Pancreatic polypeptide and intestinal motility in dogs

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Abstract
This study was designed to determine the potential role of endogenous PP in the control of intestinal motility by correlating plasma PP levels with motility patterns in fasted and fed dogs without and with administration of exogenous PP and rabbit PP antiserum. After an overnight fast, when the interdigestive myoelectric activity was recorded in each dog, mean basal PP at phase I averaged 35±7 pM with peaks of 52±5 pM coinciding with phase III (MMC) in duodenum. Postprandial rise in PP reached the peak level of 280±70 pM at the end of 1 hr after a meal when MMC was interrupted and replaced by fed-type motility pattern. Exogenous PP in a dose of 100 pmol/kg/hr infused when the phase III of the MMC passed mid-jejunum raised plasma PP to the level of 130±27 pM but failed to affect the spike activity or MMC periodicity. PP given in doses of 200 and 400 pmol/kg/hr, which raised plasma PP to 298±25 and 453±24 pM, respectively, increased dose dependently (but did not abolish) the MMC intervals and an overall spike activity due to the prolongation of phase II of the MMC. After termination of PP infusion, phase III-like activity appeared within 7–10 min. Injection of highly specific PP antiserum, which caused almost complete disappearance of plasma PP both in fasted and fed dogs, did not affect the MMC interval but increased spike activity in fasted animals and failed to affect significantly spike activity in fed animals. We conclude that PP does not play any role in fasted intestinal motility but may contribute, at least in part, to the postprandial suppression of MMC.