Amino nitrogen metabolism following administration of individual amino acids or meat in conscious dogs.

Normal conscious dogs were given a meal of meat or doses of individual amino acids by stomach tube. The concentration of amino nitrogen in systemic arterial plasma and the rate of urea production both increased; the magnitude and time course of these increases varied with the individual amino acid administered. There was a relationship between the plasma amino nitrogen concentration and urea production following L-serine, L-alanine, L-proline. dicarboxylic acids and L-cystine similar to that obtained after meat ingestion. It is suggested that these amino acids were transaminated as rapidly as they were absorbed to produce an increase in a general pool of amino acids. Following L-threonine, L-valine, D-serine and immediately after glycine, a small increase in urea production was accompanied by a larger increase in plasma amino nitrogen concentration. It is suggested that these amino acids 'escaped' transamination in the gut wall and liver and that the increase in plasma amino nitrogen was due to a high concentration of the individual amino acid administered.