Saliva biomarkers in oral disease

Saliva is a versatile biofluid that contains a wide variety of biomarkers reflecting both physiologic and pathophysiologic states. Saliva collection is noninvasive and highly applicable for tests requiring serial sampling. Furthermore, advances in test accuracy, sensitivity and precision for saliva has improved diagnostic performance as well as the identification of novel markers especially in oral disease processes. These include dental caries, periodontitis, oral squamous cell carcinoma (OSCC) and Sjögren's syndrome (SS). Numerous growth factors, enzymes, interleukins and cytokines have been identified and are the subject of much research investigation. This review highlights current procedures for successful determination of saliva biomarkers including preanalytical factors associated with sampling, storage and pretreatment as well as subsequent analysis. Moreover, it provides an overview of the diagnostic applications of these salivary biomarkers in common oral diseases.

Effect of saliva collection methods and oral hygiene on salivary biomarkers

The aim of this study was to evaluate the influence of unstimulated and stimulated saliva collection methods, as well as tooth brushing, on the secretion rate of salivary total protein, nitrite, total antioxidant capacity and alpha-amylase. Saliva of 14 healthy individuals were collected with stimulation using Salivette^®, Parafilm^® and chewing gum and without stimulation from spit with and without fluid accumulation, before and after oral hygiene. Total protein, nitrite, total antioxidant capacity and alpha-amylase concentration (sAA) were evaluated. The collection of saliva stimulated with Parafilm^® and chewing gum increased the salivary flow (1.5 ± 0.4 and 3.4 ± 0.7 mL/min, respectively) and the secretion rate of salivary total protein (1.0 ± 0.2 and 2.3 ± 0.5 mg/min, respectively). Also, chewing gum increases the salivary nitrite secretion (213 ± 58 nmol/min) and total antioxidant capacity (410 ± 47 nmol trolox eq/min). Interestingly, the unstimulated method without saliva accumulation prior to collection resulted in low sAA levels (23,531 ± 7979 pixel density). Furthermore, oral hygiene decreased salivary flow (1.3 ± 0.5 to 1.0 ± 0.4 mL/min), reduced the secretion rate of total protein (1.0 ± 0.5 to 0.6 ± 0.2 mg/min, p < .05) and increased sAA (13,159 ± 7114 to 20,075 ± 25,656 pixel density, p < .05). The type of stimulation can activate autonomous receptors responsible for the secretion and composition of saliva. Therefore, the evaluation of saliva collection methods and oral hygiene on salivary biomarkers is important for understanding and standardizing variations in salivary composition to strengthen the use of saliva as a diagnostic fluid.

Protection by sildenafil and theophylline of lead acetate-induced oxidative stress in rat submandibular gland and saliva

The role of oxidative stress in lead toxicity has been proposed in many organs, however, no study has been performed in the salivary glands, which are important parts of the gastrointestinal tract with a high implication in health of the whole body. Recently, it has been proposed that increasing the levels of cGMP and cAMP in the cells may protect from the neurotoxicity of lead. The objective of this study was to determine the ability of lead acetate to produce oxidative stress in rat submandibular as the main salivary gland of the body and to study the role of pretreatment by specific phosphodiesterase inhibitors in the prevention of oxidative stress. Lead acetate (100 mg/kg), alone or in combination with theophylline (25 mg/kg) and sildenafil (5 mg/kg), was administered intraperitoneally to rats. After 2 hours and under general anaesthesia, the submandibular gland ducts were cannulated intraorally using microcannula, and pure saliva was collected for 30 min using pilocarpine (8 mg/kg) as a secretagogue. The submandibular glands were then isolated free under surgery. Oxidative stress in the gland and pure saliva were evaluated measuring lipid peroxidation (thiobarbituric acid reactive substances assay), total thiol groups content and total antioxidant capacity (the ferric reducing ability assay). Results showed significant oxidative stress in the gland and secretions as indicated by increased lipid peroxidation, decreased total antioxidant capacity and thiol group levels. The use of cAMP and cGMP phosodiesterase inhibitors, theophylline and sildenafil, prevented leadinduced increased lipid peroxidation and also protected from decreased thiol groups content and total antioxidant power of the gland and secretions. The same trend of effects was observed in gland and saliva. It is concluded that lead toxicity is mediated through oxidative stress in salivary glands, while increasing intracellular cAMP and cGMP levels may prevent lead-induced oxidative stress.

Copy number polymorphism of the salivary amylase gene: implications in human nutrition research

The salivary α-amylase is a calcium-binding enzyme that initiates starch digestion in the oral cavity. The α-amylase genes are located in a cluster on the chromosome that includes salivary amylase genes (AMY1), two pancreatic α-amylase genes (AMY2A and AMY2B) and a related pseudogene. The AMY1 genes show extensive copy number variation which is directly proportional to the salivary α-amylase content in saliva. The α-amylase amount in saliva is also influenced by other factors, such as hydration status, psychosocial stress level, and short-term dietary habits. It has been shown that the average copy number of AMY1 gene is higher in populations that evolved under high-starch diets versus low-starch diets, reflecting an intense positive selection imposed by diet on amylase copy number during evolution. In this context, a number of different aspects can be considered in evaluating the possible impact of copy number variation of the AMY1 gene on nutrition research, such as issues related to human diet gene evolution, action on starch digestion, effect on glycemic response after starch consumption, modulation of the action of α-amylases inhibitors, effect on taste perception and satiety, influence on psychosocial stress and relation to oral health.

Molecular mechanism of pancreatic and salivary gland fluid and HCO3 secretion

Fluid and HCO(3)(-) secretion is a vital function of all epithelia and is required for the survival of the tissue. Aberrant fluid and HCO(3)(-) secretion is associated with many epithelial diseases, such as cystic fibrosis, pancreatitis, Sjögren's syndrome, and other epithelial inflammatory and autoimmune diseases. Significant progress has been made over the last 20 years in our understanding of epithelial fluid and HCO(3)(-) secretion, in particular by secretory glands. Fluid and HCO(3)(-) secretion by secretory glands is a two-step process. Acinar cells secrete isotonic fluid in which the major salt is NaCl. Subsequently, the duct modifies the volume and electrolyte composition of the fluid to absorb the Cl(-) and secrete HCO(3)(-). The relative volume secreted by acinar and duct cells and modification of electrolyte composition of the secreted fluids varies among secretory glands to meet their physiological functions. In the pancreas, acinar cells secrete a small amount of NaCl-rich fluid, while the duct absorbs the Cl(-) and secretes HCO(3)(-) and the bulk of the fluid in the pancreatic juice. Fluid secretion appears to be driven by active HCO(3)(-) secretion. In the salivary glands, acinar cells secrete the bulk of the fluid in the saliva that is driven by active Cl(-) secretion and contains high concentrations of Na(+) and Cl(-). The salivary glands duct absorbs both the Na(+) and Cl(-) and secretes K(+) and HCO(3)(-). In this review, we focus on the molecular mechanism of fluid and HCO(3)(-) secretion by the pancreas and salivary glands, to highlight the similarities of the fundamental mechanisms of acinar and duct cell functions, and to point out the differences to meet gland-specific secretions.

