Biomedical subjects

P Robberecht

Publications and source records attributed to P Robberecht.

At least 91 records · Page 5Linked to original sources

PubMed1996

Pituitary adenylate cyclase-activating polypeptide/vasoactive intestinal polypeptide receptor subtypes are differently expressed in rat transplanted pituitary tumours (SMtTW) and in the normal gland.

The expression of the pituitary adenylate cyclase-activating polypeptide/vasoactive intestinal polypeptide (PACAP/VIP) receptor subtypes was evaluated in the normal rat pituitary gland and in different rat spontaneous transplantable SMtTW tumours (SMtTW2 which expresses prolactin (PRL), SMtTW10 which expresses GH and SMtTW3 which expresses both PRL and GH) by measurement of PACAP/VIP-stimulated adenylate cyclase activity and detection of the presence of mRNA coding for the different receptor forms. In normal glands, the order of potency of the peptides suggested that adenylate cyclase activity was mediated through interaction with PACAP selective receptors (PACAP I receptors); mRNAs coding for the PACAP I receptor, but also for the PACAP II VIP2 receptor, were detected. In SMtTW2 tumours, the functional response was close to that observed in the presence of PACAP II VIP2 receptors; mRNAs coding for PACAP I and PACAP II VIP1 and PACAP II VIP2 receptors were detected. In the SMtTW10 tumours, the functional response was complex but compatible with the involvement of PACAP I and PACAP II receptors; mRNAs coding for the PACAP I and PACAP II VIP1 receptors were detected. In the SMtTW3 tumour, the profile was similar to that of the normal pituitary gland and the mRNA coding for the PACAP I receptor only was detected. Thus, while the control of normal pituitary gland adenylate cyclase activity by PACAP and VIP was mediated by PACAP-selective receptors, in spontaneous transplantable tumours a variable profile was observed and PACAP, as well as VIP1 and VIP2 receptors, may contribute to the responses.

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

Differential alternative splicing of PACAP receptor in pituitary cell subpopulations.

The capability of rat pituitary cells to express receptors for pituitary adenylate cyclase activating polypeptide (PACAP) and VIP was evaluated by binding studies and measurement of adenylate cyclase activity on whole gland preparations and by reverse transcriptase-polymerase chain reaction (TR-PCR) using specific primers on preparations from isolated cell populations enriched in PRL- and GH-producing cells. Data obtained on whole gland preparations indicated that selective PACAP receptors (PACAP Type I) predominated. The mRNA coding for PACAP Type I and for the non-selective PACAP receptors Type II VIP2 (but not VIP1) were identified. The mRNA coding for four different spliced variants of the PACAP Type I receptor were detected. In PRL producing cells, three variants and the VIP2 mRNA were detected, whereas in GH-producing cells the mRNA coding for the variant having a 28-amino acid insert (termed HOP) in the third intracellular loop was the only present.

Adenylyl Cyclases↗

PubMed1995

Properties of chimeric secretin and VIP receptor proteins indicate the importance of the N-terminal domain for ligand discrimination.

Two chimeras were obtained by substituting the DNA sequence encoding the N-terminal extracellular domain of the VIP and secretin receptors by the homologous DNA sequence encoding the secretin (N-Sn/VIP.r) and VIP receptor (N-VIP/Sn.r), respectively. These chimeric receptors were transfected and stably expressed in CHO cells. Their pharmacological properties were then compared to the corresponding recombinant "wild type" receptors, expressed in the same cell line. Binding data were obtained for the wild types and the N-VIP/Sn.r but not for the N-Sn/VIP receptor. Functional data (adenylate cyclase activation) were obtained in all cases. In order to minimize the effects of an excess of receptors and thus, to compare validly binding and functional data, we determined agonists EC50 values after down regulation of the receptors (i.e. after a pretreatment of the cells for 24 h with VIP or secretin). The order of potency of the peptides for receptor occupancy and adenylate cyclase activation indicated that the N-terminal extracellular domain of each receptor was the key element for discrimination between secretin and VIP.

Adenylyl Cyclases↗

PubMed1995

Pharmacological properties of two recombinant splice variants of the PACAP type I receptor, transfected and stably expressed in CHO cells.

