Evidence for the release and possible neural regulation of nitric oxide in human saliva.

We report the presence of nitric oxide (NO) as measured through its product NO2 in human saliva. The presence of NO is not due to oral bacterial activity but is due to a genuine release of NO from the salivary glands and can be detected in freshly secreted saliva collected from a mouth freshly rinsed with an antiseptic preparation to reduce the bacterial content significantly. In order to study the regulation of salivary NO we used lemon juice to increase salivary flow and detected an immediate transient reduction of salivary NO2 which rose to levels equal to and sometimes higher than basal levels in five minutes in most donors indicating salivary NO production might be under neural control. Salivary NO production may play a physiological role in both the natural antibacterial properties of salivary secretion and possibly in detoxification of oral carcinogens.