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P Gourlet

Publications and source records attributed to P Gourlet.

At least 19 recordsLinked to original sources
PubMed1997

Vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase-activating peptide (PACAP-27, but not PACAP-38) degradation by the neutral endopeptidase EC 3.4.24.11.

VIP (vasoactive intestinal polypeptide) and PACAP (pituitary adenylate cyclase-activating polypeptide), which are potent relaxing agents in the airways, were submitted to in vitro degradation by the neutral endopeptidase EC 3.4.24.11 (NEP), one of the most active peptidase in the lung, to test their relative resistance to proteolysis. Both VIP and PACAP(1-27) were cleaved by NEP, but PACAP(1-38) was not. The main fragments produced were VIP(1-22) and VIP(1-25), and PACAP(1-22) and PACAP(1-25), respectively. The degradation of VIP(1-27), PACAP(6-27), and PACAP(13-27) was also hindered by extending their C-terminal ends with the (28-38) sequence of PACAP(1-38). The sensitivity to enzyme degradation was gradually reduced when the C-terminal extension was increased from PACAP(1-27) to PACAP(1-29), PACAP(1-32) and PACAP(1-38). The biological activities of the degradation products were evaluated on the three classes of PACAP/VIP receptors, with VIP(1-25) and PACAP(1-25) retaining an important part of their activities on the VIP1 receptor. Thus, the degradation of VIP and PACAP(1-27) by the neutral endopeptidase 24.11 might produce a VIP1 receptor-selective active metabolite, provided that very high VIP or PACAP(1-27) concentrations are achieved in the receptor vicinity.

Amino Acid Sequence↗
PubMed1997

The long-acting vasoactive intestinal polypeptide agonist RO 25-1553 is highly selective of the VIP2 receptor subclass.

RO 25-1553 is a synthetic VIP analogue that induced a long-lasting relaxation of tracheal and bronchial smooth muscles as well as a reduction of edema and eosinophilic mobilization during pulmonary anaphylaxis. In the present study, we tested in vitro the capacity of RO 25-1553 to occupy the different VIP/PACAP receptor subclasses and to stimulate adenylate cyclase activity. The cellular models tested expressed one single receptor subtype: Chinese hamster ovary (CHO) cells transfected with the rat recombinant PACAP I, rat VIP1, and human VIP2 receptors; SUP T1 cells expressing the human VIP2 and HCT 15 and LoVo cells expressing the human VIP1 receptor. RO 25-1553 was threefold more potent than VIP on the human VIP2 receptor, 100- and 600-fold less potent than VIP on the rat and human VIP1 receptors, respectively, and 10-fold less potent than VIP and 3000-fold less potent than PACAP on the PACAP I receptor. RO 25-1553 was a full agonist on the VIP2, the PACAP I, and the rat recombinant VIP1 receptor but a partial agonist only on the human VIP1 receptor. Thus, RO 25-1553 is a highly selective agonist ligand for the VIP2 receptor subclass.

Adenylyl Cyclases↗
PubMed1996

Effect of introduction of an arginine16 in VIP, PACAP and secretin on ligand affinity for the receptors.

Rabbit secretin, which differs from all other mammalian secretins in having a Leu residue in position 6 (instead of Phe) and a basic residue (Arg) in position 16, had a lower affinity than porcine secretion on recombinant rat secretin receptors but had a greater affinity than porcine secretin on recombinant rat VIP1 and PACAP I receptors. Synthetic [L6] porcine secretin had a reduced potency on secretin and VIP1 receptors whereas [R16] porcine secretin had a similar binding profile as rabbit secretin. Thus, an arginine residue in position 16 reduced 3-fold the affinity of secretin for secretin receptors but increased 30-fold its affinity for the VIP1 and PACAP I receptors. The introduction of an arginine residue in position 16, instead of glutamine, in VIP and PACAP had a similar effect: [R16] VIP and [R16] PACAP had 3- to 10-fold higher affinities than VIP and PACAP for VIP1 and PACAP I receptors, and 3-fold lower affinities for the secretin receptors. The three [R16] peptides also had a reduced potency on the chimeric receptor consisting of the N-terminal part of the secretin receptor grafted on the VIP1 receptor, and an enhanced potency on the chimeric receptor consisting of the N-terminal part of VIP1 receptor grafted on the secretin receptor, indicating that position 16 of each ligand interacted with the N-terminal extracellular domain of the receptors.

