Relation of renal amino and amide nitrogen extraction to ammonia production

¹ Department of Physiology, Cornell University Medical College, New York City

In a series of ten experiments on dogs, net renal extraction of free amino acids and amides was compared with total renal production of ammonia. In acidosis, net extraction of amino and amide nitrogen accounts for 95% of ammonia production. In acute metabolic alkalosis, 80% of ammonia production can be so explained. However, in acute alkalosis superimposed on mild chronic alkalosis, only 11% of ammonia production can be related to amino and amide nitrogen extraction. These results suggest that in acidosis a steady state exists in which moment-to-moment extraction of amino acids and amides accounts for ammonia production. However, in acute alkalosis and especially in acute alkalosis superimposed on chronic alkalosis, nitrogen extraction is reduced disproportionately to ammonia production. For short periods of time intracellular stores of amino acids and amides can be utilized as precursors of ammonia. In confirmation of results of Van Slyke and colleagues (J. Biol. Chem. 150: 481, 1943) we have observed that glutamine is the major precursor of ammonia.