. In this study, we coupled [1,6-13C2] glucose with ammonium chloride infusion in rats in order to assess the effect of hyperammonemia on neuronal metabolism. While total glutamine was linearly increasing, the glutamine 13C enrichment curves were nevertheless reaching a dynamic steady-state in about 4 hours. From the fractional enrichment at steady-state of GluC4, GlnC4, GluC3 and GlnC3, we conclude that neuronal metabolism is hardly effected by hyperammonemia, while the glial pyruvate carboxylase activity increases significantly, as visible on the strongly diluted GlnC3.