Animals↗
PubMed1996

Interaction of amino acid residues at positions 8-15 of secretin with the N-terminal domain of the secretin receptor.

The ability of secretin, PACAP-(1-27)-peptide, and ten hybrid peptides to recognize and activate the rat secretin and vasoactive intestinal polypeptide (PACAP type II VIP1) receptors was tested on recombinant Chinese hamster ovary (CHO) cell lines. PACAP had a 2500-fold lower affinity than secretin for the secretin receptor, and secretin had a 300-fold lower affinity than PACAP for the VIP1 receptor. Amino acids 8, 13, and 15 of the PACAP molecule contributed significantly to the low affinity of PACAP for the secretin receptor. The amino acids at positions 5, 9, 10, 15, 16, and unidentified amino acid(s) between positions 17-20 made limited contributions to the low affinity of secretin for the VIP1 receptor. To identify the receptor region that interacts with these amino acids, we constructed chimeric receptors, which consist either of the N-terminal extracellular part of the secretin receptor and the core of the VIP1 receptor (N-Sn/VIP1r) or the N-terminal extracellular part of the VIP1 receptor and the core of the secretin receptor (N-VIP1/Snr), and tested the ability of the hybrid ligands to activate the adenylate cyclase of CHO cells expressing these chimeric receptors. The N-Sn/VIP1 receptors had a higher affinity for secretin than for PACAP. The hybrid peptide 6 that consists of the PACAP-(1-8)-Sn-(9-15)-PACAP-(16-27)-peptide sequence had a 30-fold to 200-fold higher potency than either parent peptide for the chimeric receptor, which suggests that while the N- and/or C-terminal part of the peptide interact with the transmembrane domain of the receptor, the discriminator region 9-15 recognizes the extracellular N-terminal domain of the receptor. This was confirmed by the observation that, out of all the peptides tested, hybrid 6 had the weakest potency for activation of the N-VIP1/Sn chimeric receptors.

Adenylyl Cyclases↗
PubMed1996

C-terminally shortened pituitary adenylate cyclase-activating peptides (PACAP) discriminate PACAP I, PACAP II-VIP1 and PACAP II-VIP2 recombinant receptors.

Pituitary adenylate cyclase-activating polypeptide (PACAP) analogues were tested for their ability to occupy the recombinant selective PACAP receptors (PACAP type I receptors) and the non-selective PACAP-vasoactive intestinal polypeptide (VIP) receptors (PACAP type II, VIP1 and PACAP type II, VIP2 receptors), stably transfected and expressed in Chinese hamster ovary cells. Their capacity to stimulate the adenylate cyclase activity was also measured. The synthetic analogues tested were peptides shortened at the carboxyl terminus by the removal of 1-4 amino acids (PACAP-26 to PACAP-23). All the peptides discriminated the 3 receptor subtypes and had the highest affinity for the VIP1 receptors, and the lowest affinity for the VIP2 receptors; PACAP-25 having the highest ability to discriminate the VIP1 and VIP2 receptors. All the peptides tested were full agonists on the PACAP I and VIP1 receptors; PACAP-25 and -26 were partial agonists on VIP2 receptors and may be appropriate tools to establish the receptor subtype involved in a given cellular response.

Animals↗
PubMed1996

The C-terminus ends of secretin and VIP interact with the N-terminal domains of their receptors.

C-terminally truncated secretin and VIP molecules were synthesized, and their ability to occupy the recombinant secretin and VIP1 receptors stably expressed in Chinese hamster ovary (CHO) cells and to stimulate adenylate cyclase activity was studied. On secretin receptors, secretin (1-26) and secretin (1-24) were 10- and 50-fold less potent but as efficient as secretin (1-27); VIP (1-27) was as potent and efficient as VIP (1-28), and VIP (1-26) and VIP (1-25) were both 100-fold less potent. On VIP1 receptor, VIP (1-28) and VIP (1-27) were equipotent and VIP (1-26) and VIP (1-25) were 10- and 300-fold less potent, respectively; secretin (1-27) and secretin (1-26) were of equally low affinity and 10-fold more potent than secretin (1-24). Thus, the secretin and the VIP1 receptors had different selectivity profiles for the recognition of C-terminally truncated secretin and VIP derivatives. The chimeric receptors consisting in the N-terminal part of the secretin receptor on the core of the VIP1 receptor (N-Sn/VIP1.r) and in the N-terminal part of the VIP1 receptor on the core of the secretin receptor (N-VIP1/Sn.r) exhibited the selectivity pattern of the secretin and VIP1 receptors, respectively. The results suggest that the C-terminal end of secretin and VIP interacts with the N-terminal domain of the secretin and VIP receptors.