Functional and proteomic analysis of submandibular saliva in rats exposed to chronic stress by immobilization or constant light

OBJECTIVE

In this study, we have evaluated the effects of stress on functional and proteomic changes in submandibular saliva of rats.

DESIGN

Male adult rats were divided in three groups: IMO (2 h/day of immobilization for 7 days), LL (constant light during 20 days), C (unstressed controls submitted to 14 h light-10h dark cycle). Body weight, food intake and the dry weight of submandibular gland were recorded. Saliva samples, collected under anaesthesia following i.p. administration of isoproterenol and pilocarpine (5 mg/kg), were assayed for total proteins (TP), amylase activity and SDS-PAGE electrophoresis.

RESULTS

Body weight, food intake and the dry weight of submandibular gland of IMO rats were lower than those of C and LL groups. The salivary volumes secreted in IMO and LL rats, were significantly higher than in controls. The TP output (μg protein/μg saliva/mg of dry tissue) and amylase activity output (AU/μg of saliva/mg of dry tissue) in IMO were significantly higher than in C and LL animals. The electrophoretic pattern of saliva proteins of LL rats, revealed the absence of a protein band of approximately 25 kDa. This band was composed by the common salivary protein-1 and a prolactin-induced protein as identified by peptide mass fingerprinting.

CONCLUSIONS

Differences in body weight and food intake between IMO and LL might be attributed to the sort and intensity of stressors stimuli. The changes in the volume of secreted saliva could be a compensatory mechanism in response to stressors. The increase of total protein in IMO rats and the absence of 25 kDa proteins in LL, would suggest that the submandibular glands respond to the sympathetic nervous system stimuli induced by the stress with an increase of activity of the sympathetic nerves in IMO and a reduction in LL rats.

Abnormal diurnal patterns of salivary α-amylase and cortisol secretion in acute patients with anorexia nervosa

OBJECTIVES

The evidence that the activity of the sympathetic nervous system (SNS) is decreased in acute anorexia nervosa (AN) is not consistent. Therefore, we aimed to assess the SNS basal activity in malnourished AN patients through the measurement of diurnal salivary levels of α-amylase, whose secretion is regulated by the SNS. As secondary aim, we measured also salivary cortisol.

METHODS

Eight symptomatic female patients with restrictive AN and eight age-matched healthy women underwent saliva sample collection at awakening and over the day. α-amylase and cortisol were assayed by ELISA method.

RESULTS

In both patients and controls, saliva α-amylase levels significantly decreased during 60 min after awakening and then progressively rose towards the afternoon/evening. AN patients exhibited significantly reduced levels of the salivary enzyme with a significant decrease in its overall diurnal secretion and a dysregulated secretory pattern. As compared to control women, AN patients exhibited significantly enhanced levels of salivary cortisol at awakening, an enhanced and advanced cortisol secretion after awakening but no significant change in the overall diurnal secretion of the salivary hormone.

CONCLUSIONS

These results suggest that the activity of the SNS, evaluated through the assessment of the diurnal secretion of salivary α-amylase, is impaired in the acute phase of AN whereas the cortisol awakening response is enhanced.

The diffuse chemosensory system: exploring the iceberg toward the definition of functional roles

The diffuse chemosensory system (DCS) is an anatomical structure composed of solitary chemosensory cells (SCCs, also called solitary chemoreceptor cells), which have analogies with taste cells but are not aggregated in buds. The concept of DCS has been advanced, after the discovery that cells similar to gustatory elements are present in several organs. The elements forming the DCS share common morphological and biochemical characteristics with the taste cells located in taste buds of the oro-pharyngeal cavity but they are localized in internal organs. In particular, they may express molecules of the chemoreceptorial cascade (e.g. trans-membrane taste receptors, the G-protein alpha-gustducin, PLCbeta2, TRPM5). This article will focus on the mammalian DCS in apparatuses of endodermic origin (i.e. digestive and respiratory systems), which is composed of an enormous number of sensory elements and presents a multiplicity of morphological aspects. Recent research has provided an adequate description of these elements, but the functional role for the DCS in these apparatuses is unknown. The initial findings led to the definition of a DCS structured like an iceberg, with a mysterious "submerged" portion localized in the distal part of endodermic apparatuses. Recent work has focussed on the discovery of this submerged portion, which now appears less puzzling. However, the functional roles of the different cytotypes belonging to the DCS are not well known. Recent studies linked chemosensation of the intraluminal content to local control of absorptive and secretory (exocrine and endocrine) processes. Control of the microbial population and detection of irritants seem to be other possible functions of the DCS. In the light of these new findings, the DCS might be thought to be involved in a wide range of diseases of both the respiratory (e.g. asthma, chronic obstructive pulmonary disease, cystic fibrosis) and digestive apparatuses (absorptive or secretive diseases, dysmicrobism), as well as in systemic diseases (e.g. obesity, diabetes). A description of the functional roles of the DCS might be a first step toward the discovery of therapeutic approaches which target chemosensory mechanisms.

Modification of innervation pattern by fluoroquinolone treatment in the rat salivary glands

Fluoroquinolone antibiotics (FQAs) are widely used in dental and medical therapy. Despite their known severe adverse actions on the central and peripheral nervous system, little attention has been directed toward the potential toxic side effects of these compounds on the oral tissues. As the saliva secretion is controlled by the nervous system and neuropeptides, the neurotoxic effect of pefloxacin (PEF), a representative member of FQAs, was studied in rats in the present work. Previously, we demonstrated a significant weight loss of parotid gland tissue, a marked decrease in 3H-thymidine incorporation, a decreased volume of saliva and amylase activity of the glandular tissue in response to PEF. Animals received intraperitoneal injection of PEF (20 mg/100 g body weight daily) for 3 and 7 days. Normal histology, and neurofilament 200, substance P (SP) and calcitonin gene-related polypeptide (CGRP) containing nerve fibers were detected with immunohistochemical methods. A marked decrease of the weights in salivary glands and the acinar diameters were measured. Similarly, a strong and significant decrease of the number of SP and CGRP containing nerve fibers were detected. These findings suggest that the impaired morphology and innervation pattern of salivary glands is related to the neurotoxic adverse effect of FQA treatment.

Effect of translocator protein (18 kDa)-ligand binding on neurotransmitter-induced salivary secretion in rat submandibular glands

BACKGROUND INFORMATION

TSPO (translocator protein), previously known as PBR (peripheral-type benzodiazepine receptor), is a ubiquitous 18 kDa transmembrane protein that participates in diverse cell functions. High-affinity TSPO ligands are best known for their ability to stimulate cholesterol transport in organs synthesizing steroids and bile salts, although they modulate other physiological functions, including cell proliferation, apoptosis and calcium-dependent transepithelial ion secretion. In present study, we investigated the localization and function of TSPO in salivary glands.

