Fine structure of the differentiating acini in submandibular glands of isoproterenol-treated rats

Cystatin S in secretory granules fractions isolated from submandibular gland of infected rats by Trypanosoma cruzi

We have measured the relative concentrations of cysteine proteinase in the granular fractions of submandibular glands of control and Trypanosoma cruzi infected rats by using a sensitive solid phase ELISA. Gland samples were homogenized in 0.34 M sucrose and 0.5 mM EDTA in 10 mM HEPES buffer at a pH of 7.4. The extract was centrifuged and filtered through Millipore filters to prepare a purer granular fraction. Immunochemical studies using antibody against cystatin S and electrophoretic analysis showed higher cystatin S levels in infected rats than in control. The role of this inhibitor during acute phase of Chagas disease is discussed.

Acute irradiation effects on morphology and function of rat submandibular glands

In this study the morphologic and functional changes were compared after irradiation (single dose, 15 Gy) of rat submandibular salivary glands. Before and 1-10 days after local irradiation of the gland region, samples of submandibular saliva were collected after stimulation by pilocarpine. At the same time-points and also 3 h postirradiation submandibular glands were carefully extirpated and prepared for histocytologic examination (LM, TEM). Maximal increase of the lag phase and decrease of the flow rate were observed 3 days after irradiation, while [K+] and [Na+] increased and decreased, respectively, from days 1 and 3 after irradiation. Morphologic changes were observed from the third hour after irradiation, were maximal 3 days after irradiation and had partially recovered by day 10. Three hours and 1 day after irradiation degranulation of convoluted granulated tubes (CGT) was observed. Three days after irradiation the most striking morphologic changes in serous and mucous cells were distension of the cisternae of the RER, degeneration of mitochondria and vacuolization of the cytoplasm. Fibril-like condensations of electron dense material in the mucous granules were observed 3 h, 1 and 6 days after irradiation. Regranulation of CGT cells was observed from day 6. From this study it is concluded that changes in salivary gland function can be observed before major morphologic changes occur. Functional changes persist after the morphologic changes seem to have virtually returned to normal.

Nerve growth factor-induced increase in [3H]thymidine incorporation into parotid and submandibular glands of young rats and its partial blockade by propranolol or partial sialoadenectomy

Administration of nerve growth factor (NGF) twice daily for 2 days to young rats (11 days old at the time of the initial injection) resulted in an 8.1-fold increase in [3H]thymidine levels of the parotid gland, and a 9.7-fold increase in levels of the submandibular gland when compared to untreated controls. Isoproterenol (ISO), a beta-adrenergic receptor agonist, caused an 8.7-fold increase in [3H]thymidine incorporation into DNA of the parotid gland, and a 10.7-fold increase in [3H]thymidine in the submandibular gland when compared to controls. The increase in thymidine was accompanied by parotid gland enlargement as well as an increase in cell surface beta 1-4 galactosyltransferase, an enzyme whose expression has been associated previously with acinar cell proliferation. Administration of NGF and ISO together were not additive in their effects on the parotid and submandibular glands. The introduction of propranolol, a beta-adrenergic receptor antagonist, completely negated the ISO effects on the salivary glands but was only partially effective in blocking the NGF effects on the glands. An assay of parotid levels of norepinephrine showed NGF treatment to cause an increase in gland-associated levels of neurotransmitter. Removal of the submandibular/sublingual glands prior to administration of ISO prevented the above changes in the parotid gland. NGF administered to partially sialoadenectomized rats was also less effective in inducing parotid gland hypertrophy and hyperplasia. Simultaneous administration of NGF and ISO to the partially sialoadenectomized rats had an additive influence on [3H]thymidine incorporation, galactosyltransferase expression and gland hypertrophy. The results suggest that NGF influences salivary gland cell growth in part through activation of cell-surface beta-adrenergic receptors.

Immunocytochemical localization of a developmentally regulated, isoproterenol-inducible protein (LM protein) in rat submandibular gland

Administration of the beta-adrenergic drug isoproterenol (IPR) produces hyperplastic and hypertrophic enlargements of the submandibular gland of the rat and induces the synthesis of specific proteins in this organ. One of these proteins, the LM (large mobile) protein, was demonstrated immunocytochemically in the submandibular glands of developing untreated and IPR-treated rats. Immunoreactive LM protein was absent in the glands of 20-day-old fetuses and 1- and 2-day-old rats. It was localized in the proacinar and immature acinar cells in the glands of 6- to 21-day-old animals, but it was undetectable at 28 days of age. In the glands of adult rats, secretory granules of the granular convoluted tubule cells showed immunostaining for the LM protein which was also present in trace amounts in the acinar cells. Daily administration of IPR for 5 days to newborn or 8- or 15-day-old rats caused an apparent acceleration of proacinar/acinar cell differentiation, and consequently it increased the frequency of cells immunostained for the LM protein as well as the amount of immunoreactive material in these cells. Thus, the expression of LM protein in the submandibular gland is developmentally regulated, and it is restricted to the stage of differentiation of proacinar cells from terminal tubule cells. IPR is capable of inducing this protein in fully differentiated acinar cells in 3-week-old or older animals.

