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Effects of ionizing irradiation and beta-adrenergic stimulation on gene expression pattern in rat submandibular glands.

Radiotherapy administrated to patients with head and neck malignancies and prior to bone marrow transplantation often results in severe xerostomia. We evaluated the expression of early response proto-oncogenes (c-fos and jun B), tissue specific genes (proline rich protein [PRP] and kallikrein), and proteolysis linked utiquitin gene following exposure to 15 Gy irradiation alone or in combination with beta-adrenergic stimulation of the rat submandibular glands. Head and neck irradiation resulted not only in dysfunction and tissue loss of the salivary glands but also in a systemic effect expressed as profound body weight loss. Irradiation alone was found to induce expression of the jun B but not the c-fos proto-oncogenes. The combination of irradiation and beta-adrenergic stimulation by isoproterenol induced earlier expression of jun B and profound expression of the c-fos proto-oncogene in comparison to irradiation alone. In contrast, the kallikrein and ubiquitin genes were expressed constitutively and were not affected by irradiation alone or in combination with beta-adrenergic stimulation. In addition, irradiation had no effect on submandibular gland mRNA translation. We observed that the expression of the genes whose regulation is associated with DNA damage (i.e. jun B and c-fos) was enhanced by irradiation alone or in combination with isoproterenol administration. In contrast, the expression of genes associated with the routine functional integrity of the cell (i.e. kallikrein, ubiquitin, and PRP) was unaffected. These findings, in addition to delayed gland dysfunction, leads us to believe that the irradiation induced injury to the submandibular glands is to be attributed to reproductive stem cell death which may be partly obliterated in the clinical setting by better understanding.

Adrenergic beta-Agonists↗

Purification and characterization of a trypsin-like protease in the submandibular gland of rats.

A trypsin-like protease (named RSP-V) was purified to homogeneity from rat submandibular glands by isoelectric focusing and high-performance liquid chromatography. The purified enzyme had an isoelectric point of 5.3 and an apparent molecular weight of 25,000, and consisted of two subunits with molecular weights of 19,500 and 6,000. RSP-V hydrolyzed BAEE, BAPA, and TAME, but not ATEE or BTPA. It had an optimum pH at around 10.0. RSP-V was strongly inhibited by soybean trypsin inhibitor, aprotinin, leupeptin, antipain, and benzamidine, but not by ovomucoid trypsin inhibitor, p-CMB, or iodoacetic acid. This enzyme partly resembled, but was not identical with, tonin. It was also different from kallikrein, salivain, and glandulain in rat submandibular gland. Although the physiological role of RSP-V has not yet been clarified, this enzyme inactivated dopa decarboxylase alone among catecholamine-synthesizing enzymes.

Amino Acids↗

Glucagon-degrading activity in acid-ethanol extract of rat submandibular gland.

To investigate whether immunoreactive glucagon really exists in salivary gland, the integrity of glucagon radioimmunoassay was tested in the acid-ethanol extract of rat submandibular gland. Though immunoreactive glucagon was apparently measured in acid-ethanol extract of rat submandibular gland, the extract contained a significant amount of intact glucagon-degrading activity. The apparent % bound in radioimmunoassay highly correlated with the degradation of [125I] glucagon during incubation. Gel filtration profiles of [125I] glucagon incubated with acid-ethanol extract were the same as those of [125I] glucagon damaged by submandibular acid-saline extract. These data suggest that the immunoreactive glucagon in acid-ethanol extract is, as in the case of acid-saline extract, an artifact due to degradation of [125I] glucagon during radioimmunoassay.

Animals↗

Amino acid sequence of an inducible cysteine proteinase inhibitor (cystatin) from submandibular glands of isoproterenol-treated rats.

