Effect of Hypophysectomy on Ammonia Response in Acidosis

Abstract

In NH4Cl acidosis in the dog ammonia output rises rapidly, reaching its maximum within 2 or 3 hours. This response is not impaired after hypophysectomy. Na output also rises rapidly and begins to fall in about 3 hrs. while ammonia output remains high. There is also a large rise in K output; this lags somewhat behind the Na rise and is sustained longer. Chloride output also rises sharply, ammonia, Na and K being largely balanced by chloride. The responses are not changed by hypophysectomy. When initial (preacidotic) urine pH is high, rising ammonia output usually goes along with falling urine pH, but when initial pH is low, ammonia output can rise greatly in acidosis with little or no fall in pH. After passing its peak, ammonia output may begin to fall while urine pH is still falling. When initial urine pH is high, urine titratable acid rises from zero or very low values as acidosis develops, but if initial pH is low, great rises in ammonia output can occur with little or no rise in titratable acid. In the dog without buffer loading, excretion of titratable acid is low even in acidosis, usually falling between 0.04 and 0.08 mEq./kg./hour and never rising above 0.1 mEq./kg./hour. No difference was observed between normal and hypophysectomized dogs in the urine pH and titratable acid responses to acidosis.