Micropuncture study of ammonia excretion in the rat

Abstract

Ammonia has been determined in blood and in samples of tubular fluid obtained by micropuncture at various sites along the nephron from two groups of rats, one untreated and the other pretreated with ammonium chloride. Ammonia has been found in tubular fluid from all segments of the nephron, the concentrations being generally higher in those animals which were pretreated with ammonium chloride. In addition, there is a tendency for the concentration of ammonia to increase as the site of micropuncture progresses along the nephron. In the proximal tubule, concentrations of ammonia have been found which are greater than can be accounted for solely by the extraction of water in this segment. This is taken to indicate tubular addition of ammonia at this site. Since the increments of ammonia along the nephron generally exceed that which could be due to water reabsorption, it is concluded that all parts of the nephron contribute to urinary ammonia excretion.