N-nitroso compounds in fresh gastric juice and their relation to intragastric pH and nitrite employing an improved analytical method.

In order to examine further the relationship between intragastric N-nitrosation, gastric pH and nitrite, 457 fresh, fasting gastric juice samples were analysed for total N-nitroso compounds (NOC) and nitrite concentrations using a recently described improved assay method. Nitrite in log values was linearly related to intragastric pH (r = 0.887, P < 0.01) with a regression equation log[nitrite] (mumol/l) = 0.489 x pH - 2.209. Significantly higher NOC concentrations were found at intragastric pH ranges of 1.13-2.99 (mean +/- SE: 1.45 +/- 0.17 mumol/l, P < 0.05) and 6.00-8.42 (3.57 +/- 0.33 mumol/l, P < 0.01) compared with that at pH 3.00-5.99 (1.02 +/- 0.12 mumol/l). NOC concentration was significantly related to log nitrite concentration at both the low pH range 1.13-4.99 (r = 0.169, P < 0.01) and the high pH range 5.00-8.42 (r = 0.450, P < 0.01). The results in the present study confirm that both acid-catalysed N-nitrosation and biologically-catalysed N-nitrosation occur in the human stomach. However, great variations in nitrite and NOC concentrations were observed in both low and high pH samples, indicating that, as expected, both the acid-catalysed N-nitrosation and biologically-catalysed N-nitrosation processes are markedly affected by factors other than intragastric pH and nitrite.