Exposure to N-nitrosamines and other risk factors for gastric cancer in Costa Rican children

Abstract

The hypothesis that endogenous chemical nitrosation in the normal stomach in early life could play a crucial role in inducing chronic atrophic gastritis/intestinal metaplasia in later life was tested by applying the N-nitrosoproline (NPRO) test to 12-h urine samples from about 50 children (aged 8-14 years) living in high- and low-risk areas for stomach cancer. The median values of NPRO and the sum of four nitrosamino acids analysed were 0.28-0.84 ag/12 h and 0.75-1.75 tig/12 h, respectively. The NPRO level after proline intake was significantly higher in children from a high-risk area than in those from a low-risk area (p < 0.04), and markedly reduced after ingestion of ascorbic acid and proline (p < 0.05). Urinary nitrate level was lower than that of adults. NPRO levels on the day of proline intake, however, correlated well with nitrate levels (p < 0.001), indicating that children in a high-risk area in Costa Rica have high endogenous nitrosation potential. Blood samples were also collected from about 300 children (aged 7-20 years) and analysed for antibodies against Campylabacter pylori, a suspected gastritis-causing bacteria. About 71% of children in both high- and low-risk areas for stomach cancer had antibodies. In addition, raw and cooked beans, which are consumed very frequently in Costa Rica, were collected from families in both areas and analysed for levels of nitrite/nitrate, total N-nitroso compounds and genotoxicity in the SOS chromotest. Mean levels of total N-nitroso compounds in an aqueous extract (pH 2) of cooked bean samples from high- and low-incidence areas were similar (0.4-0.6 nmol/g of cooked beans). Acid-catalysed nitrosation of the same aqueous extracts produced levels up to 2.4 pmol/g of cooked beans. There was no difference in mean levels of nitrosation-dependent total N-nitroso compounds between samples from the two areas. Only two out of 11 extracts from the low-incidence area and two out of 14 from the high-incidence area showed weak direct genotoxicity. After acid-catalysed nitrosation, all samples were genotoxic at similar levels