Cells Of Rat Submandibular Gland Research Articles

Intracellular signaling pathways involved in the regulation of gene expression by pilocarpine

ObjectivesPilocarpine is commonly used clinically to treat dry mouth. The long-term administration of pilocarpine reportedly improves salivary secretion more effectively than short-term administration. Therefore, we hypothesized that pilocarpine alters gene expression in salivary glands via muscarinic receptor stimulation. This study aimed to investigate the effects of pilocarpine use on gene expression mediated by mitogen-activated protein kinase (MAPK) activity. MethodsThe effects of pilocarpine on gene expression were investigated in rats and human salivary gland (HSY) cells using several inhibitors of intracellular signaling pathways. Gene expression in the rat submandibular gland and HSY cells was determined using reverse transcription–quantitative polymerase chain reaction analysis of total RNA. ResultsIn animal experiments, at 7 days after pilocarpine stimulation, Ctgf and Sgk1 expressions were increased in the submandibular gland. In cell culture experiments, pilocarpine increased Ctgf expression in HSY cells. The mitogen-activated protein kinase kinase inhibitor trametinib, the Src inhibitor PP2, and the muscarinic acetylcholine receptor antagonist atropine suppressed the effect of pilocarpine on gene expression. ConclusionsPilocarpine enhances Ctgf and Sgk1 expressions by activating Src-mediated MAPK activity. Although further studies are required to fully understand the roles of Ctgf and Sgk1, changes in gene expression may play an important role in improving salivary secretions.

Effect of silencing SSB1 gene on the expression of NBS1 in irradiated rat submandibular gland cells.

The salivary gland (SGS) is a kind of organ vulnerable to ionizing radiation. Radiotherapy is an important treatment for head and neck tumors, but in the process of radiotherapy, tumor cells will be injured by radiation to a certain extent. Infrared-induced DNA double-strand break (IR-DSBs) is one of the most serious DNA damage. DNA repair proteins such as Nymegan rupture syndrome protein 1 (NBS1) play a key role in the identification and repair of DNA damage. but the interaction between SSB1 and NBS1 has not been elucidated. In this study, we irradiated rat submandibular gland (SMG) cells, which were either infected with a rAdE5-SSB1-1p2-shRNA recombinant adenovirus to silence SSB or a control virus, to explore the effect of IR on the expression NBS1 in the absence of SSB. Our results showed that the SSB1 mRNA transcripts and protein expression of SSB1 and NBS1 initially increased and decreased later with increased doses. The relative expression reached the highest levels when the SMG cells were irradiated with 2Gy of IR. Silencing the SSB1 gene suppressed the expression of both SSB1 and NBS1 regardless of irradiation. The expression of NBS1 decreased when the SSB1 gene was silenced. We concluded that IR affected the expression of both SSB1 and NBS1 and there is a synergistic effect on IR-induced NBS1 suppression and DSBs repair in SMG cells. These observations shed light on further investigation and elucidation of IR-caused DNA repair mechanisms.

Cdc42 activates paracellular transport in polarised submandibular gland cells

ObjectiveThe physiological expression of cell division cycle 42 (cdc42) in major salivary glands, and paracellular transport of fluorescein isothiocyanate-dextran (FITC-dextran) in SMIE cells, which regulate cdc42 expression, was investigated to clarify the involvement of cdc42 in salivary production. DesignThe physiological expression of cdc42 in the rat submandibular gland, parotid gland, sublingual gland, and SMIE cells was detected using SDS-PAGE and western blotting. The paracellular transport of FITC-dextran in transwells was compared in transfected SMIE cells, exhibiting up- or downregulated cdc42 expression. ResultsCdc42 was expressed in all major salivary glands and SMIE cells. SMIE cells transfected with the cdc42 plasmid had an increase efflux. In addition, SMIE cells transfected with the cdc42 siRNA showed decreased efflux. ConclusionWe suggest that cdc42 enhances paracellular transport in salivary glands without any morphological changes, including cell-cell adhesion.