Adenylyl Cyclases↗
PubMed1996

Characterization of the VIP receptor from SUP T1 lymphoblasts.

The SUP T1 lymphoblasts express an original subtype of VIP receptors characterized by a high affinity for the VIP analogue from lizard venom named helodermin, a preference for the neuropeptide PACAP-38 over PACAP-27 and VIP, and an extremely low affinity for secretin. The molecular cloning of that receptor revealed its identity with the VIP2 receptor subtype first cloned in rat and mouse tissues. The access to selective probes permits the detection of the mRNA coding for the VIP2 receptor by Northern blot, reverse transcriptase-polymerase chain reaction (RT-PCR) and in situ hybridization. These highly selective and sensitive techniques identify the cell types that are equipped to synthesize the receptor but do not prove that the receptor is indeed efficiently expressed at the cell surface. VIP2 mRNA was detected in selected areas of the brain different from that expressing the classical VIP1 receptor, in pituitary, in pineal, in pancreatic islets, in testes and ovary. It was also detected in the stomach, in the thymus and in spleen and in T lymphoblastic cell lines. A systematic screening of the immunocompetent cells must still be performed.

Amino Acid Sequence↗
PubMed1996

Addition of the (28-38) peptide sequence of PACAP to the VIP sequence modifies peptide selectivity and efficacy.

Chimeric peptides were synthesized by adding the C-terminal extension 28-38 of the pituitary adenylate cyclase activating polypeptide (PACAP) to the sequences (1-27), (2-27), (3-27) and (6-27) of VIP. The capacity of these peptides to occupy the selective PACAP- and the non-selective PACAP-VIP receptors and to stimulate adenylate cyclase activity was studied in chinese hamster ovary (CHO) cells expressing the recombinant receptors. The results were compared to those obtained with VIP and the corresponding VIP fragments. The presence of the (28-38) PACAP extension increased at least 100-fold the VIP- or VIP fragment affinities for the selective PACAP receptor but not for the non-selective PACAP-VIP receptors. Furthermore, on both receptors, the extension increased peptide intrinsic activity: VIP(3-28) was a partial agonist while VIP(3-27)/PACAP(28-38) was as potent as VIP and was apparently a full agonist; VIP(6-28) had no intrinsic activity, but VIP(6-27)/PACAP(28-38) was a partial agonist. These results suggest: (1) the presence of a specific domain for the (28-38) PACAP sequence on the selective PACAP receptor; and (2) a stabilizing effect of the (28-38) PACAP sequence on the structure of N-terminally truncated VIP.

Adenylyl Cyclases↗
PubMed1996

Properties of the pituitary adenylate cyclase-activating polypeptide I and II receptors, vasoactive intestinal peptide1, and chimeric amino-terminal pituitary adenylate cyclase-activating polypeptide/vasoactive intestinal peptide1 receptors: evidence for multiple receptor states.

We analyzed the functional and binding properties of the "normal" pituitary adenylate cyclase-activating polypeptide (N-PACAP) type I, PACAP type II/vasoactive intestinal peptide (VIP)1, and chimeric N-PACAP/VIP1 receptors expressed in Chinese hamster ovary cells. The binding properties of the three receptors were investigated using three radioiodinated tracers: 125I-VIP, 125I-PACAP-27, and 125I-PACAP-29 (125I-PACAP-27-Gly28,Lys29-amide). The three tracers labeled very different receptor densities; 125I-PACAP-29 labeled more receptors than either 125I-VIP or 125I-PACAP-27 in the three cell lines. Analysis of the competition curves suggested that the three tracers labeled in a different manner three PACAP I receptor states, two PACAP II/VIP1 receptor states, and three chimeric N-PACAP/VIP1 receptor states in transfected Chinese hamster ovary cells. The previously described PACAP1A and PACAP1B receptors, which differ by their affinities for PACAP-27 and PACAP-38, actually correspond to different PACAP I receptor states. The three receptors were able to increase adenylate cyclase activity when activated by PACAP-38, PACAP-27, or VIP. In contrast with the two parent receptors, the chimeric N-PACAP/VIP1 receptor was activated by PACAP-38 at lower concentrations than PACAP-27, suggesting that the amino-terminal and core receptor domains influence each other and that the conformation of one or both domains was altered in the chimeric compared with wild-type receptors. Comparison of the binding and functional properties of three clones expressing different chimeric N-PACAP/VIP1 receptors densities indicated that 125I-PACAP-29 was necessary to correctly estimate the receptor number and that 125I-PACAP-27 or 125I-VIP labeled only a fraction of the functional receptors. We suspect (but could not demonstrate) that this might also be true for PACAP I and PACAP II/VIP1 receptors.

