epidermal-growth-factor and ebrotidine

Ebrotidine is a new H2-receptor antagonist also known for its gastroprotective effect against ethanol-induced mucosal injury. In this study, we investigated the effect of ebrotidine on the activity of the gastric mucosal calcium channels. The channel complex was isolated from the solubilized gastric epithelial cell membranes by affinity chromatography on wheat germ agglutinin. The complex following labeling with [3H] PN200-110 was reconstituted into phosphatidylcholine vesicles which exhibited active 45Ca2+ uptake into intravesicular space and responded in a concentration-dependent manner to calcium channel activator, BAY K8644, as well as to calcium channel antagonist, PN200-100. The 45Ca2+ uptake was inhibited by ebrotidine which caused maximum inhibitory effect of 54.9% at 50 micrograms/ml. The gastric mucosal calcium channels on epidermal growth factor binding (EGF) in the presence of ATP responded by an increase in tyrosine phosphorylation of 55 and 170 kDa proteins, and the vesicles containing the phosphorylated channels displayed a 48% greater 45Ca2+ uptake. This phosphorylation process was inhibited by ebrotidine which also interfered with the binding of EGF to calcium channel protein. The results point towards the importance of EGF in the maintenance of gastric mucosal calcium homeostasis, and suggest that ebrotidine has the ability to protect the cellular integrity from calcium imbalance by modulating the EGF-stimulated gastic mucosal calcium channel phosphorylation.

Topics: 3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; Animals; Anti-Ulcer Agents; Benzenesulfonates; Calcium; Calcium Channels; Calcium Radioisotopes; Epidermal Growth Factor; Gastric Mucosa; Histamine H2 Antagonists; Isradipine; Liposomes; Male; Membranes; Phosphorylation; Rats; Rats, Sprague-Dawley; Thiazoles

Ebrotidine is a new H2-receptor antagonist also known for its gastroprotective effect against ethanol-induced mucosal injury. In this study, we investigated the effect of ebrotidine on the activity of the gastric mucosal calcium channels. The channel complex was isolated from the solubilized gastric epithelial cell membranes by affinity chromatography on wheat germ agglutinin. After being labeled with [3H]PN200-110, the complex was reconstituted into phosphatidylcholine vesicles which exhibited active 45Ca2+ uptake into intravesicular space and responded in a concentration-dependent manner to calcium channel activator, BAY K8644, as well as to calcium channel antagonist, PN200-110. The 45Ca2+ uptake was inhibited by ebrotidine. Maximum inhibitory effect was attained at 50 micrograms/ml ebrotidine, at which point a 54.9% decrease in uptake occurred. The gastric mucosal calcium channels, on epidermal growth factor binding (EGF) in the presence of ATP, responded by an increase in tyrosine phosphorylation of 55 and 170 kDa proteins, and the vesicles containing the phosphorylated channels displayed a 48% greater 45Ca2+ uptake. This phosphorylation process was inhibited by ebrotidine. Furthermore, ebrotidine also interfered with the binding of EGF to calcium channel protein. The results point toward the importance of EGF in the maintenance of gastric mucosal calcium homeostasis, and suggest that ebrotidine has the ability to protect the cellular integrity from calcium imbalance by modulating the EGF-stimulated gastric mucosal calcium channel phosphorylation.

Topics: Animals; Benzenesulfonates; Calcium; Calcium Channels; Chromatography, Affinity; Epidermal Growth Factor; Gastric Mucosa; Histamine H2 Antagonists; Male; Rats; Rats, Sprague-Dawley; Thiazoles

The effect of ebrotidine, a new H2-blocker with gastroprotective properties, on the expression of gastric mucosal epidermal growth factor (EGF) and platelet-derived growth factor (PDGF) receptors, was investigated. Mucosal cell membranes were isolated from rats receiving twice daily for 5 days a dose of 100mg/kg ebrotidine or 100mg/kg ranitidine or vehicle only. Assays for EGF and PDGF revealed the presence of both types of receptors, activation of which led to enhanced tyrosine kinase activity. The receptor binding values in the control group were 2.4 fmol for EGF and 1.45 fmol/mg protein for PDGF, whereas the values in the ebrotidine group increased for EGF by 65.7% and 38.6% for PDGF, but no such effect was observed with ranitidine. The results suggest that the gastroprotective properties of ebrotidine stem from its ability to stimulate the epithelial proliferative activities through the enhancement of EGF and PDGF receptors expression.

Topics: Animals; Benzenesulfonates; Cell Membrane; Epidermal Growth Factor; ErbB Receptors; Gastric Mucosa; Histamine H2 Antagonists; Phosphorylation; Platelet-Derived Growth Factor; Ranitidine; Rats; Receptors, Platelet-Derived Growth Factor; Thiazoles; Tyrosine

A gastric mucosal calcium channel-epidermal growth factor (EGF) receptor complex was isolated from solubilized epithelial cell membranes by means of a wheat germ agglutinin affinity. The complex, following reconstitution into phosphatidylcholine vesicles, exhibited active 45Ca2+ uptake as evidence by concentration-dependent response to the calcium channel activator BAY K8644, and the calcium channel antagonist PN200-110. The complex on the addition of EGF and ATP showed an increase in tyrosine phosphorylation of both a 55 and a 170kDa protein, while the vesicles containing the phosphorylated complex displayed a 48% greater 45Ca2+ uptake. The phosphorylation process was inhibited by an anti-ulcer agent, ebrotidine, which also interfered with the binding of EGF to calcium channel protein. The results suggest that ebrotidine protects the cellular integrity from calcium imbalance by modulating the EGF-stimulated gastric mucosal calcium channel activation.

Topics: 3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; Animals; Anti-Ulcer Agents; Benzenesulfonates; Calcium Channels; Calcium Radioisotopes; Epidermal Growth Factor; Gastric Mucosa; Isradipine; Phosphorylation; Phosphotyrosine; Rats; Thiazoles; Tyrosine

Ebrotidine is a novel H2-receptor antagonist that exhibits both gastroprotective and ulcer-healing properties. Gastroprotection afforded by ebrotidine against ethanol damage was observed only after intragastric, but not parenteral administration, and it was accompanied by an increase in the mucosal blood flow. Ranitidine given at the same dose (100 mg/kg i.g. or s.c.) did not show any protective activity. When administered twice daily at various doses (1-100 mg/kg) for 10 days, ebrotidine reduced dose dependently the area of chronic gastric ulcers, and it was accompanied by significantly higher contents of epidermal growth factor (EGF) in the ulcer bed than in the intact mucosa. Administration of ranitidine resulted in a similar rate of ulcer healing and in a similar accumulation of EGF in the ulcer area to that observed after ebrotidine, but the increments in plasma gastrin levels in rats treated with ranitidine were observed at lower doses than in tests with ebrotidine. Concurrent administration of indomethacin delayed ulcer healing and reduced the accumulation of EGF in the ulcer area, but did not affect the ulcer healing by ebrotidine or ranitidine. We conclude that ebrotidine but not ranitidine shows gastroprotective activity, but it enhances the healing of chronic ulcerations in a similar manner to ranitidine.

Topics: Acetates; Acetic Acid; Animals; Benzenesulfonates; Epidermal Growth Factor; Ethanol; Gastric Acid; Gastric Mucosa; Gastrins; Histamine H2 Antagonists; Male; Ranitidine; Rats; Rats, Inbred Strains; Regional Blood Flow; Stomach Ulcer; Thiazoles