ラット顎下腺腺房部の細胞のtight junctionにおける物質透過性に対するE-cadherinの役割

ラット顎下腺腺房部の細胞のtight junctionにおける物質透過性に対するE-cadherinの役割

Assessment of Transfection of AdCMV-EGFP to Rat Submandibular Gland Cells

We evaluated the efficiency of transfecting adenoviral vectors encoding enhanced green fluorescent protein (AdCMV-EGFP) into rat submandibular gland cells and the effects of gene transfer on cell proliferation and secretory function. Isolated submandibular gland cells were transfected with different titers (or multiplicity of infection, MOI) of AdCMV-EGFP. The transfection efficiency was evaluated by quantifying EGFP-positive cells by inverted fluorescence microscopy, cell proliferation by MTT assay, and cell secretory activity by measuring α-amylase in culture medium. A transfection efficiency of up to 70.8% was achieved in submandibular gland cells. MTT assay showed that increased viral titers resulted in significant inhibition of cell proliferation, which occurs on day 5 post-transfection. Simultaneously, the amylase levels started to reduce with a significant decrease on day 7 after transfection. The results show that AdCMV-EGFP transfection of submandibular gland cells at higher MOI results in cytotoxicity, decreased cell proliferation, and secretory function. However, the lower adenoviral titers (e.g., 200 particles/cell) could be an efficient and safe labeling tool for gene transfer to submandibular gland cells.

Вплив канабіноїдних рецепторів GPR55 на слиновиділення підщелепної слинної залози щура

This paper is devoted to elucidation of functionally active cannabinoid receptor GPR55 in submandibular salivary gland cells of rats by introducing a specific agonist lysophosphatidylinositol. We studied the effect of GPR55 activation on the following parameters of basal salivation in vivo : rate of salivation of protein concentration and electrolytes. It was shown that in vivo activation of cannabinoid receptor GPR55 in the acinar cells of submandibular salivary gland by lysophosphatidylinositol caused a dose-dependent reduction in basal flow of saliva. We also elucidated that activation of the cannabinoid receptor GPR55 induced an increase of concentration of total protein in saliva secreted in vivo . That indicate that the activation of cannabinoid receptor GPR55 leads to an enhancement of exocytosis of secretory vesicles in acinar cells. We showed that under conditions of activation of cannabinoid receptor GPR55, changes also occured in concentration of electrolytes in basal saliva such as: reduction in concentration of calcium (Ca 2+ ), inorganic phosphorus (P i ), and increasing concentration of potassium (K + ). Based on these findings, we suggest that activation of cannabinoid receptor GPR55 leads to modulation of intracellular signaling mechanisms involved in the secretion of water and electrolytes in acinar cells of rat submandibular salivary gland. Keywords: submandibular salivary gland, cannabinoid receptor GPR55, lysophosphatidylinositol, basal salivation.

Cannabinoid receptors in submandibular acinar cells: functional coupling between saliva fluid and electrolytes secretion and Ca2+ signalling

Cannabinoid receptors (CBRs) belong to the G protein-coupled receptor superfamily, and activation of CBRs in salivary cells inhibits agonist-stimulated salivation and modifies saliva content. However, the role of different CBR subtypes in acinar cell physiology and in intracellular signalling remains unclear. Here, we uncover functional CB(1)Rs and CB(2)Rs in acinar cells of rat submandibular gland and their essential role in saliva secretion. Pharmacological activation of CB(1)Rs and CB(2)Rs in the submandibular gland suppressed saliva outflow and modified saliva content produced by the submandibular gland in vivo. Using Na(+)-selective microelectrodes to record secretory Na(+) responses in the lumen of acini, we observed a reduction in Na(+) transport following the activation of CBRs, which was counteracted by the selective CB(1)R antagonist AM251. In addition, activation of CB(1)Rs or CB Rs caused inhibition of Na(+)-K(+) 2 -ATPase activity in microsomes derived from the gland tissue as well as in isolated acinar cells. Using a Ca(2+) imaging technique, we showed that activation of CB(1)Rs and CB(2)Rs alters [Ca(2+)](cyt) signalling in acinar cells by distinct pathways, involving Ca(2+) release from the endoplasmic reticulum (ER) and store-operated Ca(2+) entry (SOCE), respectively. Our data demonstrate the expression of CB(1)Rs and CB(2)Rs in acinar cells, and their involvement in the regulation of salivary gland functioning.