Adenylyl Cyclases↗
PubMed1995

Fragments of pituitary adenylate cyclase activating polypeptide discriminate between type I and II recombinant receptors.

Pituitary adenylate cyclase activating polypeptide (PACAP) analogues were tested for their ability to occupy the recombinant selective PACAP receptors (PACAP type I receptor) or the non-selective PACAP-vasoactive intestinal polypeptide (VIP) receptors (PACAP type II, VIP1 and VIP2 receptors) stably transfected and expressed in Chinese hamster ovary (CHO) cells. The synthetic analogues consisted of N- and/or C-terminally shortened peptides. Thus, peptides starting at amino acid 1, 2, 3 or 6 and terminating at amino acid 27, 29, 30, 32 or 38 were compared on the three receptors studied. The shortening of PACAP-(1-38) to PACAP-(1-27) was of little influence. However, in N-terminally deleted peptides the PACAP-38 derivatives were of higher affinity than the PACAP-27 fragments on PACAP type I and PACAP type II, VIP2 receptors but not on PACAP type II, VIP1 receptors. The presence of the sequence 28-32 was in all cases sufficient to reproduce the data obtained with the PACAP-38 analogues. PACAP-(3-32) is able to discriminate the PACAP type II, VIP2 subtype from the other two subtypes, and PACAP-(6-30), PACAP-(6-32) and PACAP-(6-38) can discriminate the PACAP type II, VIP1 receptors from the other two subtypes. These molecules may help in the quantitative detection of receptor subclasses in complex systems when two or more receptor subtypes are found.

Animals↗
PubMed1995

Identification of a new chromogranin B fragment (314-365) in endocrine tumors.

A rabbit antiserum was raised against the fragment (350-365) of human chromogranin B corresponding to the C-terminal end of a putative proteolytic fragment generated by the cleavage of a dibasic doublet located in position 366-367 of the precursor. A radioimmunoassay was developed. Chromatographic analysis of 10 endocrine tumor extracts (one liver metastasis of a gastrinoma, one liver metastasis of a medullary carcinoma of the thyroid, one VIPoma, one insulinoma, one nonsecreting pancreatic endocrine tumor, one local recurrence of a gut carcinoid, two pituitary gonadotropinoma, and two non-secreting pituitary adenomas) revealed the presence of two forms of immunoreactive material. The most abundant form had an apparent molecular weight of 4500 and was purified to homogeneity by successive reverse-phase HPLC chromatographies and partially sequenced. The N-terminal sequence of the peptide, established by automated Edman degradation, was A-S-E-E-E-P-E-Y-G-E-E-I-K-G-Y-P-V-Q and corresponded to the 314-332 sequence of human chromogranin B. Taking into account the specificity of the antiserum used for peptide identification, we deduced that the purified peptide was chromogranin B(314-365) and represented a new form generated by limited proteolysis of chromogranin B.

Adenoma↗
PubMed1994

Inhibition of Na/Ca exchange by Phe-Met-Arg-Phe-NH2 (FMRFa)-related peptides in intact rat pancreatic B-cells.

Phe-Met-Arg-Phe-NH2 (FMRFa)-related peptides were recently shown to inhibit Na/Ca exchange in cardiac sarcolemmal vesicles. In the present study, we examined the effects of FMRFa-related peptides on Na/Ca exchange in intact (pancreatic B) cells. At 2.8 mM glucose, FMRFa-related peptides only weakly inhibited Na/Ca exchange although their effect was more marked under depolarizing conditions. The peptides blocked neither the Na/K-ATPase nor Ca2+ channels but slightly reduced membrane K+ permeability. Our data indicate that FMRFa-related peptides are weak and non-specific inhibitors of Na/Ca exchange in intact B cells. The data do not confirm the view that the peptides may exert some of their physiological modulatory role by inhibiting Na/Ca exchange.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1994

Structural requirements for the occupancy of rat brain PACAP receptors and adenylate cyclase activation.