Analysis of protein synthesis in rat salivary glands after chronic treatment with beta-receptor agonists and phosphodiesterase inhibitors

Chronic administration of the beta-adrenergic receptor agonist isoproterenol (5 mg/200 g animal for 10 days) resulted in rat parotid and submandibular gland hypertrophy, and it induced synthesis of a series of proline-rich proteins (PRPs) and glycoproteins. Treated parotid glands additionally exhibit an increase in activity for the Golgi membrane enzyme UDP-galactose; N-acetylglucosamine 4 beta-galactosyltransferase. A series of beta-receptor agonists and phosphodiesterase inhibitors were examined for their abilities to influence salivary gland protein biosynthesis in a fashion similar to that observed with chronic isoproterenol treatment. beta 1/beta 2-Adrenergic-receptor agonists exhibited the greatest effects on parotid gland hypertrophy and PRP biosynthesis. These beta-agonists were also able to increase 4 beta-galactosyltransferase activity, but they did not promote the synthesis of a 220,000 dalton glycoprotein. Terbutaline (beta 2-receptor agonist) induced parotid gland hypertrophy but was only able to induce protein biosynthesis at higher drug concentrations. Finally, methoxyphenamine was unable to produce the observed changes in protein synthesis even at increased drug dosages. The phosphodiesterase inhibitors (theophylline and caffeine) were able to induce de novo PRP biosynthesis at drug doses of 20 mg/200 g animal. However, while causing mild gland hypertrophy, there was no observable change in 4 beta-galactosyltransferase activity with either phosphodiesterase inhibitor. This same regimen of beta-receptor agonists was unable to induce submandibular gland hypertrophy, PRP or glycoprotein biosynthesis in the same animals. This was also true for the two phosphodiesterase inhibitors. Co-injection of a beta 1 antagonist along with isoproterenol blocked the above protein changes in both the submandibular and parotid glands, suggesting that the stimulation of protein synthesis takes place by beta 1-type receptors on the gland cell surfaces.

The effect of chronic isoproterenol administration on the plasma membrane of acinar cells in rat submandibular gland

The effect of chronic administration of isoproterenol on the plasma membrane of acinar cells in the rat submandibular gland was studied by biochemical and immunohistochemical methods, using dipeptidyl peptidase (DPP) IV as a marker enzyme. Chronic isoproterenol treatment led to a marked reduction of DPP IV activity as well as of its immunoreactivity in the gland. Its effect progressively increased with the age of the animals. The present study showed that chronic treatment with isoproterenol caused a qualitative alteration of the plasma membrane of the luminal surface in acinar cells of the rat submandibular gland, and that the effect of the drug on the plasma membrane was dependent on the developmental stage of the acinar cells of the gland.

Isoprenaline-induced changes in rat parotid and submandibular glands are age- and dosage-dependent

Neonatal rats treated with chronic injections of isoprenaline (isoproterenol) for 10 days revealed differential induction of proline-rich proteins and glycoprotein synthesis between the parotid and submandibular glands. Biosynthesis of proline-rich proteins (Mr 17000-35000) and a Mr-220000 glycoprotein were detectable by solubilization in 10%-trichloroacetic acid extracts from parotid glands 14 days after birth. The enzyme lactose synthase (UDP-galactose: 2-acetamido-2-deoxy-D-glucosamine 4 beta-galactosyltransferase) (EC 2.4.1.22) is also induced 4-7-fold in specific activity compared with control neonatal rats, but again only after 14 days post partum, with isoprenaline treatment. This is in accord with the ability of the parotid gland to respond to beta-receptor stimulation and subsequent increases in intracellular cyclic AMP necessary for induction of protein synthesis [Grand, Chong & Ryan (1975) Am. J. Physiol. 228, 608-612]. Induction of the proline-rich proteins and a Mr-190000 glycoprotein in the soluble fraction from the submandibular gland were not detected until 49 days after birth under identical conditions in the same animal. Cyclic AMP in the submandibular gland undergoes increases on beta-receptor stimulation similar to those achieved in the adult animal, 1 day after birth (Grand et al., 1975). This same differential induction between parotid and submandibular gland was obtained with a range of isoprenaline dosages in adult animals. Trichloroacetic acid-soluble proline-rich proteins were isolated from parotid glands at a dosage of 4.0 mg of isoprenaline/kg body wt., but 7.0 mg/kg was required to induce also biosynthesis of these proteins in the submandibular gland. Gland hypertrophy showed the same differential dosage kinetics, based on gland weight, between the two glands; however, hypertrophy could be accomplished at a lower dosage of isoprenaline than that used to induce proline-rich-protein biosynthesis.

