1. The measurement of the intestinal metabolism of the nitrogen moiety of glutamic acid has been investigated by oral ingestion of l-[15N]glutamic acid and sampling of arterialized blood.
2. Measurements have been made in six normal adults weighing an average of 72.8 kg ingesting 100 mg of l-[15N]glutamic acid after an overnight fast.
3. Measurement of the enrichment of arterial glutamic acid, glutamine and alanine was by gas chromatography–mass spectrometry. Isotopic enrichment of the amino acids was followed for 150 min after the ingestion of the amino acid.
4. Arterialized venous blood amino acid concentrations, measured by h.p.l.c., demonstrated no significant changes during the course of the experiment.
5. From the observed appearance of label in arterialized glutamic acid, alanine and glutamine, little luminal glutamic acid reaches the extracellular pool. The majority of the administered nitrogen label appears in the arterial alanine and glutamine components.