We have previously reported the purification of an inducible cysteine proteinase inhibitor from submandibular glands of isoproterenol-treated rats by sequential gel filtration and ion-exchange chromatography [G. S. Bedi (1989) Arch. Biochem. Biophys. 270, 335-343]. This inhibitor is not detected in normal rat tissues but is induced in submandibular glands following beta-adrenergic stimulation of rats. In this study the complete amino acid sequence and the position of disulfide bridges of the purified protein were determined by automated Edman degradation of the protein and its tryptic, chymotryptic, and Staphylococcus aureus V8 protease peptides and were as follows: (sequence; see text) Computer analysis revealed the presence of 40-50% sequence identity between inducible cysteine proteinase inhibitor and cystatins from human saliva, human cystatin C, bovine cystatins, and chicken cystatins, all members of Family 2 cystatins. The inhibitor has little sequence similarity with rat liver and epidermal cysteine proteinase inhibitors, which belong to Family 1 cystatins.

Amino Acid Sequence↗

In situ localization of mRNA for epidermal growth factor in the submandibular gland of the mouse.

Epidermal growth factor (EGF) is a polypeptide originally isolated from the mouse submandibular gland, where it is localized immunocytochemically in cells of the granular convoluted tubules (GCT). cDNAs encoding the precursor of mouse submandibular EGF have been cloned (Scott et al. Science 221:236, 1983; Gray et al. Nature 303:722, 1983). A fragment of one of these clones, pmegf10, containing the EGF coding region, was tritium-labeled by nick-translation and used as a probe for in situ hybridization to EGF mRNA. A specific hybridization signal for EGF mRNA was seen only in mature or developing GCT cells. The intensity of the signal was stronger in glands of intact males than in females or in castrated males. In glands of castrates treated with testosterone, or of intact females treated with triiodothyronine (T3), the signal was comparable to that in intact males. In glands of males treated with T3 the intensity of the signal was stronger than in untreated males. A weak to moderate signal was seen in developing GCT cells of 20-day-old males but not females. Hybridization for 3 days gave a stronger signal than that for 1 day. No signal was seen in either sex at 10 days of age, or in control preparations exposed to labeled DNA of pBR322. The presence of EGF mRNA exclusively in GCT cells provides strong evidence that these cells are the only site of synthesis of EGF in the submandibular gland. In situ hybridization with this cDNA probe will provide a sensitive method to determine possible cellular sites of EGF production outside of the submandibular gland.

Animals↗

Morphological changes in rat submandibular gland mucous cells during fixation with 10% formalin.

The features of mucous cells in 10% formalin (FA)-fixed submandibular glands differ markedly from those fixed in glutaraldehyde (GA). We therefore studied morphological changes in mucous cells during 10% FA fixation. Mucous cells were fixed in either 10% FA, neutral sodium-phosphate-buffered (Na-PBed) 10% FA, ice-cold 10% FA or an ice-cold fixative mixture of 2.0% paraformaldehyde (PA) and 0.5% GA. Two different methods were used: immersion fixation and venous perfusion fixation. The 10% FA-fixed tissues had elliptical or flattened nuclei, a clear cytoplasm and no secretory granules. Tissues fixed with the fixative mixture displayed almost round nuclei, a broad endoplasmic reticulum and abundant secretory granules in the cytoplasm. Tissues immersion-fixed with neutral Na-PBed 10% FA or perfusion-fixed with ice-cold 10% FA had almost the same light microscopic appearance as that of the mixture-fixed tissues. To elucidate the process of morphological changes during 10% FA fixation at room temperature, samples immersed in 10% FA for varying periods of time were postfixed immediately in the fixative mixture and exposed to microwave irradiation. This method produced a variety of findings, even within the same section. There was a significant difference in the findings seen in the center of the section and at the periphery. The initial changes caused by 10% FA were rupture of the secretory granules located in the perinuclear region and destruction of the perinuclear organelles such as Golgi apparatus, mitochondria and endoplasmic reticulum. Absorption of the endoplasmic reticulum progressed so that the perinuclear region became translucent. To obtain a better structure in mucous cells from the fixed submandibular gland tissues, an appropriate fixative such as GA should be used and the fixative should infiltrate into the tissues as quickly as possible.

Animals↗

Alpha-D-mannosidase activity in human saliva and rate of production of enzymes by parotid and submandibular glands.

