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Salivary secretion induced from isolated, perfused rat submandibular glands by sympathomimetic agents.

Saliva secretion was elicited from the isolated preparations by isoproterenol and phenylephrine, at concentrations from 10(-8) to 10(-5) M. The volumes of saliva secreted during a 60-min period, the rates of flow and the electrolyte composition of saliva secreted in response to each secretagogue were similar to those in vivo. Replacement of perfusate Na+ inhibited the secretion of fluid induced by isoproterenol (75 per cent) and by phenylephrine (99 per cent). It also reduced the Na+ and K+ concentrations of saliva elicited by the two secretagogues and inhibited isoproterenol-induced protein secretion (81 per cent). Omission of Ca2+ from the perfusate also inhibited fluid secretion (isoproterenol-stimulated, 84 per cent; phenylephrine-stimulated, 99 per cent) and isoproterenol-induced protein secretion (69 per cent). The absence of the divalent cation in the perfusate resulted in increased Na+ and decreased K+ concentrations in isoproterenol-stimulated saliva and in reduced K+ concentrations in phenylephrine-stimulated saliva. Administration of 10(-5) M phentolamine did not modify the volume of saliva secreted in response to isoproterenol, but reduced the response to phenylephrine by 90 per cent. The antagonist caused some reduction in the Na+ and K+ concentrations of isoproterenol-stimulated saliva, but did not modify those of phenylephrine-evoked secretion. Little recovery in fluid secretion was observed when the isolated gland was perfused with complete perfusate in the presence of phenylephrine after perfusion with Na+- or Ca2+-free solutions. Thus perfused rat submandibular glands are fully functional preparations, which respond to sympathomimetic agents of the alpha and beta types.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

Lumen formation during development of the rat submandibular gland.

This study utilized electron microscopy and enzyme histochemistry to examine the morphological steps associated with the formation of a lumen in the end-buds of the embryonic rat submandibular gland. Lumen formation involved the development of junctional complexes by the central cells of the end-buds late on the 16th day of gestation. These junctional complexes established the apical domains of the presecretory cells, and cytofilament aggregates were observed beneath the presumptive luminal plasma membranes. This central area of the end-buds showed strong myosin ATPase activity, presumably associated with the cytofilaments. On the 17th day of gestation, small lumina appeared at the sites delineated by the junctional complexes. The myosin ATPase activity appeared to surround the newly opened lumina. By the 18th day of gestation, microvilli were seen projecting into the lumina, and secretory granules were often visible in the apical cytoplasm near the luminal plasma membranes of the early secretory cells. Myosin ATPase activity was greatly reduced once the lumina had formed.

Animals↗

Inductive effects of triiodothyronine or dihydrotestosterone on EGF in the submandibular glands of young, middle-aged, and old C57BL/6NNia female mice.

Effects of advancing age on responsiveness to triiodothyronine (T3) or dihydrotestosterone (DHT) by granular convoluted tubule (GCT) cells in submandibular glands were studied in C57BL/6NNia female mice of 4, 12, and 24 months of age. In untreated mice, absolute GCT volume and the frequency of cells strongly immunostained for EGF increased with age. Concentrations of EGF rose fourfold. Both T3 and DHT had inductive effects at each age: GCT cells were enlarged, contained more granules, and stained very strongly for EGF; EGF concentrations and the volume of GCTs also increased. However, the pattern of induction differed with age for the two hormones. After T3 treatment EGF concentration declined with age with respect to the degree of induction over same age control levels. By contrast, after DHT treatment the level of induction of EGF over control levels was the same at all three ages. The pattern of aging of GCT cells and their responsiveness to T3 or DHT in female mice differ from that previously reported for males.

Aging↗

Parasympathetic modulation of amylase secretion by IFN gamma in murine submandibular glands.