N-terminally shortened analogues of PACAP(1-27) and PACAP(1-38), and analogues modified in position 1,2 or 3 were compared for their ability to interact with PACAP receptors and to activate or inhibit adenylate cyclase in rat brain hippocampus membranes. In the PACAP(1-27) series, deletion of the first two amino acids decreased the potency 3000-fold. PACAP fragments (3-27) to (9-27) were inactive on the enzyme. N-terminally shortened PACAP(1-38) analogues showed a similar profile but were 70 to 300-fold more potent than their PACAP(1-27) equivalents. PACAP(6-27) and PACAP(6-38) were competitive inhibitors of the PACAP(1-27) stimulated enzyme. The Kd values of PACAP(6-27) and PACAP(6-38) were of 1000 and 2 nM respectively. Surprisingly, the Kd values of PACAP(6-31) and (6-35), that were also unable to stimulate adenylate cyclase activity, were of 3 and 300 nM respectively. Replacement of His1 by Phe1 in PACAP(1-27) reduced the potency 600-fold. Replacement of Ser2 by Ala2 in PACAP(1-27) and PACAP(1-38) was of little consequence. Substitution of Ser2 by Phe2, DPhe2, Arg2 or DArg2 reduced 60 to 1000-fold the PACAP(1-27) potency but only 7 to 30-fold the PACAP(1-38) potency. Phe2 derivatives were inactive on the enzyme. Replacement of Asp3 by Asn reduced 4000-fold the PACAP(1-27) potency.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenylyl Cyclases↗
PubMed1992

Structural requirements for the occupancy of pituitary adenylate-cyclase-activating-peptide (PACAP) receptors and adenylate cyclase activation in human neuroblastoma NB-OK-1 cell membranes. Discovery of PACAP(6-38) as a potent antagonist.

In these structure activity studies, the 46 analogs of the 27-amino-acid form of the pituitary-adenylate-cyclase-activating peptide, PACAP(1-27), and the 38-amino-acid form, PACAP(1-38), were either monosubstituted or bisubstituted at positions 1-3, 20 and 21 or N-terminally shortened. All analogs were compared on human neuroblastoma NB-OK-1 cell membranes for their ability to occupy 125I-[AcHis1]PACAP(1-27)-labelled receptors (AcHis, N alpha-acetylhistidine) and to activate adenylate cyclase (in terms of potency and intrinsic activity). The monophasic slope of dose/effect curves on both parameters suggested interaction with one class of PACAP receptor. Residues 28-38 in the C-terminally extended peptide, PACAP(1-38), played a favorable role in recognition, in that receptors coupled to adenylate cyclase were, in general, more sensitive to PACAP(1-38) analogs than to the corresponding PACAP(1-27) analogs. At variance with PACAP(6-27), PACAP(6-38) was well recognized and acted as a potent competitive antagonist (Ki 1.5 nM). Residues 1-3 were all important in enzyme activation: modification of the beta-turn potential gave full agonists (the LAla2 and DAla2 derivatives) or partial agonists (LPhe2 and DPhe2; LArg2 and DArg2; Glu3 and Asn3). Finally, a proper alpha-helix was also important: the combined substitution of Lys21/Lys22 by Gly21/Gly22 decreased the binding affinity sharply.

Adenylyl Cyclases↗
PubMed1992

Receptor occupancy and adenylate cyclase activation in AR 4-2J rat pancreatic acinar cell membranes by analogs of pituitary adenylate cyclase-activating peptides amino-terminally shortened or modified at position 1, 2, 3, 20, or 21.

