Evidence for an intestinal mechanism of pancreatic polypeptide release

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Abstract
The purpose of this study was to define the existence of an intestinal phase of pancreatic polypeptide (PP) release and to assess whether it was mediated by a cholinergic-sensitive mechanism. Four conscious dogs with 20-cm upper intestinal Thiry-Vella loops and chronic gastric fistulas were used. The Thiry-Vella (T-V) loops were perfused with 10% liver extract or 0.154 M NaCl at a rate of 1 ml/min for 120 min. In a separate experiment, 240 ml of 10% liver extract was infused over a 5-min period into the stomach via the gastric fistula. Basal PP levels were 29±4 fmol/ml. The gastric infusion of liver extract caused a significant increase of plasma PP levels to a peak of 215±29 fmol/ml (PPP0.05). PP release by perfusion of the T-V loop with liver extract was abolished by atropine intravenous bolus (0.2 mg/kg). Although the combination of bethanechol (100 μg/kg/hr intravenous) and liver extract consistently increased the plasma levels of PP, the values did not attain statistical significance when compared to liver extract alone (P>0.05). The data presented are thus consistent with the hypothesis that there is an enteric phase of pancreatic polypeptide release and that this enteropancreatic reflex is mediated by a cholinergic-sensitive mechanism which might be hormonal or neural.