Nitrogen metabolism in the ovine stomach: 3. Urea in the abomasal secretions

Abstract

SUMMARY The effects of various stimuli on the secretion of urea and ammonia in gastric juice were examined in sheep with innervated pouches in the fundic and pyloric regions of the abomasum. Histamine, pentagastrin and feeding increased the rate of secretion and acidity of fundic juice, but had little or no effect on the concentration of urea and ammonia. The increased output of gastric juice meant that more urea and ammonia entered the abomasum in the secretions. The rate of secretion of pyloric juice was also increased by histamine and feeding, and there was an indication that histamine increased the concentration of urea + ammonia in the secretions after a period of starvation. Intravenous injections of urea increased the concentration of ammonia in abomasal liquor. This was due in part to higher levels of ammonia in ruminal liquor passing to the abomasum, and to higher concentrations of urea + ammonia in gastric juice. The concentration of urea + ammonia in fundic juice was 45·0±1·1% of the plasma urea level, and 60·4±1·5% in the pyloric secretions.