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At least 163 records · Page 9Linked to original sources
PubMed1986

Phenethyl ester derivative analogues of the C-terminal tetrapeptide of gastrin as potent gastrin antagonists.

A series of phenethyl ester derivative analogues of the C-terminal tetrapeptide of gastrin, in which the phenylalanyl residue has been replaced by a phenethyl group and the peptide bond between aspartic acid and phenylalanine by an ester bond, were synthesized. None of these derivatives were able to stimulate gastric acid secretion in the anesthetized rat, whereas they inhibited gastrin-induced acid secretion with ED50 values between 0.02 and 1.5 mg/kg. Among these derivatives, Boc-beta Ala-Trp-Leu-Asp phenethyl ester (9) and Boc-beta Ala-Trp-Leu-Asp p-fluorophenethyl ester (16) were very potent in inhibiting gastrin-induced acid secretion. From these studies, the significant role of the C-terminal dipeptide of gastrin was pointed out. More particularly, the functional role of the phenylalanine through the C-terminal carboxamide and its binding role through its aromatic ring were demonstrated.

Animals↗
PubMed2001

Effect of gastrin and anti-gastrin antibodies on proliferation of hepatocyte cell lines.

Gastrin (G-17) and its precursor glycine-extended gastrin (G-17-gly) have been shown to be trophic to some gastrointestinal tumors. This in vitro study assessed the effect of G-17, G-17-gly, anti-gastrin antibodies (anti-G-17), and the CCK-B receptor antagonist PD135,158 on three hepatoma cell lines (PLC/PRF/5, HepG2 and MCA-RH7777) and an embryonic liver cell line (WRL68). The pancreatic adenocarcinoma cell line AR42J was used as a positive control. G-17 and G-17-gly caused significant proliferation of AR42J and WRL68 cell lines. G-17-gly but not G-17 induced significant proliferation of the PLC/PRF/5 cell line. Anti-G-17 and PD135,158 significantly inhibited unstimulated AR42J and WRL68 cell lines. Anti-G-17 also inhibited the proliferative effects of G-17 and G-17-gly on AR42J, WRL68, and PLC/PRF/5 cell lines, whereas PD135,158 inhibited the proliferative effect of G-17 only. G-17 and G-17-gly as well as anti-G-17 and PD135,158 had no effect on HepG2 and MCA-RH77777 cell lines. It is concluded that G-17-stimulated proliferation is mediated via the CCK-B receptor and G-17-gly via a separate, as yet uncharacterized, receptor. There may therefore be a role for gastrin in embryonic hepatocellular proliferation and perhaps also in the proliferation of some hepatocellular tumors.

Animals↗
PubMed1994

Inhibitory effects of the gastrin receptor antagonist CR2093 on basal, gastrin-stimulated and growth factor-stimulated growth of the rat pancreatic cell line AR42J.

AR42J, a rat pancreatic cell line expressing receptors for both gastrin and epidermal growth factor (EGF), has been used to examine the effect of the gastrin receptor antagonist CR2093 on basal, gastrin-17 (G17), EGF and transforming growth factor (TGF)-alpha stimulated growth in vitro. In serum-free conditions, CR2093 reduced the basal growth of AR42J at a concentration known to displace physiological levels of G17 from gastrin receptors and this effect was reversed by G17 at 1 x 10(-9) M. Alone, G17 had little effect on growth, but EGF and TGF-alpha stimulated growth to 181 and 176% of control values, respectively, and marked synergy was observed when G17 was used in combination with both EGF (212%) and TGF-alpha (259%). When CR2093 was added, the synergistic effects of the G17/EGF and G17/TGF-alpha combinations were reduced to basal levels. In addition, CR2093 inhibited the growth stimulation induced by EGF and TGF-alpha alone. When the ability of CR2093 to bind to EGF receptors was assessed in a ligand binding assay, it was found that the antagonist displaced up to 23% of labeled EGF. Thus CR2093 has potent inhibitory effects on the basal growth of AR42J which can be reversed by G17. It can also inhibit type 1 growth factor-stimulated growth, but although this action may in part be related to the antagonist's ability to inhibit binding to the EGF receptor, other mechanisms may be involved.

Amino Acids↗
PubMed1977

Serum gastrin response to acute and chronic hypercalcaemia in man: studies on the value of calcium stimulated serum gastrin levels in the diagnosis of Zollinger-Ellison syndrome.

