Digestive and Nondigestive Functions of Rodents' Salivary Glands.

Major salivary glands play a role not only in digestion, but also in regulation of other functions in rodents. In this review, we analyzed and summarized the data about the rodents' parotid, submandibular and sublingual salivary glands functions, which is not limited to the production of saliva and action of its hydrolytic enzymes on food in the oral cavity. In recent decades significantly expanded understanding of major salivary glands nondigestive functions. They are involved in excretion of metabolic products, maintaining fluid and electrolyte balance. Special attention has been paid to the characteristics of specific (parotin, sialorphin, etc.) and nonspecific (epidermal growth factor, nerve growth factor, kallikrein, etc.) active substances of the major salivary glands and their involvement in wound healing, mineral metabolism, regulation of hematopoiesis and immunity system. Summarized and analyzed major salivary glands endocrine function in the organs and systems. Available literature data suggest: the structure of the major salivary glands, as well as the synthesis and secretion of a number of biologically active substances are controlled by sex hormones. In turn, these biologically active factors of the salivary glands, as epidermal growth factor, and parotin, sialorphin, whose expression is regulated by androgens, have an impact on the morphological and functional state of the gonads. Thus, major salivary glands operate a wide range of functions and involved in the regulation of sexual behavior of reproductive function and maintaining homeostasis in the body.

Gut and sublingual microvascular effect of esmolol during septic shock in a porcine model.

INTRODUCTION: Esmolol may efficiently reduce heart rate (HR) and decrease mortality during septic shock. An improvement of microcirculation dissociated from its macrocirculatory effect may a role. The present study investigated the effect of esmolol on gut and sublingual microcirculation in a resuscitated piglet model of septic shock. METHODS: Fourteen piglets, anesthetized and mechanically ventilated, received a suspension of live Pseudomonas aeruginosa. They were randomly assigned to two groups: the esmolol (E) group received an infusion of esmolol, started at 7.5 µg⋅kg(-1)⋅min(-1), and progressively increased to achieve a HR below 90 beats⋅min(-1). The control (C) group received an infusion of Ringer's lactate solution. HR, mean arterial pressure (MAP), cardiac index (CI), stroke index (SI), systemic vascular resistance (SVR), arterio-venous blood gas and lactate were recorded. Oxygen consumption (VO2), delivery (DO2) and peripheral extraction (O2ER) were computed. Following an ileostomy, a laser Doppler probe was applied on ileal mucosa to monitor gut microcirculatory laser Doppler flow (GMLDF). Videomicroscopy was also used on ileal mucosa and sublingual areas to evaluate mean flow index (MFI), heterogeneity, ratio of perfused villi and proportion of perfused vessels. Resuscitation maneuvers were performed following a defined algorithm. RESULTS: Bacterial infusion induced a significant alteration of the gut microcirculation with an increase in HR. Esmolol produced a significant time/group effect with a decrease in HR (P <0.004) and an increase in SVR (P <0.004). Time/group effect was not significant for CI and MAP, but there was a clear trend toward a decrease in CI and MAP in the E group. Time/group effect was not significant for SI, O2ER, DO2, VO2, GMLDF and lactate. A significant time/group effect of ileal microcirculation was found with a lower ileal villi perfusion (P <0.025) in the C group, and a trend toward a better MFI in the E group. No difference between both groups was found regarding microcirculatory parameters in the sublingual area. CONCLUSIONS: Esmolol provided a maintenance of microcirculation during sepsis despite its negative effects on macrocirculation. Some parameters even showed a trend toward an improvement of the microcirculation in the gut area in the esmolol group.

Influence of submandibulectomy on alveolar bone loss in rats.

