Implications of a model from olfactory research for the use of secretion rates in salivary studies

Secretion rates (amount protein per unit time) are often used as a means of adjusting saliva protein concentrations for the effects of variation in flow rate. However, findings in olfactory physiology may indicate a problem with that approach: olfactory neurones respond differently to a small amount of odorant over a short time than to twice that quantity over twice the time, although secretion rates remain the same. Whether a similar variation in amounts and times occurs in persons with similar secretion rates for lysozyme, lactoferrin, salivary peroxidase, sIgA, or total protein in stimulated parotid saliva was investigated. The data used were from 2 groups of 44 and 198 subjects previously found to differ in flow rate and concentrations of antimicrobial proteins. Multidimensional plots of secretion rates, amounts and times were generated for each protein. Wide ranges of amounts and times were seen among persons within the same percentile for secretion rate for every protein in both groups. These amounted to as much as a thirteen-fold difference in amounts and times. Experimental studies are needed to determine whether such differences affect the action of saliva proteins.