Stimulating effect of bombesin on the growth of gastrointestinal tract and pancreas in suckling rats.

The current study examines the effects of bombesin on gastrointestinal and pancreatic growth in suckling rats. During a period of 6 days, 7-day-old rats were injected twice daily with bombesin tetradecapeptide (20 micrograms/kg) in hydrolyzed gelatin or with gelatin alone. At the end of bombesin treatment, the weights of stomach, intestine, and pancreas; the heights of fundic and antral mucosae; and the density of parietal cells were significantly increased over control values. The gastrin cell population also tended to be augmented. The surface of glandular stomach, the duodenal mucosal height, and the somatostatin cell population were not modified as compared to controls. Electron morphometric analysis indicates that the increase in pancreatic weight under bombesin treatment was partly due to hypertrophy of acinar cells. This was confirmed by biochemical data that also showed that hypertrophy was associated with hyperplasia. Storage of secretory granules in acinar cells of the neonate rat pancreas under bombesin treatment seemed probable. Chymotrypsinogen and trypsinogen pancreatic contents were greatly augmented; lipase and colipase contents were not affected, whereas the amylase content tended to decrease. All these findings suggest that bombesin might be a general trophic factor for the neonatal digestive system in the rat. The mechanism of its action, however, remains to be determined.