Use of a modified N-nitrosoproline test to show intragastric nitrosation in patients at risk of gastric cancer.

Intragastric nitrosation has been implicated in the pathogenesis of gastric cancer and in precancerous conditions such as pernicious anaemia and the post-gastrectomy state. Intragastric nitrosation was assessed in at-risk patients by N-nitrosoproline (NPRO) excretion using both a conventional and a modified test. Twenty-four hour urinary excretion of NPRO was measured after oral administration of sodium nitrate (300 mg) and L-proline (500 mg) as an indirect indicator of intragastric nitrosation. In the conventional test no differences in intragastric nitrosation were found between at-risk patients and controls. In the modified test the loading dose of sodium nitrate was omitted and urinary NPRO levels were found to be significantly increased in Polya partial gastrectomy patients (P = 0.003) and post-vagotomy patients (P = 0.03) compared to controls. In pernicious anaemia patients NPRO levels were also higher than in controls but just failed to reach statistical significance. This study has confirmed that hypochlorhydria results in increased intragastric nitrosation, thus facilitating the formation of potentially carcinogenic N-nitroso compounds.