IFN gamma is a pleiotropic cytokine that exerts immunologic and non-immunologic functions. We show here that at low doses (10 U/ml), it stimulates amylase secretion in murine submandibular glands (SMG) "via" muscarinic receptor activation, comparable to that produced by the muscarinic agonist carbachol. Both effects are blocked by atropine. NG-monomethyl-L-arginine (L-NMMA) and EGTA inhibited the cytokine effect on amylase secretion, involving the participation of a calcium-dependent isoform of nitric oxide synthase (NOS). We confirm NOS activation because IFN gamma stimulates nitrite production and enzyme activity in SMG. Carbachol (10(-7) M) did not modify basal nitric oxide production. In addition, both IFN gamma and carbachol increase prostaglandin E2 production in SMG, but while indomethacin potentiates IFN gamma effect on amylase secretion, it blunted amylase secretion exerted by carbachol. Thus, IFN gamma and carbachol stimulate IFN gamma secretion on SMG in a dose-dependent manner. Our results are pointing to neuroregulatory functions of IFN gamma in murine SMG, because it regulates its own levels in oral cavity, perhaps to exert a local immuno-surveillance.

Amylases↗

Actions of adrenergic agonists on isolated excretory ducts of submandibular glands.

The effects of norepinephrine and isoproterenol on the transepithelial potential difference (PD) and the net transepithelial fluxes of Na, K, Cl, and HCO3 of the main ducts of the submandibular glands of rats and rabbits have been studied by microperfusion of ducts incubated in vitro in an artifical bathing medium. In the rabbit duct, both catecholamines caused depolarization and reduced transepithelial Na reabsorption at concentrations above 10(-29) M. In the rat duct, norepinephrine reduced PD and net Na reabsorption and, in addition, inhibited net K secretion at concentrations of 10(-7) M and above. Isoproterenol also depolarized the duct and reduced net K reabsorption, but at concentrations of 10(-9) M it stimulated net Na reabsorption, whereas at concentrations of 10(-4) M it inhibited Na reabsorption. The stimulation caused by isoproterenol at low concentrations could be blocked by prior administration of propranolol. The results suggest that electrolyte transport, by both rat and rabbit ducts, may be influenced not only by sympathetic nerve activity but also by physiological changes in the concentrations of circulating catecholamines. Inconsistencies in the literature regarding the sensitivity of the rabbit duct to catecholamines and the response of the rat duct to isoproterenol have now been resolved.

Animals↗

Transient appearance of substance P-like immunoreactivity in the granular convoluted tubules of the male mouse submandibular gland: light- and electron-microscopic studies.

The time of appearance and distribution of substance P (SP)-like immunoreactivity in the granular convoluted tubule cells of the developing male mouse submandibular glands were examined, and the subcellular localization of SP-like immunoreactivity was investiagted by electron microscopy. At 25 days of age, SP-like immunoreactivity was first detected in the supranuclear cytoplasm of the granular convoluted tubule cells, which occurred either singly or in small clusters. At 30 and 35 days of age, granular convoluted tubule cells with SP-like immunoreactivity were more numerous than in the earlier stages, as the volume ratio of the cells increased. Not all granular convoluted tubule cells demonstrated SP-like immunoreactivity. The number of cells with SP-like immunoreactivity decreased at 60 days of age, and these cells had completely disappeared at 90 days of age. Most, but not all, secretory granules in the granular convoluted tubule cells were strongly labeled with gold particles, indicating that the subcellular site of SP-like substance is in the secretory granules within the cells. The findings suggest that the physiological role of the SP-like substance secreted from the GCT cells is restricted to the early postnatal stages, and that it may be involved in the development of the oral mucosa or digestive tract as a trophic factor.

Animals↗

Unilateral aplasia of the submandibular gland.

The congenital absence of major salivary glands is an extremely rare disorder. In this case, we report a 32-year-old woman who came to us with right submandibular gland aplasia, which was detected incidentally. The literature on this rare occurrence is reviewed and the significance of the patient is discussed.

Adult↗

Ultrastructural study of the mitochondria in the submandibular gland, the pancreas and the liver of young rats, exposed to NaF in drinking water.

The aim of the experiment was to determine the effect of fluoride on ultrastructural changes in the submandibular gland, the pancreas and the liver. The experimental rats received fluoride in aqueous solutions of sodium fluoride at concentrations of 10.6 NaF/dm3 and 32.0 NaF/dm3. In the ultrastructural examination, mitochondria were most damaged.

Animals↗

Immunoelectron microscopy of carbonic anhydrase isozyme VI in rat submandibular gland: comparison with isozymes I and II.

