The composition of human lip mucous gland secretions

Physiological regulation of oral saliva ion composition and flow rate are not coupled in healthy humans-Partial revision of our current knowledge required

Appropriate composition of oral saliva is essential for a healthy milieu that protects mucosa and teeth. Only few studies, with small sample numbers, investigated physiological saliva ion composition in humans. We determined saliva ion composition in a sufficiently large cohort of healthy adults and analyzed the effect of physiological stimulation. We collected saliva from 102 adults under non-stimulated and physiologically stimulated conditions (chewing). Individual flow rates, pH, osmolality, Na+, K+, Cl-, and HCO3- concentrations under both conditions as well as the individual changes due to stimulation (Δvalues) were determined. Non-stimulated saliva was hypoosmolal and acidic. Na+, Cl-, and HCO3- concentrations remained well below physiological plasma values, whereas K+ concentrations exceeded plasma values more than twofold. Stimulation resulted in a doubling of flow rates and substantial increases in pH, HCO3-, and Na+ concentrations. Overall, stimulation did not considerably affect osmolality nor K+ or Cl- concentrations of saliva. An in-depth analysis of stimulation effects, using individual Δvalues, showed no correlation of Δflow rate with Δion concentrations, indicating independent regulation of acinar volume and ductal ion transport. Stimulation-induced Δ[Na+] correlated with Δ[HCO3-] and Δ[Cl-] but not with Δ[K+], indicating common regulation of ductal Na+, Cl-, and HCO3- transport. We present a robust data set of human oral saliva ion composition in healthy adults and functional insights into physiological stimulation. Our data show (i) that flow-dependence exists for Na+ and HCO3- but not for K+ and Cl- concentrations, (ii) osmolality is flow-independent, (iii) regulation of Na+, Cl-, and HCO3- transport is coupled, (iv) regulation of flow rate and ion concentrations are independent and (v) spatially separated between acini and ducts, respectively.

Clinical anatomy of the inferior labial gland: a narrative review

Objective

In this article we review the literature on the inferior labial gland from a clinical and anatomical perspective.

Background

Regardless of its importance in clinical practice, there are no medical literature that comprehensively reviewed the inferior labial gland.

Methods

A database search using PubMed and Google Scholar was conducted. The following keywords were used in the search: "lower labial salivary gland", "lower labial gland", "inferior labial salivary gland", AND "inferior labial gland".

Conclusions

The human labial glands are types of minor salivary gland that continuously secrete small amounts of mucous and serous substances to maintain oral health. The inferior labial glands are innervated by the inferior labial branch of the mental nerve, and the inferior labial branch of the facial artery is the main arterial supply to the lower lip. Although they only have an auxiliary role in saliva production compared to the major salivary glands, minor salivary glands provide a certain amount of lubrication in the oral cavity by the continuous outflow of saliva. The inferior labial gland not only promotes moisturization in the oral cavity but also secretes substances with antibacterial effects, which is important for the function of the oral cavity. A recent study showed that the rate of salivary secretion from the inferior labial glands does not change with age, and in some cases the inferior labial glands are used for diagnosing intractable diseases such as Sjogren's syndrome and cystic fibrosis. In addition, since the inferior labial glands themselves can be the site of cyst and/or neoplasia development, we should be careful to distinguish them from other diseases. Elucidation of the anatomy, physiology, and pathology of the inferior labial glands, is important for understanding human health and diseases.

Oral Sampling Techniques

The human oral cavity is a major point of entry for microorganisms, many of which live and multiply in the mouth. In addition, it provides an accessible site for sampling compared to other parts of the body; however, caution should be taken during oral sampling as many factors contribute to the microbial diversity in a site-dependent manner. The accessibility of the oral cavity and its microbial diversity emphasize the crucial need to avoid cross-contamination during the sampling procedure. In this chapter, we describe various detailed oral sampling procedures. These methods include supragingival dental plaque sampling, subgingival dental plaque sampling, oral mucosal sampling, and endodontic sampling methods for extracted teeth or in the patient's mouth. The proposed protocols provide tips to avoid contamination between different oral sources of bacteria and possible alternatives to the tools used.

