[Cytotoxic effect of ammonia produced by Helicobacter pylori urease on the cultural cells].

We investigated the action of the ammonia produced by Helicobacter pylori urease on the cultured cells. The urease was purified from supernatant fluid of sonicated cell of H. pylori cultured on blood agar for 2 days at 37 degrees C under microaerophilic condition. Purification was carried out by DEAE-Sepharose chromatography, Phenyl-Sepharose chromatography, Sephacryl S-200 SF chromatography and fast protein liquid chromatography on Mono-Q. Vero, HeLa and Intestin 407 cells with or without the addition of 30 mM urea were exposed to the purified urease. Those cells showed cytotoxic effects within 80 minutes after addition of purified urease in the presence of urea. The ammonia production was observed on tissue culture medium within 10 minutes, and the ammonia concentration ranged from 5.56 mg/ml to 7.3 mg/ml and pH in the medium was over pH 9.0. No such effect was observed on the cells exposed to urease without urea. Ammonia water added to Vero cells showed the same cytotoxic effect within 70 minutes on the production of ammonia and raised the pH. However, when the cells were exposed to the ammonia water pre-neutralized to a given pH 7-8 using 1 N HCl cytotoxic effect was not observed. It was concluded that the cytotoxic effect of H. pylori urease was dependent on ammonia generated by hydrolysis of urea.