Disappearance of Nitrite From the Rat Stomach: Contribution of Emptying and Other Factors

Summary

To help understand how intragastric nitrosation forms N-nitroso compounds, nitrite disappearance from the rat stomach was measured after food containing nitrite was given. In preliminary experiments, nitrite disappearance from buffered aqueous solutions became more rapid as the pH was lowered from 5 to 1 and, at a given pH, was more rapid in a slurry of commercial rat food. The disappearance of nitrite from buffer was little affected by the addition of pepsin, mucin, albumin, or rat gastric contents. When starved rats were given 5 g food with 1.82 mg NaNO₃/g, nitrate was not reduced to nitrite in the stomach. Five g food containing 154 µg NaNO₂/g was administered similarly, and the total stomach (T) and glandular and nonglandular parts (G and NG) were analyzed after 1–5 hours. Weight and nitrite concentration of the stomach contents dropped linearly and the amount of nitrite dropped exponentially (with a half-life of 1.4 hr), Mean nitrite concentration in G was less than half that in NG. From similar experiments with phenol red, emptying accounted for 60% of nitrite loss from T. In G, nitrite concentration was reduced about 3 times due to dilution and 3 times due to other causes. Conditions in G, e.g., nitrite concentration, pH, and emptying time, were discussed in relation to carcinogenesis experiments with nitrite plus amines and amides.