Two splice variants of the pituitary adenylate cyclase activating polypeptide (PACAP) type I receptor (PACAP receptor and PACAP/HOP receptor isoform) were stably expressed in Chinese hamster ovary (CHO) cells that did not express constitutively receptors for this family of peptides. The PACAP/HOP receptor protein had a 28 amino acid extension in the C-terminal part of the third intracellular loop. The two cell lines studied, CHO 2-10 (PACAP receptor) and CHO 4-12 (PACAP/HOP receptor) expressed a receptor density of 4.6 +/- 0.3 and 2.6 +/- 0.2 pmol/mg protein, respectively, with corresponding Kd values of 14.2 +/- 2.0 and 8.2 +/- 1.0 nM for [Ac-His1]PACAP-27 used as a tracer. Tracer binding was slightly decreased by GTP in both clones. The Kd values of PACAP-27, PACAP-38, vasoactive intestinal peptide (VIP), PACAP-27 fragments and analogues evaluated by binding competition curves, were higher in CHO 2-10 than in CHO 4-12, whereas the Kd for PACAP-38 fragments did not differ. The receptors were coupled to adenylate cyclase and the EC50 values were lower than the Kd values in both cell lines, suggesting an amplification process due to the existence of spare receptors.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenylyl Cyclases↗

PubMed1995

Localization of transforming growth factor beta 1 and its latent binding protein in human chronic pancreatitis.

BACKGROUND/AIMS: Transforming growth factor beta 1 (TGF-beta 1) is thought to be the mediator of fibrosis in liver, glomerular, and pulmonary fibrosis. This study investigated the expression of TGF-beta 1 precursor (beta 1 latency-associated peptide), latent TGF-beta 1-binding protein (LTBP), and TGF-beta 1 messenger RNA (mRNA) in chronic pancreatitis. METHODS: Beta 1 latency-associated peptide and LTBP expression were studied by immunohistochemistry, and TGF-beta 1 mRNA expression was studied by reverse-transcription polymerase chain reaction analysis in normal pancreatic parenchyma and in tissues from patients with chronic pancreatitis of different etiologies. RESULTS: In normal specimens, TGF-beta 1 precursor was present in islet cells and in a few ductal and acinar cells but not in periductal connective tissue. No immunoreactivity for LTBP was detected. In chronic pancreatitis, TGF-beta 1 precursor was detected mainly in mononuclear cells located in the fibrotic areas and also in ducts damaged by fibrosis, more frequently in calcifying chronic pancreatitis. LTBP was present predominantly in mononuclear cells and in the extracellular matrix around them. TGF-beta 1 mRNA was either not expressed or was faintly expressed in normal tissue, whereas intense signals were detected in chronic pancreatitis. CONCLUSIONS: The findings suggest the involvement of TGF-beta 1 in the development of fibrosis in chronic pancreatitis and the important role of inflammatory cells.

Adult↗

PubMed1995

Interleukin 10 prevents necrosis in murine experimental acute pancreatitis.

BACKGROUND/AIMS: Inflammatory events are believed to play an important role in the pathogenesis of acute pancreatitis. Interleukin 10 (IL-10) recently emerged as a major anti-inflammatory cytokine, inhibiting the secretion of proinflammatory cytokines by monocytes and/or macrophages. The potential protective role of IL-10 in a model of acute necrotizing pancreatitis in mice was tested. METHODS: Animals received two intraperitoneal injections of either 1000 U recombinant IL-10 or control supernatant before and during induction of acute pancreatitis with repeated cerulein injections (seven intraperitoneal injections of 50 micrograms/kg at hourly intervals). RESULTS: Systemic amylase and lipase release peaked 9 hours after the first cerulein injection. This peak was significantly reduced by IL-10 treatment. Histologically, edema and inflammation of the pancreas were observed in both groups, whereas necrosis was dramatically reduced in IL-10-treated animals. Serum tumor necrosis factor levels were undetectable in this model; reverse-transcriptase polymerase chain reaction analysis of resected pancreatic tissues performed at the time of maximal morphological alterations showed a dramatically decreased expression of tumor necrosis factor alpha messenger RNA after IL-10 treatment compared with control pancreatitis. CONCLUSIONS: IL-10 is able to decrease the severity of experimental acute pancreatitis, mainly by inhibiting the development of acinar necrosis. Inhibition of local tumor necrosis factor alpha might explain, at least in part, the protective effect of IL-10.

Acute Disease↗

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↗

PubMed1995

Expression of pituitary adenylate cyclase activating polypeptide and receptors in human brain tumors.

