T. Shimada

Effect of adenosine and adenosine analogs on [14C]aminopyrine accumulation by rabbit parietal cells.

Adenosine receptors that modulate adenylate cyclase activity have been identified recently in a number of tissues. Adenosine A2 receptor is stimulatory to adenylate cyclase, whereas adenosine A1 receptor is inhibitory to adenylate cyclase. We investigated the effect of adenosine and its analogs on [14C]aminopyrine accumulation by rabbit parietal cells. Rabbit gastric mucosal cells were isolated by enzyme digestion. Parietal cells were enriched by nonlinear percoll gradients. [14C]Aminopyrine accumulation was used as an indicator of acid secretion. The effect of 2-chloroadenosine on histamine-stimulated [14C]aminopyrine accumulation was studied. The effects ofN-ethylcarboxamideadenosine, 2-chloroadenosine, stable analogs of adenosine, and adenosine on [14C]aminopyrine accumulation were assessed. Cyclic AMP content of parietal cells was determined by radioimmunoassay. Histamine and carbachol, known secretagogues, stimulated [14C]aminopyrine accumulation. 2-Chloroadenosine did not suppress histaminestimulated [14C]aminopyrine accumulation. 2-Chloroadenosine,N-ethylcarboxamideadenosine, and adenosine dose dependently increased [14C]aminopyrine accumulation. The order of potency wasN-ethylcarboxamideadenosine > 2-chloroadenosine > adenosine. 8-Phenyltheophylline and theophylline, adenosine-receptor antagonists, or cimetidine did not have significant effects on the increase of AP uptake induced by 2-chloroadenosine. Coadministration of dipyridamole, an adenosine uptake inhibitor, augmented the effect of adenosine on [14C]aminopyrine accumulation. 2-Chloroadenosine,N-ethylcarboxamideadenosine, and adenosine each induced a significant increase in cellular cyclic AMP. We conclude that there may be adenosine A2 receptors on rabbit parietal cells which modulate gastric acid secretion.

Characterization of a newly established cell line (JR-St) derived from human gastric signet ring cell cancer, producing tumor markers.

SummaryDespite the importance of in vitro study of gastric cancer, there are very few established cell lines derived from human gastric carcinoma. We have recently established a new cell line derived from human gastric cancer which has the ability to produce tumor markers. This cell line has been designated JR-St. This cell line was derived from the cerebrospinal fluid of a 37-yr-old female patient who had metastatic brain tumor of signet ring cell gastric adenocarcinoma. This cell line has been maintained for more than 24 months through 80 passages with stable growth. PAS staining showed intracellular mucin granules. Transmission and scanning electron microscopy revealed cells with numerous microvilli and fine projections as well as intracellular granules, indicating mucin. This cell line had the ability to produce high concentrations of tumor markers such as carcinoembryonic antigen (CEA) and carbohydrate antigen (CA) 19-9. Thus this cell line should provide a very useful tool for the investigation of gastric cancer such as analysis of tumor markers as well as effects of anti-cancer drugs or growth factors.

Role of iron and lipid peroxidation in mediating peroxynitrite-induced toxicity to cultured gastric mucosal cells

