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Cyclosporin A: effects on the secretory process and noradrenergic activity in the submandibular gland of the rat.

OBJECTIVES: The aim of the present work was to study the effect of long-term cyclosporine (CSA) administration on norepinephrine (NE) metabolism and adrenergic-evoked secretion in the rat submandibular gland (SMG). METHODS: Dose-response curves to adrenergic agonists (methoxamine, isoproterenol, NE) were performed in control and CSA (10 and 30 mg/kg every 2 days for 1 month)-treated rats after SMG duct cannulation. In SMG tissue neuronal NE uptake, release, synthesis and endogenous content were determined. In addition phosphoinositide intracellular signaling was also investigated. RESULTS: CSA administration caused an increase in salivary secretion evoked by methoxamine (alpha-adrenergic agonist) and NE but failed to modify salivation evoked by beta-adrenergic stimulation (isoproterenol). Long-term CSA administration decreased NE release and synthesis whereas it enhanced the amine uptake and phosphoinositide hydrolysis in the SMG. CONCLUSIONS: The administration of CSA for 30 days induced salivary gland sensitization likely mediated by diminished adrenergic input. Present results suggest that the decreased sympathetic activity evoked by long-term CSA administration in the rat SMG may lead to sensitization of the gland supported by increased phosphoinositide hydrolysis and enhanced adrenergic-evoked salivation.

Adrenergic alpha-Agonists↗

Stimulated Ca2+ entry activates Cl- currents after releasing Ca2+ from the intracellular store in submandibular gland cells of the rat.

In order to examine whether Ca2+ entry is directly involved in controlling exocrine secretion, the Ca(2+)-activated Cl- currents were recorded in single and clusters of rat submandibular gland cells using the whole-cell patch-clamp method. Extracellularly applied acetylcholine (ACh, 10 nM) as well as intracellularly applied GTP gamma S and InsP3 caused repetitive transients of the Cl- currents activated by intracellular Ca2+. These responses occurred also in the absence of external Ca2+, but disappeared after several minutes. Readmission of Ca2+ to the extracellular solution restored the repetitive current transients, while introduction of Sr2+ failed to restore the current signals in spite of the presence of Sr2+ entry detected by microfluorimetry. On the other hand, direct application of Sr2+ to the cell inside caused activation of the Cl- currents although less effectively than Ca2+. When Ca2+ was introduced to the extracellular solution during an interruption of ACh stimulation after the ACh-induced depletion of intracellular Ca2+ store, the Cl- current was not elicited. However, a subsequent challenge with ACh at the same concentration in the absence of extracellular Ca2+ caused repetitive transient Cl- currents. The results suggest that in this cell type the stimulated Ca2+ entry does not by itself activate the Cl- currents but activates them indirectly by triggering Ca2+ release from the intracellular Ca2+ store which may take up Ca2+ soon after the Ca2+ entry.

Acetylcholine↗

Membrane-limited expression and regulation of Na+-H+ exchanger isoforms by P2 receptors in the rat submandibular gland duct.

1. Cell-specific reverse transcriptase-polymerase chain reaction (RT-PCR), immunolocalization and microspectrofluorometry were used to identify and localize the Na+-H+ exchanger (NHE) isoforms expressed in the submandibular gland (SMG) acinar and duct cells and their regulation by basolateral and luminal P2 receptors in the duct. 2. The molecular and immunofluorescence analysis showed that SMG acinar and duct cells expressed NHE1 in the basolateral membrane (BLM). Duct cells also expressed NHE2 and NHE3 in the luminal membrane (LM). 3. Expression of NHE3 was unequivocally established by the absence of staining in SMG from NHE3 knockout mice. NHE3 was expressed in the LM and in subluminal regions of the duct. 4. Measurement of the inhibition of NHE activity by the amiloride analogue HOE 694 (HOE) suggested expression of NHE1-like activity in the BLM and NHE2-like activity in the LM of the SMG duct. Several acute and chronic treatments tested failed to activate NHE activity with low affinity for HOE as expected for NHE3. Hence, the physiological function and role of NHE3 in the SMG duct is not clear at present. 5. Activation of P2 receptors resulted in activation of an NHE-independent, luminal H+ transport pathway that markedly and rapidly acidified the cells. This pathway could be blocked by luminal but not basolateral Ba2+. 6. Stimulation of P2U receptors expressed in the BLM activated largely NHE1-like activity, and stimulation of P2Z receptors expressed in the LM activated largely NHE2-like activity. 7. The interrelation between basolateral and luminal NHE activities and their respective regulation by P2U and P2Z receptors can be used to co-ordinate membrane transport events in the LM and BLM during active Na+ reabsorption by the SMG duct.

