Effect of extracellular K+ on saliva secretion by isolated,perfused rat submandibular glands

Changes in perfusate K⁺ concentration altered the secretory response of the glands to 10^?6 M acetylcholine. Lack of extracellular K⁺ caused a transient fluid secretory response lasting less than 10 min, and a 91 per cent reduction in the overall volume of saliva secreted in 60 min; it inhibited the response to acetylcholine even when the perfusate was changed to K⁺-containing solutions after 30 min. Absence of K⁺ in the perfusate resulted in increased Na⁺ and decreased K⁺ and Cl^? concentrations in saliva. An increase in the perfusate K⁺ concentration to 50 mM/l caused a reduced but more sustained secretory response, although the volume of saliva secreted in 60 min was still reduced by 76 per cent compared to that obtained when the perfusate contained 4.6 m-equiv./l K⁺. Acetylcholine release induced by the high K seemed mostly responsible as the response was inhibited by atropine. However, in the presence of excess of exogenous acetylcholine, perfusion with high K⁺ medium resulted in reduced Na⁺ and elevated K⁺ and Cl^? concentrations in saliva. It seems that a physiological (4–5 m-equiv./l) extracellular K⁺ concentration is required for acinar fluid secretion and for transductal electrolyte transport in the rat glands; lack of external K⁺ hyperpolarizes salivary cells and, although allowing an initial increase in Na⁺ conductance capable of causing secretion, prevents the further influx of this ion required to sustain saliva secretion. It also inhibits K⁺secretion and Na⁺ re-absorption in salivary ducts, probably by inhibiting the Na⁺, K⁺ pump in duct cells; high external K⁺ depolarizes acinar cells and may reduce Na⁺ conductance. It also enhances K⁺ secretion and Na⁺ re-absorption in salivary ducts; the effects of K⁺ omission and of high K⁺ on fluid secretion are likely to be the result of changes in the transmembrane K⁺ gradient in acinar cells and of the way they affect the opening of Na⁺ conductance pathways; perfusion with K⁺-free or high K⁺ solutions reveals a dissociation in ductal reabsorption of Na⁺ and Cl^? and unmasks the presence of independent transport mechanisms for these two ions in salivary ducts.     

Submandibular secretion in the dog after intraluminal injections of amiloride

The effects of amiloride on flow rate, osmolarity, Na⁺, K⁺ and Cl^? concentrations were studied in the submandibular glands of dogs. The drug was injected in a retrograde fashion into the duct system of the gland, which was subsequently stimulated to secrete with pilocarpine. In concentrations of 10^?4 and 10^?3 M, amiloride increased the Na⁺ concentration but did not significantly alter the K⁺ concentration of saliva. A slight decrease in Cl^? concentration was observed at high flow rates after 10^?4 M amiloride, but otherwise the drug did not significantly affect the Cl^? concentration of stimulated salivary secretion. The diuretic has a measurable mucosal (luminal) effect on Na⁺ transport in dog submandibular gland, which is similar to that reported in amphibian epithelia. Its lack of effect on K⁺ excretion differs from findings reported in other epithelial structures, where it has a marked K⁺-sparing effect. The drug increased the salivary osmolarity in a fashion similar to Na⁺, a finding that suggests a dissociation between Na⁺ and water transport in salivary duct epithelium.     

The biphasic effect of extracellular glucose concentration on carbachol‐induced fluid secretion from mouse submandibular glands

Cholinergic agonists evoke elevations of the cytoplasmic free‐calcium concentration ([Ca²⁺]_i) to stimulate fluid secretion in salivary glands. Salivary flow rates are significantly reduced in diabetic patients. However, it remains elusive how salivary secretion is impaired in diabetes. Here, we used an ex vivo submandibular gland perfusion technique to characterize the dependency of salivary flow rates on extracellular glucose concentration and activities of glucose transporters expressed in the glands. The cholinergic agonist carbachol (CCh) induced sustained fluid secretion, the rates of which were modulated by the extracellular glucose concentration in a biphasic manner. Both lowering the extracellular glucose concentration to less than 2.5 mM and elevating it to higher than 5 mM resulted in decreased CCh‐induced fluid secretion. The CCh‐induced salivary flow was suppressed by phlorizin, an inhibitor of the sodium–glucose cotransporter 1 (SGLT1) located basolaterally in submandibular acinar cells, which is altered at the protein expression level in diabetic animal models. Our data suggest that SGLT1‐mediated glucose uptake in acinar cells is required to maintain the fluid secretion by sustaining Cl^? secretion in real‐time. High extracellular glucose levels may suppress the CCh‐induced secretion of salivary fluid by altering the activities of ion channels and transporters downstream of [Ca²⁺]_i signals.     