Effects of prior culture or isoproterenol injections on the regeneration of rat submandibular gland autografts

This study compares the acinar cell regenerative response in submandibular gland (SMG) autografts that were cultured before grafting to the rat tongue with the acinar cell regenerative response in direct SMG autografts to the tongue. In addition, the effects of isoproterenol on direct SMG autografts were studied. A portion of the left SMG was excised from each rat and cut into fragments which were autografted either immediately into the middle one-third of the rat's tongue; or were cultured for 1, 4, or 7 days and then autografted to the donor's tongue. After 8 weeks the rats were killed and the tongues were removed and processed for light microscopic study. The histologic preparations showed evidence of cytodifferentiation into acinar cells in four of the previously cultured SMG autografts. Some of the direct SMG autografts did not contain acinar cells, whereas other direct SMG autografts contained numerous acinar cells and even striated ducts. In the SMG autografts that were cultured for 1 day before autografting and in the direct SMG autografts, the most pronounced regenerative responses were seen in autografts that contained ductlike structures that were apparently connected to the epithelial surface of the tongue. Lastly, isoproterenol appeared to accelerate the regenerative response in some of the direct SMG autografts, and the drug caused acinar cell hypertrophy in two of the direct SMG autografts.

Histological observations on the effects of isoproterenol on regenerating submandibular glands of the rat

The effect of isoproterenol (IPR) on acinar cell mitoses was studied in regenerating submandibular glands of the rat following partial extirpation. In controls, mitoses of acinar cells were markedly higher on the cut surface (reactive zone) than in the remainder of the gland through 10 ds post-operation. In experimental animals by 5 ds, a burst of mitoses of acinar cells was seen in all areas of the gland except the reactive zone. In the reactive zone, IPR appears to suppress or inhibit the induced mitoses seen in controls.

The secretion of protein and of some electrolytes in response to alpha- and beta- adrenergic agonists by rat parotid and submandibular salivary glands enlarged by chronic treatment with isoproterenol

In comparison with control rats. chronic administration of isoproterenol (IPR) caused enlargement of the parotid and submandibular glands and the synthesis of apparently new proteins, probably by acinar cells. The parotid and submandibular saliva secreted in response to methoxamine or IPR differed markedly in protein and electrolyte content. In addition, with each stimulus, the salivas secreted by control and experimental glands differed in flow rate, protein concentration, and in the concentrations of certain of the electrolytes.

Morphology and cytochemistry of acinar secretory granules in normal and isoproterenol-treated rat submandibular glands

Several fixation procedures have been utilized in a fine-structural study of rat submandibular glands with the aim of correlating the morphology of granule substructure with its composition. Procedures included fixation with aldehyde in a variety of buffers, with or without fixation additives such as tannic acid or calcium chloride. Both immersion and perfusion fixation studies were performed. Osmium tetroxide postfixed tissue was compared with non-postfixed tissue. Thin sections were stained for carbohydrate-containing constituents by either periodic acid-thiocarbohydrazide-silver proteinate or tannic acid-ferric chloride sequences. The morphology and cytochemistry of acinar secretory granules were highly dependent upon the fixation procedure utilized. In postfixed tissue, fine filaments and vesicles were the major granule constituents. Filaments often aggregated into fibrils in fixatives containing phosphate buffer or calcium, whereas vesicles were prominent with fixatives containing collidine buffer. Tannic acid, as a fixation additive, imparted enhanced density to the peripheral rim of aggregated filaments. If post fixation was eliminated, an amorphous meshlike material was the major granule component. This stained readily with methods for carbohydrate whereas the granules of post-osmicated tissue did not. Following chronic isoproterenol treatment the degree of filament aggregation in postfixed tissue was augmented, and this corresponded to an increase in amount of material stainable for carbohydrate in non-post-osmicated tissue.

Changes in rat parotid salivary proteins induced by chronic isoproterenol administration

Changes in the rat parotid gland and its secretion, brought about by chronic isoproterenol administration, were studied. In addition to the expected enlargement, morphological and biochemical analyses of the glands showed evidence of changes in the secretory components. Chromatographic and electrophoretic experiments revealed both qualitative and quantitative changes in the secretory proteins.