Role of Saliva and Salivary Diagnostics in the Advancement of Oral Health

The objective of this article was to provide an account of some of the developments related to saliva over the first 100 years of the Journal of Dental Research and to outline some of the many biomarkers identified in saliva in the last few years. The first section covers findings in salivary physiology, biochemistry, calcium phosphate chemistry related to saliva, microbiology, and the role of saliva in maintaining oral health. The second section highlights salivary diagnostics, salivaomics, and saliva exosomics in the context of the emerging theme of personalized and precision medicine.

Radioprotective effect of endogenous melatonin secretion associated with the circadian rhythm in irradiated rats

Purpose: We investigated the radioprotective effect of endogenous melatonin release at different times associated with the circadian rhythm on head and neck radiotherapy. Materials and methods: Two groups of animals were subjected daily to 8 Gy single fraction radiotherapy in the head and neck region from 5:00 to 6:00 (the morning group) or from 19:00 to 20:00 (the evening group). Corresponding untreated groups served as controls. Submandibular glands from rats sacrificed on the seventh day after irradiation were assessed biochemically and histopathologically. Melatonin, malondialdehyde and superoxide dismutase levels in blood collected immediately prior to irradiation were measured with rat-specific ELISA kits. Results: In irradiated rats, melatonin, malondialdehyde and superoxide dismutase levels were significantly higher in the evening group than in the morning group. In nonirradiated rats, melatonin and superoxide dismutase levels were significantly higher in the evening group than in the morning group. The areas of seromucous acinar cells were similar between the irradiated and nonirradiated evening groups, but the area was higher in the evening irradiated group than in the morning irradiated group. Conclusion: Consideration of endogenous melatonin secretion associated with the circadian rhythm may offer new therapeutic solutions for the complications of head and neck radiotherapy.

The Landscape Ecology and Microbiota of the Human Nose, Mouth, and Throat

Landscape ecology examines the relationships between the spatial arrangement of different landforms and the processes that give rise to spatial and temporal patterns in local community structure. The spatial ecology of the microbial communities that inhabit the human body-in particular, those of the nose, mouth, and throat-deserves greater attention. Important questions include what defines the size of a population (i.e., "patch") in a given body site, what defines the boundaries of distinct patches within a single body site, and where and over what spatial scales within a body site are gradients detected. This Review looks at the landscape ecology of the upper respiratory tract and mouth and seeks greater clarity about the physiological factors-whether immunological, chemical, or physical-that govern microbial community composition and function and the ecological traits that underlie health and disease.

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.

Variability in measures of exhaled breath na, influence of pulmonary blood flow and salivary na

The assessment of inflammatory markers and ions in exhaled breath condensate (EBC) is being utilized more frequently in diseases such as asthma and cystic fibrosis with marked variability in EBC measures, including those of exhaled Na⁺. We sought to determine if variability in exhaled Na⁺ was due to differences in pulmonary blood flow (PBF) or Na⁺ in the mouth (salivary Na⁺). We measured exhaled Na⁺ three times with coinciding sampling of salivary Na⁺ and assessment of PBF (using acetylene rebreathing) in 13 healthy subjects (54% female, age = 27 ± 7 yrs., ht. = 172 ± 10 cm, wt. = 70 ± 21 kg, BMI = 22 ± 7 kg/m² mean ± SD). Exhaled Na⁺ averaged 2.7 ± 1.2 mmol/l, and salivary Na⁺ averaged 5.51 ± 4.58 mmol/l. The coefficients of variation across all three measures in all 13 subjects averaged 30% for exhaled Na⁺ and 83% for salivary Na⁺, within subjects the variability across the three measures averaged 30% for exhaled Na⁺ and 38% for salivary Na⁺. Across all three measures in all 13 subjects the relationship between PBF and exhaled Na⁺ averaged 0.027 (P = 0.87), and the relationship between salivary Na⁺ and exhaled Na⁺ concentrations averaged 0.59 (P = 0.001). Also, we sought to determine the relationship between exhaled Na⁺ and serum Na⁺ in an addition 20 subjects. There was a moderate and significant relationship between serum Na⁺ and exhaled Na⁺ (r = 0.37, P = 0.04). These findings suggest there that the variability in exhaled Na⁺ is caused, at least in part, by droplet formation from within the mouth as turbulent air passes through and that there is a flux of ions from the pulmonary blood into the airways.