Adenosine Triphosphate↗

Indium-111 leukocyte accumulation in submandibular gland saliva as a cause for false-positive gut uptake in children.

Unexplained false-positive accumulation of In-111 leukocyte in the gastrointestinal tract has been reported previously. In a pediatric population, uptake in the submandibular gland was noted in 19 of 42 children. This is believed to be a normal finding in children that is not seen in adults. In some of these 19 children, unexplained gastrointestinal activity was also noted. Saliva from a patient with false-positive gastrointestinal uptake and positive submandibular activity was positive for In-111. One suggested cause of unexplained gut activity may be secondary to swallowed activity in the saliva from the normal submandibular activity in children.

Child↗

Fibroinflammatory pseudotumor of the submandibular gland.

BACKGROUND: Fibroinflammatory pseudotumors infrequently involve the major salivary glands. Much more is known regarding the clinical behavior of orbital pseudotumors, especially their steroid responsiveness. METHODS: A case of fibroinflammatory pseudotumor involving the submandibular gland is presented with its preoperative cytologic and computed tomographic scan features. The lesion had a dramatic response to steroids for residual disease. CONCLUSIONS: If preoperative cytologic features of benign spindle cells with an inflammatory component seen on fine-needle aspiration raise the possibility of fibroinflammatory pseudotumor, then responsiveness to high-dose steroids may preclude the need for more-extensive surgery.

Biopsy, Needle↗

Changes in epidermal growth factor concentrations of submandibular gland, plasma and urine of normal and sialoadenectomized female mice during various reproductive stages.

The concentrations of epidermal growth factor (EGF) were measured by radioimmunoassay in the submandibular gland, plasma and urine of adult female C3H/HeN mice whilst virgin and during pregnancy, lactation and after lactation. During gestation there was a significant increase in the submandibular EGF concentration which was five to seven times higher than that found in virgin mice. The level of EGF in the gland remained high during the period of lactation and even several weeks after lactation. Plasma EGF levels were also increased during the periods of pregnancy, lactation and after lactation when compared with those of virgin mice. These increases were, however, apparent only between 24.00 and 08.00 h, because of circadian variations in circulating EGF. The level of plasma EGF was significantly (P less than 0.05) higher during the 24.00-08.00 h period than during the 12.00-20.00 h period in all stages examined. Concentrations of EGF in the urine of virgin, pregnant, lactating and primiparous mice remained relatively constant, and the levels were much higher than those in the plasma. Similar studies using sialoadenectomized pregnant and lactating mice indicated that the plasma levels of EGF were below the level of sensitivity of the assay (less than 16.5 pmol/l (less than 0.1 ng/ml] even during the 24.00-08.00 h period, whereas urinary EGF remained at high levels which were similar to those of normal pregnant and lactating mice. These results suggest that submandibular EGF contributes to the increase in plasma EGF which occurs after gestation, but is not the major source of the urinary EGF.

Animals↗

Morphological changes of intercellular junctions in the rat submandibular gland treated by long-term repeated administration of isoproterenol.

Long-term repeated administration of isoproterenol (IPR) 2 mg/100 g bw, once daily for ten days, resulted in morphological changes in the intercellular junctions of rat submandibular glands, which were investigated by means of the freeze-fracture technique. A significantly increased number of tight-junctional strands was present. These junctional strands extended much deeper toward the basal membrane than those in normal acinar cells. The basal frontier strands that branched from the networks of tight junctions were elongated and had either free-endings or terminal loops, which were more frequently observed in the IPR-treated acinar cells than in untreated acinar cells. Some of the strands of tight junctions were connected to small gap junctions. The diameters of gap junctions were not significantly different from those of control acinar cells. However, smooth areas devoid of particles were found intermingling with the usual packed particles in irregularly shaped small gap junctions. There was no significant difference between the desmosomes of IPR-treated and untreated acinar cells, in terms of either morphology or distribution. These changes in junctional morphology in the IPR-treated acinar cells resemble those seen in salivary glands during development, and in some experimental conditions including tumorous changes.

Animals↗

[Effects of adrenergic agents on secretion of salivary kallikrein in the submandibular gland of the dog].

