Salivary Protein Secretion Research Articles

Effect of fluocinolone acetonide (0.1%) treatment in oral lichen planus patients on salivary lactoferrin levels and Candida colonization: a prospective study

BackgroundAlthough topical steroids are an effective treatment for oral lichen planus, they can have suppressive effects on oral immunity and predispose the patients to Candida overgrowth. Lactoferrin is a crucial local immunity protein in the oral cavity with important antimicrobial activity. The aim of this study was to prospectively investigate salivary lactoferrin secretion levels and Candida colonization in oral lichen planus patients treated with fluocinolone acetonide 0.1% in orabase.MethodsSaliva samples were collected from 15 oral lichen planus subjects who had never received topical steroid treatment prior to this study and 15 healthy volunteers to determine their salivary lactoferrin levels using an enzyme-linked immunosorbent assay and to investigate the presence of oral Candida species at baseline and 3 months after treatment with fluocinolone acetonide 0.1% in orabase. Statistical analysis was performed to compare lactoferrin secretion and Candida colonization levels between the groups using the Mann–Whitney U test for independent data or the Wilcoxon Signed-Rank test for paired data.ResultsThe salivary lactoferrin secretion level was not significantly different between the control group and oral lichen planus patients or between before and after treatment with fluocinolone acetonide 0.1% in orabase (P > 0.05). Candida was detected in 11 (73.33%) healthy volunteers, 8 (53.33%) oral lichen planus patients before treatment, and 9 (60%) oral lichen planus patients after treatment with fluocinolone acetonide 0.1% in orabase. There was no significant difference in Candida counts between the groups (P > 0.05).ConclusionOur study indicates that using fluocinolone acetonide 0.1% in orabase to treat oral lichen planus for 3 months did not affect salivary lactoferrin protein secretion or Candida carriage.Trial registration The trial was registered at the Thai Clinical Trials Registry (TCTR identifier: TCTR20200723002).

Endoplasmic reticulum stress affects mouse salivary protein secretion induced by chronic administration of an α1-adrenergic agonist.

Stress stimulates both the sympathetic-adrenomedullary and hypothalamus-pituitary-adrenal axes. Activation of these axes results in the release of catecholamines, which in turn affects salivary secretion. Thus, repetitive stimulation of the α1-adrenergic receptor could be useful for studying the effects of chronic stress on the salivary gland. Salivary protein concentration and kallikrein activity were significantly lower in mice following chronic phenylephrine (PHE) administration. Chronic PHE administration led to significantly increased expression of the 78-kDa glucose-regulated protein, activating transcription factor 4, and activating transcription factor 6. Histological analyses revealed a decrease in the size of the serous cell and apical cytoplasm. These results suggest that repetitive pharmacological stimulation of the sympathetic nervous system elicits ER stress and translational suppression. In addition, PHE-treated mice exhibited a decrease in intracellular Ca2+ influx elicited by carbachol, a muscarine receptor agonist in the submandibular gland. The present findings suggest that chronic psychological, social, and physical stress could adversely affect Ca2+ regulation.

Salivary protein secretion in physiological and pathological conditions

Salivary protein secretion in physiological and pathological conditions

Low-Level Laser Therapy to the Major Salivary Glands Increases Salivary Flow and MUC5B Protein Secretion in Diabetic Patients with Hyposalivation: A Preliminary Study

Background: To investigate the effect of low-level laser therapy to salivary gland function in diabetic patients with hyposalivation. Methods: Twelve diabetic patients were recruited. A 940-nm indium-gallium-arsenide-phosphide low-power semiconductor diode laser was used to stimulate the major salivary glands with an irradiation time of 40 s; this was done three times a week for 2 consecutive weeks. Patients were given questionnaires related to dry mouth symptoms. Salivary flow rates, questionnaire responses as well as MUC7, MUC5B and histatin 5 protein salivary concentrations were assessed at the first and sixth visits after laser therapy as well at the 6-week follow-up visit. Results: The unstimulated salivary flow rate and MUC5B concentration at the follow-up visit significantly increased (p < 0.01). Histatin 5 concentration significantly decreased at the follow-up visit compared with that at the first visit (p < 0.05). The mean dry mouth score revealed a significant decrease in dry mouth symptoms at the sixth visit and follow-up visit compared with those at the first visit (p < 0.001). The positive correlation between dry mouth score and flow rate was the strongest at the sixth visit (rs = 0.549). Conclusions: Low-level laser therapy increased the salivary flow rate and decreased dry mouth symptoms in diabetic patients.