BACKGROUND: The incidence of dry mouth and its public health impact are increasing as the result of a progressively larger, medicated older population and because chronic diseases, like periodontitis, are prevalent pathologies among elderly patients. Periodontitis and continuous remodeling and rebuilding alveolar processes greatly affect the margin of the alveolar bone, and there is evidence indicating the role of submandibular glands in the regulation of immune/inflammatory reactions. The purpose of this study was to assess the effect of submandibular-sublingual complex ablation (Sx) on alveolar bone loss in rats submitted or not to ligature-induced experimental periodontal disease (EP). METHODS: Wistar male rats were submitted to Sx or sham operations (day 0). Two weeks later, unilateral EP was induced on the right mandibular first molars for 7 days with the contralateral side serving as control. Bone loss at the level of the dental pieces was estimated by bone histomorphometry on mesio-distally oriented sections of the molars and by the determination on lingual and vestibular mandibular surfaces of the distances from the cemento-enamel junction to the alveolar crest. RESULTS: Sx and EP significantly increased lingual and vestibular alveolar bone loss. Molars with EP exhibited greater lingual loss in Sx animals compared to those with the sham operation. EP induced similar interradicular bone loss in sham and Sx rats. CONCLUSION: Sx has a deleterious effect on the periodontal tissues, particularly marginal alveolar bone, indicating the importance of the submandibular/sublingual glands in maintaining healthy periodontal conditions.

Expression of six mouse major urinary protein genes in the mammary, parotid, sublingual, submaxillary, and lachrymal glands and in the liver.

Mouse major urinary proteins (MUPs) are encoded by a family of about 35 to 40 highly conserved genes. In the preceding paper (K. Shahan, M. Gilmartin, and E. Derman, Mol. Cell. Biol. 7:1938-1946, 1987), we presented the sequences of the most abundant MUP mRNAs in the liver (MUP I, II, and III) and in the lachrymal (MUP IV) and submaxillary (MUP V) glands. We have shown that these five mRNAs are coded by five distinct genes, MUP I through V. In the present communication, we examine the expression of MUP genes in all of the six tissues in which MUP mRNAs are synthesized, the mammary, parotid, sublingual, lachrymal, and submaxillary glands and the liver. We show that gene MUP II is expressed in the liver and in the mammary gland, that gene MUP IV is expressed in the lachrymal and parotid glands, and that gene MUP V is expressed in the submaxillary, sublingual, and lachrymal and parotid glands, and that gene MUP V is expressed in the submaxillary, sublingual, and lachrymal glands. Furthermore, we present evidence that in addition to genes MUP I through V, another gene, MUP VI, is expressed in BALB/c mice in the parotid gland. The tissue-specific synthesis of MUP mRNAs is thus brought about by two major mechanisms: the expression, in different tissues, of different members of the family and the expression of a single gene at various levels in different tissues. When a particular MUP gene is expressed in several tissues, transcripts of this gene initiate at the same site and are spliced and polyadenylated in the same manner.

Active participation of apoptosis and mitosis in sublingual gland regeneration of the rat following release from duct ligation.

This study was designed to establish how mitotic cell proliferation and apoptotic cell death participate in the regeneration of atrophied rat sublingual glands. To induce atrophy to the sublingual gland of rats, the excretory duct was ligated unilaterally near the hilum, and after 1 week of ligation (day 0) the duct ligation was released to enable gland regeneration. The regenerating glands were examined with routine histology, immunohistochemistry for proliferating cell nuclear antigen (PCNA) as a marker of proliferating cells, terminal deoxynucleotidyl transferase-mediated dUTP-digoxigenin nick end labeling (TUNEL) as a marker of apoptotic cells, and transmission electron microscopy. At day 0, a few acini and many ducts remained in the atrophic sublingual glands, and newly formed immature acini were observed at day 3. Thereafter acinar cells progressively matured and increased in number, although the number of ducts decreased. Many PCNA- and some TUNEL-positive cells were seen in acini and ducts during regeneration. The labeling indices for both cell types were statistically significantly different from that of the control at several time points of the regeneration. Apoptotic and mitotic cells were also confirmed to be present in the experimental sublingual glands by electron microscopy. These observations suggest that apoptosis as well as mitosis of duct and acinar cells actively participate in and play important roles in sublingual gland regeneration.

Biological behavior of myoepithelial cells in the regeneration of rat atrophied sublingual glands following release from duct ligation.

