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

Abstract

The NH3 and CO2 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 nonvolatile 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 electro lytes 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 nonosmotic 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.