Rat Von Ebner's Gland Research Articles

GLP-1 expression in von Ebner's gland of diabetic rats

GLP-1, a peptidergic endocrine hormone, which associate with appetite control, glucose homeostasis and satiety. It might play an important role in the gustatory system. We tried to investigate the expression of GLP-1 in von Ebner's gland of diabetic and control rats, and the ultrastructure changes on von Ebner's gland of diabetes rats. GLP-1 expression in von Ebner's gland was evaluated by immunohistochemistry. The number of GLP-1 positive cells in diabetic rat von Ebner's gland was significantly higher than that in normal controls. Electron micrographs showed that a series of pathologic changes in von Ebner's gland of diabetes rats. The results suggest that GLP-1 have some effects within the gustatory systems, and elevated von Ebner's gland GLP-1 expression may be one cause of diabetic taste impairment.

Antioxidant enzyme immunoreactivity in rat von Ebner gland after nickel treatment

Our study was designed to clarify the role of antioxidant enzymes in the rat von Ebner gland during acute nickel toxicity. After treatment with nickel acetate, we monitored ultrastructural alterations in acinar and ductal cells, immunohistochemical staining for glutathione peroxidase (GPx) and glutathione S-transferases (GST mu and GST pi), and immunoreactivity for malondialdehyde (MDA). Immunoreactivity for MDA was present only in the acinar cells, and it was enhanced at 3 h after Ni treatment. In contrast, immunoreactivities for GPx and GSTs did not change in acinar cells but significantly increased in ductal cells after Ni treatment. Cytoplasmic vacuoles increased in acinar cells at 3 h after Ni treatment, but they almost completely disappeared at 24 h. No morphological changes were observed in taste bud cells from Ni-treated rats. Because lipid peroxidation, as monitored by immunoreactivity for MDA, was only transiently increased in the acinar cells, the enhanced antioxidant enzyme immunoreactivity in ductal cells of the von Ebner gland plays a crucial role in the self-defense system against nickel toxicity in the rat oral cavity.

Perireceptor events in taste.

The microenvironment at chemical receptor sites is important for ligand-receptor interaction as it can influence the entry, residence time or exit of odorant and sapid molecules. The perireceptor milieu at apical taste cell microvilli consists of taste pore mucus and secretions from salivary glands. The majority of taste buds are sheltered in epithelial folds of the foliate and circumvallate papillae where saliva is provided predominantly by the lingual von Ebner's glands (VEGs). To investigate possible saliva-tastant interactions, we have characterized a prominent 18 kDa secretory protein expressed in human, rat and pig VEGs. The human and rat VEG proteins share 60% sequence identity and, by virtue of their protein and gene structure, can be assigned to the lipocalin superfamily of lipophilic ligand carrier proteins. VEG proteins might function as transporters of hydrophobic molecules, for example bitter substances, like the nasal odorant-binding proteins that belong to the same protein family. Because binding experiments using various bitter substances have so far failed, and in light of the species-specific expression, other functions for VEG proteins must be considered. These include the protection of taste epithelia, pheromone transport and lipid binding.

Histological and biochemical characterization of von Ebner's glands in the Syrian hamster; comparison with rat von Ebner's glands

We report here for the first time a morphological description and observations on some of the secretory proteins of the von Ebner's lingual salivary glands (VEG) of the Syrian hamster. Hamster VEG were macroscopically less distinct, but histologically similar to rat VEG. VEG extracts of hamster and rat were assayed for lipase, α-amylase and peroxidase activities. Unlike rat VEG, which is rich in lipase activity, hamster VEG extract had no detectable lipase activity and did not react with antibodies to either rat lingual lipase or human gastric lipase in Western blots. Immunohistochemical reactions with the anti-rat lingual lipase antibody were very weak in hamster VEG and strong in rat VEG. Moderate α-amylase enzyme activities and immunohistochemical reactions were demonstrated in both hamster and rat VEG. Peroxidase activity was negligible in the VEG, unlike the high activity in the submandibular glands of both species. An 18 kDa von Ebner's gland protein (VEGP), a member of the lipocalin superfamily of hydrophobic ligandbinding proteins, was abundant in rat VEG, but not detected in hamster VEG. Thus, hamster VEG differs from rat VEG in macroscopic appearance and the absence of lipase and VEGP. It is similar to rat VEG histologically and with regard to the presence of α-amylase and absence of peroxidase.

