Detection of nitric oxide and its derivatives in human mixed saliva and acidified saliva.

Nitrate is secreted into the human oral cavity as a salivary component. The nitrate is transformed to nitrite and nitric oxide (NO) by oral bacteria. NO is oxidized by O(2) producing NO(2) and N(2)O(3) and also by O(2)(-) producing ONOO(-). Salivary peroxidase can oxidize nitrite and NO to NO(2) or its equivalent in the oral cavity. Nitrite dissolved in saliva is mixed with gastric juice, generating nitrous acid that is transformed to NO and NO(2) via N(2)O(3) by self-decomposition. In addition, nitrous acid can react with ascorbic acid and phenolics producing NO and with H(2)O(2) producing ONOOH. This chapter deals with the detection of reactive nitrogen oxide species (RNOS), especially NO, N(2)O(3), NO(2), and ONOO(-)/ONOOH, in mixed whole saliva and acidified saliva using fluorescent probes and spin-trapping reagents. It is also shown that measurements of nitration and oxygen consumption are useful in studying the formation and scavenging of RNOS in the aforementioned systems.