that endoscopically negative patients with GER-related symptoms may have enhanced protective mechanisms. Aims: 1. To assess bicarbonate, non-bicarbonate, protein, transforming growth factor ct (TGFtx) and prostaglandin E 2 (PGE2) in salivary secretion in patients with endoscopically negative [E(-)] GERD. 2. To compare the obtained results with corresponding values in asymptomatic controls (C) and patients with RE~ Subjects & Methods: The study was conducted in 30 patients with RE (12F & 18M, mean age of 49), in 39 asymptomatic volunteers (16F & 23M, mean age of 40), and in 10 patients with E(-) GERD (SF & 5M, mean age of 40). Salivary secretions were collected under basal conditions, daring mastication, and during intraesophageal mechanical and chemical stimulation, mimicking the GER scenario, using an esophageal perfusion catheter. Salivary bicarbonate and non-bicarbonate were measured using Titra-Lab (Radiometer America, IL). Salivary protein was quantitated using Lowry method, whereas TGFot, and PGE z by RIA (Amersham, IL and Biomed. Technol. Inc. MA). Statistical analysis was implemented by E-Stat (Jandel Sci. CA) software. Results: Salivary bicarbonate in patients with E(-) GERD was significantly higher than in C and in RE during intraesophageal chemical stimulation (P < 0.05). Salivary protein was significantly higher in GERD E(-) than in and RE during intraesophageai mechanical and chemical stimulation (P < 0.05). Salivary TGFot output in GERD E(-) was significantly higher than in RE (P < 0.05) but not controls during intraesophageal mechanical stimulation. Salivary PGE z output, on the other hand, in GERD E(-) was significantly higher than in C (P < 0.05) but not RE during intraesophageal chemical stimulation. Conclusion: . A strong salivary secretory response to intraesophageal mechanical and chemical stimuli in patients with GERD E(-) in terms of bicarbonate, protein, TGFa, and PGE z seem to mediate resistance to the development of endoscopic mucosal changes by GER. ° This could explain t he lack of endoscopic esophagitis in the majority of GERD patients and could be a therapeutic target in future treatment strategies.

Polaprezinc protects gastric mucosal cells from noxious agents through anti-oxidant properties in vitro

BACKGROUND Polaprezinc has been shown to exert an anti-oxidant property in a tube experiment, protect gastric mucosa from experimental ulcerations in vivo, and accelerate the healing of gastric ulcer in humans. AIM To examine a possible protective effect of polaprezinc on oxidant-mediated injury in primary monolayer cultures of rat gastric fundic mucosa. METHODS Cytotoxicity was quantified by measuring 51Cr release. Whether or not polaprezinc exerts an antioxidant property was investigated by determining the effect of this agent on hydrogen peroxide (H2O2)-induced injury. The effects of polaprezinc on superoxide (O2-. ) generation as well as on ethanol (EtOH)-induced injury were also examined. Generation of O2-. was assessed by the reduction in cytochrome c. RESULTS H2O2 caused a time- and dose-dependent increase in 51Cr release. The dose-response curve of 51Cr release by H2O2 shifted to the right in the presence of polaprezinc. Polaprezinc, at submillimolar concentrations, prevented H2O2-induced 51Cr release. EtOH also caused a dose-dependent increase in 51Cr release, which was prevented by the addition of polaprezinc. The incubation of cells with EtOH caused an increase in cytochrome c reduction, as the concentrations of EtOH increased. Polaprezinc inhibited EtOH-induced cytochrome c reduction. Protection by polaprezinc was microscopically associated with the prevention of monolayer disruption. CONCLUSIONS Polaprezinc is antioxidative and directly protects gastric mucosal cells from noxious agents through its antioxidant properties in vitro. This finding may provide the theoretical basis for the usage of an antiulcer drug with antioxidant properties for the treatment of gastric inflammation, such as that induced by ethanol.

Keratinocyte growth factor is an endogenous stimulant of rabbit gastric epithelial cell proliferation and migration in primary culture

Mesenchymal-epithelial interactions are important in the gastric mucosal repair. However, specific factors responsible for such interactions have not been established. In the present study, keratinocyte growth factor (KGF) significantly stimulated proliferation of gastric epithelial cells dose dependently and synergistically with hepatocyte growth factor (HGF), epidermal growth factor (EGF) and insulin. Restitution of gastric epithelial monolayers was also assessed, using a round wound restitution model. Keratinocyte growth factor facilitated the restitution of gastric epithelial cells significantly but did not have any effects on gastric fibroblasts. Keratinocyte growth factor receptor mRNA was expressed by gastric epithelial cells, indicating that these effects were elicited by the specific receptor mediated pathway. Northern blot analysis revealed the expression of KGF mRNA in gastric fibroblasts but not in gastric epithelial cells, indicating the production of KGF. These results suggest that KGF might be involved in gastric mucosal repair, through mesenchymal-epithelial interaction.