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.

Salivary flow patterns and the health of hard and soft oral tissues

BACKGROUND

This nonsystematic review summarizes the effects of saliva on some of the diseases affecting the hard and soft oral tissues.

RESULTS

Saliva enters the mouth at several locations, and the different secretions are not well-mixed. Saliva in the mouth forms a thin film, the velocity of which varies greatly at different sites. This variation appears to account for the site specificity of smooth-surface caries and supragingival calculus deposition. Saliva protects against dental caries, erosion, attrition, abrasion, candidiasis and the abrasive mucosal lesions seen commonly in patients with hyposalivation. These effects are the result of saliva's being a source of the acquired enamel pellicle; promoting the clearance of sugar and acid from the mouth; being supersaturated with respect to tooth mineral; containing buffers, urea for plaque base formation, and antibacterial and antifungal factors; and lubricating the oral mucosa, making it less susceptible to abrasive lesions.

CLINICAL IMPLICATIONS

For optimal oral health, people should keep food and liquids in the mouth as briefly as possible. The most important time for toothbrushing is just before bedtime, because salivary flow is negligible during sleep and the protective effects of saliva are lost. Chewing sugar-free gum or sucking on sugar-free candies stimulates salivary flow, which benefits hard and soft oral tissues in many ways.

A simple method to estimate the secretion of saliva from minor salivary glands using iodine-starch reaction

OBJECTIVE/HYPOTHESIS

This study was undertaken to detect the faculty of secretion of saliva from minor salivary glands by analyzing a color reaction on a test tape containing iodine and starch that was applied on the lower lip.

STUDY DESIGN

A study involving 63 patients with oral dryness, 7 patients with Sjogren syndrome, and 70 healthy individuals was performed.

METHODS

A test tape (1 x 1 cm) containing iodine and starch was set on the mucosal area anterior to the labia frenulum for 30 seconds. Because the number of blue spots was considered to correspond to the number of ostia of the salivary gland on the lower lip that was examined, the number of blue spots occurring as a reaction of iodine and starch on the test tape was counted and was compared among three groups. In addition, the relationship between the histopathological findings and the number of spots was analyzed.

RESULTS

The average number of spots in the patients with oral dryness (4.52+/-3.18 [mean +/- SD]) was lower than that in healthy individuals (9.49+/-2.52, P <.01), and that in the patients with Sjögren syndrome (2.14+/-1.35) was the lowest among all groups in the study. Moreover, this reduction in the number of spots in those patients was accompanied by histopathological changes of the minor salivary glands.

CONCLUSION

These findings suggest that this simple, noninvasive method can be successfully used for the estimation of the faculty of secretion of saliva from the minor salivary glands.

Study of saliva secretion and the salivary fluoride concentration of the human minor labial glands by a new method

Unstimulated and stimulated flow rate from minor lower labial glands and the fluoride concentration of resting whole and labial saliva were measured over 15 min using a novel method avoiding eversion of the lips. Resting salivary flow rate was measured as 1.09+/-0.44 microl/min/cm2 and stimulated flow rate as 3.13+/-1.05 microl/min/cm2. Secretion rates were significantly (p<0.001) increased during periods of continuous speaking. The increase in secretion elicited by labial movements and speaking may result from mechanical stimulation and/or activity of myoepithelial cells. Fluoride concentrations in resting whole saliva and in unstimulated minor labial gland saliva were 0.066+/-0.048 and 0.181+/-0.073 parts/10(6), respectively. The secretory capacity of the minor labial glands and the high F concentration in their secretions suggests a significant contribution to the F content of whole saliva. Our non-invasive method permits collection from the minor labial glands of a volume large enough for chemical analysis. It should prove useful for studying the effects of different secretory stimuli.

The flow rate and composition of human labial gland saliva

Since the flow rate of saliva from human labial salivary glands has usually been measured as the secretion from an area of labial mucosa as 0.05-4.8 microl/cm2/min. The only data for single glands gives a comparable figure of 0.1 microl/min/gland. There is no consensus on the effects of gustatory stimulation, gender or ageing, although most reports suggest that flow rate is not related to gender and ageing up to age 60. The main differences in composition between labial gland saliva and that from the major glands are the higher and variable sodium concentration, the very low phosphate and hydrogen carbonate concentrations, and the higher protein concentration despite low concentrations of amylase. The concentrations of IgA and blood group substances are notably higher in labial gland saliva. In Sjogren's syndrome and cystic fibrosis flow rates are decreased. Low rates of flow have been associated with a higher incidence of dental caries.