Carbonic anhydrase (CA) was purified from the saliva of pilocarpine-treated rats by inhibitor-affinity chromatography, and its localization in the rat submandibular gland was studied by the indirect immunoperoxidase technique using a monoclonal antibody (MAb) raised against the enzyme. SDS-polyacrylamide gel electrophoresis of the CA VI gave three bands of 33, 39, and 42 KD. Enzyme digestion experiment showed that the 42 KD molecule was degraded into the 39 KD molecule and the 39 KD molecule into the 33 KD molecule. The cleavage of the 42 KD molecule was independent and that of the 39 KD molecule was dependent on endo-beta-N-acetylglucosaminidase F. The 42 KD molecule was detected in the CA purified from the pilocarpine-treated but not the untreated salivary gland. The MAb recognized all the three components of the enzyme. Immunostaining for CA VI was seen in the cytosol and secretory granules of serous acinar cells and in the duct luminal contents. Staining specific for erythrocyte CA (CA I and CA II) was observed in the cytosol of the epithelial cells of granular, striated, and excretory ducts. Among these duct cells, the agranular varieties in the granular and excretory ducts were essentially devoid of the immunoreactivity.

Animals↗

Influences of secretory activities in rat submandibular glands on tissue kallikrein circulating in the blood.

Changes in serum levels of rat tissue kallikrein (rK1) in venous blood were measured, using a newly developed radioimmunoassay, before and after autonomic nerve stimulations of submandibular salivary secretion. rK1 secreted into saliva under these conditions was measured by radioimmunoassay and by enzymic activity assay, using the fluorogenic peptide substrate D-Val-Leu-Arg-7-amino-4-trifluoromethylcoumarin (AFC). Following an overnight fast, serum rK1 concentration was 30-40 ng ml-1. Unilateral electrical stimulation of the submandibular sympathetic nerve supply (at 50 Hz in bursts of 1 s every 10 s for 60 min) evoked a small flow of saliva with a very high rK1 concentration, resulting in a large output of rK1 of 2104.4 +/- 603.5 micrograms (n = 6). Such stimulation caused a large degranulation of granular duct cells and a corresponding reduction in glandular rK1 content. Unilateral electrical stimulation of the parasympathetic nerve supply (at 5 Hz continuously for 60 min) evoked a copious flow of saliva with a very low rK1 concentration, resulting in a low output of rK1 (18.1 +/- 4.9 micrograms; n = 6). Despite these large differences in salivary outputs of rK1, serum concentrations of rK1 were increased similarly following either sympathetic or parasympathetic stimulation by 48 and 46%, respectively. If the submandibular duct was briefly obstructed during sympathetic stimulation, inducing leakage and glandular oedema, then serum rK1 increased greatly (40-fold); a similar increase to that seen by others in previous studies without deliberate obstruction. Four days after bilateral submandibular-sublingual sialadenectomy serum rK1 concentration was reduced by approximately 50%. The results indicate that submandibular glands normally contribute to circulating levels of rK1 in rats, but this contribution is independent of the amounts of rK1 secreted into saliva by sympathetically induced exocytosis, and is likely to arise from basal vesicular transport. However, if glandular leakage occurs during sympathetic stimulation of submandibular secretion this then causes increases in the circulating levels of rK1 that correlate with the large amounts being secreted into saliva.

Animals↗

A 4-methoxy-2-naphthylamide substrate for the histochemical localization of esteroproteases in the submandibular gland of the rat.

The 4-methoxynaphthylamide (MNA) derivative of D-Val-Leu-Arg-4-MNA has been used as a substrate for the histochemical localization of esteroproteases in the submandibular gland of rats, and compared with the substrate alpha N-O-met. The hydrolysis of Val-Leu-Arg-4-MNA by esteroproteases was investigated using spectrophotometry and isoelectric focusing. Both methods demonstrated that the substrate is cleaved by different enzymes and is not a monospecific kallikrein marker, although Val-Leu-Arg-4-MNA had a much smaller spectrum of enzyme activities than alpha N-O-met. The activity against Val-Leu-Arg-4-MNA was totally inhibited by aprotinin but only partly by soybean trypsin inhibitor. A comparison of the histochemical localization of esteroproteases given by the substrate with the immunofluorescence localization of kallikrein showed that all the enzymes that hydrolysed Val-Leu-Arg-4-MNA and kallikrein were present in the same tissue structures.

