Intragastric nitrosation and precancerous lesions of the gastrointestinal tract: testing of an etiological hypothesis.

The N-nitrosoproline (NPRO) test was used to study whether subjects with precancerous conditions of the stomach have an elevated potential for endogenous nitrosation. The highest yield of NPRO after ingestion of beetroot juice (as a source of nitrate) and proline was seen in subjects whose pH of fasting gastric juice was about 1.5-2. No increased level of NPRO was detected in subjects with more advanced lesions, compared to those with a normal stomach. Counts of total and nitrate-reducing bacteria were positively correlated with the pH of gastric juice but did not correlate with the urinary level of NPRO in the same individuals. Bacteria and intragastric nitrosation are discussed as possible etiological factors in human stomach cancer.