The capacity of brain tumor samples to synthesize pituitary adenylate cyclase activating polypeptide (PACAP) was evaluated by the reverse transcriptase-polymerase chain reaction technique (RT-PCR). The expression of PACAP receptors was assessed by a combination of RT-PCR techniques, conventional binding techniques, and also by the ability of PACAP to stimulate adenylate cyclase activity. A weak PACAP mRNA and PACAP receptor mRNA expression was detected in only 3 of 16 meningiomas. A weak PACAP-stimulated adenylate cyclase activity (+20%) was detected in 10 of the 16 samples but binding of labeled PACAP was never observed. In the 16 gliomas studied (including two oligodendrogliomas and two ependymomas), PACAP mRNA was identified in 13 samples and PACAP receptor mRNA in 15 samples. PACAP receptors were identified in all the samples by binding studies and/or by PACAP stimulation of the adenylate cyclase activity. PACAP mRNA was never detected in pituitary adenomas (three prolactinomas, two mixed PRL-GH-producing tumors, three GH-secreting tumors, three gonadotrophinomas, one ACTH-producing tumor, two nonsecreting tumors) whereas PACAP receptor mRNA was highly expressed in all the tumors except prolactinomas, where it was at the limit of detection, confirming the binding and adenylate cyclase activation results. Thus, it is unlikely that the neuropeptide PACAP could influence meningioma's cell growth; PACAP secreted from extratumoral areas may influence pituitary tumors and PACAP could participate to gliomas development.

Adenoma↗

PubMed1995

Pituitary adenylate cyclase activating polypeptide (PACAP) and vasoactive intestinal peptide stimulate two signaling pathways in CHO cells stably transfected with the selective type I PACAP receptor.

The properties of the pituitary adenylate cyclase activating polypeptide (PACAP) type I receptor were studied on a clone of Chinese hamster ovary cells (CHO) stably transfected with the recombinant receptor. PACAP(1-27), PACAP(1-38) and VIP inhibited [125I-acetyl-His1]PACAP (1-27) binding, stimulated cyclic AMP and inositol phosphates production and induced [Ca2+]i increase with the same order of potency: PACAP(1-27) = PACAP(1-38) > VIP. The concentrations required for half maximal receptor occupancy, IP3- and [Ca2+]i increase were not different for both PACAPs (1 nM) and 100-fold higher than those required for cyclic AMP increase (0.010 nM). These data suggest that the occupancy of a portion of the total receptors available was sufficient for maximal cyclic AMP production but not for maximal IP3 production. It is concluded that the possibility of the type I PACAP receptor being coupled to a transduction pathway is not located at the level of the ligand but rather at the level of the G-proteins.

Adenylyl Cyclases↗

PubMed1995

Detection of c-Ki-ras gene codon 12 mutations from pancreatic duct brushings in the diagnosis of pancreatic tumours.

Differential diagnosis of pancreatic cancer and chronic pancreatitis is sometimes difficult and cytological examination of brushings or aspirated material collected during endoscopic retrograde cholangiopancreatography (ERCP) remains disappointing. As point mutations in codon 12 of the c-Ki-ras 2 gene are found in most pancreatic adenocarcinoma and not in chronic pancreatitis, this study analysed prospectively the presence of these mutations in brushing samples collected during ERCP in 45 patients (26 males, 19 females) showing a dominant stricture of the main pancreatic duct at pancreatography: 24 with pancreatic adenocarcinoma, 16 with chronic pancreatitis, and five intraductal mucin hypersecreting neoplasms. Twenty of 45 patients presented equivocal ERCP findings that did not permit a definite diagnosis. Ki-ras mutations at codon 12 were detected using a rapid and sensitive method based on polymerase chain reaction mediated restriction fragment length polymorphism analysis and confirmed by direct sequencing of polymerase chain reaction products. Results were compared with those provided by routine brush cytology. A definitive diagnosis was established for each patient. Mutations were detected in 20 of 24 patients with pancreatic adenocarcinoma (83%), but in none of the chronic pancreatitis patients and intraductal mucin hypersecreting neoplasms, irrespective of their location. By contrast, only 13 of 24 pancreatic adenocarcinoma (54%) were detected by conventional cytological examination, which yielded four false negative and seven non-contributive results. Sensitivity, specificity, and accuracy of molecular biological and cytological methods were 83%-76%, 100-83%, and 90%-58%, respectively. Notably the mutations could be detected in six patients with small tumour size (< or = 2 cm). In conclusion, Ki-ras analysis performed on pancreatic brushing samples is an efficient procedure, more accurate than cytology in the diagnosis of pancreatic adenocarcinoma, and highly specific in the differentiation between neoplastic and chronic inflammatory ductal changes, especially in patients showing inconclusive ERCP findings.

