The localization of the site of gut activation of the avian pancreatic polypeptide (APP) refeeding response in chickens

In the present study the avian pancreatic polypeptide (APP) response to refeeding after a fast was investigated In chickens. Plasma glucose, immunoreactive insulin (IRI) and APP levels were measured in young chickens after a 24-hour fast and at multiple intervals after they had begun ad libitum feeding. Examination of the gut of chickens killed at intervals after the start of refeeding, revealed the progression of ingested food with time. Measurements of fasted and refed (10 and 60 min postprandial) glucose, IRI and APP levels also were made after longer fasts (48, 72 and 96 hours). In other experiments, fasted chickens were refed after tightening previously placed (48 hour) loose ligatures at six different loci within the digestive tract. Plasma responses in glucose, IRI and APP were determined by comparing values 60 min following refeeding with those of fasted values. Acute experiments were performed on Isolated gut sacs prepared from gut sites which previously produced a response to refeedlng (with ligatures tied). Sacs were loaded with either saline or "donor digesta" from another bird similarly fasted (48 hr) then refed before killing. [...]