Delay in maturation of the submandibular gland in Chagas disease correlates with lower DNA synthesis

It has been demonstrated that the acute phase of Trypanosoma cruzi infection promotes several changes in the oral glands. The present study examined whether T. cruzi modulates the expression of host cell apoptotic or mitotic pathway genes. Rats were infected with T. cruzi then sacrificed after 18, 32, 64 or 97 days, after which the submandibular glands were analyzed by immunohistochemistry. Immunohistochemical analyses using an anti-bromodeoxyuridine antibody showed that, during acute T. cruzi infection, DNA synthesizing cells in rat submandibular glands were lower than in non-infected animals (p < 0.05). However, after 64 days of infection (chronic phase), the number of immunolabeled cells are similar in both groups. However, immunohistochemical analysis of Fas and Bcl-2 expression did not find any difference between infected and non-infected animals in both the acute and chronic stages. These findings suggest that the delay in ductal maturation observed at the acute phase of Chagas disease is correlated with lower expression of DNA synthesis genes, but not apoptotic genes.

Effect of translocator protein (18 kDa)‐ligand binding on neurotransmitter‐induced salivary secretion in rat submandibular glands

TSPO (translocator protein), previously known as PBR (peripheral-type benzodiazepine receptor), is a ubiquitous 18 kDa transmembrane protein that participates in diverse cell functions. High-affinity TSPO ligands are best known for their ability to stimulate cholesterol transport in organs synthesizing steroids and bile salts, although they modulate other physiological functions, including cell proliferation, apoptosis and calcium-dependent transepithelial ion secretion. In present study, we investigated the localization and function of TSPO in salivary glands. Immunohistochemical analysis of TSPO in rat salivary glands revealed that TSPO and its endogenous ligand, DBI (diazepam-binding inhibitor), were present in duct and mucous acinar cells. TSPO was localized to the mitochondria of these cells, whereas DBI was cytosolic. As expected, mitochondrial membrane preparations, which were enriched in TSPO, exhibited a high affinity for the TSPO drug ligand, (3)H-labelled PK 11195, as shown by B(max) and K(d) values of 10.0+/-0.5 pmol/mg and 4.0+/-1.0 nM respectively. Intravenous perfusion of PK 11195 increased the salivary flow rate that was induced by muscarinic and alpha-adrenergic agonists, whereas it had no effect when administered alone. Addition of PK 11195 also increased the K(+), Na(+), Cl(-) and protein content of saliva, indicating that this ligand modulated secretion by acini and duct cells. High-affinity ligand binding to mitochondrial TSPO modulates neurotransmitter-induced salivary secretion by duct and mucous acinar cells of rat submandibular glands.

Characterization and comparison of raft-like membranes isolated by two different methods from rat submandibular gland cells

Lipid rafts are defined as cholesterol and sphingolipid enriched domains in biological membranes. Their role in signalling and other cellular processes is widely accepted but the methodology used for their biochemical isolation and characterization remains controversial. Raft-like membranes from rat submandibular glands were isolated by two different protocols commonly described in the literature; one protocol was based on selective solubilization by Triton X-100 at low temperature and the other protocol consisted in extensive sonication. In both cases a low density vesicular fraction was obtained after ultracentrifugation in a sucrose density gradient. These fractions contained about 20% of total cholesterol but less than 8% of total proteins, and were more rigid than bulk membranes. Fatty acid analyses revealed a similar composition of raft-like membranes isolated by the two different methods, which was characterized by an enrichment in saturated fatty acids in detriment of polyunsaturated acids when compared with the whole cell membranes. Protein profile of detergent resistant membranes or raft-like membranes prepared by sonication was assessed by silver staining after SDS-PAGE and by MALDI-TOF. Both analyses provided evidence of a different protein composition of the Triton X-100 and sonication preparations. Immunoblot experiments revealed that raft-like membranes prepared by detergent extraction or sonication were free of Golgi apparatus or endoplasmic reticulum protein markers (β-COP and calnexin, respectively) and that they were not substantially contaminated by transferrin receptor (a non-raft protein). While caveolin-1 was highly enriched in raft-like membranes prepared by the two methods, the P2X 7 receptor was enriched in raft-like membrane fractions prepared by sonication, but almost undetectable in the detergent resistant membranes. It can be concluded that both methods can be used to obtain raft-like membranes, but that detergent may affect protein interactions responsible for their association with different membrane domains.

