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PubMed1980

Glucagon and glicentin immunoreactivity are topologically segregated in the alpha granule of the human pancreatic A cell.

Glicentin is a 100-amino acid polypeptide purified from the porcine intestine and containing the immunodeterminants of glucagon. We have previously reported the presence of glicentin immunoreactivity in the glucagon-containing, specific secretory granules (alpha granules) of the pancreatic and gastric A cell. With an improved immunocytochemical probe, the protein A-gold (pAg) technique, we are now able to show that glucagon and glicentin-like material are topologically segregated in the alpha granule of the human pancreatic A cell.

Glucagon↗
PubMed1982

Evidence that enteroglucagon (II) is identical with the C-terminal sequence (residues 33-69) of glicentin.

Enteroglucagon (II) was isolated from extracts of pig ileum mucosa by repeated gel filtrations, and its immunochemical and chromatographic characteristics were compared with those of a synthetic peptide corresponding to the 33-69 sequence of pig glicentin, before and after digestion with trypsin or trypsin followed by carboxypeptidase B, by using five region-specific assays covering most of the glicentin sequence. Enteroglucagon (II) and the synthetic peptide behave identically under three different conditions of chromatography as determined with all five assays (including a highly specific radioreceptor assay), and gave rise to similar fragments after enzyme digestion. It was therefore concluded that enteroglucagon (II) and the 33-69 sequence of glicentin are most probably identical.

Amino Acid Sequence↗
PubMed1991

Detection of proinsulin, C-peptide, insulin-A-chain, and glicentin in pancreatic islet cells of early human fetogenesis.

The presence of C-peptide, proinsulin, insulin-A-chain, and glicentin in human fetal pancreatic cells by using the PAP-technique was investigated and the results obtained compared with the occurrence of insulin or glucagon immunoreactive cells. In pancreatic sections obtained from 10 weeks old human fetuses we could identify cells reacting with antibodies directed against C-peptide, proinsulin, and insulin-A-chain. The majority of the cells were found in the duct epithelium and their number increased from the 10th to 14th week forming clusters near the ducts. The number and localization of the cells correspond exactly to the insulin positive cells. The presence of proinsulin and insulin-A-chains is a further proof of biological activity already in an early step of fetal development. The presence of glicentin-positive cells in the 10th week of gestational age as well as cells reacting with glucagon antibodies provide evidence for active glucagon biosynthesis. The number of these cells increased markedly in the 14th week of gestational age.

Antibodies↗
PubMed2001

Effect of glucagon, glicentin, glucagon-like peptide-1 and -2 on interdigestive gastroduodenal motility in dogs with a vagally denervated gastric pouch.

BACKGROUND: We previously reported that inhibition of gastric motility and hypertrophy of the small intestinal mucosa were observed after ileo-jejunal transposition which induced hypersecretion of enteroglucagon. Our aim was to study the effect of four enteroglucagon-related peptides (glucagon, glucagon-like peptide (GLP)-1, -2 and glicentin) on gastroduodenal motility and their mechanisms of action. METHODS: The effect of these four peptides on motilin-induced interdigestive contractions was studied in dogs with vagally denervated gastric pouches equipped with four strain gauge force transducers on the pouch, gastric body, antrum and duodenum. Whether or not nitric oxide synthase inhibitor or phentolamine and propranolol reverses the inhibitory effect of those peptides was also studied. RESULTS: Glucagon inhibited contractions in the pouch and stomach but had no effect on duodenal contractility. GLP-1 inhibited contractions at all sites. GLP-2 inhibited contractions in the pouch but did not affect motility in the neurally intact gastroduodenum. Glicentin had no effect on contractions at any site. Pretreatment with either a nitric oxide synthase inhibitor or phentolamine and propranolol reversed the inhibitory effect of glucagon, GLP-1 and GLP-2 on contractions in the pouch, but did not alter the inhibitory effect of glucagon and GLP-1 on motility in the neurally intact stomach and duodenum. CONCLUSIONS: These results suggest that the effects of four peptides on gastroduodenal motility differ, and changes occur in the enteric neural modulation of motor activity after chronic surgical extrinsic denervation.

