Gastric mucosal protection by sucralfate involves phosphoinositides participation

Antisecretory and gastroprotective effects of aescine in rats

1. This study was designed to determine the antisecretory effects of aescine in the perfused stomach of the anaesthetized rat. In addition, the effects of aescine on mucosal lesions produced by intragastric instillation of 1 ml of absolute ethanol, its action on the production of mucus and the possible role of PGs in aescine induced gastroprotection were also studied. 2. Pretreatment of aescine (10 and 50 mg/kg) inhibited the increases in acid secretion induced by histamine (5 mg/kg) and carbachol (10 micrograms/kg). At the highest dose used abolished nearly the increase induced by carbachol (P < 0.001). 3. Aescine (10, 25 and 50 mg/kg) was found to be effective in the prevention of gastric ulceration induced by absolute ethanol in rats. The degree of gastroprotection decreased with time, the optime effects occurring 60-120 min after oral administration. Pretreatment with indomethacin (10 mg/kg) partially inhibited the gastric protection but the PGE2 determination did not show an increase in prostanoid levels. Furthermore, the protective effect was not associated with an increase in the amount of gastric mucus and glycoprotein content. 4. These results indicate that aescine exerts an antisecretory action which could play a possible role in its antiulcerogentic activity. Also it shows a marked protective mucosal activity which could be partly explained through non-prostaglandin dependent mechanisms involving its antiinflammatory and vasoactive properties.

Effect of sucralfate on gastric mucosal calcium channels activity

1. The effect of anti-ulcer agent, sucralfate, on the activity of the gastric mucosal calcium channel was investigated using calcium channels purified from rat gastric epithelial cell membranes. 2. The channels on reconstitution into phosphatidylcholine vesicles responded in a concentration-dependent manner to a calcium channel activator, BAY K8644, as well as to a calcium channel antagonist, PN200-110. The 45Ca2+ uptake was inhibited by sucralfate. Maximum inhibitory effect was attained at 100 micrograms/ml sucralfate, at which point a 52% decrease in the uptake occurred. 3. EGF-induced channel protein phosphorylation showed 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 sucralfate. Furthermore, sucralfate also interfered with the binding of EGF to calcium channel protein. 4. The results indicate that sucralfate protects the cellular integrity from calcium imbalance by modulating the EGF-stimulated gastric mucosal calcium channel phosphorylation.

Enhancement of gastric mucosal epidermal growth factor and platelet-derived growth factor receptor expression by sucralfate

1. The effect of an anti-ulcer agent, sucralfate, on the expression of gastric mucosal epidermal growth factor (EGF) and platelet derived growth factor (PDGF) receptors was investigated. 2. Gastric mucosal cell membranes, isolated from the stomach of groups of rats, one receiving twice daily for 3 consecutive days a dose of 100 mg/kg sucralfate, and the other only the vehicle, were used as source for EGF and PDGF receptors. 3. Binding assays revealed the presence of both types of receptors, activation of which led to the elevation of tyrosine kinase activity as evidenced by a marked increase in membrane protein tyrosine phosphorylation patterns. 4. The specific receptor binding in the control group was 2.46 fmol/mg protein for EGF and 1.46 fmol/mg protein for PDGF, whereas the respective binding values in the sucralfate treated group increased by 61 and 65%. 5. The results suggest that sucralfate is capable of enhancement of epithelial proliferative activities through the stimulation of gastric mucosal EGF and PDGF receptors.

Mechanism of ebrotidine protection against gastric mucosal injury induced by ethanol

1. The gastroprotective properties of a new H2-receptor antagonist, ebrotidine, against ethanol-induced mucosal injury was investigated. 2. Groups of rats, with and without indomethacin pretreatment, received intragastrically either a dose of ebrotidine or vehicle only, followed by ethanol given at various intervals up to 4 hr. The gastric mucosa, 30 min after the ethanol challenge, was then subjected to macroscopic and histologic examination, and physicochemical measurements. 3. Ebrotidine at doses of 50 mg and higher per kg body wt effectively prevented the alcohol-induced mucosal injury, even in the presence of indomethacin. The protective effect was demonstrable already at 30 min, reached maximum at 1 hr, and persisted up to 3 hr. 4. Physicochemical analyses established that ebrotidine elicited 30% increase in mucus gel dimension, caused 19-20% increase in glycolipids and phospholipids, and evoked 21% increase in sulfomucin and 18% in sialomucins. As a consequence, the mucus gel viscosity increased by 1.4-fold, H+ retardation capacity by 16%, and hydrophobicity by 65%. 5. The results demonstrate that ebrotidine is a unique H2-antagonist endowed with a remarkable mucosal strengthening capability.