Localization and function of isoforms of the Cl- channel-related molecule, CLCA in ductal cells of rat submandibular gland

Localization and function of isoforms of the Cl- channel-related molecule, CLCA in ductal cells of rat submandibular gland

Differential coupling of the P2Y 1 receptor to Gα 14 and Gα q/11 proteins during the development of the rat salivary gland

In rat submandibular gland (SMG), the P2Y1 receptor (P2Y1R) mediates increases in the intracellular calcium concentration, [Ca2+]i that diminish as the animal ages from 1 to 4-6 weeks. However, P2Y1R mRNA levels do not change with age, suggesting that the age-dependent decrease in the [Ca2+]i response to P2Y1R agonists may be due to alterations in the activity of a component of the P2Y1R signalling pathway. To assess whether the decrease in P2Y1R-mediated intracellular calcium signalling in SMG cells as rats age is due to a decrease in P2Y1R coupling to G proteins or to a decrease in the expression of a cognate G protein. SMG cells were isolated from Sprague-Dawley rats. P2Y1R function was assessed by measuring 2-MeSADP-induced increases in [Ca2+]i and ERK1/2 activation. P2Y(1)R-mediated activation of G proteins was determined by the [35S]GTPgammaS binding assay. Gq protein expression was determined by RT-PCR, Northern, and Western analysis. In SMG cells from 1-week-old rats, two bands (52 and 42kDa) were detected using anti-Galpha14 antibody, whereas in SMG cells from 4- to 6-week-old rats only the 42 kDa band was detected. Furthermore, 2-MeSADP-induced GTPgamma35S binding to Galpha14 and Galphaq/11 decreases in SMG cells from 4- to 6-week-old rats as compared to 1-week-old rats. These findings suggest that the age-dependent decrease in P2Y1R-mediated intracellular calcium signalling in rat SMG cells is due to a loss of 52 kDa Galpha14 and indicate the differential coupling of the P2Y1R to Galpha14 and Galphaq/11 as the gland develops.

Staurosporine-inhibitable protein kinase activity associated with secretory granule membranes isolated from rat submandibular gland cells

Protein kinases, such as protein kinase C, have been shown to be associated with secretory granules and to regulate the event of exocytosis in various tissues including parotid salivary acinar cells. However, in submandibular acinar cells that play an important role in the secretion of proteins into the oral cavity, kinase activity on the granule membrane has not been explored. Therefore, in the present study, we isolated the secretory granules from rat submandibular acinar cells and investigated the localisation of protein kinases on the granule membrane. Initially, we isolated and purified secretory granules from rat submandibular acinar cells. Addition of [γ- 32 P ] ATP to granule-membrane lysate phosphorylated the granule-membrane-associated 26, 32, 55 and 58 kDa proteins, suggesting the presence of endogenous kinase activity on the membrane. Moreover, the phosphorylation of 26 and 32 kDa proteins was inhibited by staurosporine and K252a, both non-specific protein kinase C inhibitors. However, the phosphorylation of 26 and 32 kDa proteins was not inhibited by other protein kinase C inhibitors, such as calphostin C, GF109203X and chelerythrine, indicating that protein kinase C was not responsible for the phosphorylation. In addition, H-89, ML-9, KN-62 and genistein did not appear to inhibit this phosphorylation, indicating that protein kinase A, myosin light chain kinase (MLCK), Ca 2+/calmodulin-dependent protein kinase II (CAMKII) and tyrosine kinase were not involved in the phosphorylation of 26 and 32 kDa proteins. Moreover, Ca 2+ had no effect on the kinase activity. Therefore, our results suggest that an unidentified, staurosporine-inhibitable protein kinase activity is associated with the secretory granule membrane of rat submandibular acinar cells.

Apoptosis and proliferation of myoepithelial cells in atrophic rat submandibular glands.

