Is avian pancreatic polypeptide (APP) trophic for tissues of the embryonic chick gut?

Avian pancreatic polypeptide (APR) has been shown to be a gastric (proventricular) secretagogue in adult chickens. In mammals, gastrin (in the form of Pentagastrin) is a trophic hormone for tissues of the gut in addition to being the hormone regulating gastric secretion. The purpose of this study was to determine, using ablation of the ARP secretory source and precocious administration of APR to developing embryos, if APP is also trophic for gut tissues in addition to stimulating gastric secretion. The results of this study indicate that in the absence of APP there is a "wasting" response in the adult proventriculus mucosa. Injection of APP into two week old embryos caused an increase in proventricular total protein within two days, similar to the effect seen with Pentagastrin injected at this time. Within one hour of APP injection, radiolabeled amino acid incorporation into protein in vitro by the proventriculus was stimulated, and at higher doses the same effect seen in the liver. The evidence presented suggests that APP exerts a trophic action on the embryonic proventriculus (secretory stomach), and possibly on the liver at higher doses.