Animals↗
PubMed1984

Neurons of the A1/A2 region in the guinea pig medulla oblongata containing glucagon, glicentin, and dopamine-beta-hydroxylase immunoreactivity.

Glucagon- (GLU-IR), glicentin- (GLI-IR) and dopamine-beta-hydroxylase (DBH-IR) immunoreactive neurons were mapped in the medulla oblongata of colchicine pretreated guinea pigs. Numerous GLU-IR and GLI-IR perikarya are located in the area of the nucleus ambiguus, in the adjacent formatio reticularis, and less frequently in the nucleus reticularis lateralis, the nuclei raphe obscurus and commissuralis and the caudal part of the nucleus solitarius. In these nuclei, the coexistence of glicentin and glucagon within the same perikarya is demonstrated. DBH-IR is also found in neurons of the nuclei commissuralis, solitarius and reticularis lateralis (A1/A2 system of Dahlström and Fuxe 1964, 1965). However, a coexistence of GLU/GLI-IR and DBH-IR within the same neuron is not observed.

Animals↗
PubMed1985

Glicentin is present in the pig pancreas.

Specimens from porcine pancreas and ileal mucosa were extracted in acid/ethanol, subjected to gel permeation chromatography, ion-exchange chromatography, enzymatic peptide degradation, reverse-phase HPLC, and analysed for glucagon-like and glicentin-like immunoreactivity by region-specific radioimmunoassays. Results obtained with all methods were consistent with the hypothesis that glicentin is present in the pig pancreas in small amounts.

Animals↗
PubMed1986

Co-existence of glicentin and peptide YY in colorectal L-cells in cat and man. An electron microscopic study.

Electron microscopic immunocytochemistry using protein A-gold labelling of ultrathin sections revealed immunoreactive glicentin (gut-type glucagon) and peptide YY (PYY) in virtually all secretory granules in a population of L-type endocrine cells in feline colon and human rectum. The granules of the human glicentin/PYY cells were considerably smaller in size than those in the cat. In both species the results indicate co-existence of glicentin and PYY in the same secretory granules, despite the probable derivation of the two peptides from two different precursors.

Animals↗
PubMed1987

Glucagon, glicentin, proglucagon, PYY, PP and proPP-icosapeptide immunoreactivities of rectal carcinoid tumors and related non-tumor cells.

Glucagon/PP-related peptides were detected immunohistochemically in 18 out of 22 cases of rectal tumors investigated. The reactive tumors showed prevalence of trabecular or mixed trabecular-acinar structure and moderate staining with Grimelius' silver and lead-hematoxylin. Three of the remaining 4 cases were characterized by reactivity for 5-hydroxytryptamine only, prevalence of a solid nest structural component and intense staining with Grimelius' silver technique and lead-hematoxylin. Fifteen of the 18 glucagon/PP-reactive cases were investigated immunohistochemically with a series of 6 sera directed against different sequences of glucagon, glicentin and proglucagon, and of 7 sera directed against PP, PYY and proPP-icosapeptide. A large spectrum of glucagon-related immunoreactivities, including C-terminus and mid-portion glucagon-immunoreactivity, N- and C-terminus glicentin-immunoreactivity, GLP1- and GLP2-immunoreactivity, were detected in human rectal L cells and most rectal carcinoids. With the exception of a few scattered cells in the rectal mucosa and in 3 tumors, C-terminus glucagon-immunoreactivity was obtained only after trypsin or subtilisin treatment of tissue sections. Both PYY and PP/proPP-like peptide(s) were detected in rectal L cells and carcinoids, with prevalence of PYY in normal cells and PP/proPP-like peptides in tumor cells. It is concluded that the same or closely related hormone/prohormone sequences are synthesized and stored in rectal endocrine cells and carcinoid tumors although differences of quantitative expression, post-translational cleavage or reactivity to antibodies may occur. The usefulness of protease treatments of tissue sections to unmask immunoreactivities of uncleaved propeptides or fixative-denatured peptides is outlined.

