Direct vs. indirect effects of bombesin on pancreatic growth

Bombesin and its mammalian analogue gastrin-releasing peptide (GRP) have been reported to stimulate pancreatic growth. Whether this stimulatory effect is mediated through the release of regulatory peptides, in particular CCK, remains controversial. Since CCK is the most potent stimulant of pancreatic growth, it is a potential mediator of bombesin-induced pancreatic growth. On the other hand, there is evidence from in vitro studies, supporting a direct interaction of bombesin with receptors on acinar cells. A number of studies using potent and selective CCK antagonists have revealed controversial results. This may in part be due to considerable differences in their design and methods. The recent development of potent bombesin antagonists provides an important tool to further characterize the mechanism of bombesin-induced pancreatic growth and to determine the physiologic importance of bombesin.