P.3.014 - Diurnal salivary alpha-amylase and not cortisol differentiates major depressive disorder in out-patients

Introduction To date, there are few putative biomarkers specifically for MDD. Such biomarkers could help improve our understanding of MDD pathophysiology, and aid in the refinement of current MDD criteria. Research has shown that the stress hormone cortisol in saliva, a non-invasive marker of hypothalamus pituitary adrenal (HPA) axis activity, can differentiate between healthy controls and patients with psychiatric disorders on a group level. Another interesting system for putative biomarkers is the autonomic nervous system (ANS). Animal studies have indicated the involvement of the ANS, and specifically the sympathetic nervous system (SNS) in the release of the enzyme alpha amylase in saliva (sAA), whereby sAA has been proposed to be an index of sympathoadrenal medullary (SAM) activity. This theory is based on the premise that the (para-)sympathetic branches of the autonomic nervous system innervate salivary glands, whereby sympathetic stimulation increases salivary protein secretion [1]. In line with these findings, sAA has been positively correlated with the acute SNS stress response in adults [2]. Many studies have since demonstrated that MDD patients generally have higher sAA in comparison to healthy controls within experimental settings [i.e.3]. However, what remains unknown is the natural diurnal sAA profile of MDD patients in comparison to patients with other psychiatric disorders and healthy controls. Aims To determine the diurnal profiles of sAA and salivary cortisol in out-patients with MDD, patients with other affective disorders, and healthy controls. Methods sAA and salivary cortisol levels were determined from 7 saliva samples collected over the course of the day from 833 participants that partook in our Routine Outcome Monitoring [4] measurement (i.e., 97 MDD patients, 142 patients with other psychiatric problems, and 594 controls). ANOCVAs were conducted to examine the differences in both diurnal sAA and salivary cortisol between the MDD patient group, the other psychiatric disorder group, and healthy controls. In this, covariates were entered into the model in accordance with factors that have been found to be influential on these markers in previous research. Results On average, MDD patients had higher sAA levels upon awakening and (Area under the Curve) AUCi in comparison to both controls and patients with other psychiatric problems. Elevated evening cortisol levels were found in MDD patients in comparison to both controls and patients with other psychiatric problems. Cortisol values in MDD patients and patients with other psychiatric problems were higher after ingestion of dexamethasone upon awakening on day 2. Conclusion sAA levels were found to be higher in MDD patients at awakening and with respect to the AUCi, whereas no time-point measured indicated elevated sAA levels in the other affective disorders group or the healthy controls. Salivary cortisol was unable to differentiate between MDD and other affective disorders as successfully as sAA, suggesting that sAA levels at awakening may have stronger differentiating qualities for MDD specifically.

The imprint of salivary secretion in autoimmune disorders and related pathological conditions.

Xerostomia is a state of oral dryness associated with salivary gland dysfunction and is induced by stress, radiation and chemical therapy, various systemic and autoimmune diseases, and specific medications. Fluid secretion is interrupted by the stimulation of neurotransmitter-induced increase in cytosolic calcium ([Ca2+]i) in salivary gland acinar cells, prompting the mobilization of ion channels and their transporters. Salivary fluid and protein secretion are principally dependent on parasympathetic and sympathetic nerves. Various inflammatory cytokines allied with lymphocytic infiltration cause glandular damage and Sjogren's syndrome, an autoimmune exocrinopathy associated with hyposalivation. A defect in IP3Rs, a major calcium release channel, prompts inadequate agonist-induced [Ca2+]i in acinar cells and deters salivary flow. The store-operated calcium entry-mediated Ca2+ movement into the acini activates K+ and Cl- channels, which further opens a water channel protein, aquaporin-5, and triggers the release of fluid secretion from the salivary glands. The cellular mechanism of salivary gland dysfunction and hyposalivation has not yet been elucidated. In this review, we focused mainly on the proteins responsible for deficient saliva, the correlation between inflammation and salivation, autoimmune disorders and other ailments or complications associated with hyposalivation.

Stress and Salivary Glands.