Animals↗
PubMed1983

Gastric inhibitory peptide-like immunoreactivity in glucagon and glicentin cells: properties and origin. An immunocytochemical study using several antisera.

Although gastric inhibitory peptide (GIP) has never been detected outside the upper small intestine by immunochemical methods, GIP-like immunoreactivity has been demonstrated by immunocytochemistry in the glucagon/glicentin cells of pancreas, and gut. In the present study several GIP antisera (five polyclonal and one monoclonal) were tested on specimens from pancreas and intestines of several mammalian species, including man. Two of the polyclonal antisera and the monoclonal one stained cells in the upper small intestine only, while the other three also stained cells in the pancreas, ileum, and colon. Monoclonal anti-GIP did not stain GIP cells in man. The immunostaining produced could not be abolished by pretreatment of the antisera with glucagon or glicentin in excess, whereas small amounts of synthetic or natural porcine GIP prevented the immunostaining. Thus, three of the antisera are specific for GIP, while the other three recognize not only GIP but also GIP-like peptides. The results suggest that the glucagon/glicentin cells contain peptides distinct from GIP but sharing an immunodeterminant with GIP. The GIP-like immunoreactivity in the glucagon cells of the rat pancreas was not altered by infusion of GIP or by elimination of the bulk of endogenous GIP by resection of the upper small intestine, indicating that the GIP-like peptide is produced in the glucagon cells rather than accumulated from the circulation. The nature of this GIP-like peptide is unknown. Conceivably, it represents the cryptic portion of the glucagon precursor molecule. In some species a proportion of the GIP cells in the proximal small intestine displayed glicentin-like immunoreactivity as well, emphasizing the relationship between GIP cells on the one hand and glucagon/glicentin cells on the other.

Animals↗
PubMed2001

Large lymph node metastasis gives hint to a glicentin positive small endocrine rectal carcinoma.

In a patient with a small endocrine carcinoma of the rectum, an unusually large lymph node metastasis was the only preoperative clinical finding. Low anterior rectal resection with total mesorectal excision and lymph node dissection was performed. The tumor demonstrated some highly unusual characteristics: it was classified as a small, low-grade neuroendocrine rectal carcinoma of L-cell type with three large lymph node metastases and morphological consistency with an endocrine tumor and focal positivity of glicentin, demonstrating a proliferation of smooth muscle cells. The established Capella classification of endocrine tumors of the rectum by morphological findings would have characterized this primary tumor as benign. In this case, however, clinical and histopathological findings more accurately reflected its malignant potential.

Aged↗
PubMed1997

Effect of glicentin, oxyntomodulin and related peptides on isolated gastric smooth muscle cells.

Glicentin (proglucagon 1-69 GLIC) and oxyntomodulin (proglucagon 33-69 or OXM) are two peptide hormones that are co-released from ileum and large intestine during digestion. They modulate in vivo gastric acid secretion and the gastro-pyloro-duodenal activity. The specificity of their effects is linked to the presence of their C-terminal octapepide. As yet, no isolated target cell that responds specifically to this family of peptides has been described. The present report describes the in vitro effect of human synthetic GLIC, OXM and octapeptide-bearing fragments on smooth muscle cells isolated from the rabbit antrum. GLIC or OXM decreased the mean length of the cells by: 13.9 +/- 0.8% and 15.5 +/- 0.9%, respectively - GLIC being 16 times more potent than OXM (respective EC50 values: 5 and 83 pM). The C-terminal fragments OXM(19-37) and OXM(30-37) were as efficient as GLIC or OXM. Their potencies were OXM = OXM(19-37)>>OXM(30-37). Glucagon, which corresponds to OXM without the C-terminal octapeptide, or glucagon-like peptide-1 (7-36 amide) did not have any effect. The response to OXM was not influenced by antagonists to muscarinic, cholecystokinin or substance P receptors. In conclusion, our studies demonstrate for the first time an isolated target cell that responds specifically to GLIC, OXM and other octapeptide-bearing peptides.

