ceruletide and Hypoglycemia

Pancreatic polypeptide (PP) is a potent inhibitor of pancreatic exocrine secretion in vivo. The mechanism of pancreatic inhibition by PP is unknown, but the absence of PP receptors on pancreatic exocrine cells makes a direct effect of this hormone on the gland unlikely. In this study, we investigated the hypothesis that PP exerts its inhibitory effect via extrinsic neural pathways. Ten dogs with gastric and pancreatic fistulas were given an intravenous infusion of 250 ng/kg-1 h-1 secretin and 50 ng/kg-1 h-1 caerulein over 3 h. One hour after starting the infusion, 400 pmol kg-1 h-1 porcine PP were administered over 1 h. Pancreatic bicarbonate and protein secretions were measured. Later, the pancreas was extrinsically denervated. PP infusion decreased bicarbonate secretion in the intact gland by 47% and in the denervated pancreas by 57%. Protein secretion was diminished by exogenous PP by 31% in the intact and by 44% in the denervated pancreas. Despite pancreatic denervation, PP still exerted a significant inhibitory effect. Atropine infusion completely blocked the inhibitory effect of PP on caerulein-stimulated pancreatic protein secretion both in the intact and denervated pancreas and of secretion-evoked bicarbonate output in the denervated gland. We conclude that the inhibitory action of the hormone is not mediated via extrinsic neural pathways of the pancreas, but PP may exert its effect via intrinsic atropine-sensitive mechanisms.

Topics: Animals; Atropine; Bicarbonates; Ceruletide; Dogs; Hypoglycemia; Insulin; Pancreas; Pancreatic Juice; Pancreatic Polypeptide; Secretin; Vagotomy

Pancreatic polypeptide (P.P.) is a potent hormonal peptide which has been isolated from the pancreas. Its role in human physiology and pathology is not yet established. After a standard hospital lunch the plasma concentration of P.P. showed a rapid and identical rise in 10 healthy controls, 11 duodenal-ulcer patients, and 6 post-vagotomy patients but remained undetectable in 4 totally pancreatectomised subjects. In contrast plasma-P.P. was unaffected by intravenous administration of glucose, aminoacids, or fat. However, during intravenous infusion of caerulein, a cholecystokinin analogue, P.P. rose by nearly five-fold, and an even greater rise was seen after intravenous injection of Boots secretin. In 19 duodenal-ulcer patients insulin hypoglycaemia produced a rapid rise in plasma-P.P. but this did not occur in any of the 17 patients studied after a truncal vagotomy. Thus P.P. is released by oral but not intravenous nutriments and the existence of an entero-P.P. axis is postulated. One component of this axis may be the vagal innervation but the normal postprandial rise seen after vagotomy suggests that other control mechanisms, such as the intestinal hormones, are more important.

Topics: Adult; Aged; Amino Acids; Ceruletide; Dietary Carbohydrates; Dietary Fats; Dietary Proteins; Duodenal Ulcer; Gastrointestinal Hormones; Humans; Hypoglycemia; Infusions, Parenteral; Middle Aged; Pancreas; Pancreatectomy; Pancreatic Hormones; Parenteral Nutrition; Peptides; Secretin; Vagotomy