Renal Excretion of Carbon Dioxide and Ammonia by the Alligator.)

Summary

The NH3 and C02 produced by the kidney in normal well hydrated alligators accounts for over 2/3 of the osmotic pressure of the urine. Since the volume of urine required to excrete the non-volatile cations and anions is normally low, NH₃ and CO₂ production by the kidney appears to have a diuretic function. In dehydration, NH₃ and CO₂ production decreases, but the quantity of extracellular electrolytes excreted remains essentially the same as in well hydrated animals. Ammonia and CO₂ also function in acid and base conservation. In inorganic anion excretion, CO₂ production is decreased, whereas in cation excretion NH₃ production is decreased. Due to the urine “osmolar ceiling” NH₃ and CO₂ are decreased to “make room” for any injected cations and anions. Hydration or the injection of non-osmotic diuretics appears to be the only stimulus to increased NH₃ and CO₂ production, the blood or urine pH playing no detectable part in this mechanism. Since the greatest amount of urinary NH₃ appears in well hydrated animals when the blood pH is normal and the urine pH is quite alkaline, NH₃ or NH₄ ⁺ appears to have little difficulty in diffusing into an alkaline urine.