Animals↗
PubMed2004

Oxyntomodulin and glicentin are potent inhibitors of the fed motility pattern in small intestine.

Glicentin (GLIC) and oxyntomodulin (OXM or GLIC 33-69) are gut hormones which regulate digestion. They are known to reduce digestive secretions and to delay gastric emptying. Their biological activities on intestinal motility are still unknown. The effect of a systemic GLIC or OXM increase was investigated in rats on the food intake, the postprandial myoelectrical activity of small intestine and the orocaecal transit. An OXM or GLIC i.v. infusion was applied during the 5 min preceding food onset and during the first 15 min of food intake. This determined a three- to fourfold increase of the preprandial OXM-GLIC level. The OXM or GLIC plasma increase did not modify food intake. OXM infusion slowed down gastric emptying when the stomach contained 3/4 of the ingested food (before T 3 h). The quantity of food delivered in jejunum was subsequently smaller (P < 0.05). In the small intestine, the duration of postprandial myoelectrical activity (50-60 min g(-1) of ingested food) was reduced by 70% (P < 0.001) on duodenum or jejunum and by 54% (P < 0.01) on ileum in OXM-treated rats. An interdigestive motility profile was settled and an acceleration of both gastric emptying and transit rate was thereafter evidenced (after T 3 h). GLIC also reduced the duration of the postprandial myoelectrical activity on duodenum and jejunum (65 and 63% respectively, P < 0.05), but was not as efficient as OXM on ileum. In pathological states such as acute adult gastroenteritis, OXM and GLIC exhibit a two- to fivefold increase in their plasma concentrations. The present findings suggest that OXM and GLIC could, in that disease, contribute to exclude pathogens, due to their joined action on gut motility.

Animals↗
PubMed1999

Glicentin and oxyntomodulin modulate both the phosphoinositide and cyclic adenosine monophosphate signaling pathways in gastric myocytes.

We have investigated the transduction pathways mediating the contractile effect of two glucagon-containing peptides, glicentin (GLIC) and oxyntomodulin (OXM), on smooth muscle cells isolated from rabbit antrum. Low concentrations of GLIC induced a biphasic and rapid (first phase at 5-8 sec) Ins(1,4,5)P3 production. By comparison, higher concentrations of OXM or OXM(19-37) were required to obtain biphasic time-courses of Ins(1,4,5)P3 production. In a Ca2+ free medium, the first phase of Ins(1,4,5)P3 production induced by GLIC or OXM was maintained, while the second phase disappeared. In saponin-permeabilized cells, all three peptides induced cell contraction with similar efficacies and potencies. Exogenous Ins(1,4,5)P3 mimicked the contractile effect of the peptides and heparin, which inhibits the Ins(1,4,5)P3 binding to its receptor, prevented contraction stimulated by each effector. We conclude that a Ca2+ mobilization from the intracellular stores is essential in the contractile effects of GLIC and OXM. Using the fluo-3 probe, a [Ca2+]i increase was observed in the presence of GLIC, OXM, or OXM(19-37). The three peptides reduced by 30-40% the cAMP content of cells stimulated by forskolin. This effect was pertussis toxin sensitive as demonstrated with OXM(19-37). Our data constitute important clues for the existence in smooth muscle cells of receptor(s) specific for the GLIC/OXM hormones, coupled via G protein(s) to both Ca2+ and cAMP pathways.

Animals↗
PubMedDate not supplied

Role of recombinant human glicentin in the normal human jejunum: an in vitro study.

