Age-related Changes Of Stimulated Whole Saliva Flow Rates And Nitric Oxide Levels In Healthy Adults

BACKGROUND Salivary flow rates and components are two major factors affecting the salivary barrier, and also are parameters for evaluating the secretory function of salivary glands. Past researches have indicated that there exist age-related changes of salivary flow rates and components and that nitric oxide is an active component in saliva. But age-related changes of stimulated whole saliva flow rates and nitric oxide levels are still in dispute.OBJECTIVE To study age-related changes of stimulated whole saliva flow rates and nitric oxide levels in healthy adults.METHODS The effect of age on stimulated whole saliva flow rates and nitric oxide levels was determined in 97 healthy adults. The subjects were divided into four age groups: 20-39years (youth group), 40-59 years (middle-aged group), 60-79 years (elderly group), and 80 years and over (macrobian group). After the donor rinsed the mouth with 0.25% chlorhexidine in order to reduce bacterial contamination, the donor was dropped with 2% citrate on the anterior third dorsum of the tongue for two minutes at the pace of 1 drop every 20 seconds, then rinsed the mouth out 3 times with twicely-distilled water within 1 minute following which saliva was collected for 5 minutes. The volume of saliva was documented. Samples were frozen at -70 until assayed. Flow rates were calculated as collected volume/collected time. Nitric oxide concentrations were measured with nitrate reductase and the Griess reagent, and then nitric oxide output (nmol/min) was calculated by multiplying flow rate and concentration.RESULTS (1) Flow rates of stimulated whole saliva in youth group were significantly different from those in middle-aged, aged and macrobian group. Flow rates in the latter three groups were not significantly different. (2) There were no significant differences of nitric oxide concentrations between any age groups. Outputs of nitric oxide in youth groupwere significantly different from those in middle-aged , aged and macrobian group. Outputs of nitric oxide in the latter three groups were not significantly different.CONCLUSION Nitric oxide was found in saliva of healthy adults. There was no significant influence of age on nitric oxide concentrations. But stimulated whole saliva flow rates and nitric oxide outputs had a decremental tendency with aging.