The effects of sympathetic nerve stimulation and administrations of sympathomimetics on the secretion of salivary kallikrein induced by stimulation of Chorda tympani were examined quantitatively and qualitatively in the dog submandibular gland. Both sympathetic stimulation and administrations of sympathomimetics such as norepinephrine, epinephrine, and isoproterenol caused increased secretion of salivary kallikrein. Among these effects, those of the sympathetic stimulation, norepinephrine, and epinephrine were not completely abolished by pretreatment with phenoxybenzamine or propranolol, but the effect of isoproterenol was abolished by pretreatment with propranolol, and was hardly influenced by pretreatment with phenoxybenzamine. From these results, it would appear that secretion of salivary kallikrein may be mediated through adrenergic alpha- and beta-receptors. On the other hand, in contrast with the activities of the salivary kallikrein secreted by Chorda tympani stimulation or administration of isoproterenol which were not inhibited by SBTI, the activities of the salivary kallikrein secreted by sympathetic stimulation as well as administration of norepinephrine or epinephrine were markedly inhibited by SBTI. From these results, it is concluded that secretion of glandular kallikrein is due either to Chorda tympani stimulation or is mediated through adrenergic beta-receptor, while secretion of plasma kallikrein is mediated through adrenergic alpha-receptor.

Animals↗

Relationship of fluid and mucin secretion to morphological changes in the perfused rat submandibular gland.

Transport of electrolytes/water and exocytosis are activated by elevation of the cytosolic Ca(2+) concentration and are potentiated by elevation of cytosolic cyclic AMP. To correlate mucin and fluid secretion with morphological changes, rat submandibular glands were vascularly perfused and the fluid secretion and N-acetylgalactosamine in the saliva were measured during stimulation with various concentrations of carbachol (CCh) and/or isoproterenol (ISP). Single stimulation with 1 microM CCh induced a transient increase of N-acetyl galactosamine followed by a decline to a low level during sustained stimulation. The overload of 1 microM ISP increased secretion of N-acetyl galactosamine to a higher sustained level of 40-50 microg/g-min. However, at 1 microM CCh, fluid secretion was maintained at the same level during stimulation and even overload of 1 microM ISP did not significantly affect its level, whereas addition of 0.5 microM ISP to the gland stimulated with 0.1 microM CCh increased fluid secretion. Morphological observation was carried out by HRSEM and TEM. Combination of CCh and ISP in different concentrations resulted in distinctive morphological changes which reflect fluid secretion and mucin secretion. The kinetics of ATP and creatine phosphate (PCr) were measured using P-31 NMR, which indicated that the potentiation of fluid secretion is limited under a higher level of CCh stimulation due to a limited energy supply.

Acetylgalactosamine↗

Transient occurrence of 27 kDa heat-shock protein in the terminal tubule cells during postnatal development of the rat submandibular gland.

It has been suggested that the 27 kDa heat-shock protein (Hsp27) plays a role at crucial cellular checkpoints for proliferation, apoptosis, and differentiation. We examined the immunolocalization of Hsp27 in the rat submandibular gland during postnatal development, wherein acinar cells proliferate and differentiate at earlier postnatal periods. At 2 weeks of age, weak Hsp27 immunoreactivity was distributed diffusely over all gland components. At 3 weeks, Hsp27 immunoreactivity disappeared in most parts of the acini and ducts, but was intensely accumulated in a small cell population located in the acinar center. This population was composed mostly of terminal tubule (TT) type I cells. At 4 weeks, the Hsp27-immunopositive cell population in the acinar center was composed primarily of immature (type II) acinar cells, partly of immature (granulated) intercalated duct (ID) cells, and occasionally of apoptotic cells. After 5 weeks, all acinar components became mature and were no longer immunoreactive for Hsp27. When acinar cell differentiation was accelerated by administration of isoproterenol to 3-week-old rats for 7 days, the number of Hsp27-positive cells was significantly lower than in the control gland at 4 weeks, confirming that Hsp27 expression is downregulated in mature acinar cells. These results suggest that at around 3-4 weeks in postnatal development, the centroacinar TT cells stop proliferating and begin to differentiate into acinar and ID cells, and occasionally undergo apoptosis. Hsp27 is transiently expressed in the centroacinar TT cells during this critical period, and thus may play a role in their differentiation into the immediate descendants.