The aim of the investigation was to study alpha-D-mannosidase activity in samples of whole, parotid and submandibular saliva and the rate of production of alpha-D-mannosidases by parotid and submandibular glands. alpha-D-mannosidase activity was determined spectrophotometrically and spectrofluorimetrically. alpha-D-mannosidase activity was found at three different pH optima in whole saliva, around pH 4.8, 6.1 and 6.9. In parotid and submandibular saliva there were two different pH optima, around pH 4.8 and 6.1. The rate of production of alpha-D-mannosidase by parotid glands varied between 0.48 and 13.66 U/min and by submandibular glands between 0.25 and 2.52 U/min. The present study shows that two of the three alpha-D-mannosidases found in whole human saliva are produced by parotid and submandibular glands.

Adult↗

Quantitative and qualitative fluctuation of water in the mouse submandibular gland under secretagogue effect.

The short-term effects of two different secretagogues on the water contained in the mouse submandibular gland were studied using the thermal analysis as investigation method. Isoproterenol induced a retention while pilocarpine promoted a release of weakly and strongly bound water. In addition, submandibular glands of subjects administered with isoproterenol were characterized by a thermal behaviour different in males and females above all as concerns the time of reaction to the secretagogue; the reaction delay observed in females was correlated with the effects of this pharmacological substance on the convoluted granular tubules that are responsible for the sexual dimorphism in mice.

Animals↗

Immunocytochemical localization of epidermal growth factor during the postnatal development of the submandibular gland of the mouse.

The time of appearance and the pattern of localization of epidermal growth factor (EGF) in submandibular glands of mice was studied during postnatal development immunocytochemically. EGF was first detectable in the granular convoluted tubule (GCT) cells in the glands of males at 20 days of age and of females at 30 days of age. Development of GCT cells containing EGF was rapid in males, approaching adult conditions by 45 days of age. In females EGF- containing GCTs developed more slowly and irregularly, and did not reach adult status by 45 days of age. It is concluded that EGF is restricted during postnatal development to the GCT cells, and that these cells and the distribution of EGF are represented dimorphically from their first appearance in the submandibular glands of both sexes.

Age Factors↗

Effect of castration and administration of testosterone on cytosol and nuclear androgen receptor in mouse submandibular gland.

The effect of castration or administration of testosterone propionate on the subcellular distribution of androgen receptor in mouse submandibular gland was investigated. Within 10 h after castration of male mice, most of the androgen receptor in nuclei was significantly reduced, the androgen receptor in cytosol increased and the increased cytosol receptor retained for at least 40 h. A single injection of testosterone propionate to female mice resulted in the translocation of cytosol androgen receptor to the nuclei by 30 min. The nuclear receptor level remained for at least 24 h and the cytosol receptor was replenished by 24-72 h. These results reveal that the endocrine manipulations such as castration and testosterone injection cause the change in the subcellular distribution of androgen receptor from mouse submandibular gland in both sexes.

Animals↗

Relationship between submandibular gland epidermal growth factor and spermatogenesis in C3H mice.

Epidermal growth factor (EGF), a potent mitogen produced primarily in the submandibular gland of adult male mice, has been implicated in modulating processes known to be of vital importance in the regulation of spermatogenesis. In the present investigation we demonstrate that submandibular gland EGF from adult male mice is indeed capable of displacing radiolabeled EGF from testicular membranes. Scatchard analysis of this binding site reveals that it is of high affinity (Kd = 0.77 nM) and low capacity (Bmax = 8.15 fmol/mg protein). Cross-linking of 125I-EGF to the identical membrane preparation resulted in the SDS-PAGE/autoradiography identification of a single band at approximately 170 kDa. Next, we examined the cellular distribution of the EGF receptor in the testis using biotin-streptavidin immunoperoxidase and employing different antisera probes generated to a conserved sequence of the EGF receptor. The Scatchard and cross-linking data described above, along with the immunocytochemistry results, suggest strongly that there is only one functional binding site for EGF in the adult testis and that this receptor is present in Sertoli and Leydig cells.

Animals↗

Induction of adenocarcinoma containing myoepithelial cells in rat submandibular gland by 7,12-dimethylbenz(a)anthracene.

