Abstract

ORF 17583, a histamine H2-receptor antagonist, inhibited gastric acid secretion in pylorus-ligated rats (ED50 = 4.9 mg/kg intraduodenal; 3.4 mg/kg p.o.; and 0.21 mg/kg i.p.) and in total gastric fistula or Heidenhain pouch dogs stimulated by betazole (ED50 = 0.12 mg/kg p.o. and 0.08 mg/kg i.v.), histamine, tetragastrin, bethanechol, 2-deoxy-D-glucose or a meal (ED50 values ranged from 0.11-0.26 mg/kg p.o.). The nonspecific inhibition of gastric acid by ORF 17583 supports the existence of interdependence between histamine and the gastrin and cholinergic receptors on the parietal cell surface. Antisecretory potency of ORF 17583 after intraduodenal administration in pylorus-ligated rats was 6.4 times greater than cimetidine, 1.8 times greater than ranitidine, equal to that of omeprazole and 8 times less than that of famotidine. Oral antisecretory potency of ORF 17583 in gastric fistula dogs was 31 times greater than cimetidine, 3.7 times greater than ranitidine and equal to that of omeprazole and famotidine. Studies using equieffective antisecretory doses of ORF 17583 and ranitidine in dogs suggested that ORF 17583 has a short duration of antisecretory activity similar to that of ranitidine.