Effect of ranitidine bismuth citrate on the phospholipase A(2) activity ofNaja naja venom and Helicobacter pylori: a biochemical analysis

Background: Helicobacter pylori has become recognized as a fundamental path ogen in the development of gastritis and peptic ulcer disease, Bismuth comp ounds in combination with antibiotics are widely used to treat H. pylori as sociated peptic ulcer disease. Methods: In this study we measured and analysed the inhibitory effect of ra nitidine bismuth citrate (RBC, Pylorid, Tritec) on the activity and kinetic s of phospholipase A(2) (PLA(2)) (E.C.3.1.1.4) of commercial cobra (Naja na ja) venom and H. pylori (French press lysates) using L-alpha-dipalmitoyl-(2 [1-C-14]palmitoyl)-phosphatidylcholine as substrate, Results: Our data suggest that RBC might exert a dose-dependent uncompetiti ve inhibition on PLA(2) activity of both H. pylori and Naja naja venom. the inhibitory effect of RBC on the PLA(2) activity cannot be abolished by the optimal concentration of calcium (10 mM), indicating its mechanism to be u nrelated to the displacement of calcium from the activation site of the enz yme. Conclusion: Our results suggest that one of the mechanisms by which bismuth compounds are therapeutically effective in the treatment of H. pylori asso ciated gastritis is by inhibiting the activity of the degradative PLA(2) en zyme secreted by H. pylori, As a consequence of the inhibitory action of RB C on PLA(2) of the bacteria, the extracellular and/or intracellular phospho lipid components of the gastric mucosal barrier are preserved.