The role of gastric urease in acid secretion.

The experiments described in this paper were undertaken to throw light on the possible role of gastric urease in the secretion of hydrochloric acid by the stomach. Mathews (1925) first suggested thatgastric hydrochloric acid might be produced by the reaction NJEI4Cl-NH3+HCl, and Luck (1924) showed that ammonia can be formed from urea by suspensions of ground dog gastric mucosa. Rigoni (1930), Martin (1932), Cardin (1933), Mann & Mann (1939), and Martinson (1950), all suggested that ammonium ions, derived from the enzymic hydrolysis of urea, form hydrogen ions according to the hypothesis of Mathews (1925). Histochemical investigations by Linderstr0mLang & Ohlsen (1936) on dog mucosa, and Glick (1949a), on human stomachs, showed that the urease is localized in the oxyntic-cell region of the stomach. Glick (1949a) wrote 'the intensity of the (urease) activity appeared to be proportional to the acid-secretory response elicited by histamine', and put forward a tentative scheme for the formation of hydrochloric acid from the enzymic decomposition of urea. Luck & Seth (1925) first suggested that a possible function of the urease is to protect the mucosa from attack by acid. All these hypotheses are based on qualitative evidence. In the present work quantitative data bearing on the hypotheses were obtained by comparing in vitro the rates of urea breakdown, ammonia production, respiration, and acid secretion, of isolated frog gastric mucosae. These experiments, and measurements ofthe urea content offrog gastric mucosae and mouse stomachs, show that gastric urease plays no direct role in the mechanism of acid secretion. Any neutralization of acid in our experiments is also excluded. Part of this work has been communicated to the Biochemical Society (Davies & Kornberg, 1950a).