Animals↗

Intracellular K+ activity in canine submandibular gland cells in resting and its change during stimulation.

Intracellular K+ activity (alpha Ki) and transmembrane potential differences were simultaneously measured with double-barreled K+ selective microelectrodes in superfused canine submandibular glands at rest and during stimulation. Also intracellular K+ and N+ concentrations in the same gland were determined by chemical analyses for comparison with the intracellular K+ activity data. The activity coefficient for intracellular K+ thus obtained was 0.67, indicating that virtually all K+ ions in the cells are in diffusible and osmotically active form. Under control conditions, measured values of the resting membrane potential (Em), alpha Ki and K+ equilibrium potential (EK) were -40.2 +/- 0.6 mV (S.E., n = 163), -88.5 +/- 1.4 mM (S.E., n = 163), -83 mV respectively. Electrochemical potential differences for K+ across the basolateral membrane (delta micro K/F) were approximately +43 mV. Acetylcholine (ACh) induced an abrupt membrane hyperpolarization followed by a temporary fall of alpha Ki. The maximum rate of alpha Ki change in the cytoplasm during stimulated conditions was -35.5 +/- 0.9 mM/min on the average (n = 10). These results suggest that the membrane permeability increases to K+ upon stimulation. Possible changes in membrane permeabilities to Na+ and Cl- were also discussed.

Acetylcholine↗

Involvement of cytochrome c and caspases in apoptotic cell death of human submandibular gland ductal cells induced by concanamycin A.

In the present study, we found that a specific inhibitor of vacuolar type H+-ATPase (V-ATPase), concanamycin A, induced apoptosis in a human submandibular gland ductal cancer cell line, HSG. Immunoblot analysis revealed that cytochrome c was released from mitochondria into the cytoplasm when HSG cells were cultured with concanamycin A for 6 h. The maximum activities of caspase-3 and -9 were reached in HSG cells after 18 and 12 h culture of concanamycin A, respectively. Both caspase-3 and -9 were cleaved to an active form in HSG cells cultured with concanamycin A. Interestingly, concanamycin A decreased the level of heat shock protein 27 (HSP27) in HSG cells. Taken together, these findings suggest that apoptosis in HSG cells induced by concanamycin A is regulated by cytochrome c released from mitochondria into cytoplasm and the subsequent activation of caspases, and that HSP27 may interfere with caspase-dependent apoptotic cell death induced by concanamycin A.

Anti-Bacterial Agents↗

Toxicity and biodistribution of a first-generation recombinant adenoviral vector, encoding aquaporin-1, after retroductal delivery to a single rat submandibular gland.

Before conducting a phase 1/2 clinical trial of a serotype 5 adenovirus encoding human aquaporin-1 (AdhAQP1) for the treatment of radiation-damaged salivary glands, we have conducted a detailed toxicity and biodistribution study in adult rats. AdhAQP1 (2x108-2x1011 particles) was delivered to a single submandibular gland by retroductal cannulation. Administration of this vector resulted in no animal mortality or morbidities, and no adverse signs of clinical toxicity. In addition, over the 92-day time course of the study, with both male and female rats, there were no consistent treatment-related changes in serum indicators of hepatic, renal, and cardiac functions. Importantly, we also observed no vector-associated effects on either water consumption by, or hematocrit levels in, study animals. However, three suggestive mild gender-related response differences were seen. Female, but not male, rats exhibited small reductions in food consumption (10-15%) and body weight gain (5-10%), and evidence of persistent inflammation, after vector treatment. These were vector, but not dose, related. Three days after delivery of 2x1011 particles of AdhAQP1, vector was detected primarily in the targeted gland; 9 of 10 samples from the targeted gland were positive, whereas only 5 of 90 nonoral samples were positive. There was no evidence of the generation of replication-competent adenovirus in saliva or blood samples. In aggregate, these findings show that localized delivery of AdhAQP1 to salivary glands appears to occur without significant toxicity.

Adenoviridae↗

Promiscuous coupling of receptors to Gq class alpha subunits and effector proteins in pancreatic and submandibular gland cells.

