Abstract
Plasma levels, urinary excretions and renal clearances of free amino acids were measured in 11 normal adults, 3 normal olds and 57 patients with renal and metabolic disorders using paper or gas chromatographical analysis. Hypoaminoacidemia was observed in old subjects. Hyperaminoacidemia was found in patients with diabetes mellitus (valine, leucine and isoleucine), hyperparathyroidism (almost all amino acids) and gout (glutamic acid, glutamine, glycine and tyrosine). In cases with glomerulonephritis or nephrotic syndorome whose renal function was moderately disordered, renal clearances of glutamic ocid, threonine, serine, lysine or throsine were elevated, while in cases with uremia, renal clearances of almost all amino acids were conversely decreased. Increased renal clearances of amino acids were seen in cases with renal tubular acidosis (glutamic acid, glutamine and lysine) and Prader-Willi syndorome (glutamic acid and alanine). The patients with Fanconi syndorome, Willson's disease (almost all amino acids) and cystinuria (cystine, lysine, arginine and ornitine) showed extremely high values of renal amino acid clearance. In order to elucidate the transport mechanism of neutral amino acid in tubular cells, amino acid solution (alanine, threonine, serine, proline and glycine) was each injected intravenously to normal subjects and patients with renal disease, and plasma levels and renal clearances of amino acids were compared before and after infusion. The amount of amino acid infused was 0.65 mmole/kg of each according to Scriver's method. The ratio of elevation of both plasma level and renal clearance of infused amino acid in these experiments were generally higher in cases with glomerulonephritis and nephrotic syndrome than in normal adults; this is probably due to differences of glomerular filtration rate and utilization of injected amino acid between two groups. Proline and glycine were found to compete each other in the transport system of renal tubular cells, but alanine, threonine and serine were not; this may reflect that latter amino acids have greater tubular maximal reabsorption rates.