Animals↗

Identification of the adenylyl cyclase-activating 5-hydroxytryptamine receptor subtypes expressed in the rat submandibular gland.

1. Serotonin (5-hydroxytryptamine, 5-HT) has been shown to increase cyclic AMP production in dispersed cell aggregates from the major salivary glands of the rat. The goal of the present study was to identify the 5-HT receptor subtypes that mediate these effects in rat submandibular glands (SMG). 2. Among the 5-HT receptor subtypes identified in the rat, 5-HT(4(a,b)), 5-HT(6) and 5-HT(7(a,b,c)) activate adenylyl cyclase (AC). We used subtype specific primers to screen rat SMG by reverse transcription-PCR. Results indicate the presence of mRNA for 5-HT(4(b)) and 5-HT(7(a)) but not for 5-HT(4(a)), 5-HT(6) and 5-HT(7(b,c)). 3. In dispersed SMG cells, 5-carboxyamidotryptamine (5-CT), a 5-HT(7) receptor agonist, stimulated cyclic AMP synthesis with higher potency (EC(50)=27+/-5 nM) but lower efficacy than 5-HT, suggesting a 5-HT(7) component and an additional component in the response to 5-HT. The 5-HT(7) contribution was further supported by antagonism of the 5-CT effect by metergoline, a 5-HT(7) antagonist, which exhibited an affinity (K(i)=50 nM) similar to that obtained at the cloned 5-HT(7) receptor. 4. In the presence of a maximally effective concentration of 5-CT, 5-HT produced an additional increase in cyclic AMP production that was inhibited by the 5-HT(4) receptor antagonist, GR113808, suggesting that the second component of cyclic AMP production is mediated by 5-HT(4) receptors. 5. These findings indicate the presence in rat SMG of both 5-HT(4(b)) and 5-HT(7(a)) receptors positively coupled to AC.

Adenylyl Cyclases↗

Significance of adrenergic alpha-effect on salivary kallikrein secretion in the submandibular gland of the dog.

The effects of the sympathetic nerve stimulation and the administrations of sympathomimetics on the secretion of salivary kallikrein induced by the chorda tympani stimulation were examined quantitatively and qualitatively in the submandibular gland of the dog. The secretion of salivary kallikrein may be mediated through both adrenergic alpha- and beta-receptors. The activities of salivary kallikrein secreted by either the chorda tympani stimulation or isoproterenol were not inhibited by soy bean trypsin inhibitor in vitro, but those secreted by the sympathetic nerve stimulation and noradrenaline or adrenaline were markedly inhibited in vitro. These results suggested that secretion of glandular kallikrein was induced by the chorda tympani stimulation and the sympathetic beta-stimulation, and secretion of plasma kallikrein was induced by the sympathetic alpha-stimulation.

Animals↗

Regulation of Na+,K+-ATPase in submandibular glands of hypophysectomized male mice by steroid and thyroid hormones.

The effects of thyroid hormone, androgen, glucocorticoid, and mineralocorticoid on Na+,K+-ATPase activity and on levels of its alpha-subunit protein (alpha 1 isoform) in mouse submandibular gland (SMG) were studied by enzyme assay for ouabain-sensitive ATP hydrolysis, by quantitative densitometric scanning of Western blots, and by immunohistochemistry. To define the specific regulatory effects of various pituitary-dependent hormones on expression of Na+,K+-ATPase in the SMG, we treated hypophysectomized (hypox) male mice with triiodo-L-thyronine (T3), 5 alpha-dihydrotestosterone (DHT), dexamethasone (Dex), and aldosterone (Ald), injected singly or in combination. Na+,K+-ATPase was confined to the duct system of the SMG. In intact mice there was a gender difference in SMG Na+,K+-ATPase, with levels of the enzyme's activity and of its alpha 1-subunit being less in the glands of males. In males, hypophysectomy caused a rise in levels of Na+,K+-ATPase activity and in levels of the alpha 1-subunit protein of this enzyme, and in intensity of immunocytochemical staining for this subunit but there were no such changes in the SMG of hypox females. Changes caused by hormonal replacement to hypox males in Na+,K-ATPase activity, levels of its alpha 1-subunit, or the intensity of immunocytochemical staining for this subunit were complex. Ald had no effect. T3 or dexamethasone, given alone, induced Na+,K+-ATPase activity above control values (hypox males) and increased levels of its alpha 1-subunit protein and immunohistochemical staining for this subunit. By contrast, DHT did not cause a decline in any of these parameters. However, when treatment with T3 was combined with administration of Dex or DHT, enzymatic activity of Na+,K+-ATPase decreased but levels of the alpha 1-subunit protein and immunohistochemical staining for this subunit increased. Therefore, inductions of the alpha 1-subunit of this enzyme are not always correlated with increases in levels of activity of Na+,K+-ATPase, and we propose that both enzymatic and immunochemical analyses are essential for evaluation of hormonal regulation of Na+,K+-ATPase in salivary gland and in other tissues.