The present study aimed to clarify how myoepithelial cells behave during regeneration of an atrophied sublingual gland by investigating cell proliferation and ultrastructure. Atrophy of rat sublingual glands was induced by unilateral ligation of the excretory duct near the hilum with metal clips, which were then removed after one week of ligation for regeneration. The sublingual glands 0-14 days after unligation were examined with single immunohistochemistry for actin as a marker of myoepithelial cells, double immunohistochemistry for actin and proliferating cell nuclear antigen (PCNA) as a marker of proliferating cells, and transmission electron microscopy (TEM). The single immunohistochemistry and TEM showed that myoepithelial cells surrounded residual ducts in the atrophied glands and immature and mature acini in the regenerating glands. Although PCNA-positive myoepithelial cells were identified during regeneration, PCNA labeling indices of myoepithelial cells were low at all time points except at day 7. Ultrastructurally, myoepithelial cells showing bizarre shaped structures in the atrophy changed with maturation of differentiating acinar cells and appeared normal in the regenerated glands. There was no differentiation of the remaining duct cells to myoepithelial cells. These observations suggest that proliferation of myoepithelial cells and differentiation to myoepithelial cells do not commonly participate in the regeneration of atrophied sublingual glands and that the bizarre shaped myoepithelial cells in the atrophied sublingual glands recover the original shapes with acinar cell regeneration.

Factors That Influence the Extensional Rheological Property of Saliva.

The spinnbarkeit of saliva reflects the ability of saliva to adhere to surfaces within the mouth, thereby serving as a protective role and aiding in lubrication. Therefore, alterations in the extensional rheology of saliva may result in the loss in adhesiveness or the ability to bind onto surfaces. Mucin glycoproteins and their structures are known to be important factors for the extensional rheological properties of saliva. The conformation of mucin depends on factors such as pH and ionic strength. Chewing is one of the main stimuli for salivary secretion but creates significant sheer stress on the salivary film which could influence mouthfeel perceptions. The current study investigates the possible factors which affect the extensional rheological properties of saliva by comparing submandibular/sublingual saliva with different oral stimuli within the same group of subjects. Unstimulated and stimulated saliva (chew, smell and taste) salivas were collected primarily from submandibular/sublingual glands. The saliva samples were measured for Spinnbarkeit followed by the measuring mucin, total protein, total calcium and bicarbonate concentrations. The results indicated correlations between rheological properties and mucin/ion concentrations. However, chewing stimulated submandibular/sublingual saliva is shown to have significantly lower Spinnbarkeit, but factors such as mucin, protein and calcium concentrations did not account for this variation. Analysis of the concentration of bicarbonate and pH appears to suggest that it has a prominent effect on extensional rheology of saliva.

Galanin-like innervation of rat submandibular and sublingual salivary glands: origin and effect on acinar cell membranes.

The distribution and source of a galanin-like innervation of rat salivary glands has been examined. Additionally, submandibular and sublingual acinar cell membrane responses to galanin or a cholinergic agonist were studied. Galanin-immunoreactive fibers were observed throughout the submandibular and sublingual glands in association with ducts and acini. A subset of submandibular ganglion cells expresses galanin immunoreactivity. Parasympathectomy resulted in a marked decrease in galanin immunoreactivity in the glands. Sympathectomy resulted in marked reduction of dopamine beta-hydroxylase immunoreactivity with no appreciable change in galanin immunoreactivity. Retrograde labeling experiments demonstrated that galanin-immunoreactive sensory neurons in the trigeminal ganglion do not innervate the submandibular or sublingual gland. These results indicate that the galanin-like innervation of rat salivary glands is derived from parasympathetic nerves to the glands. Since rat sublingual glands contain largely mucous acini while rat submandibular gland acini are seromucous, electrophysiological responses to galanin and the muscarinic agonist, bethanechol, were compared. Agonist-induced voltage shifts varied between the two glands. The galanin-induced response at the level of the resting membrane potential in submandibular acinar cells was a hyperpolarization, while that in sublingual acinar cells was a depolarization. There was also a greater voltage dependence to the galanin-induced submandibular response than to the sublingual response. Differences were also noted in the acinar cell response to cholinergic stimulation between these glands. These results demonstrate the existence of a galanin-like innervation to salivary glands that may be functionally relevant. Moreover, the results challenge the idea that agonist-induced membrane responses are similar among acinar cells of different glands.

The effect of selective desalivation on wound healing in mice.