Secretion of Carbonic Anhydrase Isoenzyme VI (CA VI) from Human and Rat Lingual Serous von Ebner's Glands

Salivary carbonic anhydrase VI (CA VI) appears to contribute to taste function by protecting taste receptor cells (TRCs) from apoptosis. The serous von Ebner's glands locating in the posterior tongue deliver their saliva into the bottom of the trenches surrounding the TRC-rich circumvallate and foliate papillae. Because these glands deliver their saliva directly into the immediate vicinity of TRCs, we investigated whether CA VI is secreted by the von Ebner's glands, using immunochemical techniques. The immunohistochemical results showed that CA VI is present in the serous acinar cells, ductal cells, and ductal content of von Ebner's glands and in the demilune and ductal cells plus ductal content of rat lingual mucous glands. More importantly, CA VI was also detected in taste buds and in the taste pores. Western blotting of saliva collected from the orifices of human von Ebner's glands and CAs purified from rat von Ebner's glands confirmed that CA VI is expressed in these glands and secreted to the bottom of the trenches surrounding the circumvallate and foliate papillae. These findings are consistent with the hypothesis that locally secreted CA VI is implicated in the paracrine modulation of taste function and TRC apoptosis. (J Histochem Cytochem 49:657-662, 2001)

Immunohistochemical Localization and MRNA Detection of Rab3D and/or Rab3B in rat von Ebner's Glands, Parotid Gland, Pancreas, and Liver

In examining the secretory mechanism of exocrine glands, we focused on the small GTP-binding proteins, Rab3D and Rab3B, which function in the final steps of exocytosis in non-neuronal tissues. These proteins were observed in von Ebner's glands by 32P-GTP overlay. mRNA isolated from von Ebner's glands, the pancreas, parotid glands, and liver was subjected to reverse transcription PCR and probed with primers and nested primers for Rab3D and Rab3B. Rab3D was found in all three exocrine glands and the liver, while Rab3B was found in the liver. Utilizing immunofluorescence histochemistry, Rab3D was localized to hepatocytes of the liver and to secretory granules of the exocrine glands, and Rab3B to liver and pancreatic islets. Isoproterenol evoked decreases in α-amylase- and Rab3D-labelled parotid secretory granules, and pilocarpine stimulated decreases in secretory granules labelled for lingual lipase and Rab3D from von Ebner's glands, and amylase and Rab3D from pancreas. Neither secretagogue affected Rab3B in pancreatic islets. These observed parallel decreases in response to β-adrenergic (parotid) or cholinergic (von Ebner's and pancreas) secretagogues indicate that the function of Rab3D in exocytosis in these exocrine organs is similar and that the type of secretagogue does not determine the function.

Effect of Substance P and Receptor Antagonists on Secretion of Lingual Lipase and Amylase from Rat von Ebner's Gland

Field, R. B., S. J. Chirtel and R. S. Redman. Effect of substance P and receptor antagonists on secretion of lingual lipase and amylase from rat von Ebner's gland. Peptides 18(2) 277–285, 1997.— Substance P (SP, 1 μM) when incubated with minced von Ebner's glands for 15, 30, and 60 min, stimulated secretion of lingual lipase (12.14%±0.90) and amylase (8.30%±0.42). Only 10 μM of the SP receptor antagonist CP-96,345 significantly inhibited SP-evoked secretion. d-Pro2-d-Phe7-d-Trp9-SP (Ia), d-Pro2-d-Trp7,9-SP (Ib), d-Arg1-d-Trp7,9-d-Leu11-SP (Ic), or 1 μM CP-96,345 were not effective, suggesting that the SP receptor of von Ebner's gland might be an isoform. Propranolol and timolol, β1/β2-adrenergic receptor antagonists were not effective and the cholinergic receptor antagonist, atropine, was effective in only slightly reducing amylase secretion but not lingual lipase. Differential secretion of the two enzymes was observed for basal and stimulated secretion. Thus, exocytosis may not be the only pathway involved in SP-evoked protein secretion.

Substance P immunoreactivity in rat von Ebner's gland

Substance P immunoreactivity in rat von Ebner's gland

Substance P immunoreactivity in rat von Ebner's gland

The present immunohistochemical study revealed substance P-immunoreactive neuronal elements in the von Ebner's gland of rats. Immunoreactive ganglion cells were observed as single cells or groups of several immunoreactive ganglion cells among intra-lingual muscles, at the base of the vallate papillae and near the von Ebner's gland. Very numerous substance P-immunoreactive varicose nerve fibres ran closely associated with the serous cells and excretory duct cells, and were seen to run along blood vessels in the gland. Since substance P-immunoreactive ganglion cells were present near the glands, the immunoreactive varicose nerve fibres in the von Ebner's gland may be partly derived from the intra-lingual ganglion cells. These substance P-immunoreactive varicose nerve fibres may have an effect on the secretory activity of the serous cells and duct cells, and on the vasodilation of blood vessels of the von Ebner's gland. Actin immunoreactivity was seen in numerous myoepithelial cells embracing serous cells and duct cells, and in the smooth muscle cells of blood vessels of the gland. By using a double immunolabelling technique with anti-substance P and anti-actin sera, substance P-immunoreactive varicose nerve fibres were found to be in close contact with myoepithelial cells.

