title: Characterization of PACAP receptors and signaling pathways in rabbit gastric muscle cells.
abstract: Pituitary adenylate cyclase-activating peptide (PACAP) receptors and their signaling pathways were characterized in dispersed rabbit gastric muscle cells. 125I-PACAP-27 and 125I-vasoactive intestinal peptide (VIP) binding to muscle cells were inhibited equally by PACAP and VIP (mean inhibitory concentration 0.8 to 1.3 nM) and desensitized to the same extent (70-80%) by exposure to either peptide. PACAP, like VIP, increased cytosolic free Ca2+ and the formation of L-[3H]citrulline, NO-3/NO-2, guanosine 3',5'-cyclic monophosphate (cGMP), and adenosine 3'5'-cyclic monophosphate (cAMP) and induced relaxation (mean effective concentration 1.8 +/- 0.1 nM) that was partly inhibited by NG-nitro-L-arginine (L-NNA), VIP-(10-28), and PACAP 6-38. L-[3H]citrulline and cGMP formation were blocked by nifedipine, L-NNA, and pertussis toxin (PTx), implying activation of a G protein-coupled, Ca(2+)-calmodulin-dependent nitric oxide (NO) synthase. PACAP-induced relaxation was inhibited to the same extent (46-49%) by nifedipine, L-NNA, PTx, and the protein kinase G inhibitor KT-5823; the inhibition reflected the component of relaxation mediated by the NO-cGMP pathway. The residual relaxation was abolished by the protein kinase A inhibitor H-89. The pattern of inhibition of all responses was identical to that observed with VIP. Desensitization with VIP or PACAP abolished cAMP formation but had no effect on L-[3H]citrulline and cGMP formation induced by either peptide. Receptor protection with VIP or PACAP preserved fully all responses (L-[3H]citrulline, cGMP, and cAMP formation and relaxation) to either peptide. The complete cross-competition, cross-desensitization, cross-antagonism, and cross-protection of receptors by either VIP or PACAP are consistent with interaction of both peptides with the same receptors; the receptors consist of two classes, each coupled to a distinct signaling pathway.
authors.affiliation: Department of Physiology, Medical College of Virginia, Richmond 23298, USA.
authors.forename: K S
authors.initials: KS
authors.lastname: Murthy
authors.forename: J G
authors.initials: JG
authors.lastname: Jin
authors.forename: J R
authors.initials: JR
authors.lastname: Grider
authors.forename: G M
authors.initials: GM
authors.lastname: Makhlouf
mesh_terms: D037361:Adenylate Cyclase Toxin; D000470:Alkaloids / Q000494:pharmacology; D000634:Aminoquinolines / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002227:Carbazoles; D002478:Cells, Cultured; D002956:Citrulline / Q000378:metabolism; D000242:Cyclic AMP / Q000494:pharmacology; D006152:Cyclic GMP / Q000378:metabolism / Q000494:pharmacology; D003600:Cytosol / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000378:metabolism; D006162:Guanylate Cyclase / Q000037:antagonists & inhibitors; D007211:Indoles; D007546:Isoquinolines / Q000494:pharmacology; D007700:Kinetics; D009126:Muscle Relaxation; D009130:Muscle, Smooth / Q000187:drug effects / Q000502:physiology*; D009479:Neuropeptides / Q000378:metabolism / Q000494:pharmacology*; D018377:Neurotransmitter Agents / Q000378:metabolism; D009543:Nifedipine / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000378:metabolism; D019335:Nitroarginine / Q000494:pharmacology; D037342:Pertussis Toxin; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide; D047428:Protein Kinase Inhibitors; D011817:Rabbits; D051236:Receptors, Pituitary Adenylate Cyclase-Activating Polypeptide; D011979:Receptors, Pituitary Hormone / Q000502:physiology*; D015398:Signal Transduction; D013270:Stomach / Q000187:drug effects / Q000502:physiology*; D013449:Sulfonamides; D014660:Vasoactive Intestinal Peptide / Q000378:metabolism / Q000494:pharmacology; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
chemical_list: D037361:Adenylate Cyclase Toxin; D000470:Alkaloids; D000634:Aminoquinolines; D002227:Carbazoles; D004791:Enzyme Inhibitors; D007211:Indoles; D007546:Isoquinolines; D009479:Neuropeptides; D018377:Neurotransmitter Agents; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide; D047428:Protein Kinase Inhibitors; D051236:Receptors, Pituitary Adenylate Cyclase-Activating Polypeptide; D011979:Receptors, Pituitary Hormone; D013449:Sulfonamides; D010566:Virulence Factors, Bordetella; C073601:KT 5823; D019335:Nitroarginine; D002956:Citrulline; D014660:Vasoactive Intestinal Peptide; C041715:6-anilino-5,8-quinolinedione; D000242:Cyclic AMP; D019001:Nitric Oxide Synthase; D037342:Pertussis Toxin; D019204:GTP-Binding Proteins; D006162:Guanylate Cyclase; D006152:Cyclic GMP; D009543:Nifedipine; C063509:N-(2-(4-bromocinnamylamino)ethyl)-5-isoquinolinesulfonamide; D002118:Calcium