The effectiveness of wound licking in the acceleration of wound healing was evaluated in selectively desalivated mice. Rate of healing of experimentally induced cutaneous wounds was evaluated macroscopically by photography at 0, 2, 4, and 6 days after wounding. Sialadenectomy of submandibular and sublingual glands significantly slowed down wound healing in animals caged together compared to sham-operated controls. Separate caging as compared to caging in groups slowed down healing in sham-operated animals at day 2 but not at day 4 and 6. No effect on the rate of healing in sialadenectomized mice was observed in separate caging compared to mice caged in groups. Ligation of the parotid duct had an insignificant effect. The rate of wound healing of sublingual sialadenectomized mice was slower than that of sham-operated controls, but not as slow as those of sublingual and submandibular sialadenectomized mice. The results suggest that the rate of healing of experimentally induced cutaneous wounds of mice is slowed down when licking is prevented by separate caging which confirms previous reports. Licking with submandibular saliva seems to be more effective than sublingual saliva. Parotid saliva or minor salivary glands secretions are the least effective.

Role of amino acids in salivation and the localization of their receptors in the rat salivary gland.

The distribution of gamma-aminobutyric acid (GABA) receptor subunits such as GABAAR-gamma 1 and GABAAR-gamma 2, and alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) type receptor subunits such as GluR-1, GluR-2/3 and GluR-4, and N-methyl-D-aspartic acid (NMDA) type subunits such as NR1 were investigated by immunocytochemistry. Furthermore, the roles of these amino acids, GABA and glutamate, on salivation were analyzed in the rat submandibular and sublingual glands. Some similarities were observed in the distribution patterns of GABAA type receptors and AMPA receptors. In the submandibular ganglion cells, collecting ducts and striated ducts, these subunits were expressed strongly; however, there were some differences in their expression patterns between the submandibular and sublingual gland acinar cells. Since these receptor subunits were expressed in the acinar cell bodies of the submandibular gland, they were not expressed in the acinar cells but were expressed in the myoepithelial cells in the sublingual gland. On the other hand, no NR1 expression was observed. To examine the roles of GABA and glutamate in salivation, the submandibular and sublingual glands were perfused partially with Ringer's solution via a facial artery to avoid systemic influence, and substrates were infused into the perfusion solution. No salivary secretion was evoked by GABA or glutamate infusion in the absence of electrical stimulation (2-3 V, 5 ms, 20 Hz). Salivary flow evoked by electrical stimulation of the chorda-lingual nerve caused significant inhibition by GABA (10(-6), 10(-5), 10(-4) and 10(-3) M) and the GABAAR agonist muscimol 10(-3) and 10(-6) M) (n = 6, P < 0.05). Such GABA-induced inhibition was antagonized by the GABAAR antagonists bicuculline (BCC; 10(-6) and 10(-3) M) and picrotoxin (PTX; 10(-6) and 10(-3) M). On the other hand, salivary flow evoked by electrical stimulation (8-10 V, 5 ms, 20 Hz) of the superior cervical ganglion (SCG) was not affected by GABA. While high doses of glutamate (10(-1) M) and NMDA (10(-1) M) showed no effects on salivary flow despite application of electrical stimulation, AMPA at a high concentration (10(-1) M) significantly inhibited salivary secretion (n = 6, P < 0.05). These studies revealed that inhibitory and excitatory amino acid receptors such as GABAA and AMPA type receptors are coexpressed in the rat salivary glands, and that GABA inhibits salivary secretion via GABAA receptors which may act with acetylcholine. However, the role of glutamate in salivation remains unclear despite the presence of AMPA type receptors. The present findings suggest that glutamate does not act alone but with other substances such as peptides and/or other amino acids.

Sialogogue-related radioprotection of salivary gland function: the degranulation concept revisited.

