The Metabolism of Parenterally Administered Amino Acids

Studies previously reported (l-3)) involving the constant intravenous infusion of a number of amino acids, singly and in combination, have permitted the authors to obtain data concerning a number of physiological and biochemical phenomena associated with amino acid metabolism. The present report deals with the effect of amino acid infusion upon the renal excretion of ammonia. In this phase of metabolism, as in others previously reported, it has been found that the infusion of the dicarboxylic amino acids, glutamic and aspartic acids, and their amides, glutamine and asparagine, have yielded the data of greatest potential interest. Present concepts of the mechanism of ammonia formation by the kidney are based primarily upon two observations: those of Van Slyke and his associates (4), who found a renal arteriovenous drop in plasma glutamine and amino acid concentration associated with formation of ammonia by the kidney, and those of Lotspeich and Pitts (5), who found an increase in urinary ammonia excretion during the infusion of a number of amino acids to acidotic dogs. Thus, it is generally believed that, under conditions of acidosis, about two-thirds of urinary ammonia is derived from plasma glutamine and the other third from plasma amino acids.