Morphological features of the minor salivary glands

The minor salivary glands are important components of the oral cavity, present in most parts of the mouth, and their secretions directly bathe the tissues. Individual glands are usually in the submucosa between muscle fibres, and consist of groups of secretory endpieces made up of mucous acinar cells and serous or seromucous demilune cells. The ductal systems comprise intercalated ducts, intralobular ducts usually lacking basal striations, and excretory ducts opening directly through the mucosa Minor glands secrete highly glycosylated mucins, containing blood group determinants, and probably active in tissue lubrication and bacterial aggregation. They also secrete several antimicrobial proteins and immunoglobulins, and the lingual serous (von Ebner's) glands secrete digestive enzymes and proteins with possible taste perception functions. Minor gland morphology and function can conveniently be studied in the rat. There are substantial differences between major and minor salivary glands, as well as among the minor glands, in the nature and composition of their mucous and serous secretory products. The role of minor salivary glands in the function and defence of the oral cavity may be better understood as a result of new physiological and molecular methods applicable to samples of limited size and availability.

The intra-oral distribution of unstimulated and chewing-gum-stimulated parotid saliva

The objective was to determine the percentage contribution of parotid saliva to whole saliva and to the saliva at 11 sites in the mouth, when flow rate was unstimulated or stimulated with chewing-gum. The marker substance used was alpha-amylase, as this is in much higher concentration in parotid saliva than in secretions from other salivary glands. Formulae were derived for calculation of the minimum, maximum, and mean percentage contributions of parotid saliva to saliva in different areas of the mouth. The results, from 10 individuals, showed that the contributions of parotid to unstimulated and stimulated whole saliva averaged 30.1% and 35.6%, respectively, whereas the corresponding values for samples from the region vestibular to the upper molars were 56.1% and 61.4%, but only 2.8% and 6.8% for samples from an area vestibular to the upper incisors. Thus parotid saliva was not evenly distributed throughout the mouth. Stimulated samples mostly contained significantly higher proportions of parotid saliva, but the distribution of the parotid saliva was still extremely variable. Because the different regions of the mouth are not exposed to the same fluid environment, this may influence the site-specificity of supragingival calculus deposition and of various diseases such as dental caries.

Measurement and comparison of the residual saliva on various oral mucosal and dentition surfaces in humans

Using a paper-strip absorption method, the amounts of residual saliva on 20 soft-tissue sites in different regions of the mouths of 20 individuals were surveyed once in the morning after a 12-h fast and again approx. 1-2 h after lunch. After swallowing, saliva at each site was immediately collected on filter-paper strips in a dipstick fashion for 5 s and the volumes were measured electronically with a Periotron micro-moisture meter. A clear pattern of wetness was evident and was almost identical for fasting and postprandial determinations. The hard palate and labial mucosa were covered with the least residual saliva; the floor of the mouth and back of the tongue were the wettest. In the same 20 participants, the amounts of residual saliva on various dentition sites were next measured and, as expected, much higher residual amounts were found in approximal embrasures and occlusal fossae than on adjacent facial or lingual smooth areas. Molars gave higher values than premolar and incisor embrasures. To relate residual saliva dipstick volumes to saliva thickness values, filter-paper strips were applied flat against the same mucosal or dentition surfaces in 10 of the participants, and the volume of the saliva absorbed was measured electronically as before. As the areas of the strips used were known, saliva thicknesses could be calculated. These ranged from 0.01 mm on the hard palate to 0.07 mm on the posterior of the dorsum of the tongue. For the incisor teeth, the calculated residual saliva thickness determined in the same way was about 0.01-0.02 mm. Blotting values plotted against dipstick values for oral sites where blotting could be readily performed showed a linear relation, which could be used as a standard curve to enable the easily done dipstick measurements in microlitres to be converted to saliva thicknesses in millimeters. As blotting could not be done in embrasures and occlusal fossae, this paper-strip absorption method was unsuitable for similar quantification of residual saliva in these sites but was done in another way described elsewhere. Overall, the results indicated that variations in dental morphology, and in the saliva secreted and available to the different oral regions, are the basic factors responsible for the wide variations in residual amounts of saliva seen on the diverse hard- and soft-tissue surfaces of human mouths. Also, finding that the hard palate and inner lips are covered by very thin films of residual saliva suggested that only a small reduction in their quantity would be needed to trigger the dry mouth sensation in hyposalivators.

