Action of Pancreatic Polypeptide on Exocrine Pancreas and on Release of Cholecystokinin and Secretin*

Abstract

We have studied the effect of exogenous porcine pancreatic polypeptide (PP; 0.8 and 2.1 microgram/kg . h, iv) on endogenously stimulated pancreatic exocrine secretion in five pancreatic-fistula dogs. Plasma levels of cholecystokinin (CCK), secretin, and PP were measured in addition to pancreatic secretion of water, bicarbonate, and protein. Intraduodenal infusions of acid and a mixture of phenylalanine and tryptophan were used to stimulate hormone release. PP caused a dose-dependent inhibition of endogenously stimulated pancreatic secretion, whereas the release of CCK and secretin was not affected. Duodenal acidification and intraduodenal infusion of phenylalanine and tryptophan caused a significant release of PP. This study shows that: 1) PP suppresses pancreatic secretion by means of a mechanism that is probably direct; this effect is not mediated through inhibition of release of CCK or secretin, and 2) phenylalanine and tryptophan, both strong stimulants of CCK release, cause a substantial rise in PP in peripheral blood. The mechanism of PP release may involve CCK (in previous studies, we have shown a rise in circulating PP levels after iv CCK infusion).

The Release of Pancreatic Polypeptide by Exogenous CCK in Man and Dog

“…Lonovics et al [4] also observed an increase of PP in response to 99% pure CCK-33. which, however, was not dose dependent.…”

“…Our data in man confirm the findings of Regan et al [5], but are in contrast to those of Taylor et al [6], who did not observe a significant PP response to intrave nous CCK-33. The discrepancies are hard to explain, but may partly depend on differ ences in the handling of the very labile CCK peptides [4].…”

“…Since CCK-OP displays the entire activity of CCK-33, it seems likely that CCK itself might stimulate PP release. As the results reported so far are few and somewhat controversial [4][5][6], we Studies in Dogs. 4 mongrel dogs (body weight 22-30 kg) with chronic gastric and duodenal fistulas (Tho mas type) were studied.…”

Elevation of serum pancreatic amylase and distortion of pancreatic cyto-architecture in type 1 diabetes mellitus rats treated with Ocimum gratissimum

“…Pancreatic polypeptide (PP) and somatostatin may contribute to the regulation of acinar cell function. Infusion of exogenous PP to plasma levels comparable to those observed after meal inhibits pancreatic secretion 9. This is indicative of a possible role of this peptide in the physiological control of exocrine pancreatic secretion.…”

Receptors on phaeochromocytoma cells for two members of the PP‐fold family — NPY and PP

“…Only high-capacity, low-affinity receptors of doubtful physiological relevance have been detected [19]. The action of PP is demonstrable in vivo only, not in in vitro preparations of pancreatic or biliary tissues [20,21]. Thus, it was suggested that PP must act through nerves [7].…”