This study was designed to determine whether apoptosis and proliferation of myoepithelial cells occur in atrophic rat submandibular glands. The excretory duct of the right submandibular gland was doubly ligated with metal clips. The atrophic right submandibular glands removed after 1-28 days of duct ligation were investigated using immunohistochemical double staining for actin as a marker for myoepithelial cells and proliferating cell nuclear antigen (PCNA) as a marker for proliferating cells, double staining for actin immunohistochemistry, nick end-labeling (TUNEL) as a marker for apoptotic cells, and transmission electron microscopy (TEM). A few PCNA- and no TUNEL-positive myoepithelial cells were found in the control submandibular glands taken from animals with no operation. In the experimental glands, PCNA-positive myoepithelial cells were common 2 and 3 days after duct ligation and then decreased in number. TUNEL-positive myoepithelial cells appeared at 2 days and were observed most frequently at 5 days. Apoptotic myoepithelial cells were also identified by TEM. These observations suggest that both apoptosis and proliferation of myoepithelial cells occur, especially in the early phase of atrophy, in the rat submandibular gland.

The transcriptional response to androgens of the rat VCSA1 gene is amplified by both binary and graded mechanisms.

In higher eukaryotes, gene expression can be highly modified in response to small variations of circulating hormonal inducers. To determine the mechanisms responsible for the 100- to 200-fold enhancement of expression of an androgen-regulated gene, VCSA1, in the acinar cells of rat submandibular glands during puberty, we performed a detailed analysis of VCSA1 expression at the single cell level. Using in situ detection of mature and primary VCSA1 transcripts, we show that VCSA1 expression is activated in only a small proportion of differentiated acinar cells in the presence of low levels of circulating androgens in prepubescent and in castrated males, as well as in females. During the time course of sexual maturation in males, we demonstrate an increase in the proportion of acinar cells expressing VCSA1 and an increase in VCSA1 heterogeneous nuclear RNA and mRNA content in the positive cell population. Finally, we show that changes in the methylation pattern of VCSA1 are correlated with VCSA1 transcriptional activation. These results demonstrate that androgens can, in physiological conditions, elicit both a binary and a graded response. They also provide evidence that the range of gene regulation may be expanded by a transcriptional repression in a majority of cells under basal conditions.

Apoptosis and mitosis of parenchymal cells in the duct-ligated rat submandibular gland

Apoptosis and proliferation of parenchymal cells during atrophy of rat submandibular glandinduced by double duct ligation were investigated using immunohistochemistry for proliferating cell nuclear antigen (PCNA), terminal deoxynucleotidyl transferase (TdT)-mediated dUTP-digoxigenin nick end labelling (TUNEL) and transmission electron microscopy (TEM). At 2 and 3 days after ligation, increased PCNA positive cells and mitoses were seen inducts; thereafter PCNA positive cells decreased in number. At 3 and 4 days, the acinar cell population rapidly decreased, with many remaining TUNEL positive acinar cells. During this period, TEM showed typical apoptotic acinar cells that were phagocytosed by adjacent acinar cells or intraepithelial macrophages. After 7 days, most acinar cells had disappeared, leaving prominent residual ducts; a few acinar cells remained, especially at the lobule periphery. Submandibular gland duct ligation thus induced marked depletion of acinar cell by apoptosis and a concurrent short-lived cycle of duct cell proliferation.

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.

Trp1, a Candidate Protein for the Store-operated Ca2+Influx Mechanism in Salivary Gland Cells

The trp gene family has been proposed to encode the store-operated Ca(2+) influx (SOC) channel(s). This study examines the role of Trp1 in the SOC mechanism of salivary gland cells. htrp1, htrp3, and Trp1 were detected in the human submandibular gland cell line (HSG). HSG cells stably transfected with htrp1alpha cDNA displayed (i) a higher level of Trp1, (ii) a 3-5-fold increase in SOC (thapsigargin-stimulated Ca(2+) influx), determined by [Ca(2+)](i) and Ca(2+)-activated K(+) channel current measurements, and (iii) similar basal Ca(2+) permeability, and inhibition of SOC by Gd(3+) but not by Zn(2+), as compared with control cells. Importantly, (i) transfection of HSG cells with antisense trp1alpha cDNA decreased endogenous Trp1 level and significantly attenuated SOC, and (ii) transfection of HSG cells with htrp3 cDNA did not increase SOC. These data demonstrate an association between Trp1 and SOC and strongly suggest that Trp1 is involved in this mechanism in HSG cells. Consistent with this suggestion, Trp1 was detected in the plasma membrane region, the proposed site of SOC, of acinar and ductal cells in intact rat submandibular glands. Based on these aggregate data, we propose Trp1 as a candidate protein for the SOC mechanism in salivary gland cells.