The flow rate of unstimulated human labial gland saliva

Although the minor salivary glands contribute an important fraction of the resting flow of saliva, which may be particularly relevant in xerostomia, there is currently no precise method of measuring the flow from individual glands or recording the number of active glands in a given area. These experiments were devised to test a photographic method of assaying labial gland saliva and to see whether subjects of different ages had differing flow rates and/or numbers of glands. Unstimulated saliva secretion from labial salivary glands was measured in healthy non-medicated subjects aged 20 to 55 years by a photographic method. The number of glands in a unit area, the individual gland flow rates, and the flow rates per unit area were assessed. There was a high correlation between flow rate per unit area as measured by this method and measurements from weighing filter paper before and after absorption of the saliva droplets when the latter method could be used. The mean flow rate for 22 subjects was 2.35 +/- 1.65 microL/min over the whole area photographed. Subjects with higher flow rates had both more active glands and a higher rate of secretion from individual glands. There was no correlation between either number of active glands in a unit area or of flow rate and age in the age range represented by these subjects.

The distribution of saliva and sucrose around the mouth during the use of chewing gum and the implications for the site-specificity of caries and calculus deposition

Over a 20-minute period, subjects expectorated 8 samples of whole saliva (EWS) while chewing gum. Flow rates were calculated, and sucrose was analyzed in these samples as well as in saliva collected on filter paper strips from different tooth surfaces. Salivary film velocity (SFV), based on a 0.1-mm-thick film, was estimated from the clearance half-times of KCl in agarose disks positioned in different regions of the mouth. Salivary flow rate peaked at 5.1 mL/min in the first min but fell to about 1.25 mL/min by the end of the 20 min of gum-chewing. In contrast, flow rate when subjects sucked sour lemon drops averaged about 5.3 mL/min throughout the 20-minute period. The mean salivary sucrose concentration during gum-chewing peaked in the second min at 384 mmol/L (13.1%) but had fallen to 14 mmol/L by the 15-20-minute time interval. The sucrose concentrations on the palatal surfaces of the upper incisors and the facial and lingual surfaces of the lower molars were not significantly different from that in EWS but were much lower on the facial surfaces of the upper incisors and molars, and on the lingual surfaces of the lower incisors. When flow was unstimulated, SFV was 0.8-1.0 mm/min on the facial surfaces of the upper incisors and lower molars but about 5-8 mm/min on the facial surfaces of the upper molars and on the lingual surfaces of the lower incisors and molars.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of age on immunoglobulin content and volume of human labial gland saliva

Stimulated lower labial (LLGF) and parotid salivary volumes and IgG, IgA, and IgM concentrations were measured in 264 subjects whose ages ranged from 17 to 76 years. A significant (p < 0.001) age-related decline in LLGF output was observed for subjects over this age range. Sixty-three percent of the subjects in the 18-20-year-old group (n = 46) secreted at least 10 microL of labial saliva in a 7-10-minute period, while approximately 70% of the subjects in the two oldest groups (61-70 and 71-76 years old) secreted less than 1 microL of LLGF during this time period (n = 64). No significant gender-based differences occurred in the volumes of labial saliva secreted. Stimulated parotid salivary flow showed no age-related trend in these subjects. Lower labial gland salivary IgA concentrations in an older population (mean age +/- SD = 55.6 yr +/- 1.3) were significantly lower (p < 0.025) than IgA concentrations in a younger population (20.7 yr +/- 0.8), when IgA was expressed as microgram/mL LLGF collected. Immunoglobulin A concentrations in parotid saliva and IgG and IgM concentrations in labial and parotid saliva were not significantly different when the two age populations were compared. These data suggest that the physiological and immunological potential of labial gland saliva may decrease with age.