Adenocarcinoma↗

PubMed1994

Molecular cloning and functional characterization of a human VIP receptor from SUP-T1 lymphoblasts.

We have cloned and sequenced a cDNA isolated from a human SUP-T1 lymphoblast cell line library. It encoded a 457 amino acids protein having 87% identity with the rat PACAP type II, VIP2 receptor. Chinese hamster ovary (CHO) cells stably transfected with cloned cDNA expressed a specific binding of 125I[Acetyl-His1]PACAP-27. This binding was inhibited by GTP, and by the peptides helodermin, VIP, PACAP-27 and PACAP-38 that also stimulated adenylate cyclase activity. The order of potency was PACAP-38 > VIP > or = helodermin > or = PACAP-27. Comparison of the results in two cell lines expressing different receptor densities suggested that helodermin and PACAP-38 had a higher intrinsic activity than VIP and PACAP-27.

Amino Acid Sequence↗

PubMed1994

Properties of the VIP-PACAP type II receptor stably expressed in CHO cells.

The VIP receptor cloned from rat lung (VIP1 receptor from the group of the PACAP-VIP type II receptors) was inserted into a mammalian expression vector and stably transfected into Chinese hamster ovary cells (CHO). Two clones were selected, expressing respectively a high (850 +/- 50 fmol/mg protein, for clone 3) and a low (100 +/- 30 fmol/mg protein for clone 16) number of receptors. Both clones had the same apparent Kd value of binding for VIP and related peptides. The receptor expressed had the same binding properties as the natural VIP receptor, judged from the relative potency of VIP and PACAP analogues and fragments. The EC50 value of adenylate cyclase activation were 3 to 10 fold lower in clone 3 than in 16. The values observed in clone 16 were closer to the binding Kd values. The differences between the two clones were explained by the existence of spare receptors in clone 3, since: (a) the relative efficacy of some fragments were lower in clone 16 than in clone 3; (b) pretreatment of the cells with VIP reduced the number of receptors in both clones and increased the EC50 value for VIP in clone 3 but decreased peptide efficacy in clone 16 without significant change of the EC50 value.

Adenylyl Cyclases↗

PubMed1994

Presence of calcitonin gene-related peptide receptors coupled to adenylate cyclase in human gliomas.

Eleven surgical samples of gliomas (1 of grade II, 3 of grade III and 7 of grade IV) were analyzed. Calcitonin gene-related peptide (CGRP) receptors were identified by 125I-alpha h-CGRP binding in 9 cases and the presence of a CGRP-stimulated adenylate cyclase in all the 11 cases. Tracer binding was inhibited by unlabelled alpha h-CGRP (Kd of 0.3 nM), by (8-37) alpha h-CGRP (Kd of 30 nM), by (12-37) alpha h-CGRP (Kd of 3.000 nM) but not by human calcitonin. The mean density of CGRP receptors (120 fmol/mg membrane protein) was comparable to that of beta-adrenergic receptors. CGRP stimulated 1.4 to 4.7-fold (mean 2.7) the adenylate cyclase activity with a K(act) of 2.0 nM. The CGRP fragments had no intrinsic activity but inhibited the CGRP effect. The (8-37)CGRP fragment had a Ki of 30 nM. Thus, at variance with previous reports on rat and human brain membranes, that showed the presence of CGRP receptors not coupled to adenylate cyclase, we observed in human gliomas the presence of CGRP receptors that, when occupied, stimulated efficiently the adenylate cyclase activity.

Adenylyl Cyclases↗

PubMed1994

Stimulation of tyrosine phosphatase and inhibition of cell proliferation by somatostatin analogues: mediation by human somatostatin receptor subtypes SSTR1 and SSTR2.

