Intestinal formation of N-nitroso compounds in the pig cecum model.

N-Nitroso compounds (NOC) are a group of compounds including N-nitrosamines and N-nitrosamides, which are well-known for their carcinogenic, mutagenic, and teratogenic properties. Humans can be exposed to NOC through the diet and environmentally, or NOC can be formed endogenously in the stomach and intestine. In the intestine, the formation of NOC is supposed to be afforded by the gut microbiota. In this study, the formation of the N-nitrosamines, N-nitrosomorpholine (NMOR) and N-nitrosopyrrolidine (NPYR), and the N-nitrosamides, N-nitrosomethylurea (NMU) and N-nitrosoethylurea (NEU), was investigated in the pig cecum model after the incubation of the corresponding precursor amine or amide with nitrite or nitrate. Following the incubation with nitrate, the formation of NMOR, NPYR, NMU, and NEU was detectable with the microbiota being responsible for the reduction of nitrate to nitrite. After the incubation of nitrite a chemical formation of NOC was shown.