PACAP and VIP stimulate enzyme secretion in rat pancreatic acini via interaction with VIP/PACAP-2 receptors: additive augmentation of CCK/carbachol-induced enzyme release.
The binding and biological effect of pituitary adenylate cyclase activating polypeptide (PACAP), a novel hypothalamic peptide with high sequence homology to vasoactive intestinal polypeptide (VIP), were studied in rat AR 4-2 J pancreatic carcinoma cells and isolated rat pancreatic acini. PACAP(1-27) and analogue PACAP(1-23, VIP-24-28), but not VIP, displaced potently and reversibly 125I-PACAP(1-27) from binding to an abundantly expressed high affinity PACAP-preferring receptor on AR 4-2 J cells, referred to as "PACAP-1 receptor." High affinity binding was dependent on N-terminal and C-terminal residues of PACAP(1-27): PACAP(1-24,Cys-25) (7.3 +/- 1.6 microM), PACAP(1-23) (8.2 +/- 1.5 microM), VIP (> 30 microM), PACAP(3-27), PACAP(1-19), PACAP(3-19), PACAP(1-12), and PACAP(18-38) (all > 50 microM) showed low or no binding potency. In contrast, high and low affinity binding of 125I-VIP to AR 4-2 J cells was displaced equipotently by PACAP(1-27) and VIP, thus defining on these cells, in addition, two scarcely expressed binding sites, designated "VIP/PACAP-2 receptor," similar or identical to the previously described high and low affinity acinar VIP receptor. Binding of 125I-PACAP(1-27) to a high and low affinity binding site on rat pancreatic acini was inhibited equipotently by PACAP(1-27) and VIP, identifying these sites as VIP/PACAP-2 receptors. PACAP(1-23) recognized both type 2 binding sites with only slightly lower affinity. PACAP(1-27), PACAP(1-38), PACAP(1-23, VIP-24-28), and PACAP(1-23) equipotently stimulated acinar lipase release and cyclic AMP production in pancreatic acini. Co-incubation of PACAP(1-27) or VIP with cholecystokinin-8 or carbachol revealed additive effects on enzyme secretion. Our results suggest the predominant expression of VIP/PACAP-2 receptors on rat pancreatic acini, whereas AR 4-2 J cells express mainly PACAP-1 receptors. PACAP is a potent ligand for both receptor types and has to be regarded as a novel VIP-like pancreatic secretagogue.
Schmidt
W E
WE
Department of Medicine, Georg August University of Göttingen, Germany.
Seebeck
J
J
Höcker
M
M
Schwarzhoff
R
R
Schäfer
H
H
Fornefeld
H
H
Morys-Wortmann
C
C
Fölsch
U R
UR
Creutzfeldt
W
W
D000595:Amino Acid Sequence; D000818:Animals; D002217:Carbachol / Q000494:pharmacology; D002766:Cholecystokinin / Q000494:pharmacology; D066298:In Vitro Techniques; D007457:Iodine Radioisotopes; D008049:Lipase / Q000187:drug effects / Q000378:metabolism; D008969:Molecular Sequence Data; D009479:Neuropeptides / Q000378:metabolism / Q000494:pharmacology*; D018377:Neurotransmitter Agents / Q000494:pharmacology*; D010179:Pancreas / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D010190:Pancreatic Neoplasms / Q000378:metabolism; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide; D051381:Rats; D011964:Receptors, Gastrointestinal Hormone / Q000378:metabolism*; D018005:Receptors, Vasoactive Intestinal Peptide; D015290:Second Messenger Systems / Q000502:physiology; D017386:Sequence Homology, Amino Acid; D014407:Tumor Cells, Cultured; D014660:Vasoactive Intestinal Peptide / Q000378:metabolism / Q000494:pharmacology*
C495403:Adcyap1 protein, rat; D007457:Iodine Radioisotopes; D009479:Neuropeptides; D018377:Neurotransmitter Agents; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide; D011964:Receptors, Gastrointestinal Hormone; D018005:Receptors, Vasoactive Intestinal Peptide; D014660:Vasoactive Intestinal Peptide; D002217:Carbachol; D002766:Cholecystokinin; D008049:Lipase