To investigate whether secretory granules play a role in the radiosensitivity of the salivary glands of rats, parotid acinar cells, submandibular acinar cells and/or submandibular granular convoluted tubule (GCT) cells were degranulated prior to irradiation. Degranulation of GCT cells was obtained by pretreatment with phenylephrine (5 mg/kg, t = -60 min) and methacholine (3.75 mg/kg, t = -120 min). Degranulation of acinar cells was attained by pretreatment with isoproterenol (5 mg/kg, t = -90 min). Combinations of pretreatments were also tested. Irradiation was performed with a single dose of 15 Gy of X rays. Samples of parotid and submandibular/sublingual saliva were collected 4 days prior to and 1, 3, 6, 10 and 30 days after irradiation. Pretreatment with phenylephrine, isoproterenol and methacholine plus phenylephrine resulted in less radiation damage to parotid gland function as indicated by the lag phase and flow rate. Since the pretreatment with phenylephrine and phenylephrine plus methacholine did not degranulate parotid gland acinar cells, the observed protective effect on this gland cannot be explained by the "degranulation concept." Furthermore, salivary gland function was significantly greater 3 days after irradiation as a result of pretreatment with phenylephrine and phenylephrine plus methacholine compared to rats given only radiation. This may indicate recovery from damage rather than a reduced amount of initial damage. The sparing was most obvious for the later effects (6-30 days). Submandibular/sublingual gland function was improved significantly after pretreatment with methacholine plus phenylephrine, although no increase in degranulation of GCT cells was observed compared to pretreatment with phenylephrine alone, again not favoring the degranulation concept. The results indicate that the secretory granules do not play the often-assumed important role in the radiosensitivity of the salivary gland. The mechanism underlying the observed improvement of salivary gland function may involve second messenger-induced increases in proliferation of salivary gland cells resulting in recovery of tissue after the irradiation.

The effect of desalivation on coronal and root surface caries in rats.

Although the presence of coronal caries is declining in much of the Western Hemisphere, the prevalence of root surface caries is likely to increase as teeth are retained longer than heretofore. At the same time, an increasing number of the population suffer from dry mouth as a result of taking prescription drugs, with an apparent concomitant increased susceptibility to root surface caries. This study attempted to develop an animal model which would aid in the exploration of the effects of desalivation and the development of root surface caries. Animals were desalivated, infected with Actinomyces viscosus and Streptococcus mutans (sobrinus) 6715, and fed a cariogenic diet. Coronal caries developed rapidly in the animals; sufficient disease was present after two weeks to permit evaluation of potential therapeutic agents. Alveolar bone loss and root surface lesions developed in three to four weeks. S. mutans (sobrinus) and A. viscosus established readily in all animals; however, as the investigation progressed, populations of the latter declined, possibly because of the highly acidogenic environment. This model will facilitate investigation of the influence of hyposalivation and help in the exploration of agents to alleviate the adverse effects of salivary gland dysfunction.

Salivary glands.

This article discusses the anatomy, physiology, and pathology of the parotid, submandibular, and sublingual glands, which often are referred to as the major salivary glands. Overall, diseases of the salivary glands are relatively uncommon; however, as an organ system, they have the greatest diversity of pathology. Acute viral and bacterial inflammatory diseases are the most common salivary gland abnormalities; tumors are uncommon. The imaging approach to these lesions is discussed.

Salivatory neurons in the brainstem nucleus parvocellularis of the rat: effects of electrolytic lesions.

This study was based on several recent anatomical studies suggesting that the superior salivatory nucleus is located within the area parvocellularis of the brainstem reticular formation. The aforementioned zone was lesioned in order to observe the alterations produced in salivary secretion. Electrolytic lesion of the area parvocellularis was followed by salivary hypersecretion as an immediate and transitory effect of the stimulatory capacity of the electrolytic lesioning method. Some days later the animals presented a markedly impaired salivary secretion as shown by the appearance of inefficient feeding behavior and the development of a prandial drinking pattern. The prandial behavior, which was characterized by numerous drinking episodes during dry food intake, was reversed when wet food was offered, suggesting a true deficit in salivary secretion caused by the parvocellularis lesion. Following the administration of pilocarpine, the submandibular and sublingual salivary glands of experimental animals showed an increased capacity for response (postsynaptic supersensitivity) in comparison to the control group.

Interactions between sialoadenectomy and capsaicin-sensitive afferent fibers on gastric acid secretion in rats.

In this study we have investigated the relative influence of capsaicin-sensitive afferents and sialoadenectomy on gastric acid secretion. Sialoadenectomized (SALX) rats showed a decrease in gastric acid secretion and an increase in gastric calcitonin gene-related peptide-like immunoreactivity (CGRP-li) as compared to sham-operated animals. Capsaicin pretreatment (50 + 100 mg kg-1 in two days) markedly decreased gastric CGRP-li in both sham and SALX-operated rats and increased acid concentration and output only in SALX animals. In this latter case the concomitant absence of two potent endogenous antisecretory agents (CGRP and epidermal growth factor; EGF) may contribute to the observed hypersecretion. Gastric content of vasoactive intestinal polypeptide (VIP)-li was unaffected in SALX and capsaicin-treated rats. Capsaicin-sensitive afferents and EGF contained in the salivary glands may interact in the regulation of the gastric acid secretion.

