Normal conscious dogs were given 100 mmol glycine, L‐serine, L‐alanine, L‐threonine, L‐proline, L‐glutamic acid (50 mmol), L‐aspartic acid and L‐valine by stomach tube. All these amino acids increased glomerular filtration rate (G.F.R.). There was no increase in G.F.R. following L‐cystine or D‐serine. The intravenous infusion of L‐proline, but not glycine, caused increase in G.F.R. The results suggest that the increase in G.F.R. was not due to a high plasma concentration of the individual amino acids but was related to the metabolism of amino acids with production of urea. It is postulated that after meat and during the metabolism of amino acids a factor is released which reaches and acts on the kidney to cause the increase in G.F.R.

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 large 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.