Urinary Excretion of Amino Acids Following the Rapid Injection of a Solution of Amino Acids in Man 12

Abstract

The parenteral administration of partial and complete protein hydrolysates is accompanied by an appreciable excretion of the infused amino acids and polypeptides in the urine (1-5). The renal loss of amino nitrogen following parenteral administration may be as great as 28 times the loss from the administration of an equivalent amount of nitrogen as whole protein orally (6). If, in addition to such urinary losses, one or more of the essential amino acids were present in "limiting" amounts or were preferentially excreted, the amount of a protein just capable of maintaining nitrogen equilibrium when given orally might be insufficient when given intravenously as a hydrolysate (6).The experiments reported here were undertaken to determine the extent of the renal loss of amino acids after their intravenous infusion. Determinations were made of the renal excretion of the eight amino acids essential for man (7) and of arginine and histidine, the urinary excretion of alpha amino nitrogen, and the blood alpha amino nitrogen following the intravenous administration to normal subjects of a 10 per cent solution of amino acids. The results indicate that the administration of protein or amino acids orally or intravenously, slowly or rapidly, and in large or small quantity is followed by the excretion in the urine of but a small portion of that administered. MATERIALS AND METHODSThe amino acid mixture 3 was made by the complete acid hydrolysis of casein, contains no peptides, is essen1The expenses of this investigation were defrayed in part by a grant from Merck and Company, Inc., Rahway, New Jersey, to Harvard University.

Improvement of Active Liver Cirrhosis in Patients Maintained With Amino Acids Intravenously as the Source of Protein and Lipotropic Substances 12

“…The present study presents further evidence that parenterally administered amino acids are excreted in patients with severe liver disease in a manner differing little from normal. The loss of alpha amino nitrogen in the urine by the patients with liver disease (Table V) was similar to that observed in a previous study in normals following infusions of equivalent quantities of the same hydrolysate (35 (Table IV).…”

“…The observation that patients with severe liver disease excreted fairly large percentages of administered threonine and histidine and smaller percentages of the other amino acids following infusions of the amino acid solution is further evidence that amino acid excretion in liver disease is normal, since these amino acids were similarly excreted following amino acid infusions in normal subjects (35). Furthermore, the post-infusion pattern of the "essential" amino acids excreted in the urine of the patients with cirrhosis was similar to that in normals, although the individual amino acids were not excreted in the same proportion as administered in either group (Table VI, Figure 5).…”

“…The excretion pattern following the larger (100 gram) infusions in the patients with liver disease more closely resembled the pattern of the solution given than that following the 50 gram infusions. It was previously observed in normals that the amino acid pattern following rapid infusions of the amino acid solution more closely resembled the pattern of the amino acids given than that following infusions given more slowly (35). Thus, the administration of amino acids intravenously slowly and in small quantity is followed by excretion in the urine of but minimal amounts of amino acids in a pattern differing from the pattern of the amino acids given, while the infusion of amino acids rapidly and in large amounts results in a greater excretion loss of alpha amino nitrogen and of individual amino acids in a proportion quite similar' to that in the solution administered.…”

“…Thus, the administration of amino acids intravenously slowly and in small quantity is followed by excretion in the urine of but minimal amounts of amino acids in a pattern differing from the pattern of the amino acids given, while the infusion of amino acids rapidly and in large amounts results in a greater excretion loss of alpha amino nitrogen and of individual amino acids in a proportion quite similar' to that in the solution administered. As discussed previously (35), an interpretation of these observations is not possible until further data relating to renal clearance studies in man are available. Nevertheless, the similarity in the renal excretion of amino acids by normals and by patients with liver disease is apparent.…”

Renal Clearance of Eighteen Individual Amino Acids in Human Subjects 1

“…Earlier work in this laboratory, as well as that of other investigators, has shown that histidine ( 17,18,(24)(25)(26) and glycine ( 17,18,26) are among those amino acids normally excreted in the largest amounts. It also should be mentioned that Eckhardt and Davidson found a proportionately larger excretion of threonine and histidine following intravenous infusion of the same amino acid solution used in this study than of any other of the amino acids studied (25).…”