Mice with deficiencies in one or more Gq class alpha subunit genes were used to examine the role of the alpha subunit in regulating Ca2+ signaling in pancreatic and submandibular gland cells. Western blot analysis showed that these cells express three of the four Gq class subunits, Galphaq, Galpha11, and Galpha14 but not Galpha15. Surprisingly, all parameters of Ca2+ signaling were identical in cells from wild type and four lines of mutant mice: 1) Galpha11-/-, 2) Galpha11-/-/Galpha14-/-, 3) Galpha14-/-/Galpha15-/-, and 4) Galphaq-/-/Galpha15-/-. These parameters included the Kapp for several Gq class coupled receptors, induction of [Ca2+]i oscillations by weak stimulation, and a biphasic [Ca2+]i response by strong stimulation. Furthermore, Ca2+ release from internal stores and Ca2+ entry were not affected in cells from any of the mutant mice. We conclude that Galphaq, Galpha11, and Galpha14 promiscuously couple several receptors (m3 muscarinic, bombesin, cholecystokinin, and alpha1 adrenergic) to effector proteins that activate both Ca2+ release from internal stores and Ca2+ entry.

Animals↗

Thyroxine accelerates the differentiation of granular convoluted tubule cells and the appearance of epidermal growth factor in the submandibular gland of the neonatal mouse. A fine-structural immunocytochemical study.

The effects of the administration of thyroxine (T4) on the postnatal cytodifferentiation of granular convoluted tubule (GCT) cells of the submandibular gland (SMG) of Lewiss-Webster mice were studied by light and electron microscopy. From birth, mice of both sexes were injected daily with T4 (sc 0.4 micrograms/g BW) and were sacrificed 24 h after the last injection at 7, 9, 11, 14 and 21 days of age. Control mice received vehicle only. In control mice, granulated striated duct (SD) cells were first detected at 9 days and 7 days of age by light- and electron microscopy, respectively. Furthermore, a few scattered granulated SD cells were observed by light microscopy as early as day 7 in T4-treated mice of both sexes. At 21 days of age, in mice given T4, GCT cells were larger and more numerous and the Golgi apparatus, rough endoplasmic reticulum, and secretion granules were more abundant. In control mice, immunocytochemical staining for epidermal growth factor-(EGF) was first detectable at day 21 at the light- and electron-microscopic levels. However, positively stained cells were first observed in T4-treated mice by light- and electron-microscopic immunocytochemistry at 14 and 11 days of age, respectively. Moreover, in the 21-day-old T4-treated mice, the number of immunoreactive GCT cells, as well as the intensity of the staining per cell, was markedly increased as compared to controls. EGF immunostaining was restricted to GCT cells, and by immuno-electron-microscopy was only seen in apical secretory granules in granulated SD cells and GCT cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗

Thyroxine increases submandibular gland nerve growth factor and epidermal growth factor concentrations precociously in neonatal mice: evidence for thyroid hormone-mediated growth factor synthesis.

Thyroxine (T4) administration to adult female mice significantly increases submandibular gland (SMG) nerve growth factor (NGF) and epidermal growth factor (EGF) concentrations and does so in a time- and dose-dependent manner. Postnatal maturation of the SMG can be markedly accelerated by T4 treatment. We, therefore, performed a series of experiments to examine the effect of T4 on SMG NGF and EGF content and concentration as a function of postnatal age in neonatal mice. In experiment 1, male and female neonatal Swiss-Webster mice received daily subcutaneous injections of T4 (0.4 micrograms/g body weight) for 6, 13, or 20 days and were sacrificed 24 h after the last injection. Vehicle injected mice served as controls. SMG NGF and EGF content and concentration were measured by specific double antibody radioimmunoassay systems. Pools were made using either female or male SMGs. Since no significant differences were noted for NGF or EGF content using sex of the animal as the determining variable, the values were combined. At 7 days of age, mean SMG NGF and EGF content and concentration of control mice significantly exceeded those of T4-treated animals (p less than 0.05). At 14 days of age, mean SMG NGF and EGF content in T4-treated mice significantly exceeded those in control mice by 39- and 22-fold, respectively (p less than 0.001). At 21 days of age, these increases were 4100- and 2400-fold, respectively. In order to determine more precisely the time of onset of responsivity of the SMG to thyroid hormones, a second series of experiments was performed.(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