Specific expression of salivary maxi-K channel variant is augmented in diabetic mice

Background and objective

A genetically diabetic mouse strain (db/db) exhibits severe obesity and a syndrome resembling human non-insulin-dependent diabetes mellitus. Our histological study of submandibular glands revealed that the size and area of the granular convoluted tubules was substantially decreased in db/db mice. We hypothesized that this structural difference reflected a specific alteration in salivary duct function.

Methods

The saliva evoked by pilocarpine was used for the measurement of ion concentrations, and submandibular glands were dissected out for the immunohistochemistry and real-time PCR study.

Results

The K⁺ concentration of the salivary secretion was higher in db/db than in control m+/m+ mice, while neither saliva volume nor the concentrations of Na⁺ or Cl⁻ differed between these strains. In db/db mice (vs. m+/m+ mice): quantitative PCR analysis revealed an increased mRNA expression of large-conductance Ca²⁺-activated K⁺ (maxi-K) channels, immunohistochemistry revealed an increase in the luminal surface expression of the maxi-K channel protein, and a particularly interesting finding was that there was a substantial increase in the salivary tissue-specific splice variant ParSlo.

Conclusion

These results suggest that in db/db mice, the K⁺ content of saliva may be elevated due to an expression of a maxi-K channel variant, which results from a modification of ductal structure. General significance: Our data may shed some light on the mechanism responsible for determining the dynamics of salivary K⁺ concentration increased in diabetic patients.     

Salivary anticandidal activity and saliva composition in an HIV‐infected cohort

This study investigated salivary anticandidal activity and salivary composition in stimulated whole saliva of 18 advanced HIV‐infected patients and compared these values to healthy controls. Stimulated whole saliva from HIV‐infected patients showed decreased anticandidal activity. The flow rate was reduced by 40% as compared with controls. The saliva flow rate for HIV‐infected patients who had recoverable yeast in their saliva was reduced as compared to HIV‐infected patients without recoverable yeast. For HIV‐infected patients, the saliva concentrations of lactoferrin, secretory IgA and Cl^? were increased while the secretion rate of lysozyme, total protein and K⁺ were reduced. There was no difference in any parameter as a function of taking the antifungal drug fluconazole. There was no association between salivary anticandidal activity and any salivary component. This study shows reduced anticandidal activity and salivary flow rate in HIV‐infected patients. These alterations may contribute to their increased incidence of oral candidal infections.     

Studies on ion transport during potential cycling of a Prussian blue (inner) | polyaniline (outer) bilayer electrode by quartz crystal microbalance and Fourier transform infrared reflection spectroscopy

Ion transport during the redox switching of a Prussian blue (PB) | polyaniline (PAn) bilayer electrode has been investigated by means of an electrochemical quartz crystal microbalance (EQCM) and in situ Fourier transform infrared (FTIR) reflection spectroscopy. The movement of ions in the potential cycling of the bilayer electrode is affected considerably by the thickness ratio of PB to PAn and the electrode potential. It is at the bilayer electrode with the medium thickness ratio (2.5–3.25) of PB (165 nm) to PAn that cation (K⁺) and anion (Cl^?) move simultaneously in opposite directions. On the positive scan of such an electrode, K⁺ ions are first ejected from PB to the PAn layer into which Cl^? ions are concurrently taken from solution to maintain the charge balance. The oxidation of PAn at more positive potential leads to the expulsion of K⁺ ions to solution and the simultaneous incorporation of Cl^? ions.     

