The role of gastric urease in acid secretion

Abstract

The avg. urea content of frog gastric mucosa was found to be 0.039[mu] mol./mg. dry wt. (8.3 m[image], wet wt.). In whole mouse stomach the avg. concn. was 0.015[mu] mol./mg. dry wt. (3.2 m[image], wet wt.). Urea (2, 10 or 20 m[image]) did not affect the rates of respiration or acid secretion of isolated frog gastric mucosae. The urease activity of ground samples of frog gastric mucosa was low and variable; only 8 of 37 samples possessed activity. Active urease prepns. were obtained from all mouse stomachs examined. No urease activity occurred in the gastric mucosa of 30 intact frogs. The incubation media or secretions of resting or acid-secreting tied bags of mucosa contained no detectable quantities of ammonia, either in the presence or absence of urea. Added urea was recovered quantitatively, thus any acid-neutralizing role of urease in these expts. is excluded. The amts. of acid secreted by isolated frog gastric mucosa or whole mouse stomach in absence of added urea were more than 30 times the urea content of the tissue. Urea and urease play no direct or catalytic role in the mechanism of acid secretion for there is no evidence that urea is synthesized by gastric mucosa.