In AR 4-2J rat pancreatic acinar cell membranes, receptors for the two pituitary adenylate cyclase-activating peptides (PACAP) PACAP-27 (the short version of PACAP) and PACAP-38 [the long version, with a carboxyl-terminal (residues 28-38) extension] can be subdivided into (a) type A receptors, with high affinity (Kd, 0.3-0.5 nM) for both PACAP-27 and PACAP-38, and (b) type B receptors, with high affinity for PACAP-38 (Kd, 0.3 nM) but low affinity for PACAP-27 (Kd, 20 nM). Determinants of agonist/antagonist activity in 47 PACAP-27 and PACAP-38 analogs (mono- or disubstituted in positions 1, 2, 3, 20, and 21) or amino-terminally shortened were tested by (a) the occupancy of PACAP-A receptors, preferentially labeled with [125I-N-acetyl-His1]PACAP-27, and that of PACAP-A and -B receptors, both labeled with 125I-PACAP-38, and (b) the resulting activation or inhibition of adenylate cyclase. For PACAP-A receptor recognition, deprotonated His1 was a major determinant for PACAP-27 but not PACAP-38; the Kd of 125I-PACAP-27 decreased 2.4-fold at 37 degrees between pH 6.0 and 7.5 and 3.6-fold at 15 degrees, whereas the IC50 of [N-acetyl-His1]PACAP-27 was less affected and that of PACAP(2-27), PACAP(2-38), and PACAP(1-38) was pH independent. In addition, PACAP-A receptors coupled to adenylate cyclase were much more sensitive to PACAP-38 derivatives than to PACAP-27 derivatives; for instance, [D-Phe2]PACAP-38 was a more potent antagonist (Ki, 5 nM) than [D-Phe2]PACAP-27 (Ki, 350 nM), and PACAP(6-38) was a more potent antagonist (Ki, 7 nM) than PACAP(6-27) (Ki, 300 nM). PACAP-B receptors, apart from showing high affinity for PACAP-38, displayed relatively high affinity for amino-terminally shortened PACAP-38 fragments and poor affinity for PACAP-27 and PACAP-27 fragments.

Adenylyl Cyclase Inhibitors↗
PubMed1991

Properties and distribution of receptors for pituitary adenylate cyclase activating peptide (PACAP) in rat brain and spinal cord.

A high density (in the pmol/mg protein range) of specific functional receptors for PACAP (pituitary adenylate cyclase activating polypeptide) was observed in membranes from rat brain cortex, olfactory bulb, hypothalamus, hippocampus, striatum, cerebellum, pons and cervico-dorsal spinal cord, using [125I]PACAP-27 (PACAP 1-27). The tracer bound rapidly, specifically and reversibly. Competition binding curves were compatible with the coexistence, in the eight central nervous areas explored, of high and low affinity binding sites for PACAP-27 (Kd of 0.2 nM and 3.0 nM, respectively), and of only one class of binding sites for PACAP-38 (PACAP (1-38), Kd 0.2-0.9 nM). VIP inhibited only partially the binding of [125I]PACAP-27, and PHI, GRF(1-29)NH2 and secretin were ineffective at 1 microM. Chemical [125I]PACAP-27 cross-linking revealed a single specific 64 kDa protein species. In rat brain cortical membranes, saturation and competition experiments, using [125I]PACAP-38 as radioligand, indicated the presence of both high (Kd 0.13 nM) and low (Kd 8-10 nM) affinity binding sites for PACAP-38 and of low affinity (Kd 30 nM) binding sites for PACAP-27. These data taken collectively suggest the coexistence of PACAP-A receptors with a slight preference for PACAP-27 over PACAP-38 and of PACAP-B receptors that recognize PACAP-38 with a high affinity and PACAP-27 with low affinity. Both PACAP-27 and PACAP-38 stimulated adenylate cyclase with similar potency and efficacy. VIP was markedly less potent in this respect and also less efficient, except on cerebellar membranes.

Adenylyl Cyclases↗
PubMed1991

The two forms of the pituitary adenylate cyclase activating polypeptide (PACAP (1-27) and PACAP (1-38)) interact with distinct receptors on rat pancreatic AR 4-2J cell membranes.

The existence of specific receptors for the two PACAPs (Pituitary Adenylate Cyclase Activating Peptides of 27 and 38 amino acids) was previously demonstrated on membranes from the pancreatic acinar cell line AR 4-2J (Buscail et al., FEBS Lett. 202, 77-81, 1990) by [125I]PACAP-27 binding. Here we demonstrate, by comparing Scatchard analysis of saturation curves and competition binding curves obtained with [125I]PACAP-27 and [125I]PACAP-38 as radioligands, the coexistence of two classes of receptors: 1/PACAP-A receptors that recognize PACAP-27 and PACAP-38 with the same high affinity (Kd 0.3 nM) and 2/PACAP-B receptors that recognize PACAP-38 with a high affinity (Kd 0.3 nM) and PACAP-27 with a lower affinity (Kd 30 nM). These two receptors are coupled to adenylate cyclase but can be clearly distinguished by the ability of PACAP(6-27) to specifically inhibit PACAP-27 adenylate cyclase activation.

Animals↗