Sialochemistry and cortisol levels in patients with Sjogren's syndrome

Oral Diseases (2012) 18 , 255–259 Objectives: (i) To determine whether salivary cortisol and electrolyte levels differ between patients with Sjogren’s syndrome (SjS) and healthy individuals. (ii) To assess correlations between whole‐saliva cortisol and some clinical manifestations in patients with SjS. Methods: A total of 24 healthy women (mean age 49.3 ± 9.8) served as controls (C) vis‐à‐vis 17 patients with SjS (mean age 55.5 ± 15.7). Salivary cortisol concentration was determined, and sialochemistry analysis was performed. Results: Significantly lower saliva flow rates and higher salivary chloride (Cl^?), potassium (K⁺), and Ca²⁺ levels were found in the SjS group. No significant differences or correlations were found in other parameters, including sodium (Na⁺), magnesium (Mg²⁺), phosphate (^?), urea (U), and salivary cortisol levels. Conclusion: Increased whole‐salivary output of Cl^? and K⁺ in SjS may reflect release from apoptotic rests of acinar cells after secondary necrosis. Normal levels of salivary Na⁺, Mg²⁺, and ^? argue against concentration effect, deranged tubular function or cortisol (mineralocorticosteroid) effect as the cause for these findings. Increased salivary Ca²⁺ levels probably reflect leakage of plasma Ca²⁺ through the injured oral mucosa in SjS. In spite of disease‐associated stress, salivary cortisol, a stress biomarker, was not increased, suggesting insufficient hypothalamus–pituitary–adrenal (HPA) axis response and/or local consumption of cortisol by lymphocyte infiltrates.     

EMF measurements across hydroxyapatite membranes

An attempt was made to develop models applicable to the study of ionic transport in dental enamel. Membranes of hydroxyapatite, made by compression of the powdered salt, were mounted on the septum of concentration cells. Electrical potential differences, PD, were measured across the membranes using solutions of CaCl₂, NaCl, KCl, and potassium and sodium phosphates. With CaCl₂, the membrane acquired a net positive charge and the PD values were close to those expected for an ideal permselective membrane. High permselectivity and a net negative charge on the membrane were observed with solutions of Na₂HPO₄ and K₂HPO₄. The PD values obtained with NaCl and KCl solutions were close to those calculated for the junction potentials of the electrolytes; thus, for these uni-univalent salts the membrane behaved as an inert porous barrier. The permselective behaviour was interpreted in terms of sorption of Ca²⁺ and phosphate ions probably related to defects in the hydroxyapatite crystals. The lack of interaction with K⁺, Na⁺, and Cl^? was ascribed to the reduced ionic charge and the relatively large pore sizes of the membrane.When the membranes were mounted on an intraoral device and exposed to the oral environment prior to the PD measurements, the electrochemical behaviour of the membrane changed drastically. The PD values obtained were consistent with the acquisition of a net negative charge on the membrane surface. This negative charge decreased during the initial time (several hours) of measurements but persisted if saliva was added to the electrolyte solutions. A rapid adsorption of salivary proteins is thought to be responsible for the change of the membrane properties after intraoral exposure.It was concluded that any model developed to study ionic transport in dental enamel should include the interactions with the salivary constituents and the presence of the tooth pellicle.     

Membrane transporters in salivary exosomes and microvesicles as biomarkers of systemic or oral disease

Backgroundsaliva is useful to assess health or disease states. Recently, proteomic technologies have allowed rapid progress in saliva analysis.Highlight(1) saliva contains three main types of extracellular vesicles; (2) the vesicles are exosomes, microvesicles, and apoptotic bodies; (3) proteome is analyzed in saliva, salivary exosomes, and salivary microvesicles; (4) membrane transporters are in saliva, and salivary exosomes and/or microvesicles; (5) biomarker discovery in exosomes and microvesicles of saliva is progressing.Conclusionmembrane transporters such as aquaporin, ion channels, carriers in saliva, and salivary exosomes or microvesicles, might be valuable biomarkers of systemic or oral health.     