Salivary glands produce a bicarbonate-rich fluid containing digestive and protective proteins and other components to be delivered into the gastrointestinal tract. Its function is under strict control of the autonomic nervous system. Salivary electrolyte and fluid secretion are primarily controlled by parasympathetic activity, while protein secretion is primaily triggered by sympathetic stimulation. Stress activates the hypothalamic - pituitary - adrenal axis. The peripheral limb of this axis is the efferent sympathetic/adrenomedullary system. Stress reaction, even if it is sustained for long, does not cause obvious damage to salivary glands. However, stress induces dramatic changes in the constituents of secreted saliva. Since salivary protein secretion is strongly dependent on sympathetic control, changes in saliva can be utilized as sensitive stress indicators. Some of the secreted compounds are known for their protective effect in the mouth and the gut, while others may just pass through the glands from blood plasma because of their chemical nature and the presence of transcellular salivary transporting systems. Indeed, most compounds that appear in blood circulation can also be identified in saliva, although at different concentrations. This work overviews the presently recognized salivary stress biosensors, such as amylase, cortisol, heat shock proteins and other compounds. It also demonstrates that saliva is widely recognised as a diagnostic tool for early and sensitive discovery of salivary and systemic conditions and disorders. At present it may be too early to introduce most of these biomarkers in daily routine diagnostic applications, but advances in salivary biomarker standardisation should permit their wide-range utilization in the future including safe, reliable and non-invasive estimation of acute and chronic stress levels in patients.

Exercise, But Not Acute Sleep Loss, Increases Salivary Antimicrobial Protein Secretion

Sleep deficiencies may play a role in depressing immune parameters. Little is known about the impact of exercise after sleep deprivation on mucosal immunity. The purpose of this study was to quantify salivary antimicrobial proteins (AMPs) in response to sleep loss before and after exercise. Four men and 4 women (age: 22.8 ± 2; : 49.1 ± 7.1 ml · kg(-1) · min(-1)) completed 2 exercise trials consisting of 45 minutes of running at 75% VO2peak after a normal night of sleep (CON) and after a night without sleep (WS). Exercise trials were separated by 10 ± 3 days. Saliva was collected before, immediately after, and 1 hour after exercise. LL-37, HNP1-3, Lactoferrin (Lac), and Lysozyme (Lys) were measured. Sleep loss did not affect the concentration or secretion rate of AMPs before or in response to exercise. However, exercise increased the concentration from pre- to post-exercise of LL-37 (pre: 15.5 ± 8.7; post: 22.3 ± 16.2 ng · ml(-1)), HNP1-3 (pre: 2.2 ± 2.3; post: 3.3 ± 2.5 µg · ml(-1)), Lac (pre: 5,234 ± 4,202; post: 12,283 ± 10,995 ng · ml(-1)), and Lys (pre: 5,831 ± 4,465; post: 12,542 ± 10,755 ng · ml(-1)), p <= 0.05. The secretion rates were higher immediately after and 1 hour after exercise compared with before exercise for LL-37 (pre: 3.1 ± 2.1; post: 5.1 ± 3.7; +1: 6.9 ± 8.4 ng · min(-1)), HNP1-3 (pre: 0.38 ± 0.38; post: 0.80 ± 0.75; +1: 0.84 ± 0.67 µg · min(-1)), Lac (pre: 1,096 ± 829; post: 2,948 ± 2,923; +1: 2,464 ± 3,785 ng · min(-1)), and Lys (pre: 1,534 ± 1,790; post: 3,042 ± 2,773; +1: 1,916 ± 1,682 ng · min-(1)), p <= 0.05. These data suggest that the major constituents of the mucosal immune system are unaffected by acute sleep loss and by exercise after acute sleep loss. Exercise increased the concentration and secretion rate of each AMP suggesting enhanced immunity and control of inflammation, despite limited sleep.

Vps15 is required for stress induced and developmentally triggered autophagy and salivary gland protein secretion in Drosophila.

Autophagy is a catabolic process used to deliver cellular material to the lysosome for degradation. The core Vps34/class III phosphatidylinositol 3-kinase (PI3K) complex, consisting of Atg6, Vps15, and Vps34, is highly conserved throughout evolution, critical for recruiting autophagy-related proteins to the preautophagosomal structure and for other vesicular trafficking processes, including vacuolar protein sorting. Atg6 and Vps34 have been well characterized, but the Vps15 kinase remains poorly characterized with most studies focusing on nutrient deprivation-induced autophagy. Here, we investigate the function of Vps15 in different cellular contexts and find that it is necessary for both stress-induced and developmentally programmed autophagy in various tissues in Drosophila melanogaster. Vps15 is required for autophagy that is induced by multiple forms of stress, including nutrient deprivation, hypoxia, and oxidative stress. Furthermore, autophagy that is triggered by physiological stimuli during development in the fat body, intestine, and salivary gland also require the function of Vps15. In addition, we show that Vps15 is necessary for efficient salivary gland protein secretion. These data illustrate the broad importance of Vps15 in multiple forms of autophagy in different animal cells, and also highlight the pleiotropic function of this kinase in multiple vesicle-trafficking pathways.

