Protein and mucin retention on oral mucosal surfaces in dry mouth patients.

Oral homeostasis depends largely on proteins and mucins present in saliva that coat all oral surfaces. The present study compared the protein composition of residual fluid on mucosal surfaces in subjects with normal salivary flow with that of patients with dry mouth caused by salivary hypofunction. Samples of residual mucosal fluid were collected using paper strips and then analysed by protein electrophoresis and immunoblotting. In both patients and controls, residual fluids on mucosal surfaces (except the anterior tongue in control subjects) had higher protein concentrations than unstimulated whole-mouth saliva. High-molecular-weight mucin (MUC5B) was present in greater amounts on the anterior tongue than on other surfaces in control subjects. In dry mouth patients who were unable to provide a measurable saliva sample, MUC5B was often still present on all mucosal surfaces but in reduced amounts on the anterior tongue. The membrane-bound mucin, MUC1, was prominent on buccal and labial surfaces in patients and controls. Statherin was still present on surfaces that were dried to remove salivary fluid, suggesting that it may be adsorbed as a protein pellicle. It is concluded that oral mucosal surfaces in dry mouth patients can retain MUC5B and other salivary proteins, although the functional integrity of these proteins is uncertain.

Intraoral duct ligation without inclusion of the parasympathetic nerve supply induces rat submandibular gland atrophy.

The atrophic effect of ligating the main duct of the right submandibular gland was examined in rat using a novel intraoral approach that did not include the chorda lingual (CL) nerve. Comparison was made with the effect of duct ligation including the attached CL nerve as carried out in previous studies. In all animals, the contralateral, unligated left submandibular gland was used as a control. At different times (1, 2, 7, 14 and 21 days) after ligation, glands were removed and weighed. Tissue was fixed for morphological analysis and homogenized for biochemical assay of secretory proteins. After 21 days, ligated glands showed a significant decrease in wet weight compared with unligated glands. Weight loss was the greatest (P < 0.05) in glands ligated with the CL nerve included. Light microscopy revealed that following ligation, an initial inflammatory reaction was followed by severe atrophy of acini and granular ducts. The atrophy was less severe when the CL nerve was not ligated. Secretory proteins were decreased from day 1 onwards following duct ligation in both groups. It can be concluded that most of the atrophy induced by duct ligation is independent of damage caused to the parasympathetic nerve supply, although the latter causes a greater atrophy presumably due to denervation.

Recovery of rat submandibular salivary gland function following removal of obstruction: a sialometrical and sialochemical study.

Functional recovery of the rat submandibular gland following ligation of the main excretory duct was examined. Rat submandibular glands were ligated for 1, 4 and 8 weeks using a micro-clip with a plastic tube. Micro-clips were removed and glands were allowed to recover for periods of 8, 16 and 24 weeks. Submandibular glands were stimulated with autonomimetic drugs (methacholine and isoprenaline) and salivas were collected from atrophic or de-ligated and contralateral control glands. Glands recovered almost full size (92% of control gland) following 24 weeks of de-ligation. Saliva volume secreted by ligated/de-ligated (RSM) and control (LSM) glands were similar with different doses of agonists. Protein output expressed per gram of tissue wet weight was similar from both ligated/de-ligated and control glands with all doses of agonist. Sodium and chloride levels were higher from de-ligated glands than contralateral control glands. Protein electrophoresis showed similar profiles of salivary proteins in all samples with some minor differences. Acinar cells in de-ligated glands showed a normal morphology, as indicated by light microscopy, whilst granular ductal cells were fewer and contained fewer secretory granules. Sodium potassium ATPase staining of striated ducts in de-ligated glands was similar to that of control glands. It can be concluded that rat submandibular glands can regenerate following severe atrophy and secrete normal amounts of saliva containing broadly a full profile of secretory proteins. In contrast to acinar cells, ductal cells appear not to recover full function.