Correlation between Extensional Rheology and Composition of Saliva

Objectives:

The aim of the study was to analyze and relate the rheological properties of saliva with mucin concentrations between secretions from major and minor salivary glands and different secretory stimuli.

Methods:

Unstimulated saliva was collected from submandibular/ sublingual (SM/SL) and labial glands (minor) in 5 subjects.  Chewing, taste and smell stimulated SM/SL salivas were also collected.  Spinnbarkeit was measured using the Neva Meter (Ishikawa Iron Works, Japan). Relative concentrations of the mucins MUC5B and MUC7 determined by western blotting and image analysis. Statistical significance was tested using one-way ANOVA and post-hoc Tukey’s test.

Results:

Labial gland saliva had significantly higher (p<0.05) mucin concentrations compared to the unstimulated and stimulated SM/SL gland secretions and analysis of the extensional rheology showed labial saliva had significantly higher (p<0.05) spinnbarkeit than the SM/SL samples. The mucin concentrations of unstimulated and stimulated SM/SL saliva were similar but spinnbarkeit of chewing stimulated saliva was significantly (p<0.05) lower. Labial saliva had a significantly lower (p<0.005) contact angle (greater wetting ability) than unstimulated and stimulated SM/SL saliva whilst chewing stimulated saliva had a higher contact angle (lower wetting ability) among salivas stimulated by smell and taste.

Conclusions:

The results suggest that there exists a positive correlation between the extensional rheological properties and mucin concentrations in saliva. A higher mucin concentration appears to influence the wetting ability of saliva which may contribute to mucosal wetness. The lower spinnbarkeit of chewing stimulated SM/SL saliva despite similar concentrations of mucins suggests that chewing might have caused changes in the macromolecular structure of mucins.