URINARY EXCRETION OF AMINO ACIDS FOLLOWING THE RAPID INJECTION OF A SOLUTION OF AMINO ACIDS IN MAN 12

Open Access
Publisher Website
Google Scholar
Abstract
The avg. excretion of the 10 "essential" amino acids (microbiological assay) by 8 nor-mal subjects eating ad libitum was: arginine 9.5; histidine 163; isoleucine 13.8; leucine 7.2; lysine 46.8; methionine 4.4; phenyla-lanine 14; threonine 20.9; tryptophane 12.7; and valine 7.4 mg./24 hrs. Approx. 0.4% of the alpha amino N ingested in the diets was excreted in the urine. A complete acid hydrolysate of casein, devoid of glutamic and aspartic acids and supplemented with DL-tryptophane and glycine, was then admd. the subjects intraven. in amts. of 500 ml. of the 10% soln. at a slow, moderate, and rapid rate. There was an avg. loss from excretion into the urine of 1 to 16% of the individual amino acids infused, 4.3% of the total 10 "essential" amino acids injd., and 9.5% of the amino N admd. The increased excretion of both amino N and individual amino acids was completed within 4 hrs. after the infusion by which time the elevated blood amino N had returned to within normal limits. The "essential" amino acids in the infusion mixture were preferentially retained by the subjects while the dispensable amino acids were more freely excreted in the urine. The greatest retention of the "essential" amino acids was observed at the slowest rate of infusion. The individual amino acids were not excreted in the urine in the same proportion as admd., so that fairly large percentages of admd. threonine and histidine were excreted, intermediate percentages of lysine and tryptophane, and smaller percentages of the other amino acids. With each increase in the rate of the infusion, however, the additional excretion of all the "essential" amino acids more closely resembled the composition of the amino acids infused. The admn. of protein or amino acids orally or intraven., slowly or rapidly, and in large or small quantity is followed by excretion in the urine of but a small portion of the amino acids given so that the body retains for metabolic purposes most of that admd.