PROFOUND INCREASE OF HELICOBACTER-PYLORI UREASE ACTIVITY IN GASTRIC ANTRAL MUCOSA AT LOW PH

The effect of pH on H. pylori urease activity in its ecological niche was studied in gastric antral biopsy specimens. Specimens were incubat ed in 10 mmol/liter urea solutions at pH range 3.3-8.2, Activity of ur ease was studied by measuring production of ammonia and change in pH o f the solutions. Urease activity was reduced at pH 8.2 (1424 +/- 218 m u mol/liter) but decreasing initial pH to neutral and acidic values re sulted in significant maximal 6.5-fold increase in ammonia production (9491 +/- 1073 mu mol/liter, P < 0.0005), which considerably raised th e pH of the test solutions, Peak urease activity was between pH 5.0 an d 7.0, In contrast to specimens incubated initially at pH 8.0, reincub ation of washed specimens from solutions with initial pH 7.0 showed ei ghtfold decreased urease activity, It is concluded that urease activit y is markedly pH dependent with pH optima below the physiological muco sal surface pH, Furthermore, availability of urease is limited. Thus, an impaired gastric mucosal integrity allowing back diffusion of hydro gen ions may release urease activity, which might further weaken the m ucus barrier and damage the gastric epithelium.