Corrigendum to: “Use of dynamically adaptive grid techniques for the solution of electrochemical kinetic equations. Part 13. Patch-adaptive simulation of wave propagation along ring electrodes: one-dimensional approximation” [J. Electroanal. Chem. 529 (2002) 51–58]

A new electroactive polynuclear inorganic compound of a rare earth metal hexacyanoferrate, samarium hexacyanoferrate (SmHCF), was prepared by electrochemical deposition on the surface of a glassy carbon electrode with a potential cycling procedure. The cyclic voltammogram of SmHCF exhibits a pair of well-defined redox peaks with a formal potential of 191 mV (vs. SCE) at a scan rate of 100 mV/s in 0.2 M NaCl solution and the redox peak currents increase linearly with the scan rate up to 100 mV/s. The effects of the concentration of supporting electrolyte on the electrochemical characteristics of SmHCF and the transport behavior of K⁺, Na⁺ and Li⁺ counter ions through the ion channels of SmHCF were studied by voltammetry. The different electrochemical behavior of SmHCF in various cation-containing supporting electrolytes was investigated by cyclic voltammetry and scanning electron microscopy. The SmHCF was also characterized by FTIR techniques.     

Transepithelial ion transport across duct cells of the salivary gland

Fluid and electrolyte secretions are vital for all epithelia and when aberrant lead to numerous pathophysiological conditions. Electrolyte transport across epithelia generates the osmotic force for fluid movement and is mediated by several membrane proteins expressed on both apical and basolateral poles of epithelial cells. Sodium and chloride are crucial for regulation of fluid secretion, thus regulating salivary volume. Bicarbonate (), on the other hand, is the major pH buffer; hence, aberrant secretion is a major factor in diseases such as cystic fibrosis (CF) causing altered mucin hydration and solubilization. Here, the structure–function mechanisms of the major membrane transporters involved in salivary duct electrolyte transport are reviewed focusing on transepithelial movement of Cl^? and .     

Cholinergic autoantibodies from primary Sjögren’s syndrome modulate submandibular gland Na+/K+‐ATPase activity via prostaglandin E2 and cyclic AMP

Passafaro D, Reina S, Sterin‐Borda L, Borda E. Cholinergic autoantibodies from primary Sjögren’s syndrome modulate submandibular gland Na ⁺ /K ⁺ ‐ATPase activity via prostaglandin E ₂ and cyclic AMP. Eur J Oral Sci 2010; 118: 131–138. © 2010 The Authors. Journal compilation © 2010 Eur J Oral Sci We demonstrate that patients with primary Sjögren’s syndrome (pSS) produce functional IgG autoantibodies that interact with the glandular M₃ muscarinic acetylcholine receptors (mAChRs). These autoantibodies act as a partial muscarinic agonist, increasing prostaglandin E₂ (PGE₂) and cyclic AMP production through modifying Na⁺/K⁺‐ATPase activity, but also interfere with the secretory effect of the parasympathetic neurotransmitter. The IgG from patients with pSS has two effects on the submandibular gland. On the one hand, it may act as an inducer of the proinflammatory molecule (PGE₂) that, in turn, inhibits Na⁺/K⁺‐ATPase activity. On the other hand, it plays a role in the pathogenesis of dry mouth, abolishing the Na⁺/K⁺‐ATPase inhibition and the net K⁺ efflux stimulation of the salivary gland in response to the authentic agonist pilocarpine, decreasing salivary fluid production.     

Influence of bacterial cell concentration and inorganic anions on lysis of Streptococcus mutans BHT by salivary lysozyme

The aim of this work was to study the influence of bacterial cell concentrations and inorganic anions on lysis of Streptococcus mutans BHT by human salivary lysozyme (HSL). HSL was partly purified from saliva by ion exchange chromatography. The bacteria were grown in a synthetic medium containing ³H-thymidine to monitor DNA release. The experiments demonstrated that release ³H-thymidine was dependent on the bacterial cell concentration and an apparent K_m-value corresponding to approximately 2.9 × 10⁸ cells/ml was calculated. The influence of I^?, Br^?, Cl^?, F^?, HCO₃^? and SCN^? on bacteriolysis was studied. All anions tested were slightly inhibitory on the action of HSL. The inhibition varied from 7 to 76% depending on the ion and ionic strength. The order of addition of HSL and sodium chloride caused different lytic responses. This was reflected by the amount of HSL adsorbed by the bacteria.     

