Subject(s)
Ceruletide/pharmacology , Pancreas/drug effects , Animals , Dogs , Dose-Response Relationship, Drug , Female , Humans , Pancreas/physiology , Pancreatic Juice/metabolism , RatsABSTRACT
The present experiments have been carried out in order to establish whether the stimulatory effect of bombesin on the chicken gastric acid secretion is a direct effect or is mediated by the release of hormones, such as the Avian Pancreatic Petide and/or Gastrin. removal of the pancreas, which is known to be the site of starage of the Avian Pancreatic Polypeptide, does not produce any decrease of the stimulant effect of bombesin on gastric secretion. Removal of the zone between the gizzard and duodenum, which shows histological features similar to those of the mammalian antrum and in which gastrin cells have been described, sharply decreases the basal values of gastric secretion as well as the stimulant effect of bombesin, while the effectiveness of caerulein, a gastrin-like peptide directly acting on oxintopeptic cells, is maintained. In chickens deprived of the duodenum-gizzard zone, bombesin shows a stimulant effect on pancreatic secretion indistinguishable from that observed in intact animals. It is concluded that the gastric but not pancreatic, action of bomtesin is mediated through the release of a factor(gastrin) from the gizzard-duodenum junction. Release of Avian Pancreatic Polypeptide from the pancreas is not involved in the mechanism of the action of bombesin on gastric secretion of the chicken.
Subject(s)
Bombesin/pharmacology , Gastric Juice/metabolism , Pancreas/metabolism , Peptides/pharmacology , Animals , Ceruletide/pharmacology , Chickens , Duodenum/physiology , Gizzard, Avian/physiology , Pancreas/drug effects , Pancreas/physiology , Time FactorsABSTRACT
Bombesin strongly stimulated the chicken pancreatic secretion. When given by i.v. infusion, the threshold dose was of the order of 7.5-45.0 ng/kg/min and maximum enzyme output was obtained at a rate of 60 ng/kg/min. In addition to total enzyme output, enzyme concentration was also increased. Caerulein displayed a more potent stimulant effect, but composition of juice produced by the two polypeptides was similar. Tachyphylaxis occurred only with bombesin. Neither atropine nor gastric acidification affected the response to bombesin. Bombesin was totally ineffective in promoting gall bladder emptying. It is suggested that in the chicken, bombesin acts on the exocrine pancreas indirectly through release of an endogenous pancreozymin possibly devoid of cholecystokinetic activity.
