AbstractThis paper describes an experimental protocol designed to optimize13C NMR spectra from the liver of the living anesthetized rat at 1.9 T. The protocol involves the use of a Helmholtz NMR coil which is positioned around the liver after surgical exposure.1H decoupling is facilitated by double tuning this coil to both the1H and the13C frequencies. The protocol was shown to be suitable for studying the hepatic metabolism of13C‐labeled substratesin vivoby investigating the metabolism of [3‐13C] alanine. Labeled glucose, glutamate, glutamine, and aspartate were formed and detected by13C NMRin vivoin this experiment. The labeling patterns in these metabolites provided evidence that the major flow of alanine carbon into the Krebs cycle is via the pyruvate carboxylase reaction rather than through pyruvate dehydrogenase. © 1986 Academic Press,