Study on the Mechanism of Nitrite Production in the Saliva

It is well known that nitrite is one of the precursors of potential carcingenic nitroso compounds. The presence of nitrite in human saliva has been also reported by some workers, but the mechanism of nitrite production in the saliva is not yet clear. The purpose of this study is made to determine how nitrite is produced in the saliva in vivo and in vitro.The concentrations of nitrite and nitrate were estimated in the mixed and the parotid saliva, the gargle water, blood and urine in human under several conditions.The results obtained were as follows.1) After oral administation of sodim nitrate, large amounts of nitrite were detected in the mixed saliva, but it was not contained in the parotid saliva, the blood and the urine at all. On the other hand, nitrate concentration was increased in the mixed saliva, the parotid saliva and the urine. However nitate concentration in the blood did not change and showed constant level after the administration of sodium nitrate.2) When sodium nitrate was kept in the oral cavity in a few minutes, the decrease in nitrate and the increase in nitrite were observed in the gargle water.3) Nitrite was produced in parallel with the amounts of salivaly sediment in vitro. Activity of nitrate reduction of salivary sediment disappeared by both heating and filtration. It was also decreased to 20% by sonication at 10 _??_ KC for 10 mins.4) Number of Veillonella, habitual oral microorganism, had correlation with the ratio of nitrite to nitrate in the gargle water.From these results, it might be concluded that nitrite in the mixed saliva was not derived derectly from the blood, but it was formed from nitrate, which was concentrated in the salivary gland, and reduced by the oral microorganisms, mainly Veillonella.