Abstract
Abstract
Fasting and refeeding studies were carried out in young normal chickens (6-8 weeks old) in an effort to establish a correlation between movement of the digesta through the alimentary tract and perturbations in plasma insulin (IRI) and pancreatic polypeptide (APP) levels. In some experiments the gut was blocked by an exteriorized ligature to prevent movement of the digesta past that locus. Six different gut sites were selected for these refeed-blockade experiments. Progressive fasting of chicks for 24-96 hr decreased basal plasma APP levels to values 27.8-40.2% below fed control levels, was without effect on glucose levels, and either was without effect or slightly elevated basal IRI levels (96 hr only). Refeeding for 10 min after varying periods of fasting led to a rapid tripling of APP levels, little or no change in plasma glucose, and slight increases in IRI levels (except in the 96-hr fasted group). Chicks fasted 24 hr and then allowed to eat ad libitum up to 90 min were analyzed for plasma glucose, APP, IRI, and the gut examined for the distance of digesta movement through the GI tract. Measurements were made at seven times between 5 and 90 min postprandial. APP levels tripled before the first (5 min) sample; at this time the digesta had already passed through the duodenum and entered the ileum. A second “burst” of APP release appeared to occur at later times as the food particles traversed the small intestine. Insulin levels peaked at 10 min, a time at which the digesta reached the upper one-third of the ileum and plasma glucose rose to equal the prefast control level (215 mg/dl). Studies with ligature-blockades at different gut sites indicated that crop distention alone probably was responsible for the initial, rapid release of APP to the plasma.
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