RESULTS

Immunohistochemical analysis of TSPO in rat salivary glands revealed that TSPO and its endogenous ligand, DBI (diazepam-binding inhibitor), were present in duct and mucous acinar cells. TSPO was localized to the mitochondria of these cells, whereas DBI was cytosolic. As expected, mitochondrial membrane preparations, which were enriched in TSPO, exhibited a high affinity for the TSPO drug ligand, (3)H-labelled PK 11195, as shown by B(max) and K(d) values of 10.0+/-0.5 pmol/mg and 4.0+/-1.0 nM respectively. Intravenous perfusion of PK 11195 increased the salivary flow rate that was induced by muscarinic and alpha-adrenergic agonists, whereas it had no effect when administered alone. Addition of PK 11195 also increased the K(+), Na(+), Cl(-) and protein content of saliva, indicating that this ligand modulated secretion by acini and duct cells.

CONCLUSIONS

High-affinity ligand binding to mitochondrial TSPO modulates neurotransmitter-induced salivary secretion by duct and mucous acinar cells of rat submandibular glands.

Magnesium–calcium signalling in rat parotid acinar cells: effects of acetylcholine

This study investigated the effects of extracellular Mg(2+) ([Mg(2+)](o)) on basal and acetylcholine (ACh)-evoked amylase secretion and intracellular free Ca(2+) ([Ca(2+)](i)) in rat parotid acinar cells. In a medium containing 1.1 mM [Mg(2+)](o), ACh evoked significant increases in amylase secretion and [Ca(2+)](i). Either low (0 mM) or elevated (5 and 10 mM) [Mg(2+)](o) attenuated ACh-evoked responses. In a nominally Ca(2+) free medium, elevated [Mg(2+)](o) attenuated basal and ACh-evoked amylase secretion and [Ca(2+)](i). In parotid acinar cells incubated with either 0, 1.1, 5 or 10 mM [Mg(2+)](o), ACh evoked a gradual decrease in [Mg(2+)](i). These results indicate that the ACh-evoked Mg(2+) efflux is an active process since Mg(2+) has to move against its gradient. Either lidocaine, amiloride, N-methyl-D: -glucamine, quinidine, dinitrophenol or bumetanide can elevate [Mg(2+)](i) above basal level. In the presence of these membrane transport inhibitors, ACh still evoked a decrease in [Mg(2+)](i) but the response was less pronounced with either [Na(+)](o) removal or in the presence of either amiloride or quinidine. These results indicate marked interactions between Ca(2+) and Mg(2+) signalling in parotid acinar cells and that ACh-evoked Mg(2+) transport was not dependent upon [Na(+)](o).

Low-frequency noise effects on the parotid gland of the Wistar rat

BACKGROUND

Long-term low-frequency noise (LFN) (<or=500 Hz) exposure is known to cause extracellular matrix proliferation by fibrosis in the absence of inflammatory signs.

AIM

We have examined the morphofunctional alterations of the parotid glands of Wistar rats exposed to LFN. The hypothesis is that the parotid glands are a target for LFN-induced lesions.

MATERIALS AND METHODS

Ten rats were exposed to LFN for 2184 consecutive hours while 10 rats were kept under similar conditions but in silence for control purposes. The parotid glands were surgically removed. One gland was sectioned and stained with hematoxylin-eosin and periodic acid Schiff for light microscopy observation. The other was used for functional amylase secretion measurements, basal and nerve-mediated [with electrical field stimulation (EFS)] and secretagogue-evoked secretion [acetylcholine (ACh) 10(-5) m] with established fluorimetric techniques.

RESULTS

All the rats exposed to LFN showed marked morphological lesions including vacuolar degeneration, hyalinization, cell death and blood vessels wall focal thickening. No morphological changes were detected in the control group. The functional results presented significantly diminished basal, EFS and ACh-evoked amylase secretion when compared with the control group.

CONCLUSION

These results suggest that the parotid gland is a target for LFN-induced lesions with an impairment of its function.

Determinants of the diurnal course of salivary alpha-amylase

OBJECTIVE

Previous data from our group and others have shown that salivary alpha-amylase activity increases in response to stress. It has been suggested that salivary alpha-amylase may be a marker for adrenergic activity. Less is known about other determinants of salivary alpha-amylase activation. The objective of the current study was to describe the diurnal pattern of salivary amylase and its determinants.

METHODS

Saliva samples were collected immediately after waking-up, 30 and 60 min later, and each full hour between 0900 and 2000 h by 76 healthy volunteers (44 women, 32 men). Compliance was controlled by electronic monitors. In order to control factors which might influence the diurnal profile of salivary alpha-amylase (such as momentary stress, mood, food, or body activity), at each sampling time point the subjects filled out a diary examining the activities they had carried out during the previous hour.

RESULTS

Salivary alpha-amylase activity shows a distinct diurnal profile pattern with a pronounced decrease within 60 min after awakening and a steady increase of activity during the course of the day. Mixed models showed a relative independence of diurnal salivary alpha-amylase from momentary stress and other factors, but significant associations with chronic stress and mood.

CONCLUSIONS

Our results suggest that diurnal profiles of salivary alpha-amylase are relatively robust against momentary influences and therefore may prove useful in the assessment of sympathetic nervous system activity. The findings underscore the need to control for time of day in studies using salivary alpha-amylase as a dependent variable.

Functional relationship between subfornical organ cholinergic stimulation and nitrergic activation influencing cardiovascular and body fluid homeostasis

We have studied the effects of L-NG-nitro arginine methyl esther (L-NAME), L-arginine (LAR), inhibitor and a donating nitric oxide agent on the alterations of salivary flow, water intake, arterial blood pressure (MAP) and heart rate (HR) induced by the injection pilocarpine into the subfornical organ (SFO). Rats (Holtzman 250-300 g) were anesthetized with 2, 2, 2-tribromoethanol (20 mg/100 kg b. wt.) and a stainless steel cannula were implanted into their SFO. The volume of injection was 0.2 microl. The amount of saliva secretion was studied over a 5-min period. Pilocarpine (40 microg), L-NAME (40 microg) and LAR (30 microg) were used in all experiments for the injection into the SFO. Pilocarpine (10, 20, 40, 80 and 160 microg) injected into SFO elicited a concentration-dependent increase in salivary secretion. L-NAME injected prior to pilocarpine into the SFO increased salivary secretion and water intake due to the effect of pilocarpine. LAR injected prior to pilocarpine into the SFO attenuated the salivary secretion and water intake. Pilocarpine, injected into the SFO increased the MAP and decreased heart rate (HR). L-NAME injected prior to pilocarpine into the SFO potentiated the pressor effect of pilocarpine with a decrease in HR. LAR injected into the SFO prior to pilocarpine attenuated the increase in MAP with no changes in HR. The present study suggests that the SFO nitrergic cells interfere in the cholinergic pathways implicated in the control of salivary secretion, fluid and cardiovascular homeostasis.