Effects of salivary bicarbonate content and film velocity on pH changes in an artificial plaque containing Streptococcus oralis, after exposure to sucrose

Chewing-gum stimulation of salivary flow (at the time of the pH minimum following exposure of plaque to carbohydrate) has been shown to cause a rapid increase in plaque pH. The objective of this study was to determine whether the rise in plaque pH is primarily due to the increased buffering capacity of stimulated saliva, or to the fact that an increased flow rate increases the concentration gradient for acid to diffuse from the plaque into the overlying salivary film, which will be moving at a higher velocity. This was investigated with an in vitro technique in which artificial plaque (0.5 or 1.5 mm deep) containing S. oralis cells was exposed to 10% sucrose for one min. The pH values at the proximal and distal undersurfaces of the plaque were then monitored during the passage of a 0.1-mm-thick film of a sucrose-free artificial saliva over the surface, at a range of film velocities (0.8-8 mm/min) that have been estimated to occur in vivo. When a minimum plaque pH had been achieved, the salivary film velocity was either (a) kept the same, with or without 15 mmol/L HCO3 (the concentration measured in chewing-gum-stimulated saliva), (b) increased to 86.2 mm/min, or (c) increased to 86.2 mm/min with 15 mmol/L HCO3 added to the artificial saliva. The findings suggest that after sucrose ingestion, the rapid rise from minimum plaque pH values, which can occur with gum-chewing stimulation of salivary flow, is due to the combined effects of the increase in salivary film velocity, and of a greater availability of bicarbonate.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunoglobulin isotypes in human minor gland saliva

Lower labial, upper labial, palatine (minor), and parotid (major) gland saliva samples from 18 young adult males were quantitatively assayed for the presence of IgA1, IgA2, IgM, and IgG. The mean (+/- standard deviation) concentrations of IgA (sum of IgA1 + IgA2) were 79 +/- 42 micrograms/mL (parotid), 111 +/- 42 micrograms/mL (lower labial), 69 +/- 72 micrograms/mL (upper labial), and 88 +/- 68 micrograms/mL (palatine). Total IgA concentrations were positively correlated among different minor-gland samples from the same subject, although these correlations did not reach significance. Upper-labial-gland saliva samples contained significantly (at least p less than 0.05) lower concentrations of IgA1 than those found in parotid or lower-labial minor-gland secretions. All three minor-gland sources of saliva contained significantly (p less than 0.002) higher levels of IgG than did parotid saliva. Upper-labial fluids had significantly (p less than 0.02) higher IgG concentrations than lower-labial saliva. IgM could be detected in 89% of parotid saliva samples and 75% of the palatine saliva samples. Palatine IgM concentrations (8.2 +/- 17.8 micrograms/mL) were significantly (p less than 0.05) higher than parotid IgM concentrations (0.6 +/- 0.4 micrograms/mL). IgM was detected much less frequently and at lower concentrations in lower- and upper-labial-gland saliva. These data reveal that minor-gland saliva from different oral sites may contain distinctive immunoglobulin isotype patterns, and expressions of host defense may vary within each micro-environment.

A method for measuring the flow of saliva from the minor salivary glands

This investigation evaluated a procedure to measure the quantity of secretion by the minor salivary glands from various locations in the mouth before and after citric acid stimulation. Fourteen healthy non-medicated adults were assessed on each of two morning visits at the same specific areas of the mucosa (labial, buccal, and palatal). During each assessment, an absorbent paper strip was placed on each designated location for 30 s, removed, and its moisture content determined with a calibrated Periotron. Calibration procedures indicated that readings were linearly associated with known saliva volumes and were negligibly influenced by differences in salt concentration and viscosity. At each visit, the buccal flow was significantly greater than those from the lip and palate. The flow from glands in each area was unaffected by a single application of the gustatory stimulant. The mean flow rates at each specified site were similar during the two visits.