Aldosterone↗

[Quantitative and qualitative aspects of the representation of aging curves for the histological composition of the human submandibular gland by empirical regression].

A discussion of the possibilities is given of parametric and of nonparametric description of measured aging processes. As examples serve the counted volume portions of different histological structures in the human submandibular gland. As best suited approach the nonparametric evaluation of data by empirical regression is recommended. It is studied which qualitative changes are shown by the empirical regression curves if the sample size will be modified. For this the original sample size of 42 measured values is reduced in 2 steps to 35 and 29 values by removing at random firstly 7 and secondly additional 6 values. The tendencies in the aging courses represented by empirical regression curves will hardly altered by these reductions whereas a nonrandom elimination of outstanding points yields to marked changes in the calculated empirical regression curves. The influence of different local sample variances and densities of the measured points on the shape of the aging curves is stressed.

Adolescent↗

Effects of a phorbol ester and diacylglycerols on secretion of mucin and arginine esterase by rat submandibular gland cells.

The effects of a phorbol ester, 12-O-tetradecanoyl-phorbol-13-acetate (TPA) and a diacylglyceride, 1-oleoyl-2-acetyl-glycerol (OAG) on the secretion of two major exocrine products by dispersed rat submandibular cells were investigated. TPA stimulated the release of acinar cell mucin and ductal cell protease (arginine esterase) in a dose- and time-dependent manner. Mucin secretion was also provoked by OAG, which, however, had no effect on arginine esterase release. The unsaturated diacylglycerol, 1,2-diolein, elicited a greater mucosecretory response than did OAG at the same concentration, while the saturated 1,2-distearin produced a smaller response. Mucin and enzyme secretion caused by TPA or OAG in the rat submandibular model was not inhibited by either of two putative antagonists, the antipsychotic drug, fluphenazine, and the antibiotic, polymyxin B. The involvement of extracellular Ca2+ in TPA-induced secretion was examined by comparing responses of cells maintained in normal or Ca2+-free medium, or in medium containing the ionophore A23187. Although extracellular Ca2+ was not an absolute requirement for a secretory response, the results indicate a synergistic relationship between TPA and Ca2+ in stimulating the release of both mucin and arginine esterase. These results suggest a role for the Ca2+-, phospholipid-dependent enzyme, protein kinase C in the secretory mechanism of mucous and serous cells in the submandibular gland. This is consistent with the proposal that receptor-mediated hydrolysis of membrane phosphoinositides is an initial event in stimulus-response coupling in exocrine cells.

Animals↗

Bilateral submandibular gland excision with parotid duct ligation for treatment of sialorrhea in children: long-term results.

BACKGROUND: Multiple procedures have been advocated for the surgical control of chronic sialorrhea in children. However, some of them are associated with significant complications or only short-term success. OBJECTIVES: To evaluate the safety of bilateral submandibular gland excision (SGE) with parotid duct ligation (PDL) and to assess its long-term complications and efficacy in the treatment of chronic sialorrhea in children. DESIGN: Case series. Telephone interview of patients' families. SETTING: Tertiary care children's hospital. PATIENTS: Ninety-three patients with chronic sialorrhea who underwent bilateral SGE with PDL from 1988 to 1997. MAIN OUTCOME MEASURES: Operative and postoperative complications, length of postoperative hospitalization, postoperative drooling, care requirements, xerostomia, dental caries, and overall satisfaction. RESULTS: The mean postoperative stay was 2.4 days. There were 3 postoperative complications. Seventy-two families were interviewed (follow-up time, 1-10 years): 62 (87%) reported no further drooling or significant improvement; 7 reported the occurrence of dry mouth; and 2 reported an increase in dental caries. CONCLUSION: Bilateral SGE with PDL is a safe and consistently efficient procedure for the treatment of chronic sialorrhea in children.

Chronic Disease↗