Oral and salivary parameters in patients with rheumatic diseases

We studied the presence of secondary Sjögren's syndrome (SS) and the composition of saliva, prevalence of oral pathogens, periodontitis, mouth mucosa, and teeth in patients with various rheumatic diseases and in healthy controls. The hypothesis was that different rheumatic diseases might cause differences in oral health characteristics because of the liability of secondary SS in the patients. The study involved 77 patients and 77 age-matched and sex-matched controls. Twenty patients were suffering from spondylarthropathy (SPA), 18 from ankylosing spondylitis (AS), 24 from rheumatoid arthritis (RA), and 15 from mixed connective tissue disease (MCTD). Clinical and radiographic oral health status was recorded and salivary flow rates were measured. Selected salivary proteins and immunoglobulins were analysed by routine methods. Minor salivary gland biopsy samples were taken from the patients for assessment of inflammatory focus scores. Differences between patients and controls and in between the different rheumatic diseases were analysed statistically. Secondary SS was diagnosed in 39% (30/77) of the patients. A severe periodontal condition (community periodontal index of treatment needs score 3 or 4) occurred in 58% (45/77) of the rheumatic patients compared with only 26% (20/77) of the controls (p < 0.0001). The severity of focal sialadenitis (focus score) correlated significant with salivary IgA, IgG, and IgM concentrations. Salivary albumin, total protein, IgG, and IgM concentrations were higher in all patient groups than in the controls. The number of patients with low salivary flow rates was higher in all patient groups compared to controls. Oral yeast counts were significantly higher in the patients than in the controls (p < 0.001). In a subgroup analysis, patients with SS had higher values for salivary IgA and IgM than patients without SS. Dental caries and oral lactobacilli were more frequent in patients with SS, but SS was not associated with periodontitis. No major differences were noted in other salivary biochemical parameters between these two groups. Patients with rheumatic diseases, irrespective of specific diagnosis, thus had various alterations in salivary flow and composition and oral health. The findings may reflect the autoimmune inflammation of the salivary glands frequently observed in these patients.

On the relation of nitric oxide to nifedipine-induced gingival hyperplasia and impaired submandibular glands function in rats in vivo

Calcium-channel blockers such as nifedipine could be associated with gingival overgrowth. The aim of this study was to examine the role of nitric oxide (NO) on nifedipine-induced gingival hyperplasia along with submandibular secretory function in rats. Animals in divided groups received nifedipine (250 mg/kg diet) alone and in combination with L-arginine (2.25% w/v) or N(omega)-nitro-L-arginine methyl ester (L-NAME) (0.7% w/v) in drinking water for 20 days. Controls received only tap water. Pure submandibular saliva was collected intraorally by micropolyethylene cannula and the mandibular gingiva was examined by means of dissecting microscope for signs of redness, thickness, inflammation and exuda. Twenty-day nifedipine treatment induced gingival hyperplasia accompanied with reduced salivary flow rate and concentrations of total protein, epidermal growth factor (EGF) and calcium in comparison with controls. Co-treatment of animals with nifedipine and L-arginine protected from gingival hyperplasia and retained flow rate, and concentrations of total protein, EGF and calcium in normal levels. Co-treatment of animals with nifedipine and L-NAME potentiated nifedipine-induced gingival hyperplasia and reductions in flow rate and concentrations of total protein, EGF, and calcium. It is concluded that nifedipine-induced gingival hyperplasia is associated with salivary dysfunction. Activation of cGMP-dependent positive signal-transduction mechanisms in salivary glands might be the mechanism for protective effects of NO against nifedipine-induced gingival hyperplasia.

Submandibular gland acinar cells express multiple alpha1-adrenoceptor subtypes

We evaluated an acinar cell line (SMG-C10) cloned from rat submandibular glands as a possible model for alpha(1)-adrenoceptor regulation of submandibular function. alpha(1)-Adrenoceptors are subdivided into three subtypes called alpha(1A), alpha(1B), and alpha(1D), which can be distinguished from one another by their differential affinity values for subtype-selective alpha(1)-adrenoceptor antagonists. Thus, alpha(1)-adrenoceptor subtypes in SMG-C10 cells were characterized with reverse transcription-polymerase chain reaction (RT-PCR) and [(3)H]prazosin binding in side-by-side experiments with native submandibular glands. RT-PCR identified mRNAs for alpha(1A)-, alpha(1B)-, and alpha(1D)-adrenoceptors in SMG-C10 cells and submandibular glands. The inhibition of [(3)H]prazosin binding by 5-methylurapidil (alpha(1A)-selective) was biphasic and fit best to a two-site binding model with 40 +/- 8% high (K(iH))- and 60 +/- 10% low (K(iL))-affinity binding sites in SMG-C10 cells, and 76% high- and 24% low-affinity binding sites in submandibular glands. Respective K(iH) and K(iL) values for 5-methylurapidil were 1.9 +/- 0.4 and 100 +/- 30 nM in SMG-C10 cells and 3.2 +/- 0.8 and 170 +/- 20 nM in submandibular glands. BMY-7378 [8-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-8-azaspiro[4.5]decane-7,9-dione dihydrochloride (alpha(1D)-selective)] bound with low affinity in SMG-C10 cells and submandibular glands with K(i) values of 81 +/- 20 and 110 +/- 20 nM, respectively. Chloroethylclondine, an irreversible alkylating agent selective for alpha(1B) adrenoceptors, reduced the density of [(3)H]prazosin binding sites by 42 and 26% in SMG-C10 and submandibular membranes, respectively. Thus, SMG-C10 cells and submandibular glands are similar in expressing receptor protein for alpha(1A)- and alpha(1B)-adrenoceptor subtypes, establishing SMG-C10 cells as a potential model for alpha(1)-adrenoceptor-mediated secretion.

Salivary phospholipid secretion in response to beta-adrenergic stimulation is mediated by Src kinase-dependent epidermal growth factor receptor transactivation

Communication between receptor tyrosine kinase and G protein-coupled receptor (GPCR)-mediated signaling is recognized as a common integrator linking diverse aspects of intracellular signaling systems. Here, we report that G protein-coupled beta-adrenergic receptor activation leading to stimulation of salivary phospholipid release occurs with the involvement of epidermal growth factor receptor (EGFR). Using sublingual gland acinar cells, we show that prosecretory effect of isoproterenol on phospholipid release was subjected to suppression by EGFR kinase inhibitor, PD153035, and wortmannin, an inhibitor of PI3K, but not by PD98059, an inhibitor of extracellular signal regulated kinase (ERK). Furthermore, wortmannin, but not the ERK inhibitor, caused the reduction in the acinar cell secretory responses to beta-adrenergic agonist-generated cAMP as well as adenyl cyclase activator, forskolin. The acinar cell phospholipid secretory responses to isoproterenol, moreover, were inhibited by PP2, a selective inhibitor of tyrosine kinase Src responsible for ligand-independent EGFR phosphorylation. Taken together, our data are the first to demonstrate the requirement for Src kinase-dependent EGFR transactivation in regulation of salivary phospholipid secretion in response to beta-adrenergic GPCR activation.