The effects of 5-bromodeoxyuridine and isoproterenol on the postnatal differentiation of rat submandibular gland

The effects of 5-bromodeoxyuridine (BrdU) on the postnatal differentiation of rat submandibular gland and on the isoproterenol-induced changes of differentiation were studied. The rats were injected with BrdU for three consecutive days, beginning at two days of age. The total dose of BrdU was 0.9 mg/g body weight. BrdU caused a severe retardation of growth up to 15 days of age. A rapid growth of the animals between 15 and 22 days indicated a recovery from the effect of BrdU. The growth of the submandibular gland was retarded similarly with a corresponding decrease in DNA, RNA and protein content. Incorporation of tritiated thymidine into the submandibular gland was not altered in the BrdU-treated animals at one and three days after the last injection of the analog. At days 15 and 22 the rate of thymidine incorporation was greater in the submandibular gland of BrdU-treated rats as compared to littermate controls. Isoproterenol stimulated thymidine incorporation into the submandibular glands of two-week-old rats. This stimulation was not observed in rats which received BrdU at age 7-9 days, prior to the administration of isoproterenol. Election microscopic observations, including a quantitative analysis of the frequency distribution of the various cell types in the terminal tubules and developing acini, indicated a retardation of acinar cell differentiation in the glands of BrdU-treated rats. In addition, there was an increase in the number and size of the secretory granules in the terminal tubule cells. BrdU treatment, however, caused no obvious pathologic alterations in the submandibular gland. Administration of isoproterenol for five days, beginning at five days of age, caused an apparent acceleration of the differentiation of acinar cells. In the glands of isoproterenol-treated rats the acinar cells were enlarged and were filled with homogeneous secretory granules. Pretreatment with BrdU partially inhibited the effects of isoproterenol on differentiation and hypertrophy of the submandibular gland. With the given dose of BrdU, approximately 5% of thymine was replaced by bromouracil in the DNA of the submandibular gland. Such a replacement would be consistent with a direct effect of BrdU on the cytodifferentiation in the submandibular gland. However, because of the severe retardation of growth of the BrdU-treated rats, indirect effects can not be excluded.

Cell differentiation in the terminal tubule of fetal rat submandibular gland in organ culture

Submandibular glands from 17-day-old rat fetuses were maintained in organ culture for five days in a medium consisting of Eagle's MEM (87%), horse serum (10%), and chick embryo extract (3%). Each day of the culture period explants were incubated for the demonstration of peroxidase activity and processed for light and electron microscopic observations. In some experiments cultures were exposed to 3H-thymidine one hour prior to fixation and incubation for the demonstration of peroxidase activity. Labelling index was determined using radioautographs of 1 mu Epon-embedded sections. At the time of explantation the submandibular gland rudiment consisted of undifferentiated epithelial cells arranged in cords. On day 3 of culture two additional cell types could be distinguished: terminal tubule cells and proacinar cells. The proacinar cells were characterized by peroxidase activity in their granules and cytoplasm. By day 4 acinar cells begin to appear. On the fifth day of culture the four cell types of the terminal tubule were present in the following proportions: undifferentiated cells, 44%; terminal tubule cells, 19%; proacinar cells, 31%; acinar cells, 6%. These results indicate that the cytodifferentiation of the secretory unit of rat submandibular gland in vitro is comparable to the differentiation in vivo.

The postnatal development of the sexually dimorphic duct system and of amylase activity in the submandibular glands of mice

The submandibular glands of developing and mature Strong A mice were studied by light and electron microscopy. The glands of both sexes show the same cell types during development, but during maturation the glands display a degree of sex-dimorphism. Striated ducts, which differentiate from the larger intralobular ducts present in the neonatal gland, first appear by 5 days of age and reach their mature condition by 20 days of age. Granular convoluted tubule cells, which differentiate from striated duct cells, are first seen at 15 days of age in both sexes. Subsequently, they show a more rapid development in males than in females, and are dimorphically represented by 20 days of age. Intercalated ducts in the neonatal gland contain nongranular and granular cells. With maturation the number of granular cells decreases, apparently due to their conversion into the nongranular type, with their eventual disappearance from the glands of adult males. Their retention in adult females further defines the sexual dimorphism shown by these glands. Amylase activity in gland homogenates is first detectable at 20 days of age in both sexes. During development the male glands show a rapid rise in levels of amylase activity, whereas female glands show a more gradual rise. In mature animals, male glands have higher levels of amylase activity than female glands. The developmental and adult status of amylase activity parallels that of the granular convoluted tubules.