Alpha amylase as a salivary biomarker of acute stress of venepuncture from periodic medical examinations.

Periodic occupational health examinations often require venepuncture. Acute psychological and physical stressors during such procedure result in sympathetic stimulation and increased salivary protein secretion, including salivary α-amylase (SAA). We studied SAA response to venepuncture during such examination. Fifty-eight healthy males undergoing periodic medical examination reported perceived stress level (PSL) scores (on a five-point scale) and provided passive drool saliva samples at 15-min (T1) and 1-min before (T2); and 1-min (T3) and 15-min after venepuncture (T4). A subset of 33 participants available for repeat examination on a control day when there was no venepuncture provided saliva samples at the corresponding times for comparison. Saliva SAA activity levels were analyzed using a SAA assay kit (Salimetrics LLC, USA). Among 58 participants, mean SAA increased from T1 (89.95 U/L) to T2 (109.5 U/L) and T3 (116.9 U/L). SAA remained elevated 15 min after venepuncture (121.0 U/L). A positive trend in the difference of SAA between T3 and T1 was noted among subjects with increasing mean PSL scores. T3–T1 values were 0.6 (among those with PSL ≤ 1, n = 24), 11.3 (among those with PSL between 1 and 1.5, n = 18), and 78.9 (among those with PSL > 1.5, n = 16). SAA increment over four-time points was significantly higher on the venepuncture compared to the control day (P = 0.021). SAA increases in response to the acute stress of venepuncture during a periodic medical examination, and remains elevated 15 min after the procedure. In comparison, such fluctuations in SAA were not seen on a control day. During venepuncture, increase in SAA from baseline is higher among those who reported greater self-perceived stress during the procedure.

Effect of the neuropeptides vasoactive intestinal peptide, peptide histidine methionine and substance P on human major salivary gland secretion

The parasympathetic transmitters vasoactive intestinal peptide (VIP) and substance P (SP) are secretagogues in salivary glands of animals. Currently, we hypothesise that in human salivary glands, these neuropeptides and the VIP-related peptide histidine methionine (PHM) also exert secretory actions, reflected morphologically by exocytosis of acinar protein/glycoprotein-storing granules. Submandibular and parotid gland tissues, exposed in vitro to VIP and PHM, and SP, respectively, were examined by light and transmission electron microscopy. For comparison, the response to in vitro stimulation of isoproterenol, phenylephrine and carbachol was examined. Moreover, the peptidergic innervation of the glands was examined by immunohistochemistry. Vasoactive intestinal peptide- and PHM-immunoreactive nerves were in close proximity to acini and ducts in the two glands, while these elements lacked a SP-positive innervation. While no morphological changes occurred in response to SP (parotid glands), VIP and PHM administration (submandibular glands) caused conspicuous acinar degranulation accompanied by luminal space broadening. In the two glands, both α1 - and β-adrenergic receptor stimulation and muscarinic receptor stimulation caused similar changes as to VIP/PHM, although to varying extent. Vasoactive intestinal peptide and PHM, but not SP, are likely transmitters in the parasympathetic control of salivary (protein) secretion in humans.

Insights into the insect salivary gland proteome: Diet-associated changes in caterpillar labial salivary proteins

The primary function of salivary glands is fluid and protein secretion during feeding. Compared to mammalian systems, little is known about salivary protein secretion processes and the effect of diet on the salivary proteome in insect models. Therefore, the effect of diet nutritional quality on caterpillar labial salivary gland proteins was investigated using an unbiased global proteomic approach by nanoLC/ESI/tandem MS. Caterpillars of the beet armyworm, Spodoptera exigua Hübner, were fed one of three diets: an artificial diet containing their self-selected protein to carbohydrate (p:c) ratio (22p:20c), an artificial diet containing a higher nutritional content but the same p:c ratio (33p:30c) or the plant Medicago truncatula Gaertn. As expected, most identified proteins were associated with secretory processes and not influenced by diet. However, some diet-specific differences were observed. Nutrient stress-associated proteins, such as peptidyl-propyl cis–trans isomerase and glucose-regulated protein94/endoplasmin, and glyceraldehyde 3-phosphate dehydrogenase were identified in the labial salivary glands of caterpillars fed nutritionally poor diets, suggesting a link between nutritional status and vesicular exocytosis. Heat shock proteins and proteins involved in endoplasmic reticulum-associated protein degradation were also abundant in the labial salivary glands of these caterpillars. In comparison, proteins associated with development, such as arylphorin, were found in labial salivary glands of caterpillars fed 33p:30c. These results suggest that caterpillars fed balanced or nutritionally-poor diets have accelerated secretion pathways compared to those fed a protein-rich diet.