The diagnostic applications of saliva--a review

This review examines the diagnostic application of saliva for systemic diseases. As a diagnostic fluid, saliva offers distinctive advantages over serum because it can be collected non-invasively by individuals with modest training. Furthermore, saliva may provide a cost-effective approach for the screening of large populations. Gland-specific saliva can be used for diagnosis of pathology specific to one of the major salivary glands. Whole saliva, however, is most frequently used for diagnosis of systemic diseases, since it is readily collected and contains serum constituents. These constituents are derived from the local vasculature of the salivary glands and also reach the oral cavity via the flow of gingival fluid. Analysis of saliva may be useful for the diagnosis of hereditary disorders, autoimmune diseases, malignant and infectious diseases, and endocrine disorders, as well as in the assessment of therapeutic levels of drugs and the monitoring of illicit drug use.

Role of nitric oxide of the median preoptic nucleus (MnPO) in the alterations of salivary flow, arterial pressure and heart rate induced by injection of pilocarpine into the MnPO and intraperitoneally

We investigated the effect of L-NAME, a nitric oxide (NO) inhibitor and sodium nitroprusside (SNP), an NO-donating agent, on pilocarpine-induced alterations in salivary flow, mean arterial blood pressure (MAP) and heart rate (HR) in rats. Male Holtzman rats (250-300 g) were implanted with a stainless steel cannula directly into the median preoptic nucleus (MnPO). Pilocarpine (10, 20, 40, 80, 160 g) injected into the MnPO induced an increase in salivary secretion (P<0.01). Pilocarpine (1, 2, 4, 8, 16 mg/kg) ip also increased salivary secretion (P<0.01). Injection of L-NAME (40 g) into the MnPO prior to pilocarpine (10, 20, 40, 80, 160 g) injected into the MnPO or ip (1, 2, 4, 8, 16 mg/kg) increased salivary secretion (P<0.01). SNP (30 g) injected into the MnPO or ip prior to pilocarpine attenuated salivary secretion (P<0.01). Pilocarpine (40 g) injection into the MnPO increased MAP and decreased HR (P<0.01). Pilocarpine (4 mg/kg body weight) ip produced a decrease in MAP and an increase in HR (P<0.01). Injection of L-NAME (40 g) into the MnPO prior to pilocarpine potentiated the increase in MAP and reduced HR (P<0.01). SNP (30 g) injected into the MnPO prior to pilocarpine attenuated (100%) the effect of pilocarpine on MAP, with no effect on HR. Administration of L-NAME (40 g) into the MnPO potentiated the effect of pilocarpine injected ip. SNP (30 g) injected into the MnPO attenuated the effect of ip pilocarpine on MAP and HR. The present study suggests that in the rat MnPO 1) NO is important for the effects of pilocarpine on salivary flow, and 2) pilocarpine interferes with blood pressure and HR (side effects of pilocarpine), that is attenuated by NO.

Structural and functional changes by Ciprofloxacin of rat submandibular gland

In the present study, the effects of Ciprofloxacin (Cipro), a fluoroquinolone antibiotic, on rat submandibular gland structure and function were examined in an acute experiment. Cipro was administered intraperitoneally at various doses (20, 40 and 80 mg/kg). Pure submandibular saliva was collected intraorally by micropolyethylene tubes under anaesthesia using a dissecting microscope. After collection of saliva, submandibular glands were removed and weighed. Flow rate, amylase activity, total protein and electrolyte concentrations were measured in saliva. Concentrations of DNA and protein were measured in the gland. All doses of Cipro (20, 40, 80 mg/kg) reduced salivary flow rate. Concentrations of salivary total protein and calcium and gland DNA were reduced by all doses of Cipro. Treatment by Cipro (80 mg/kg) induced an increase in salivary sodium and potassium concentrations. Histopathological examination of glands revealed that Cipro at doses of 40 mg/kg and 80 mg/kg induces morphological changes in the glands including irregular shape of the cerous and mucous bobbles, lack of nucleus in some cells, damage of the cytoplasmic and cell walls and presence of oncocytes in secretory ducts. It is concluded that Cipro inhibits rat submandibular gland functions consistent with structural damages to the gland that might be observed as a side effect in humans. Properties of fluoroquinolones to alter intracellular cAMP and their ability to suppress DNA and protein synthesis of acinar cells might be possible reasons for observed changes.

The impact of saliva on patient care: A literature review

Decreased salivary flow results in a clinically significant oral imbalance that may manifest as increased caries, susceptibility to oral candidosis, altered taste sensation, or a host of other problems. This article reviews the role of saliva in oral health, highlights the causes and consequences of xerostomia, and outlines treatment modalities for patients with xerostomia. Journal articles were investigated through Medline, and relevant textbooks and handbooks were consulted. A summary of the literature pertinent to clinical prosthodontics is presented.

Mechanisms underlying the structural alterations of the rat submandibular gland induced by Tityus serrulatus tityustoxin

As the mechanisms underlying the structural changes induced in rat submandibular glands by Tityus serrulatus tityustoxin have not been reported, the present study was undertaken to investigate the participation of adrenergic and muscarinic cholinergic receptors in these alterations. Most of the stimulatory effects of the toxin are observed in the secretory cells of the acini and granular convoluted tubules (GCT). We evaluated the ability of the toxin to induce morphological changes in acinar and GCT cells after adrenoreceptor and cholino receptor blockage. The influence of tityustoxin-induced adrenal discharge on the acinar and GCT cells was also investigated after bilateral adrenalectomy. We show that the intense cytoplasmic vacuolation of the acinar cells induced by tityustoxin was prevented by prazosin (alpha(1) adenoreceptor blockade) and atropine (muscarinic cholinoreceptor blockade). The decrease of GCT cell granules following tityustoxin injection was completely blocked by prasozin and partially by propranolol. These results indicate that acinar vacuolation, degranulation of GCT cells, reduction of GCT diameter and height of its epithelium depends on tityustoxin induced adrenergic and cholinergic mechanisms. In contrast, tityustoxin induced acinar cell degranulation was not modified by atropine, prasozin or propranolol (beta(1)-beta(2) adenoreceptor blockade). Thus, acinar degranulation seems to be due to a direct action of tityustoxin on of the rat submandibular glands. The degranulation of the GCT cells and the acinar vacuolation was also prevented by bilateral adrenalectomy, suggesting that these effects are mostly due to catecholamines released from the adrenal glands.

