Analysis of food stimulation of gastrin release in dogs by a panel of inhibitors

Stress-induced changes in gastric emptying, postprandial motility, and plasma gut hormone levels in dogs

The influence of acoustic stress on postprandial gastrointestinal motility, gastric emptying, and plasma gastrin, pancreatic polypeptide, motilin, and somatostatin was evaluated in conscious dogs. Six dogs were equipped with strain-gauge transducers and were exposed from 1-3 h after the meal to prerecorded music (80-90 dB broad frequency noise), which produced a significant (p less than or equal to 0.05) lengthening of the gastric (31.2%) and jejunal (37.0%) postprandial pattern. In 4 other dogs with gastric cannula, a 2-h session of acoustic stress beginning just after eating a radiolabeled standard meal induced a slowing of gastric emptying of both liquid (45.7%) and solid (47.1%) phases of the test meal when measured 0.5 h after feeding. In contrast, when measured 2 h after feeding, similar values of gastric emptying of liquids and solids were observed in stressed and control animals. Compared with controls, the postprandial increases of plasma gastrin and pancreatic polypeptide levels were significantly enhanced in stressed animals and occurred early (15 min after the meal). Although postprandial decrease in plasma motilin was unchanged by acoustic stress, the rise in plasma somatostatin level was significantly (p less than or equal to 0.05) prolonged in stressed dogs. These results indicate that acoustic stress affects gastric and intestinal postprandial motility in dogs, delaying the recovery of the migrating motor complex pattern, inducing a transient slowing of gastric emptying, and enhancing the feeding-induced release of gastrin, pancreatic polypeptide, and somatostatin. Such hormonal changes might be due to a direct effect of stress rather than being the consequence of acoustic stress-induced slowing of gastric emptying.

Amine trapping: physical explanation for the inhibitory effect of gastric acidity on the postprandial release of gastrin. Studies on rats and dogs

We investigated the relationship between the pH dependence of meal-stimulated gastrin release and the permeability of the antral mucosa to dietary amines. This study was undertaken after previous work from our laboratory had demonstrated that dietary amines are potent in vivo and in vitro stimulants of gastrin release and that it is well established that amines are trapped in acidic environments. Three contrasting experimental model systems were employed to investigate the association of these two pH-dependent properties. In the first in vivo study, it was demonstrated that ingestion of standard rat Chow resulted in an increase in circulating gastrin and ammonia levels, whereas the postprandial increases in both properties were abolished if the rats ingested Chow that was preacidified to a pH of 2.4. Second, the antral uptake of the fluorescent cyclic amine, quinacrine, from the gastric lumen of pylorus-ligated rats was monitored by fluorescent microscopy and spectrophotometry and was demonstrated to be inhibited in a step-wise fashion as the luminal pH was decreased. Lastly, our in vitro studies suggested that the transport of [14C]methylamine into canine antral mucosa mounted in Ussing chambers was pH-dependent, as was gastrin release into the incubation medium. Thus, all the data are consistent with the possibility that meal-stimulated gastrin release is inhibited at low pH, due (in part) to the protonation of dietary amines, preventing their diffusion into the G cell to activate hormone secretion.

Effect of 11R, 16, 16-trimethyl prostaglandin E2 on meal-stimulated gastric acid secretion in duodenal ulcer subjects

The effect of varying oral doses of 11R, 16, 16-trimethyl prostaglandin E2 (TmPGE2) on meal-stimulated gastric acid secretion and serum gastrin concentrations was studied in 10 male subjects with asymptomatic duodenal ulcer disease. A liquid protein meal was infused intragastrically 0.5 h and 3.5 h after drug administration. TmPGE2 inhibited gastric acid secretion in a dose dependent manner during the first meal and no significant effect was observed during the second meal. Except for the highest dose, no TmPGE2 was detected in plasma 3 h after drug administration. The degree of inhibition of meal-stimulated gastric acid was positively correlated with the plasma level of TmPGE2, but it was not due to inhibition of postprandial gastrin release. The results indicate that oral TmPGE2 inhibits meal-stimulated gastric acid secretion but not gastrin release in humans with asymptomatic duodenal ulcer disease.

Somatostatin, prostaglandin E2 and atropine inhibition of the gastric actions of bombesin in the dog

Bombesin, acetylcholine, prostaglandins and somatostatin are all thought to be involved in the regulation of gastrin release and gastric secretion. We have studied the effects of low doses of atropine, 16-16(Me)2-prostaglandin E2 (PGE2) and somatostatin-14 on bombesin-stimulated gastrin release and gastric acid and pepsin secretion in conscious fistula dogs. For reference, synthetic gastrin G-17 was studied with and without somatostatin. Bombesin, in a dose-related manner, increased serum gastrin, which in turn stimulated gastric acid and pepsin secretion in a serum gastrin, concentration-dependent manner. Somatostatin inhibited gastrin release by bombesin as well as the secretory stimulation by G-17; the combination of sequential effects resulted in a marked inhibition of bombesin-stimulated gastric acid and pepsin secretion. PGE2 also strongly inhibited gastrin release and acid and pepsin secretion. Atropine had no significant effect on gastrin release, but greatly inhibited gastric secretion. Thus somatostatin and PGE2 inhibited at two sites, gastrin release and gastrin effects, while atropine affected only the latter.