A comparison of the effects of bilateral sections of the chorda tympani nerve and extirpation of the submaxillary and sublingual salivary glands on the eating and drinking patterns of the rat.

The chorda tympani nerve (CT) innervates the fungiform papillae on the tip of the tongue and has been considered an important nerve for the sense of taste. The CT also contains the parasympathetic supply to the submaxillary and sublingual salivary glands. Therefore, changes in taste or feeding behavior following bilateral sections of CT are caused by both degeneration of fungiform papillae and the inevitable partial desalivation of the rat. In the present experiments we compared the effects of bilateral chorda tympani nerve sections with extirpation of submaxillary and sublingual glands on daily home cage eating and drinking patterns in the rat. Before and after surgery we analyzed the daily eating and drinking patterns, including such measures as intake, bout number, bout length, interbout interval and rate of consumption during bouts. The results of desalivation and bilateral CT sections were indistinguishable. The most profound change was that eating bout duration was increased following surgery. Since food intake did not increase, the results indicate a marked loss in eating efficiency over the daily ingestion periods. Although the eating patterns of desalivated and chorda tympani sectioned rats are quite similar, the evidence is not compelling that they have the same physiological basis. A second experiment was designed to test the hypothesis that the atypical eating patterns observed following bilateral sectioning of CT were the direct result of partial desalivation resulting from the denervation of the salivary glands. In this experiment a unilateral section was made of one CT and it was shown that the eating behavior was not affected. Then the contralateral submaxillary and sublingual salivary glands were removed. This resulted in a six-fold increase in feeding bout length. In all cases a unilateral CT section combined with extirpation of the contralateral salivary glands resulted in rats whose eating behavior was indistinguishable from the earlier data following either the bilateral CT sections or bilateral desalivations. The conclusion is drawn that the eating irregularities noted following bilateral CT sections result from this partial desalivation. CT sections were verified by taste bud counts in the fungiform papillae and histological examinations were made of salivary glands in rats receiving CT sections.

Ionotropic NMDA receptor evokes an excitatory response in superior salivatory nucleus neurons in anaesthetized rats.

Extracellular recordings were taken from preganglionic superior salivatory nucleus (SSN) neurons projecting to submandibular and intra-lingual ganglia, in order to study the action of SSN neurons resulting from ionophoretic application of ionotropic NMDA receptor agonist in urethane-chloralose anaesthetized rats. Single SSN neurons were identified by their antidromic spike responses following stimulation of the chorda-lingual nerve (CLN), chorda tympani branches (CTBs) and the lingual nerve (LN). About one-third (33%, 10/30) of the identified SSN neurons were induced to fire by ionophoretic application of the NMDA receptor agonists used, dl-homocysteic acid (DLH) and N-methyl-D-aspartic acid (NMDA). More than half exhibited firing at high frequencies, often exceeding 40 Hz. About one-fifth (20%; 6/30) of the identified SSN neurons exhibited orthodromic spike responses to the combination of NMDA receptor agonist application and sensory nerve (CLN or LN) stimulus. These excitatory responses evoked by application of NMDA receptor agonist were attenuated (n = 4) by ionophoretic application of DL-2-amino-5-phosphonovaleric acid (AP5; NMDA receptor antagonist). About half (47%) of the neurons did not respond to any combination of NMDA receptor agonist and sensory nerve stimuli. No differences were observed between SSN neurons with B fibre axons and those with C fibre axons in response to ionophoresis of the NMDA receptor agonists. The NMDA-sensitive neurons, which exhibited high frequency firing, were predominantly found in the rostral part of the SSN. In summary, activation of ionotropic NMDA receptors exerts an excitatory effect on about half of the SSN neurons. These data support the view that NMDA receptors are involved in information processing and transmission on SSN neurons.

Effect of donor age on the concentrations of histatins in human parotid and submandibular/sublingual saliva.