Effects of Repeated Administration of Pilocarpine and Isoproterenol on Aquaporin-5 Expression in Rat Salivary Glands

Aquaporins are water channel proteins which enable rapid water movement across the plasma membrane. Aquaporin-5 (AQP5) is the major aquaporin and is expressed on the apical membrane of salivary gland acinar cells. We examined the effects of repeated administration of pilocarpine, a clinically useful stimulant for salivary fluid secretion, and isoproterenol (IPR), a stimulant for salivary protein secretion, on the abundance of AQP5 protein in rat salivary glands by immunofluorescence microscopy and semi-quantitative immunoblotting. Unexpectedly AQP5 was decreased in pilocarpine-administered salivary glands, in which fluid secretion must be highly stimulated, implying that AQP5 might not be required for fluid secretion at least in pilocarpine-administered state. The abundance of AQP5, on the other hand, was found to be significantly increased in IPR-administered submandibular and parotid glands. To address the possible mechanism of the elevation of AQP5 abundance in IPR-administered animals, changes of AQP5 level in fasting animals, in which the exocytotic events are reduced, were examined. AQP5 was found to be decreased in fasting animals as expected. These results suggested that the elevation of cAMP and/or frequent exocytotic events could increase AQP5 protein. AQP5 expression seems to be easily changed by salivary stimulants, although these changes do not always reflect the ability in salivary fluid secretion.

Reduced statherin reactivity of human submandibular gland in diabetes

Statherin is a salivary protein involved in the formation of enamel pellicle and in regulation of calcium homeostasis. Diabetes and other pathologies affect both salivary flow and protein secretion by salivary glands, causing increased susceptibility to mucosal infections, tooth demineralization, and caries. The purpose of this study was to compare the statherin expression in submandibular glands of healthy and diabetic subjects. Fragments of submandibular glands obtained from diabetic and non diabetic patients were fixed, dehydrated, embedded in Epon Resin and processed for the immunogold histochemistry. The results were statistically evaluated. Specific statherin labeling was demonstrated in secretory granules of acinar cells in both diabetic and normal samples. The staining was much more intense in the latter compared to those of diabetics. The labeling density was quantified by evaluating the number and spatial distribution of gold particles within the granules. The number of gold particles was significantly lower in glands from diabetics than in control glands. The results obtained suggest that a reduced statherin secretion by salivary glands might be partly responsible for a less effective protection of the oral tissues, resulting in an higher incidence of caries and oral infections associated with diabetes.

Salivary secretion, mucin concentrations and candida carriage in HIV‐infected patients

To test whether the submandibular/sublingual (SMSL) salivary secretion, mucin concentration and candida carriage status were altered in human immunodeficiency virus-positive (HIV+) patients. SMSL saliva collected from 48 HIV-infected and 31 HIV-negative men were analyzed for flow rates, total protein and mucin concentrations. Salivary cultures were performed for Candida assessment. The salivary flow rate and protein secretion of the HIV+ patients was 37% and 32% less than that of the controls (P < 0.0001, P = 0.0087). The mucin concentrations (MG1 and MG2) were higher in the HIV+ subjects compared with controls (P = 0.0186, P = 0.0014); however, the mucin secretions were not different. The frequency of Candida-positive cultures was higher in the HIV+ subjects than in the controls (61.4%vs 24.1%, P = 0.0018). In the HIV-infected group, the unstimulated SMSL flow rates were lower in Candida-positive than in Candida-negative patients (P = 0.0158). The salivary secretion of the SMSL glands was reduced in HIV infection. Although the mucin concentration increased in HIV+ subjects, mucin secretion was not altered. Highly active antiviral therapy had no effect on salivary function. We found an association between the level of candida carriage and salivary flow rate in HIV-infected patients.

