Figure 5.

Chemical reactions occurring when nitrite enters acidic gastric juice. Nitrite is converted to nitrous acid and nitrosating species, including nitrosothiocyanate. In the absence of ascorbic acid, these can react with nitrososatable species to form N-nitroso compounds which may diffuse into the adjacent epithelium. Ascorbic acid in gastric juice prevents this luminal nitrosation by converting the nitrosating species to nitric oxide. However, nitric oxide can diffuse into the adjacent epithelium and there react with oxygen to reform nitrosating species and N-nitroso compounds. In the acid secretory stomach, both these pathways of N- nitroso compound generation operate maximally at the gastric cardia. GO, gastro- oesophageal.