Salivary contribution to exhaled nitric oxide

Dietary and metabolic nitrate is distributed from the blood to the saliva b y active uptake in the salivary glands, and is reduced to nitrite in the or al cavity by the action of certain bacteria. Since it has been reported tha t nitric oxide may be formed nonenzymatically from nitrite this study aimed to determine whether salivary nitrite could influence measurements of exha led NO. Ten healthy subjects fasted overnight and ingested 400 mg potassium nitrate , equivalent to similar to 200 g spinach. Exhaled NO and nasal NO were regu larly measured with a chemiluminescence technique up to 3 h after the inges tion, Measurements of exhaled NO were performed with a single-breath proced ure, standardized to a 20-s exhalation, at a flow of 0.15 L s(-1), and oral pressure of 8-10 cmH(2)O. Values of NO were registered as NO release rate (pmol s(-1)) during the plateau of exhalation, Exhaled NO increased steadily over time after nitrate load and a maximum wa s seen at 120 min (77.0+/-15.2 versus 31.2+/-3.0 pmol s(-1), p<0.01), where as no increase was detected in nasal NO levels, Salivary nitrite concentrat ions increased in parallel; at 120 min there was a four-fold increase compa red with baseline (1.56+/- 0.44 versus 0.37+/-0.09 mM, p<0.05), The nitrite -reducing conditions in the oral cavity were also manipulated by the use of different mouthwash procedures. The antibacterial agent chlorhexidine acet ate (0.2%) decreased NO release by almost 50% (p<0.01) 90 min after nitrate loading and reduced the preload control levels by close to 30% (p<0.05), S odium bicarbonate (10%) also reduced exhaled NO levels, but to a somewhat l esser extent than chlorhexidine acetate, In conclusion, salivary nitric oxide formation contributes to nitric oxide in exhaled air and a large intake of nitrate-rich foods before the investig ation might be misinterpreted as an elevated inflammatory activity in the a irways. This potential source of error and the means for avoiding it should be considered in the development of a future standardized method for measu rements of exhaled nitric oxide.