Saliva: a Dynamic Proteome

The proteome of whole saliva, in contrast to that of serum, is highly susceptible to a variety of physiological and biochemical processes. First, salivary protein secretion is under neurologic control, with protein output being dependent on the stimulus. Second, extensive salivary protein modifications occur in the oral environment, where a plethora of host- and bacteria-derived enzymes act on proteins emanating from the glandular ducts. Salivary protein biosynthesis starts with the transcription and translation of salivary protein genes in the glands, followed by post-translational processing involving protein glycosylation, phosphorylation, and proteolysis. This gives rise to salivary proteins occurring in families, consisting of structurally closely related family members. Once glandular secretions enter the non-sterile oral environment, proteins are subjected to additional and continuous protein modifications, leading to extensive proteolytic cleavage, partial deglycosylation, and protein-protein complex formation. All these protein modifications occur in a dynamic environment dictated by the continuous supply of newly synthesized proteins and removal by swallowing. Understanding the proteome of whole saliva in an environment of continuous turnover will be a prerequisite to gain insight into the physiological and pathological processes relevant to oral health, and be crucial for the identification of meaningful biomarkers for oral disease.

Muscarinic receptors and salivary secretion

The release of acetylcholine from parasympathetic nerves and its interaction with muscarinic acetylcholine receptors (mAChRs) regulates many fundamental functions in the periphery (smooth muscle contraction, glandular secretion, modulation of cardiac output) and central nervous system (motor control

Water Channels and Zymogen Granules in Salivary Glands

Salivary secretion occurs in response to stimulation by neurotransmitters released from autonomic nerve endings. The molecular mechanisms underlying the secretion of water, a main component of saliva, from salivary glands are not known; the plasma membrane is a major barrier to water transport. A 28-kDa integral membrane protein, distributed in highly water-permeable tissues, was identified as a water channel protein, aquaporin (AQP). Thirteen AQPs (AQP0 - AQP12) have been identified in mammals. AQP5 is localized in lipid rafts under unstimulated conditions and translocates to the apical plasma membrane in rat parotid glands upon stimulation by muscarinic agonists. The importance of increases in intracellular calcium concentration [Ca(2+)](i) and the nitric oxide synthase and protein kinase G signaling pathway in the translocation of AQP5 is reviewed in section I. Signals generated by the activation of Ca(2+) mobilizing receptors simultaneously trigger and regulate exocytosis. Zymogen granule exocytosis occurs under the control of essential process, stimulus-secretion coupling, in salivary glands. Ca(2+) signaling is a principal signal in both protein and water secretion from salivary glands induced by cholinergic stimulation. On the other hand, the cyclic adenosine monophosphate (cAMP)/cAMP-dependent protein kinase system has a major role in zymogen granule exocytosis without significant increases in [Ca(2+)](i). In section II, the mechanisms underlying the control of salivary protein secretion and its dysfunction are reviewed.

The effect of parasympathetic postganglionic denervation on parotid salivary protein secretion in anaesthetized sheep

Effects of unilateral parasympathetic denervation of ovine parotid glands were examined in anaesthetized sheep 21–28 days after nerve section. Parasympathetic denervation reduced the mass of the ipsilateral gland while increasing that of the contralateral gland to the extent that total gland mass was greater than in sheep with normally innervated glands. The spontaneous secretion (8.8±1.1 μl min −1 g gland −1) was significantly less from denervated than from innervated glands of normal control animals (26.0±2.7 μl min −1 g gland −1; P<0.01) and contained more protein. Rates of flow, and the outputs of sodium and potassium, in response to sympathetic stimulation, were similar from normally innervated and chronically denervated glands, when allowance was made for the discrepancy in weights, whereas the output of protein was significantly enhanced following parasympathetic denervation (innervated—31.4±7.3 μg g gland −1, denervated—83.4±26.6 μg g gland −1; P<0.05). Intra-arterial infusions of acetylcholine (130 pmol min −l kg −1) elicited a flow of parotid saliva, the protein content of which was significantly enhanced by prior parasympathetic denervation. Intra-arterial infusions of vasoactive intestinal peptide (VIP; 2.5 pmol min −1 kg −1) produced a small but statistically significant ( P<0.05) increase in the flow of parotid saliva from the contralateral, innervated but not from denervated glands. It also caused a small increase in protein output, which was significantly enhanced by prior denervation. VIP had no synergistic effect on the parotid responses to acetylcholine. The results show that the parasympathetic innervation to the parotid gland of the sheep exerts important trophic effects on the gland. Interaction of adrenergic and cholinergic receptors makes an important contribution to stimulation of the secretion of protein and prior denervation potentiates the protein responses to both acetylcholine and VIP.

Understanding salivary fluid and protein secretion.

Understanding salivary fluid and protein secretion.