Some chemical characteristics of human minor salivary gland secretions

Use of Human Minor Salivary Glands in Basic and Applied Secretion Research

Previous findings from studies utilizing human labial and palatine minor salivary glands are reviewed. These studies took histopathological, biochemical, and ultrastructural approaches, and focused on control and diseased glands. Disease-oriented summarizations are used, and control results are discussed in the context of disease-related findings. Findings are reviewed separately for electrolytes, macromolecules, and ultrastructure. In control subjects, minor gland salivary electrolyte concentrations are dependent on flow rate, and this dependence may be altered by diseases such as cystic fibrosis as-well as by inflammatory situations such as graft-versus-host disease. There is also evidence that salivary electrolyte secretion processes are not similar in labial and palatine minor glands. Studies of salivary macromolecular composition are reviewed for control subjects and for patients with graft-versus-host disease and Sjögren's syndrome. The findings indicate that the macromolecular contents of labial and palatine gland saliva are similar, but that both are significantly different from that for major gland saliva. Finally, studies attempting to measure disease-related changes in intracellular composition are reviewed. It is concluded that the minor salivary glands are important models for the study of exocrine gland physiology and pathophysiology in man.

An update on minor salivary gland secretions

In this article, the literature on minor salivary gland secretion rates, composition, and function is reviewed. Measurements of the minor salivary gland secretion rates and composition are complicated, and the secretions display large biological variability. Despite this, some characteristics of these secretions have been found repeatedly in independent investigations. Minor gland saliva varies between different oral sites. Buccal saliva flow is higher than labial saliva flow, which in turn is usually higher than the palatal gland secretion rate. It is generally agreed that minor gland saliva is important for the whole saliva composition, and especially for the secretory immunoglobulin A and mucins. The secretion from these glands seems also important for subjective feelings of dry mouth and general wellbeing. Further research is essential for understanding the role of these secretions for oral, as well as for general, health.

Comparison of the composition of oral mucosal residual saliva with whole saliva

OBJECTIVE

Compared with whole saliva, residual saliva comprising the oral mucosal film shows a high protein concentration. The purpose of this study was to compare the composition of residual saliva with unstimulated and stimulated whole saliva in normosalivators.

MATERIALS AND METHODS

The composition of oral mucosal residual saliva in 30 healthy individuals was investigated and compared with that of whole saliva. The concentrations of total protein, secretory immunoglobin A (sIgA), lactoferrin, total carbohydrate, and sialic acid were examined. The activities of peroxidase, lysozyme and alpha-amylase were determined.

RESULTS

Residual saliva had higher levels of total protein and carbohydrate than whole saliva, with a higher carbohydrate to protein ratio in the residual saliva suggesting that salivary glycoproteins are concentrated on the oral mucosal surface. sIgA, lactoferrin and sialic acid were present as highly concentrated forms in residual saliva. The enzymatic activity of peroxidase in residual saliva was higher than that of whole saliva.

CONCLUSIONS

These concentrated carbohydrate and antimicrobials on the oral mucosal surface work for mucosal defence and could be used for targeting sites for the delivery of therapeutic agents.

Surgical treatment of dry eye syndrome: conjunctival graft of the minor salivary gland

Despite the availability of efficient tear substitutes, many patients with dry eye syndrome experience severe corneal injuries and a subsequent loss of vision. Surgical techniques using mayor salivary glands to provide a substitute for tears have been reported; with this technique the drainage of saliva goes into the conjunctival fornix, permitting corneal and conjunctival humidification. The authors describe a new surgical approach in which minor salivary glands are autotransplanted into the conjunctival fornix by means of a graft of the intraoral mucosa-transporting salivary glands. This approach was used in a 56-year-old woman with a 2-year history of refractory and pharmacologically untreatable dry eye syndrome caused by Sjögren's syndrome. The right eye had more severe corneal and conjunctival lesions than did the contralateral one, so the treatment was planned in the right eye only. A weekly follow-up during the first 6 months confirmed the significant improvement of dry eye symptoms in the surgically treated eye. Three months after surgery, a biopsy was performed in the minor salivary gland graft, and the histologic findings revealed the presence of glandular acinus, duct with mucin content, and lymphocyte infiltration. The significant improvement obtained in this patient suggests that the secretion from the grafted salivary minor glands was better in promoting homeostasis of the ocular surface than are artificial tears. This may be explained by: (1) The lacrimal and salivary secretions contain biologically active constituents that may protect from infection and promote normal growth epithelium; (2) The secreted mucin is thought to coat the epithelial surface, reducing the high surface tension of the eye wetted by aqueous tears; (3) The thick secretions of the minor gland might act in reducing the evaporation of the underlying tear layer and form a hydrophobic barrier along the lid margin that can retain the lid margin tear string and prevent its flow onto the skin. Minor gland salivary autotransplant is a new surgical technique with effectiveness demonstrated in one patient, but the scientific explanation is not clear; additional experience with more cases could confirm the initial success.

Significance of saliva for the denture-wearing population

This paper summarises a series of studies already published in German and presents new data related to the aetiology of the 'dry mouth' and its associated problems.

AIMS

To study factors affecting mucous and serous salivary gland secretion, the aetiology of the 'dry mouth' and its associated problems, causative factors for hyposalivation and it's treatment.

SETTING

Two university dental hospitals.