In an attempt to induce adenocarcinoma containing myoepithelial cells (MECs) in the rat submandibular gland, we injected 7,12-dimethylbenz(a)anthracene (DMBA) dissolved in acetone into the glands of rat pups at the age of 10 days. In both male and female pups, the glands, including their developing terminal secretory units, contained far greater numbers of cells positive for proliferating cell nuclear antigen (PCNA) than did adult glands. A single administration of 1% DMBA (0.05 ml/130 g b.w.) did not produce adenocarcinoma, but did induce occasional sarcomas, such as rhabdomyosarcoma and fibrosarcoma, in 2 months. Most glands regenerated with minimal scar formation. Microscopically, these glands were atypical in that they contained increased numbers of PCNA-positive cells, underdeveloped granular ducts, and striated ducts surrounded by MECs positive for alpha smooth muscle actin (alphaSMA). Though these features were also observed in the regenerated glands after acetone injection, the number of PCNA-positive cells was relatively high in the glands of DMBA-treated females, especially in the terminal secretory unit. The second DMBA injection at 10 weeks of age produced adenocarcinoma made up of alphaSMA-positive MECs and keratin 19-positive duct cells. Such MEC-associated adenocarcinoma was induced in the glands of more than half the female but not the male animals. Replacement of either of the double DMBA treatments with acetone, or DMBA treatment, single or double, of adult glands did not produce adenocarcinoma, but did produce sarcoma and squamous cell carcinoma. These results suggest that (1) at least two genetic mutations are necessary for induction of adenocarcinoma with MECs in the rat submandibular gland, (2) the mutation is efficiently introduced to pup glands whose terminal secretory units exhibit extreme proliferative activity, and (3) the second mutation is difficult to introduce in male glands, whose proliferative activity is relatively low, and/or transformed cells need some female hormone after the mutation to propagate.

9,10-Dimethyl-1,2-benzanthracene↗

The role of the rat submandibular gland in the excretion of bis (tributyltin) oxide: electron microscopy, X-ray microanalysis and atomic absorption analysis.

The role of the submandibular glands in the excretion of parenterally administered bis (tributyltin) oxide (TBTO) was studied. Fine structural alterations of the submandibular glands were observed with an electron microscope. Accumulation sites of TBTO were determined with an X-ray microanalyzer and tin concentrations in saliva and blood were measured by atomic absorption spectrophotometry.

Animals↗

Epidermal growth factor in the submandibular glands of inbred mice.

Epidermal growth factor (EGF), and androgen-dependent polypeptide, occurs in high concentration in male mouse submandibular gland. Glands of adult male and female mice of six inbred strains (129/J, C57BL/6J, C58/J, SWR/J, RF/J, A/J) were assayed for EGF by radioimmunoassay. In all strains, the glands of males contained 30 to 500-fold more EGF than those of females. Furthermore, significant differences in EGF content were found among the various strains in both sexes, the highest amount of EGF was present in RF/J and the lowest in C57BL/6J, with a ratio of three in the males and four in the females of the two strains, respectively. Factors that effect EGF levels were analyzed further, using these two strains. EGF was measurable in the glands of mice of both strains at 21 days of age and increased rapidly thereafter, up to 14 weeks of age. Throughout postnatal development, the level of EGF was greater in the glands of RF/J mice than in those of the C57BL/6J animals. Thirty days after castration, the EGF levels were reduced by about 98% in both strains, but the strain difference was not abolished. Testosterone implants (1 mg in Silastic tube) in castrated mice induced EGF levels six- to ten-fold compared to castrates. Even in induced animals, which had similar plasma testosterone levels, as measured by radioimmunoassays, the difference in EGF levels between the two strains was manifest. Such a difference, however, was not seen after the daily administration of 5-alpha-dihydrotestosterone for 3-14 days. Immunocytochemical straining for EGF also indicated a higher concentration of the polypeptide in the glands of RF/J mice than in those of C57BL/6J animals, and confirmed the exclusive localization of EGF in the cells of the granular convoluted tubules (GCT). According to our morphometric analysis, in the glands of male RF/J mice the GCT compartment occupied a greater portion (8% greater, P less than 0.001) of the gland volume than in C57BL/6J mice. The difference in the relative GCT volumes in the glands of female mice of the two strains was, however, statistically not significant. There was no direct correlation between the amount of EGF and the relative volume of the GCTs in the two strains. The evidence obtained implies that strain difference in submandibular-gland EGF levels are determined genetically.

Aging↗