Characteristics of neurokinin A-induced salivary fluid secretion in perfused rat submandibular gland

Tachykinins such as neurokinin A (NKA) and substance P have been demonstrated to induce salivary fluid secretion in vivo. However, characteristics of salivary fluid secretion induced by tachykinins in salivary glands have not been well elucidated. In this study, the effects of the tachykinin NKA on salivary fluid secretion were investigated in isolated, perfused rat submandibular gland. NKA provoked salivary fluid secretion, which consisted of transient and sustained phases, in a dose-dependent manner. In fura-2-loaded dispersed cells of the rat submandibular gland, the doses of NKA in which induced salivary fluid secretion caused an increase in intracellular Ca²⁺ concentration. When Ca²⁺ was removed from the perfusate to examine the effect of Ca²⁺ mobilization on NKA-induced fluid secretion, only the transient salivary fluid secretion occurred. When the gland was perfused with the Ca²⁺-free perfusate containing the intracellular Ca²⁺ chelator BAPTA-AM, NKA failed to induce salivary fluid secretion. NKA also induced an increase in oxygen consumption, but which was reduced by the removal of Ca²⁺ from perfusate. Salivary fluid is secreted via transcellular and paracellular pathways in acinar cells of salivary glands. To examine the contribution of paracellular pathway to NKA-induced salivary fluid secretion, the glands were perfused with a perfusate containing Lucifer yellow (LY), a cellular impermeable substance, and then were stimulated with NKA, which provoked secretion of LY in the saliva. These results suggest that the NKA-induced salivary fluid secretion is Ca²⁺-dependent and that the paracellular pathway contributes to the secretion.     

DFT calculations of the interaction of alkali ions with copper and silver

The interaction of alkali ions with the Cu(100) and Ag(100) surfaces is studied using the DFT method. The results of the B3LYP calculations performed for five cations, Li⁺, Na⁺, K⁺, Rb⁺ and Cs⁺, adsorbed on the surface of the M₁₂(6,6) cluster (M=Cu, Ag) are presented. On both metals the interaction is found to be strongest for the Li⁺ ion and weakest for the Cs⁺ ion. Three sites were tested for the adsorption of ions on the (100) surface: top, bridge and hollow. For the two smaller ions, Li⁺ and Na⁺, the hollow site is found to be the most stable. For the three larger ions the top position is more attractive. Nevertheless, the energy value at the different sites for a given ion in most cases, differs by less than 5 kJ mol^?1. For all ions the interaction with silver is stronger than the interaction with copper.     

Calcium-stimulated ATPase of dog submandibular gland

A Ca^2?-stimulated ATPase present in a microsomal fraction prepared from canine submandibular glands was investigated. The Ca²⁺ concentration for half maximal activation of the enzyme was about 0.3 mM. Addition of Mg²⁺ to incubation media containing Ca²⁺ decreased the ATPase activity. The presence of neither Na⁺ nor K⁺ is required for Ca²⁺-activation of the enzyme. Also, Ca²⁺ will not substitute for Mg²⁺ in the Mg²⁺-dependent (Na⁺ + K⁺)-ATPase reaction. The Ca²⁺-activation was not appreciably affected by ouabain (10^?4M), but was inhibited by about 50 per cent by 5 × 10^?3M ethacrynic acid. These studies provide a possible enzymatic basis for the calcium uptake by salivary gland microsomes that has been reported by other workers.     

Effect of mono- and divalent ions on diffusion and binding in bovine tooth enamel

A radiochemical method was used to determine quantitatively the effect of RbCl, CaCl₂ and MgCl₂ on the transport of [³H]-sorbitol, [¹⁴C]-glycerol, ⁴⁵Ca²⁺, ³⁶Cl^? and ⁸⁶Rb⁺ through dental enamel. The findings indicate that the transport of ⁴⁵Ca²⁺ is influenced strongly by surface exchange reactions. The influence of Ca²⁺ and Mg²⁺ on the transport of ⁸⁶Rb⁺ and ³⁶Cl^? indicates that, at a concentration of ~10mmol/l, these ions alter the fixed charge of enamel from negative to less negative, or positive values. Previously adsorbed ⁴⁵Ca²⁺ ions are desorbed at higher Ca²⁺ and Mg²⁺ concentrations. Rb⁺ ions at 10 mmol/l have no such effect. The results indicate that Ca²⁺ and Mg²⁺ can be adsorbed reversibly on the crystal surfaces or in their Stern layers in the pores of dental enamel.     