Denatonium bitter tasting among transgenic mice expressing rat von Ebner's gland protein

Von Ebner's gland protein (VEGP) is a secretory protein, which is abundantly expressed in the small von Ebner's salivary glands of the tongue. VEGP as component of the perireceptor environment around taste papillae might function as transporter of hydrophobic molecules, for example bitter substances. Here we report a new approach to investigate the physiological role of VEGP by expression of the cloned rat VEGP gene in transgenic mice. Taste papillae of mice, in contrast to rats, do not contain VEGP. The founder mouse 4345 and three offspring carry the transgene as shown by PCR analysis and saliva of the transgenic mice contains high amounts of VEGP. In two-bottle preference tests, transgenic and nontransgenic siblings show significantly different capabilities to taste the bitter compound denatonium benzoate at 10 μM. The reduced sensitivity of transgenic mice to denatonium benzoate points to a clearance function of VEGP the specificity of which for taste compounds and other molecules remains to be seen.

Molecular cloning of human von Ebner's gland protein, a member of the lipocalin superfamily highly expressed in lingual salivary glands

Von Ebner's glands (VEG) are small lingual salivary glands. Their ducts open into trenches of circumvallate and foliate papillae, thus influencing the milieu where the interaction between taste receptor cells and sapid molecules takes place. The major secretions of human VEG is a protein with a molecular mass of 18 kDa. The human VEG protein crossreacts with antibodies raised against the rat VEG protein, indicating sequence similarity between the rat and human VEG proteins. This was subsequently confirmed by N-terminal protein sequencing. A cDNA clone, isolated from a human VEG library, contained an insert of 735 bp including an open reading frame that encodes the human VEG protein of 176 amino acids. Comparison of the human and rat VEG proteins revealed an overall identity of 60%. Immunocytochemistry, in situ hybridization and in vitro translation studies demonstrated the human VEG protein to be highly and exclusively expressed in VEG. The VEG proteins are members of the lipocalin protein superfamily and, together with the rat odorant binding protein II, they constitute a new subfamily. Sequence similarity to proteins such as the retinol binding protein and the odorant binding protein which are lipophilic ligand carriers, suggests a possible function for the human VEG protein in taste perception.

The effects of histamine, pyrilamine, cimetidine, and ranitidine on secretion of lingual lipase and amylase from rat von Ebner's glands.

Minced von Ebner's glands of rat tongue were incubatedin vitro with histamine and histamine receptor antagonists. At various time intervals, media and homogenates of the tissue were assayed for lingual lipase and amylase activity and percentage secretion calculated. Histamine elicited moderate secretion (≈10%) of lingual lipase and amylase. In contrast, pyrilamine, and H1 receptor antagonist, elicited>60% secretion. There were statistically significant differences between the percentage secretion of lingual lipase and amylase for basal secretion, as well as for histmine-and pyrilamine-evoked secretion of lingual lipase and amylase for basal secretion, as well as for histamine-and pyrilamine-evoked secretion above basal. The H2 receptor inhibitors, cimetidine and ranitidine, stimulated secretion of only amylase, but not lingual lipase. When combined with histamine, these antagonists partially inhibited only the secretion of histamine-evoked lingual lipase, but not amylase. The differences in percentage secretion between the two enzymes indicate that exocytosis may not be the only process involved in protein secretion. The anomalous effects of the H1 and H2 receptor antagonists necessitate a more detailed characterization of the receptors of von Ebner's glands.

Postnatal development of von Ebner's glands: accumulation of a protein of the lipocalin superfamily in taste papillae of rat tongue.

Antibodies produced against rat von Ebner's gland (VEG) protein, a recently characterized member of a lipophilic ligand carrier protein family, detect this protein immunocytochemically in von Ebner's gland acini and show that it is present at high concentrations in the clefts of circumvallate and foliate papillae. During embryonic development, von Ebner's gland anlagen are innervated (as shown immunocytochemically using neuronal specific antibodies) as early as embryonic day 20, before lateral glandular outgrowth and VEG protein can be observed. Expression of the VEG protein as determined by in situ hybridization and immunocytochemistry begins at postnatal day-2 cells in differentiating and branching off from von Ebner's gland ducts, and sharply increases with further enlargement and maturation of the gland. The close temporal correlation of von Ebner's gland innervation and VEG protein expression with papilla innervation and taste-bud development suggests a functional relationship of both structures. VEG protein might control access of lipophilic sapid molecules, such as bitter substances, to the gustatory receptors.