Source and function of urinary ammonia in the alligator

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Abstract
The rate of renal deamination of 18 amino acids was determined by injecting them into alligators and measuring the ammonia excreted. Not only did glycine, alanine, glutamine and leucine account for nearly half of the plasma amino acids, they were also deaminated more rapidly than any of the others. In view of this it was concluded that these four amino acids are the natural precursors of urinary NH3 in the alligator. Increased NH3 and CO2 excretion following glycine injections resulted in increased renal reabsorption of Na and Cl when NaCl was injected and increased Na reabsorption when NaHCO3 or Na phosphate solutions were injected. The fact that excess NH4HCO3 excretion enhances salt reabsorption independent of plasma pH makes it probable that the excretion of N is the chief function of the ammonia mechanism and that salt conservation is incidental. Insulin decreased the plasma amino acid level and drastically reduced the NH3 excretion. With the decrease in ammonia, NaCl and NaHCO3 were excreted in increased amounts.

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