SUBJECTS

587 denture wearers and 521 control subjects, and autopsy material.

INTERVENTIONS

Exercise, chewing, water, oestrogen, pilocarpine, and anetholtrithion therapy, biopsy of the minor glands.

MAIN OUTCOME MEASURES

Palatal secretion (PAL, microL/cm2/min) and parotid salivary flow (PAR), subjective complaints and clinical findings.

RESULTS

Resting flow rates for PAL between 0 and 65 microliters/cm2/min were seen in every age group. The flow rates of PAR (0 to 3.7 ml/10 min) were not correlated with PAL. Most patients with a resting flow rate of PAL < or = 6.0 microliters/cm2 suffer from a 'dry mouth' and Burning Mouth Syndrome (BMS) or oral dysaesthesia (OD) with or without chronic lesions of the oral mucosa. Etiological factors for the incidence of reduced PAL and associated problems include xerostomic drugs, oestrogen deficiency, radiotherapy, thyroid dysfunction, smoking or continuous wearing of complete upper dentures. PAL also correlated with the retention of upper complete dentures. PAL was correlated with the water content of epithelial tissues. PAL and PAR were both increased by drinking ample fluid, improving their circulation by physical exercises, chewing intensively, or taking oestrogens, pilocarpine, anetholtrithion.

CONCLUSIONS

Variation in palatal salivary secretion occurs and is clinically important.

Sialolithiasis of a Blandin's gland duct

A case of sialolithiasis in a Blandin's gland duct is reported. Although minor salivary glands calculi are not uncommon, Blandin's glands are rare sites of occurrence. In this case, a calculus without decalcification is reported. Not only clinico-pathological features but also electron probe micro analyzer plus energy dispersive X-ray spectroscopy studies are presented. These studies reveal that phosphorus is contained in only the basophilic part of the calculus and sulphur in both the basophilic and the eosinophilic parts.

Free amino acids in human palatine gland secretions

Human palatine gland saliva (HPS) was collected from young adult subjects (mean age 22 yr) of both sexes by gentle mechanical stimulation. The HPS contained 9-13 of the common amino acids within the range of 2-850 nmol/ml, but most samples had low or no concentrations of arginine, tryptophan and proline. Methionine and cysteine were not reliably detected. The molar ratios of most amino acids varied between subjects, but the ratio of leucine to isoleucine was remarkably constant (mean +/- SD = 1.86 +/- 0.28; n = 28). The minimum average secretion rate of HPS, using gentle mechanical stimulation, was estimated to be about 25 mg/min (wet weight).

Use of human minor salivary glands in basic and applied secretion research

Previous findings from studies utilizing human labial and palatine minor salivary glands are reviewed. These studies took histopathological, biochemical, and ultrastructural approaches, and focused on control and diseased glands. Disease-oriented summarization are used, and control results are discussed in the context of disease-related findings. Findings are reviewed separately for electrolytes, macromolecules, and ultrastructure. In control subjects, minor gland salivary electrolyte concentrations are dependent on flow rate, and this dependence may be altered by diseases such as cystic fibrosis as well as by inflammatory situations such as graft-versus-host disease. There is also evidence that salivary electrolyte secretion processes are not similar in labial and palatine minor glands. Studies of salivary macromolecular composition are reviewed for control subjects and for patients with graft-versus-host disease and Sjögren's syndrome. The findings indicate that the macromolecular contents of labial and palatine gland saliva are similar, but that both are significantly different from that for major gland saliva. Finally, studies attempting to measure disease-related changes in intracellular composition are reviewed. It is concluded that the minor salivary glands are important models for the study of exocrine gland physiology and pathophysiology in man.

Analysis of salivary proteins by thin layer sodium dodecylsulphate polyacrylamide gel electrophoresis

Samples of the whole, parotid, submandibular and palatine salivas and serum, all collected from the same human subject, were developed by simultaneous electrophoresis on a single SDS thin layer gel plate, and simple proteins, glycoproteins and sialoglycoproteins in the samples were isolated and analysed. Simultaneous electrophoresis of the salivas and serum showed the presence of thirty-four protein bands in serum, twenty-two bands in whole saliva, sixteen bands in parotid saliva, nineteen bands in submandibular saliva and ten bands in palatine saliva. Glycoprotein bands in the isolating gel zone presented five bands in whole saliva, four bands in submandibular saliva, three bands in parotid saliva and no band in palatine saliva. Palatine saliva, however, showed a single clear band in the concentrating gel zone. Palatine saliva showed only one sialoglycoprotein band in the concentrating gel zone.

Lipid composition of human labial salivary gland secretions

Extraction of the dialysed and lyophilized labial saliva with chloroform/methanol yielded 423.8 +/- 73.0 micrograms of lipids/ml of saliva, a level 4-5 times higher than in the major salivary glands. Of the total lipids, 32.4 per cent were represented by neutral lipids, 44.6 per cent by glycolipids and 23.0 per cent by phospholipids. Neutral lipids had a high content of free fatty acids (43.8 per cent), cholesteryl esters (26.9 per cent) and triglycerides (15.4 per cent). The glycolipids consisted mainly of neutral (74.6 per cent) and sulphated (25.4 per cent) glyceroglucolipids, whereas phosphatidylethanolamine, phosphatidylcholine, sphingomyelin and phosphatidylserine accounted for 54.7 per cent of the total phospholipids.