Interaction of saliva and taste

In spite of the coexistence of saliva and taste in the oral cavity, an understanding of their interactions is still incomplete. Saliva has modulating effects on sour, salt, and the monosodium-glutamate-induced savory or umami taste. It has a diminishing effect on sour taste as a result of the buffering by salivary bicarbonate. It probably also contributes to the umami taste with endogenous salivary glutamate levels. Salt taste is detected only when above salivary sodium-chloride concentrations; thus saliva influences salt taste threshold levels. It also provides the ionic environment for taste cells, probably critical in signal transduction. Salivary flow rate and composition are influenced by the type of taste stimuli. In general, sour taste, elicited by citric acid or sour food, induces the highest flow rate and Na+ concentrations, while salt gives rise to high protein and Ca2+ concentrations. Stimulation with the four basic taste modalities (sour, sweet, salty, and bitter), however, does not increase the relative proportion of any of the salivary proteins. This review examines the literature on the interactions of saliva with taste, and the effect of taste on salivary composition. The possible role of the von Ebner's salivary glands and the role of saliva as a chemical cue are also discussed.

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).

Immunological features of minor salivary gland saliva

Concentrations of IgA, IgG, IgM, and IgA subclasses were measured in 138 pairs of parotid gland saliva (PS) and labial gland saliva (LS), using an enzyme-linked immunosorbent assay (ELISA) technique in which levels of Ig were quantitated using affinity-purified anti-heavy chain reagents for capture and development. Both PS and LS were collected simultaneously during sour lemon drop stimulation. As previously observed, IgA was the dominant immunoglobulin in both salivary fluids, the concentrations of which were highly correlated within the subjects studied. The mean proportion of IgA1 to total IgA was slightly higher in LS (0.66), compared with PS (0.60). Little IgM was usually detected in either secretion. In contrast, LS had IgG concentrations (mean, 8.1 micrograms/ml) which were significantly higher (P less than 0.001) than those found in parotid saliva (mean, 0.3 micrograms/ml). Over 30% of the subjects had mean LS IgG levels above 10 micrograms/ml. The mean percentage of LS IgG to IgA was 20% in the 138 samples tested. Gel filtration of pairs of PS and LS from four individuals revealed IgM, IgA, and IgG to elute in positions commensurate with pentameric IgM, secretory IgA, and monomeric IgG. Little or no monomeric IgA could be detected. These results suggest that, in addition to IgA, the IgG isotype may also be important in antibody-mediated phenomena which occur in oral microenvironments bathed by 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 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.

Isolation, chemical and biological characterization of sulphated glycoproteins synthesized by rat buccal and palatal minor salivary glands in vivo and in vitro

35S-labelled sulphated glycoproteins (SGP) were isolated from these glands after the incorporation of radiosulphate in vivo and in vitro by fractionation of tissue and medium extracts on Sepharose 4B and partial purification by DEAE-Sephacel anion exchange chromatography. Fractions were assessed for purity by SDS-PAGE and by cellulose-acetate electrophoresis. Molecular weights ranged from 34,000 to 5 X 10(6). It was notable that the molecular size of SGP from the in vitro media was generally lower than from the corresponding tissue fractions, particularly for the palatal samples. The fractions were heterogeneous and contained no sulphated glycosaminoglycans; they had high levels of aspartic acid, glutamic acid, threonine and serine, but there was no major difference in amino-acid composition between them. Carbohydrate analysis indicated typical components associated with sulphated glycoproteins, including fucose, galactose, glucose, mannose, N-acetylgalactosamine, N-acetylglucosamine and N-acetylneuraminic acid. Protein:carbohydrate ratios ranged from 0.1:1.0-3.5:1.0 and ester sulphate from 0.8 to 16.2 per cent. All fractions exhibited blood-group A reactivity and aggregated Streptococcus sanguis NCTC 7864; several fractions interacted similarly with Streptococcus mutans OMZ61.

Incorporation of inorganic [35S]-sulphate into glycoproteins of rat buccal and palatal minor salivary glands in vivo and in vitro

The incorporation of sodium [35S]-sulphate into the buccal and palatal minor glands of the albino rat was studied in vivo and in vitro. The biosynthesis of 35S-labelled macromolecules possessing the characteristics of sulphated glycoproteins was evident in both. Uptake of [35S]-sulphate into the palatal tissue in vivo was more rapid (approx. 10-fold at 2 h) and produced compounds of higher specific activity by comparison with buccal extracts. Following in-vitro culture in the presence of [35S]-sulphate, the 35S-labelled glycoproteins secreted into the medium contained a greater proportion of lower molecular-weight products and were of higher specific activity (in the range 10-20-fold greater) than those in the tissue fraction. No sulphated glycosaminoglycans were apparent in any of the products isolated.

