Abstract
Antisecretory effects of ranitidine on secretagogue-stimulated gastric secretion in acute fistula rats were studied. Histamine 2HCl (8mg/kg/hr), pentagastrin (125μg/kg/hr) or carbachol (128μg/kg/hr) was continuously given i. v. by an infusion pump, through the tail vein to acute fistula rats. Gastric secretion was collected hourly for 5hr and analyzed for its components. Cimetidine was used as a reference drug. Both drugs were given ix. by a bolus injection in the tail vein 30min after the injection of each stimulant. Both ranitidine (1 and 10mg/kg) and cimetidine (10 and 60mg/kg) significantly (P<0.05) inhibited the histamine-stimulated gastric secretion (volume, acid and pepsin output) for 1 to 4hr. Both ranitidine (10mg/kg) and cimetidine (60mg/kg) significantly (P<0.05) inhibited the pentagastrin-stimulated gastric secretion for 2 to 3hr. Both ranitidine (10mg/kg) and cimetidine (10 and 60mg/kg) markedly inhibited the gastric acid secretion in response to carbachol. However, cimetidine (10 or 60mg/kg) significantly (P<0.05) stimulated the volume and pepsin output by carbachol. We conclude that ranitidine is about 6 times more potent than cimetidine for histamineor pentagastrin-stimulated gastric secretion and almost equal to cimetidine for carbachol-stimulated gastric acid output in rats.