Protection by nitric oxide of morphine-induced inhibition of rat submandibular gland function

The effects of morphine, l -arginine (nitric oxide precursor) and l -NAME (nitric oxide synthesis inhibitor ) and their concurrent therapy on rat submandibular secretory function were studied. Pure submandibular saliva was collected intraorally by micro polyethylene cannula from anaesthetized rats using pilocarpine as secretagogue. Single intraperitoneal injection of morphine (6 mg kg(-1)) to rats induced significant (P< 0.01) inhibition of salivary flow rate (28%), total protein (12%) and calcium concentrations (27%). Sodium output was increased (23%, P< 0.01). Single intraperitoneal administration of l -arginine (100 mg kg(-1)) and l -NAME (10 mg kg(-1)) affected salivary gland function. Saliva flow rate was reduced by l -NAME (23%, P< 0.01). The total protein concentration of saliva was increased by l -arginine (21%, P< 0.05) and decreased by l -NAME (19%, P< 0.01). Calcium concentration of saliva was increased by l -arginine (25%, P< 0.01) and reduced by l -NAME (21%, P< 0.01). In combination treatment, l -arginine prevented (P< 0.01) morphine-induced reduction of flow rate while l -NAME potentiated it (P< 0.01). The secretion of total protein and calcium were influenced in a similar trend by concurrent therapy. l -NAME potentiated morphine-induced decrease of total protein and calcium concentrations (P< 0.01) while l -arginine restored (P< 0.01) them to levels close to control and morphine groups respectively. It is concluded that morphine inhibits salivary gland function and nitric oxide (NO) plays a positive role in this system. Also it is confirmed that morphine inhibitory effects on submandibular function are somewhat restored by l -arginine and expanded by l -NAME. The modulatory effect of the l -arginine/NO system on salivary gland function is suggested.

Use of muscarinic agonists in the treatment of Sjögren's syndrome

Two muscarinic agonists (pilocarpine and cevimeline) have recently been approved for the treatment of symptoms of xerostomia in Sjögren's syndrome (SS). These agents stimulate the M1 and M3 receptors present on salivary glands, leading to increased secretory function. The use of these agents emphasizes the importance of neuroendocrine mechanisms in SS, which is considered an autoimmune disorder. We review recent studies on the release of cytokines and metalloproteinases in SS-affected glands and their influence on the release of and response to neurotransmitters. Also, we review the structure and function of muscarinic receptors as they may relate to SS and the potential use of novel muscarinic agonists in SS.

Prevalence of subjective dry mouth and burning mouth in hospitalized elderly patients and outpatients in relation to saliva, medication, and systemic diseases

OBJECTIVE

The purpose of this study was to investigate the prevalence of self-reported symptoms of dry mouth and burning mouth in the frail elderly. We expected to find the studied symptoms more frequently in the frail elderly than in those who were healthier.

STUDY DESIGN

We examined 175 home-living elderly patients (mean age with SD, 82 +/- 5.7 years) hospitalized because of sudden worsening of their general health. For comparison, 252 elderly outpatients (mean age with SD, 77 +/- 5.7 years) from the same community were studied. The subjects' medical diagnoses and prescribed drugs used daily were recorded, their oral health examined, and saliva samples taken for analyses of flow rates, yeasts, and a variety of biochemical factors.

RESULTS

The results showed that 63% of the hospitalized patients and 57% of the outpatients complained of dry mouth. The respective percentages of burning mouth were 13% in the hospitalized and 18% in the outpatients. The dentate status affected the feeling of dry mouth and burning mouth, but there were no consequent differences in concentrations of salivary biochemical constituents, yeast counts, and buffering capacity between patients with or without the symptoms except that hospitalized patients complaining of dry mouth more often had low salivary buffering than those without the symptom. Dry mouth was also more prevalent among the hospitalized patients who used several drugs daily, whereas no such association was found with the burning-mouth symptom. Use of analgesics appeared to safeguard against both the symptoms. Dry mouth and burning mouth were seldom reported simultaneously, although low salivary flow rate was a common finding in patients with burning mouth. The strongest explanatory factors for burning mouth were psychiatric disease among the outpatients (OR 8.7, CI 1.4-54.1, P <.05) and use of psychiatric drugs among the hospitalized (OR 4.2, CI 0.9-20.0, P =.07). For dry mouth, the strongest explanatory factors were respiratory disease in the outpatients (OR 2.0, CI 1.0-3.8, P <.05) and low salivary flow rate in the hospitalized elderly (OR 3.7, CI 1.4-10, P <.05). In all patients (n = 427), use of psychiatric drugs was the strongest explanatory factor for dry mouth (OR 2.1, CI 1.2-3.5, P <.01), whereas analgesic medication was found to protect against burning mouth (OR 0.5, CI 0.3-0.9, P <.05).

CONCLUSION

The subjective feelings of dry mouth and burning mouth appeared to be a complex issue among the elderly population studied. The 2 symptoms were seldom reported at the same time. The appearance of symptoms did not directly correlate with general health, except in the case of psychiatric diseases and medications, which should be taken into account.

Inhibition of rat parotid and submandibular gland functions by ofloxacin, a fluoroquinolone antibiotic

While fluoroquinolones are widely used in the treatment of various infectious disease, not enough attention has been paid to their adverse effects on salivary glands functions. In the present study, the effects of ofloxacin, a fluoroquinolone antibiotic, on rat parotid and submandibular gland functions, were examined in an acute experiment. Ofloxacin (OFLX) was administered intraperitoneally at various doses (20, 40, and 80 mg/kg). Pure parotid and submandibular saliva were collected intraorally by microployethylene tubes under anaesthesia using a dissecting microscope. Flow rate, amylase activity, total protein, and calcium concentrations were reduced by all doses of OFLX (20, 40, 80 mg/kg, P < 0.01) in parotid saliva. In parotid saliva, sodium and potassium were increased by doses of 20 and 40 mg/kg (P < 0.01) and 20, 40, 80 mg/kg (P < 0.01) respectively. In submandibular saliva, flow rate, total protein and calcium concentrations were significantly reduced by all doses (20, 40, 80 mg/kg, P < 0.01). Sodium and potassium concentrations were also increased by a dose of 80 mg/kg, (P < 0.05) in submandibular saliva. It is concluded that ofloxacin inhibits rat salivary gland functions, which might be observed as a side-effect in humans. Properties of fluoroquinolones to alter intracellular cAMP and calcium levels and their ability to suppress DNA, RNA and protein synthesis of acinar cells might be possible reasons for the observed changes.

Salivary gland dysfunction: a review of systemic therapies

Xerostomia may result from salivary dysfunction secondary to a variety of conditions, including medications, autoimmune disease, and tumoricidal therapy. As the geriatric population increases, the incidence of xerostomia will increase and the oral manifestations will continue to be a challenge to the clinician. Common oral manifestations resulting from decreased salivary flow include increased dental caries, fungal infections, and dysphagia. Treatment for salivary gland dysfunction is currently limited because of a lack of controlled clinical trials. Medications that have been studied in clinical trials are emphasized in this article. The aim of this article is to briefly review salivary gland physiology and to summarize the suggested systemic treatment modalities for xerostomia that emphasize controlled clinical trials.