BACKGROUND/AIMS: Glicentin (GL) is known as an inhibitory factor for alimentary tract movement and the possibility that GL may be a neuromodulator of the non-adrenergic non-cholinergic (NANC) inhibitory nerves has been reported from animal experiments. Since sufficient amounts of GL have not been available for the physiological studies, there is no report concerning the effects of GL on the enteric nervous system in the normal human small intestine. Recently synthesized recombinant human GL (rh-GL) has become available to study the physiological action of GL. To clarify the physiological significance of GL in the normal human small intestine, enteric nervous responses to GL in the normal small bowel were investigated. METHODOLOGY: Normal jejunal muscle strips (thirty-two preparations) derived from patients who underwent jejunal resection for advanced gastric cancers (14 cases) were used. The subjects consisted of 10 men and 4 women, aged from 48 to 66 years with a mean age of 59.9 years. A mechanographic technique was used to evaluate the in vitro jejunal muscle responses to GL (recombinant human GL; rh-GL) of adrenergic and cholinergic nerves before and after treatment with various autonomic nerve blockers. All muscle strips used in this study reacted to the electrical field stimulation (EFS), which was thus suitable for stimulation of enteric nervous system. RESULTS: In experiment I (the responses to rh-GL after blockade of the adrenergic and cholinergic nerves) the inhibition reaction ofjejunal contraction movement was concentration-dependent; 0% at 1 x 10(-9) g/mL, 6.3% at 1 x 10(-8) g/mL, 12.5% at 1 x 10(-7) g/mL, and 43.8% at 1 x 10(-6) g/mL. The remaining muscle strips demonstrated no reaction to rh-GL. In addition, significant differences were noted between 1 x 10(-9) and 1 x 10(-6) g/mL, between 1 x 10(-8) and 1 x 10(-6) g/mL, and between 1 x 10(-7) and 1 x 10(-6) g/mL (P=0.0005, P=0.0066, P=0.0359, respectively). Rh-GL concentration-dependently inhibited a contraction reaction after blockade of the adrenergic and cholinergic nerves. In experiment II (responses to rh-GL following administration of tetrodotoxin) tetrodotoxin did not block the inhibition of contraction reaction in response to rh-GL in the human jejunum. Inhibition reaction of contraction movement was seen in the jejunal muscle strips, as in experiment I. CONCLUSIONS: GL plays an important role in the regulating inhibition of the contraction reaction in normal human jejunum via NANC nerves, and has a direct action on the jejunal muscle receptor.

Aged↗
PubMed1984

Coexistence of peptide YY and glicentin immunoreactivity in endocrine cells of the gut.

Endocrine cells containing peptide YY (PYY) were numerous in the rectum, colon and ileum and few in the duodenum and jejunum of rat, pig and man. No immunoreactive cells could be detected in the pancreas and stomach. Coexistence of PYY and glicentin was revealed by sequential staining of the same section and by staining consecutive semi-thin sections. Since the PYY sequence is not contained in the glucagon/glicentin precursor molecule the results suggest that the PYY cell in the gut expresses two different genes coding for regulatory peptides of two different families.

Animals↗
PubMed1982

Glicentin-immunoreactive perikarya and varicosities in the guinea pig central nervous system.

Glicentin-immunoreactive (GLI-IR) neurons and nerves were studied in the central nervous system of guinea pig. GLI-IR perikarya were found in the medulla oblongata located in the nucleus tractus solitarii, in the nucleus commissuralis, in the nucleus reticularis lateralis and the formation reticularis. Immunoreactive varicosities, however, were seen in many other areas of the central nervous system such as in the hypothalamus, in the nucleus proprius striae terminalis, in the nuclei thalami mediani, in the substantia grisea centralis, in the nuclei raphe, in the formatio reticularis and in the vagus neucleus tractus solitarii-system. Some of the described GLI-IR varicosities may therefore be extensions of the neurons located in the medulla oblongata. Furthermore, the role of GLI as a putative neurotransmitter is discussed.

Animals↗
PubMed1980

Transformation of glicentin-containing L-cells into glucagon-containing cells by enzymatic digestion.

Exposure of sections of ileal mucosa to enzymatic digestion with trypsin and carboxypeptidase B reveals a population of immunofluorescent cells after incubation with a specific C-terminally directed antiglucagon serum. These cells, unreactive before enzyme treatment, were identified as L-cells by their immunoreactivity to antiglicentin serum and to cross-reacting (N-terminal) antiglucagon sera. The presence in the L-cells of antigenic sites characteristic of the glucagon-containing cells (A-cells) emphasizes the close relationships between these two cell types, and it further supports the hypothesis of glicentin as a glucagon precursor.

Animals↗