Polarized secretion of transgene products from salivary glands in vivo.

Previously (Kagami et al. Hum. Gene Ther. 1996;7:2177-2184) we have shown that salivary glands are able to secrete a transgene-encoded protein into serum as well as saliva. This result and other published data suggest that salivary glands may be a useful target site for vectors encoding therapeutic proteins for systemic delivery. The aim of the present study was to assess in vivo if transgene-encoded secretory proteins follow distinct, polarized sorting pathways as has been shown to occur "classically" in cell biological studies in vitro. Four first-generation, E1-, type 5 recombinant adenoviruses were used to deliver different transgenes to a rat submandibular cell line in vitro or to rat submandibular glands in vivo. Subsequently, the secretory distribution of the encoded proteins was determined. Luciferase, which has no signal peptide, served as a cell-associated, negative control and was used to correct for any nonspecific secretory protein release from cells. The three remaining transgene products tested, human tissue kallikrein (hK1), human growth hormone (hGH), and human alpha1-antitrypsin (halpha1AT), were predominantly secreted (>96%) in vitro. Most importantly, in vivo, after a parasympathomimetic secretory stimulus, both hK1 and hGH were secreted primarily in an exocrine manner into saliva. Conversely, halpha1AT was predominantly secreted into the bloodstream, i.e., in an endocrine manner. The aggregate results are consistent with the recognition of signals encoded within the transgenes that result in specific patterns of polarized protein secretion from rat submandibular gland cells in vivo.

Immunohistochemical study of fibroblast growth factor-2 (FGF-2) and fibroblast growth factor receptor (FGF-R) in experimental squamous cell carcinoma of rat submandibular gland.

Fibroblast growth factor-2 (FGF-2) is a member of the heparin-binding growth factor family and has mitogenic activity. Immunohistochemical expression of FGF-2 and its receptor (FGFR) was evaluated in experimentally induced squamous cell carcinoma as well as transforming cells of rat submandibular gland (SMG) induced by 9,10-dimethyl-1,2-benzanthracene (DMBA)/sponge implantation. Proliferating cells detected by proliferating cell nuclear antigen (PCNA) staining during carcinogenesis were also compared with FGF-2 and FGFR stainings. In the normal SMG, FGF-2 and FGFR were present in the excretory, striated and intercalated duct cells. Pillar and transition cells of granular convoluted tubule (GCT) showed FGF-2 staining, PCNA-labeled cells in normal SMG were rarely observed. In 2-3 weeks after carcinogen implantation, the reactions of FGF-2 and FGFR were expressed in epithelial islands, duct-like structures and affected ductal segments. PCNA-positive cells were developed in these epithelial structures. In 4-8 weeks after carcinogen implantation squamous epithelium appeared surrounding DMBA/sponge and gradually transforming with high PCNA labeling in the based cells and strong staining of FGF-2 and FGFR. Squamous cell carcinoma arose within about 12 weeks of the experiment. In squamous cell carcinoma, there was an intense immunohistochemical expression of FGF-2 and FGFR. Basal and parabasal layers of the squamous cell carcinoma showed high PCNA labeling. FGF-2-positive cells were found in the connective tissue stroma and in inflammatory cells around the proliferating duct-like structure. Coexpression of FGF-2 and FGFR was indicated in transforming cells during carcinogenic processes and in experimental squamous cell carcinoma of rat SMG. These findings suggested that FGF may play an important role for squamous metaplasia and carcinogenesis in rat SMG as an autocrine factor and FGF-positive stromal cells may also act to stimulate epithelial proliferation.