Protection by selenium of lead-acetate-induced alterations on rat submandibular gland function

Pure submandibular saliva was collected intraorally by micro polyethylene cannulation of anaesthetized rats using pilocarpine as a secretagogue. Twenty-four days treatment with lead acetate 0.05% in drinking water altered salivary function. Except for flow rate that was (P<0.01) increased by lead acetate, the reminder of parameters, concentrations of total protein and calcium and the activity of N-acetyl-beta-D-glucosaminidase (NAG) in submandibular secretions were decreased significantly (P<0.01) by lead acetate. Selenium (2.5 mg l(-1)) in drinking water for 24 days did not induce any significant change in saliva secretory function. Pretreatment by selenium, prevented the lead acetate-induced decrease of NAG activity and concentrations of calcium and protein (P<0.01). The increased flow rate by lead acetate was also affected by selenium pretreatment and reached the level of control. It is concluded that selenium can protect rat submandibular gland function from lead-acetate-induced adverse effects. Properties of selenium as an antioxidant, free radical scavenger and maintenance of cell membrane integrity may be possible mechanisms of its protective effects.

Alteration by cadmium of rat submandibular gland secretory function and the role of the l-arginine/nitric oxide pathway

The effects of cadmium, l-arginine (nitric oxide precursor) and N(omega)-nitro-l-arginine methyl ester (l -NAME) as a nitric oxide synthesis inhibitor and cotreatment of them on rat submandibular secretory function were studied. Pure submandibular saliva was collected intraorally by micro polyethylene cannula from anaesthetized rats using pilocarpine as secretagogue. Fourteen days treatment with 10 mg l(-1)cadmium as cadmium chloride in drinking water caused significant alterations on salivary function. Salivary flow rate, total protein concentration and amylase activity of saliva were decreased while secretion of calcium was increased by cadmium. Two weeks treatment of rats with l -arginine (2.25%) in drinking water caused an increase in submandibular gland weight. Flow rate was reduced by l-NAME. The total protein concentration of saliva was increased by l-arginine while decreased by l-NAME. Calcium concentration of saliva was reduced by l-arginine and increased by l-NAME. Cotreatment of cadmium with l-arginine prevented cadmium-induced reduction of flow rate while l-NAME cotreatment potentiated cadmium-induced reduction of flow rate. l-arginine showed a preventive effect on cadmium-induced decrease of protein concentration and reached control levels. l-arginine potentiated cadmium-induced increase of saliva calcium concentration. It is confirmed that nitric oxide (NO) has a role in salivary gland function. It is also concluded that cadmium inhibitory effects on salivary gland function are modulated by the NO system as it is observed that the cadmium inhibitory effect on submandibular gland function is diminished by l-arginine and extended by l-NAME. Considering the properties of cadmium substitution for calcium in many intracellular events, different types of alterations can be discussed.

What can transgenic and gene-targeted mouse models teach us about salivary gland physiology?

Thousands of genetically modified mice have been developed since the first reports of stable expression of recombinant DNA in this species nearly 20 years ago. This mammalian model system has revolutionized the study of whole-animal, organ, and cell physiology. Transgenic and gene-targeted mice have been widely used to characterize salivary-gland-specific expression and to identify genes associated with tumorigenesis. Moreover, several of these mouse lines have proved to be useful models of salivary gland disease related to impaired immunology, i.e., Sjögren's syndrome, and disease states associated with pathogens. Despite the availability of genetically modified mice, few investigators have taken advantage of this resource to better their understanding of salivary gland function as it relates to the production of saliva. In this article, we describe the methods used to generate transgenic and gene-targeted mice and provide an overview of the advantages of and potential difficulties with these models. Finally, using these mouse models, we discuss the advances made in our understanding of the salivary gland secretion process.

Regulation of calcium in salivary gland secretion

Neurotransmitter-regulation of fluid secretion in the salivary glands is achieved by a coordinated sequence of intracellular signaling events, including the activation of membrane receptors, generation of the intracellular second messenger, inositol 1,4,5, trisphosphate, internal Ca2+ release, and Ca2+ influx. The resulting increase in cytosolic [Ca2+] ([Ca2+]i) regulates a number of ion transporters, e.g., Ca2+-activated K+ channel, Na+/K+/2Cl- co-transporter in the basolateral membrane, and the Ca2+-activated Cl- channel in the luminal membrane, which are intricately involved in fluid secretion. Thus, regulation of [Ca2+]i is central to the regulation of salivary acinar cell function and is achieved by the concerted activities of several ion channels and Ca2+-pumps localized in various cellular membranes. Ca2+ pumps, present in the endoplasmic reticulum and the plasma membrane, serve to remove Ca2+ from the cytosol. Ca2+ channels present in the endoplasmic reticulum and the plasma membrane facilitate rapid influx of Ca2+ into the cytosol from the internal Ca2+ stores and from the external medium, respectively. It is well-established that prolonged fluid secretion is regulated via a sustained elevation in [Ca2+]i that is primarily achieved by the influx of Ca2+ into the cell from the external medium. This Ca2+ influx occurs via a putative plasma-membrane-store-operated Ca2+ channel which has not yet been identified in any non-excitable cell type. Understanding the molecular nature of this Ca2+ influx mechanism is critical to our understanding of Ca2+ signaling in salivary gland cells. This review focuses on the various active and passive Ca2+ transport mechanisms in salivary gland cells--their localization, regulation, and role in neurotransmitter-regulation of fluid secretion. In addition to a historical perspective of Ca2+ signaling, recent findings and challenging problems facing this field are highlighted.

alpha(1)-adrenoceptor-induced trafficking of aquaporin-5 to the apical plasma membrane of rat parotid cells

Incubation of rat parotid tissue with 10 microM epinephrine resulted in a transient and marked trafficking of aquaporin-5 (AQP5) from intracellular membranes to the apical plasma membrane (APM) that was maximal at 1 min. This effect of epinephrine was mimicked by phenylephrine, but not by clonidine, dobutamine, or salbutamol, and it was inhibited by phentolamine, but not by propranolol. Furthermore, the epinephrine-induced trafficking of AQP5 was inhibited by phospholipase C inhibitor U73122 as well as dantrolene and TMB-8, both of which inhibit the release of Ca(2+) from intracellular stores. Cytochalasin D and tubulozole-C also inhibited this action of epinephrine. These results indicate that epinephrine, acting at alpha(1)-adrenoceptors, induces the trafficking of AQP5 to the APM by triggering the release of Ca(2+) from intracellular stores through inositol 1,4,5-trisphosphate and ryanodine receptors. In addition, the potent involvement of the cytoskeleton was shown in the epinephrine-induced trafficking of AQP5.

Are salivary glands cell lines in culture a good model for purinergic receptors in salivary glands?