Diffusion through bovine tooth enamel as related to the water structure in its pores

Diffusion coefficients of ⁸⁶Rb⁺, ³⁶Cl^?, [³H]-sorbitol and [¹⁴C]-glycerol through enamel were determined both in the absence and the presence of urea or t-butanol which are known for their structure-breaking and structure-promoting properties respectively in aqueous solutions. Their effect on the diffusion coefficients could be explained solely on the basis of the respective shifts in the relative viscosities of the aqueous solutions, indicating that the water of the transport phase is probably free water, in accord with explanation for the extra increase of diffusion coefficients with temperature (Burke and Moreno, Archs oral Biol.17, 433–437 (1975)) by the hypothesis that the amount of free water increases with temperature at the expense of bound water.     

Primary Sjögren''s syndrome: salivary gland function and clinical oral findings

OBJECTIVE: To evaluate salivary gland function, saliva composition and oral findings in patients with primary Sjogren's syndrome (pSS) subdivided into patients with and without focus score ≤1 (FS) and/or antibodies to SSA/SSB (AB) as well as in healthy controls. SUBJECTS AND METHODS: Unstimulated (UWS) and chewing stimulated (SWS) whole saliva, and stimulated parotid saliva (SPS) were collected in 16 patients fulfilling the European classification criteria for pSS subdivided into those with FS and/or AB (n= 8) and those without FS and AB (n= 8), and in age-matched (n= 14) and young healthy controls (n= 13).UWS and SWS were analysed for Na⁺ and K⁺.SPS was analysed for Na⁺, K⁺, statherin, and proline-rich proteins (PRPs).Sicca symptoms, DMFT/DMFS, plaque (PI) and gingival (GI) scores, periodontal pocket depth (PPD), and mucosal status were recorded. RESULTS: The young healthy controls had lower UWS as compared to the aged controls (P= 0.03).However, the aged controls had higher DMFT/DMFS (P < 0.001) and PI, GI and PPD (P < 0.01).Patients with FS and/or AB generally had lower saliva secretory rates than patients without FS and/or AB (P= 0.01 for UWS and SPS) and age-matched healthy controls (P= 0.001). There was no significant difference in the content of Na⁺ and K⁺, statherin and PRPs between groupS. Patients with FS and/or AB had the highest frequency of oral mucosal changes and higher DMFT/DMFS than patients without FS and/or AB and healthy controls (P < 0.01).However, PI, GI, and PPD did not differ significantly. CONCLUSION: Patients with FS and/or AB had lower salivary secretory rates, higher DMFT/DMFS, and more oral mucosal changes than patients without FS and/or AB.Additionally, data suggest that salivary gland function in healthy individuals do not decrease with age.     

Unilateral maxillary molar extraction influences AQP5 expression and distribution in the rat submandibular salivary gland

ObjectiveMastication has been regarded as a crucial factor for maintaining the morphology and function of secretion in salivary glands. Although it is known that occlusion affects mastication, the detailed process for how occlusal changes affect the secretory function of salivary glands is still unknown. Aquaporin 5 (AQP5) is a membrane protein that forms water channels, and plays an important role in water transport. In this study, we investigated the structural changes and alterations in the expression and distribution of AQP5 in the rat submandibular salivary gland (SMG) under occlusal hypofunction after unilateral molar extraction.MethodsSeven-week-old male Wistar rats (n = 36) were used in the study. In the experimental group, all of the right maxillary molars were extracted. Rats with no molar extraction were used as the control group. The rats were euthanized at 7, 14 or 28 days after the procedure, and the right SMGs were isolated and subjected to histological analyses. The expression and distribution of AQP5 were detected by immunohistochemistry.ResultsMorphological analyses revealed hypertrophic changes in the acinar cells in the experimental group. Immunohistochemical staining of AQP5 was detected in the apical membrane (APM) and intercellular secretory canaliculi of acinar cells in both groups. On the other hand, the AQP5 expression in the APM and intercellular secretory canaliculi of acinar cells was less prominent in the experimental group than in the control group.ConclusionsThe present findings suggest that unilateral molar extraction has significant influences on the function of water transport in the rat SMG.