Secretion of saliva by human lip mucous glands and parotid glands in response to gustatory stimuli and chewing

To test the suggestion that minor salivary glands, such as the lower lip mucous glands, respond to stimulation in a similar manner to major glands such as the parotid, an appliance was constructed for each subject using an organopolysiloxane dental impression material which held a strip of filter paper against the inner aspect of the lower lip. The volume of labial secretion produced was determined by weight difference. Saliva from the right parotid duct was collected into pre-weighed tubes using a Lashley cannula. Test stimuli, applied for 4-min periods in triplicate, were ascorbic acid (0.08 and 0.16 M), sodium chloride (0.4 and 0.8 M) and the chewing of pieces of polyurethane foam and chicle. In 7 of 13 subjects, the response patterns of labial and parotid glands were qualitatively similar. With acid stimulation, the percentage increase in flow from the parotid was much greater than from labial glands. A significant difference was noted between the mean volumes of unstimulated secretion from the lip glands in a group of 8 subjects with restorations in lower anterior teeth and in 12 controls.

The predictive value of elevated labial saliva sodium concentration: its relation to labial gland pathology in bone marrow transplant recipients

Labial minor gland salivary flow rate and sodium concentration were analyzed in relation to 1) histologic findings in labial biopsy specimens and 2) the occurrence of chronic graft-versus-host disease (GVHD) in patients who received bone marrow transplants. Biopsy specimens and samples were obtained from 61 recipients of marrow transplants (including three twins) 51 to 1,260 days post transplantation. Labial saliva sodium concentrations were elevated in some patients, and these increases were associated with inflammation and destruction of minor salivary gland acini and ducts by chronic GVHD or other factors. The predictive value of the salivary sodium changes in evaluating labial salivary gland pathologic changes was 91 per cent, and the sensitivity was 74 per cent. Thus, if a transplant recipient is found to have an elevated labial saliva sodium level, then the probability that he has pathologic labial gland changes is 91 per cent. When analyses were restricted to include only patients who received no irradiation during transplantation, then elevated labial saliva sodium concentration was significantly associated with the occurrence of chronic GVHD. The sensitivity of this relationship was 42 per cent, but the predictive value was 100 per cent. Thus, if a nonirradiated transplant recipient is found to have an elevated labial saliva sodium concentration, then it is virtually certain that he has chronic GVHD. We found no significant changes in labial saliva flow rates in these bone marrow transplant recipients.

Some chemical characteristics of human minor salivary gland secretions

The minor salivary glands contribute to the composition of whole saliva, but little information has been available about their chemical constituents. Pilocarpine-stimulated labial and palatine secretion from 4 human subjects was investigated by paper and disc electrophoresis, immunochemical analysis, and for content of carbohydrates, amino acids, lipids, hexuronic acids and sulphate. No significant differences were noted between the labial and palatine secretions by any of the methods employed. The minor gland secretions appeared to consist mainly of mucosubstances, possibly with blood group specificity. In addition, three water-soluble components with the characteristics of albumin, alpha-amylase and secretory IgA were seen. The minor gland secretions had an amino acid profile different from those of the major salivary glands and contained higher proportions of carbohydrate. Only one lipid component, with the characteristics of a polar lipid, was seen. Hexuronic acids were not detected in either secretion, whereas both contained sulphate. It would appear that the minor mucous glands contribute to the content of mucosubstances in whole saliva, whereas their content of water-soluble material is negligible in this respect.

Minor salivary glands as a major source of secretory immunoglobin A in the human oral cavity

Secretory immunoglobulin A is the predominant immunoglobulin in labial minor salivary gland secretions. Its mean concentration is four times higher in these secretions than in parotid gland secretion. The minor salivary glands can produce 30 to 35 percent of the immunoglobulin A that enters the oral cavity. This, together with the potential accessibility of these glands to antigenic stimulation, suggest that they may be an important source of the immune factors that are involved in the regulation of the microorganisms in the oral environment.