Histatins are small proteins of human glandular saliva that have antifungal properties. Recent studies show that oral candidal infections increase with age, suggesting an age-associated compromise in oral host defence. Here, the effect of age and of physiological gland stimulation on the concentration and secretion of salivary histatins was investigated. Parotid and submandibular/sublingual salivas were collected from six young adults under unstimulated, mechanical (chewing) and gustatory (0.025 M and 0.1 M citric acid) stimulation, and the concentration and secretion of histatins was measured by cationic polyacrylamide gel electrophoresis with subsequent densitometric scanning of the stained gels. With gland stimulation, parotid saliva showed no significant increase in histatin concentration (microg/ml); however, histatin secretion (microg/min) increased up to 26-fold (p<0.005; ANOVA). Stimulation of submandibular/sublingual saliva resulted in significant increases in both histatin concentration (p<0.005) and secretion (p<0.0005). Ageing effects on salivary histatins were determined in citric acid (0.1 M)-stimulated parotid and submandibular/sublingual saliva samples collected from 80 individuals (divided into four age groups having approximately equal numbers of males and females: 35-44 years; 45-54 years; 55-64 years and 65-76 years). None of the patients was taking medications or wore dentures. ANOVA showed no sex differences in histatins. Regression analysis showed significant age-associated decreases for parotid saliva histatin concentration (p<0.002) and secretion (p<0. 002) as well as for submandibular/sublingual saliva histatin concentration (p<0.0001) and secretion (p<0.0001). Both saliva types showed significant (p<0.0001) decreases in the histatin concentration per mg of total protein, suggesting a preferential decrease in salivary histatins compared to total salivary protein. These results suggest that the salivary histatin component of the oral host defence system is compromised with increasing age.

Characteristics of palatal wound healing in desalivated rats.

The healing of excisional wounds in the palate of desalivated rats was evaluated. Experimental rats became desalivated after extirpation of the submandibular and sublingual glands and ligation of the parotid ducts. Small or large circular wounds, 3 or 5 mm in diameter, were produced in the palate. The wound area, area of inflammation, area of connective tissue formation and the number of myofibroblasts were determined at 0, 3, 7, 14, 21 and 28 days after surgery. The area of the small wound (3 mm) was similar in experimental and control groups; however, the area of the large wound (5 mm) was greater in the experimental group (p < 0.05-0.01). The area of inflammation was greater in the experimental group with small or large wounds (p < 0.05-0.01). Connective tissue formation was less (p < 0.01) in desalivated rats with a small wound at day 14 and with a large wound at days 21 and 28. There were fewer myofibroblasts in the large wound of desalivated rats (p < 0.01) than in controls between days 3 and 14. The results indicate that palatal wound healing is delayed in desalivated rats and that larger wounds are more sensitive to desalivation than smaller wounds.

Salivary gland nucleotide receptors: evidence for functional expression of both P2X and P2Y subtypes.

A growing body of information now supports the suggestion that P2 receptors for extracellular nucleotides (primarily ATP) have a role in regulating salivary gland function. There is solid pharmacological and molecular evidence for the presence of P2X ligand-gated ion channel nucleotide receptors (P2X4 and P2X7/P2Z). More recently, our group and others have obtained evidence that multiple P2Y G protein-coupled nucleotide receptors (P2Y1 and P2Y2) are also expressed. Our studies have focused on defining the conditions under which P2Y receptors are expressed, the functional consequences of their activation, and the importance of co-expression of P2X and P2Y receptors. Functional and molecular approaches have been used to identify the P2 subtypes in salivary glands and in salivary cell lines. Assays include measurement of changes in [Ca2+]i, changes in transcellular short circuit current in monolayers, and RT-PCR to assess changes in receptor mRNA levels. The main observations are: (1) P2Y1 receptor activity is present in the submandibular gland (SMG) of immature rats but decreases over the first four weeks following birth, although mRNA levels remain relatively constant; (2) P2Y2 receptors are present in the cell lines and are up-regulated during short-term culture of normal parotid, sublingual, and SMG cells and following ligation of the main excretory duct of SMG; and (3) the P2X subtypes, P2X4 and P2X7, and the P2Y subtypes, P2Y1 and P2Y2, are co-expressed in salivary glands and salivary cell lines, and exhibit distinct basolateral versus apical localization in polarized cell monolayers as well as discrete patterns of intracellular signaling.