Influence of Different Feeds and Antibiotics on the Behavior of Nitrate and Nitrite in the Digestive Tract of Rats

It has been reported that nitrate and nitrite, precursors of nitrosoamines, can be formed from ammonium ion and organic nitrogen compounds by intestinal bacterial flora.The authors thus investigated the behavior of nitrate and nitrite in rats given hard flour and cheddar with and without nitrate or antibiotics. Nitrate and nitrite concentrations in the contents of stomach and intestines as well as in the feces were compared. Nitrate was detected in the gastric contents of rats given abundant nitrate, while nitrate and nitrite were found in the feces. Furthermore, the nitrate concentration detected in the gastric contents depended on the amount of nitrate intake. However, neither nitrate nor nitrite was detected in the intestinal contents of rats to which high protein and lipid feeds had been given.On the other hand, when kanamycin (KM) was given together with nitrate, the amount of nitrate in the gastric contents was significantly higher than that in the case when KM was not given.Furthermore, to determine the proportion of reduction of nitrate in the gastric and rectal contents, in vitro experiments were carried out under various conditions. It was found that the reduction of nitrate was influenced by the addition of KM, the culture conditions and the kind of culture medium.