A major obstacle in studying the physiological and biochemical processes of salivary secretion is the lack of a good ductal cell line model. HSY, an immortalised cell line originating from human parotid gland intercalated ducts, provides a possible model for purinergic mechanisms in ductal cells. Unlike the biphasic dose response to ATP of isolated submandibular ductal cells, the rise in [Ca2+]i in HSY cells shows single Michaelis-Menten kinetics with an apparent Ka of 0.8 microM. Pre-incubation with thapsigargin inhibited the ATP induced [Ca2+]i rise. Both ATP (10 microM) and carbachol (100 microM) increased IP3 production. Intercalated duct cells may differentiate into acinar or ductal cells in response to appropriate stimuli from extracellular matrix We therefore attempted to induce a duct-like phenotype in the striated duct-derived HSY cells by growing them on microcarrier beads coated with type I collagen. In Ca-containing medium cells grown on all substrates showed similar responses to ATP. In contrast, in Ca-free medium, [Ca2+]i rose only slightly in cells grown on beads relative to those on glass. This probably resulted from reduced IP3 production. Carbachol also induced a much smaller increase in [Ca2+]i and less IP3 production in cells grown on Cytodex-3. The HSY response to purinergic stimuli by an increase in [Ca2+]i and IP3 means that they can be used to study the metabotropic purinergic pathway. The impairment in the HSY responses grown on Cytodex-3 can be used to probe phosposinositol signal transduction in salivary cells.

Nitric oxide modulates salivary amylase and fluid, but not epidermal growth factor secretion in conscious rats

The involvement of the L-arginine/NO pathway in the control of salivary fluid, amylase and epidermal growth factor (EGF) secretion was investigated in conscious rats. For the collection of saliva, an oesophageal cannula was implanted. To obtain steady secretion, submaximal carbachol background infusion was given. Different treatments included NO synthase inhibitor N(G)-nitro-L-arginine (NOLA; with or without phentolamine, propranolol), L-arginine, D-arginine and NO donor 3-morpholinosydnonimine (SIN-1) administration. Volume, amylase activity and EGF output in the secreted fluid were determined in 30 min mixed saliva samples. Carbachol infusion alone produced a modest, sustained salivary fluid and amylase secretion. NOLA (30 mg/kg) further increased both fluid (p<0.001) and amylase outputs (p<0.001). These latter effects were prevented by L-arginine but not by D-arginine or by phentolamine. Propranolol administration decreased both fluid and amylase secretion below the carbachol plateau, and NOLA did not modify this suppressed secretory rate. SIN-1 did not alter either volume or amylase secretion. Interestingly, NOLA given without carbachol did not modify salivation. Neither carbachol nor NOLA changed salivary EGF output. The present results suggest that the L-arginine/NO pathway has a modulatory role in the cholinergic control of salivary amylase secretion, but not in EGF output. The mechanisms of inhibitory action of NO on salivary fluid and amylase secretion remain to be identified.

Alkalization produced by high-dose carbachol in HSG cell line is independent of Ca2+

OBJECTIVES

The aim of this investigation was to clarify the mechanism of alkalization induced by carbachol in HSG cells.

MATERIALS AND METHODS

Cells of the HSG cell line derived from a human submandibular gland adenocarcinoma and those of the A-431 human epidermoid carcinoma cell line were loaded with a fluorescent pH indicator, BCECF/AM, and the change in the intracellular pH of adherent cells and suspended ones were measured following stimulation with various concentrations (10(-7) M to 10(-2) M) of neurotransmitters (carbachol, noradrenaline, and isoproterenol).

RESULTS

Isoproterenol did not cause alkalization of either cell type, whereas, noradrenaline and carbachol alkalized both types over the concentration ranges of 10(-6) M to 3 x 10(-3) M (HSG cell by noradrenaline), 10(-7) M to 2 x 10(-4) M (A-431 cell by noradrenaline), and 7 x 10(-5) M to 10(-4) M (A-431 cell by carbachol). On the other hand, alkalization induced by carbachol in the HSG cells was recognized at concentrations higher than 6 x 10(-5) M, and it showed no upper limit in terms of carbachol concentration. This high-dose carbachol alkalization was not eliminated by preincubation with nifedipine (100 microM), a Ca2+ channel blocker, or with thapsigargin (100 microM), a microsomal Ca(2+)-ATPase inhibitor.

CONCLUSIONS

The alkalization system induced by carbachol in the HSG cell was quite different from that in the A-431 cell, and that induced by high-dose carbachol in HSG cells appeared to be independent of intracellular Ca2+. These findings will be useful to clarify the mechanism of salivary secretion stimulated by neurotransmitters.

The influence of nerves on the secretion of immunoglobulin A into submandibular saliva in rats

1. The influence of sympathetic and parasympathetic nerve stimulations on salivary secretion of immunoglobulin A (IgA) was studied in the submandibular glands of anaesthetized rats by stimulating the nerve supplies with bipolar electrodes. 2. Although the flow of saliva from sympathetically stimulated glands was only 23% of that from parasympathetically stimulated glands the output of IgA was over 2-fold greater. This difference was attributable to influences of the nerves on IgA secretion through the epithelial cell polymeric immunoglobulin receptor-mediated pathway, as Western blotting with specific antibodies to IgA and secretory component revealed that secretory IgA (SIgA) dominated in all saliva samples. 3. Study of saliva secreted in sequential periods of nerve stimulation or following rest pauses suggested that SIgA secretion occurred in the absence of stimulation but this was upregulated 2.6- and 6-fold by parasympathetic and sympathetic nerve stimulations, respectively, compared with the calculated unstimulated rate. 4. The IgA content of extensively stimulated glands was 77% of levels in unstimulated contralateral control glands despite a secretion into saliva equivalent to almost 90% of the glandular IgA content. The IgA may be synthesized and secreted by glandular plasma cells at a rate which exceeds demand and/or such synthesis may be upregulated by nerve impulses. 5. The results indicate that salivary secretion of SIgA is upregulated by nerve impulses and that sympathetic nerves induce a greater effect than parasympathetic nerves.

Saliva composition and exercise

Little attention has been directed toward identifying the changes which occur in salivary composition in response to exercise. To address this, our article first refers to the main aspects of salivary gland physiology. A knowledge of the neural control of salivary secretion is especially important for the understanding of the effects of exertion on salivary secretion. Both salivary output and composition depend on the activity of the autonomic nervous system and any modification of this activity can be observed indirectly by alternations in the salivary excretion. The effects of physical activity (with reference to factors such as exercise intensity and duration, or type of exercise protocol) on salivary composition are then considered. Exercise might indeed induce changes in several salivary components such as immunoglobulins, hormones, lactate, proteins and electrolytes. Saliva composition might therefore be used as an alternative noninvasive indicator of the response of the different body tissues and systems to physical exertion. In this respect, the response of salivary amylase and salivary electrolytes to incremental levels of exercise is of particular interest. Beyond a certain intensity of exercise, and coinciding with the accumulation of blood lactate (anaerobic threshold or AT), a 'saliva threshold' (Tsa) does indeed exist. Tsa is the point during exercise at which the levels of salivary alpha-amylase and electrolytes (especially Na+) also begin to rise above baseline levels. The occurrence of the 2 thresholds (AT and Tsa) might, in turn, be attributable to the same underlying mechanism, that of increased adrenal sympathetic activity at high exercise intensities.