The effects of somatostatin analogues RC-160 and SMS-201-995 on tyrosine phosphatase and cell proliferation were investigated in COS-7 and NIH 3T3 cells expressing human somatostatin receptor subtype 1 or 2 (SSTR1 or SSTR2). Binding experiments were performed on membranes from COS-7 cells expressing human SSTR1 or SSTR2 using 125I-labeled [Tyr11]S-14 or [Tyr3]SMS-201-995, respectively. The somatostatin analogues RC-160 and SMS-201-995 exhibited low affinity for SSTR1 (IC50 of 0.43 and 1.5 microM, respectively) and high affinity for SSTR2 (IC50 of 0.27 and 0.19 nM). Addition of these analogues to cells expressing either SSTR1 or SSTR2 did not result in an inhibition of adenylate cyclase activity. In SSTR2-expressing cells, both analogues induced a rapid stimulation of a tyrosine phosphatase activity (EC50: RC-160, 2 pM; SMS-201-995, 6 pM) and an inhibition of serum-stimulated proliferation (EC50: RC-160, 6.3 pM; SMS-201-995, 12 pM). In SSTR1-expressing cells, only RC-160 induced stimulation of a tyrosine phosphatase activity. Both analogues caused an inhibition of cell proliferation at a concentration higher than 10 nM in accordance with their affinities for the SSTR1 receptor subtype. A good correlation between the affinities of RC-160 and SMS-201-995 for each receptor subtype and their potencies to inhibit cell proliferation suggests the involvement of these receptors in cell growth regulation. Tyrosine phosphatase was stimulated by both these analogues in SSTR2 and by RC-160 in SSTR1 at affinities similar to their ability to inhibit growth and bind to receptors, implicating tyrosine phosphatase as a transducer of the growth inhibition signal. We also found that mRNAs of receptor subtypes were variably expressed in different pancreatic and colon cancer cell lines, indicating the necessity of a precise analysis of receptor subtypes in target tissues before therapy with analogues.

3T3 Cells↗

PubMed1994

Characterization of ocular receptors for pituitary adenylate cyclase activating polypeptide (PACAP) and their coupling to adenylate cyclase.

Pituitary adenylate cyclase activating polypeptide (PACAP), a recently discovered neuropeptide, has large structural homology with vasoactive intestinal polypeptide (VIP). Two molecular forms exist, one with 27 (PACAP-27) and one with 38 (PACAP-38) amino acids. PACAP-27 is identical to the N-terminal of PACAP-38. Two major types of PACAP receptors have been identified; selective PACAP receptors, which bind PACAP with a much higher affinity than VIP, and non-selective VIP/PACAP receptors, which bind PACAP and VIP with equally high affinity. In the present investigation, PACAP receptors in different parts of the albino rabbit eye, and their coupling to adenylate cyclase were characterized. Crude tissue homogenates from iris, ciliary body, retina and choroid were used. Competition binding curves were established for VIP, PACAP-27 and PACAP-38, with [125I]VIP or [125I-Acetyl-His1]PACAP-27 as tracer. The effects on adenylate cyclase activity were determined by plotting dose-response curves (10(-10)-10(-6) M) for VIP, PACAP-27 and PACAP-38. The anterior uvea had mainly (approximately 80%) non-selective VIP/PACAP receptors, but a small amount of selective PACAP receptors was detected. In the retina, the selective PACAP receptor predominated (approximately 85%), while the choroid (including the retinal pigment epithelium) had approximately 60% selective PACAP receptors. PACAP-27 and PACAP-38 stimulated the formation of cAMP with the same efficacy: 6.9-fold in the ciliary body, 3.6-fold in the iris, 5.1-fold in the retina and 2.3-fold in the choroid.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenylyl Cyclases↗

PubMed1994

Chromogranin A(210-301) is the major form of pancreastatin-like material in human gut extracts and endocrine tumors.

A radioimmunoassay of human pancreastatin was developed using a rabbit antiserum that selectively recognized the C-terminal amidated end of the peptide, and it was used for the identification of the molecular forms of pancreastatin in human gut (stomach, duodenum, small intestine, colon) and endocrine tumor extracts (liver metastasis of a gastrinoma and a medullary carcinoma of thyroid, one nonsecreting pancreatic tumor, one recurrence of a gut carcinoid, one vipoma and one insulinoma). In all gut extracts, a gel filtration chromatography revealed the presence of three peaks of pancreastatin-like immunoreactivity. The predominant form eluted with an apparent molecular weight higher than that of pancreastatin. This form was also predominant in the endocrine tumors analyzed, except in the insulinoma, where a lower molecular weight form predominated. The high molecular form was further purified from a liver metastasis of a gastrinoma. The pancreastatin-like immunoreactivity eluted in all the chromatographical systems (reverse-phase, ion exchange) as a single peak that was finally purified to homogeneity and sequenced. The sequence of the first 29 N-terminal amino acids was obtained unambiguously and corresponded to the sequence 210-238 of chromogranin A. Considering the selectivity of the assay used for peptide identification, this major form was identified as the fragment 210-301 of chromogranin A. It is likely that the predominant form of pancreastatin in human gut extracts and noninsular tumors is a 92 amino acid peptide.

Amino Acid Sequence↗