In this study the effect of calcium infusion over 3 h without gastric aspiration on serum gastrin was determined in fifteen normal subjects, ten patients with duodenal ulcer, nine with stomal ulcer, five with total gastrectomy, six with achlorhydria and sixteen with proved or presumed Zollinger-Ellison (ZE) syndrome. Serum gastrin only rose significantly in the patients with ZE-syndrome or achlorhydria. An increase of above or below 50% of basal value seems to be a valuable criterion by which to differentiate between patients with and without ZE-syndrome. Serum gastrin levels in forty-four patients with chronic hypercalcaemia (72+/-24 pg/ml, mean+/-SD) were not significantly different from the levels in 100 normal subjects (66+/-18 pg/ml; P greater than 0.10). However, in one patient with ZE-syndrome and in two patients with achlorhydria serum gastrin values were markedly higher during chronic hypercalcaemia than during normocalcaemia. It is concluded that acute or chronic hypercalcaemia without gastric aspiration does not lead to hypergastrinaemia in the absence of ZE-syndrome or achlorhydria.

Acute Disease↗
PubMed1994

Identification of gastrin component I as gastrin-71. The largest possible bioactive progastrin product.

Gastrin component I is the largest hormonally active form of gastrin. In order to determine its structure, we isolated progastrin-derived peptides from normal human antral tissue. A radioimmunoassay specific for sequence 20-25 of human progastrin was developed to monitor the purifications. After four or five steps of reverse-phase chromatography, the peptides were pure and could be identified by a combination of microsequence, amino acid and mass spectral analysis as well as by a library of sequence-specific immunoassays. In addition to intact progastrin 1-80, fragments 1-71, 1-35, 6-35, 20-35, and 20-36 of progastrin were identified. Only the 71-amino-acid peptide contained at its C-terminus the alpha-amidated bioactive site (Trp-Met-Asp-Phe-NH2). This unoheptacontapeptide amide (gastrin-71) corresponds to component I and is the largest possible bioactive product of progastrin. Its structure shows that progastrin is used in its entirety for biosynthesis of active peptides. The occurrence of fragments 6-35, 20-35, and 20-36 demonstrate that antral progastrin is partially cleaved at two monobasic sites (Arg5 and Arg19) in addition to processing at the three C-terminal dibasic sites. The results show that both the N- and C-terminal parts of antral progastrin undergo extensive processing. The results also suggest that progastrin may follow two different processing pathways of which the less trafficked releases gastrin-71.

Amino Acid Sequence↗
PubMed1999

A comparison of the therapeutic effectiveness of gastrin neutralisation in two human gastric cancer models: relation to endocrine and autocrine/paracrine gastrin mediated growth.

BACKGROUND: Gastrin is a growth factor for established tumours. AIMS: To investigate the therapeutic effect of antibodies, raised against the Gastrimmune immunogen, which neutralise the glycine extended and carboxy amidated forms of gastrin 17 in two human gastric cancer models. METHODS: MGLVA1 cells (which have a gastrin autocrine/paracrine phenotype) and ST16 cells (which have an endocrine phenotype) were injected into the peritoneal cavity of SCID mice. Peritoneal tumours, ascites, and cachexia formation occurred, with the monitored endpoint being morbidity. RESULTS: In MGLVA1 cells, intravenous administration of antibodies raised against Gastrimmune increased the 50% median survived by 25% at three different initial cell seeding concentrations (1 x 10(6)-5 x 10(5) per mouse). In ST16 cells, the effect of Gastrimmune induced antibodies on time to morbidity was greatest at the lowest cell seeding concentration (5 x 10(5) cells/mouse) with the 50% median survival increased by 74% and overall survival achieved in 38% of the mice. CONCLUSIONS: Gastrimmune may have potential therapeutic benefit on gastrin sensitive gastric tumours and may interact with both endocrine and autocrine mediated growth pathways.

Animals↗
PubMed1977

Bioassay and radioimmunoassay of gastrin and significance of gastrin degradation products.

Inactivation of gastrin was studied (a) in vitro by incubation with a high-speed supernatant fraction of rat small bowel mucosa and (b) in vivo by perfusing gastrin through the small bowel vascular bed in anaesthetized dogs. In both types of experiment there was a highly significant loss in the bioactivity of gastrin, but no significant change in its immunoreactivity. This showed that gastrin was inactivated by a subtle chemical change which rendered the molecule biologically inactive, yet left its immunoreactivity unimpaired.

Animals↗
PubMed1976

The effect of intravenous infusion of synthetic human gastrin-I on lower esophageal sphincter (LES) pressure in the dog and its relation to gastrin level.

To demonstrate the relation between gastrin level and lower esophageal sphincter (LES) pressure, experiments with intravenous infusions of synthetic human gastrin-I (SHG-I) were performed in anaesthetized dogs. The results show that infusions with 5 mug-kg-1-h-1 SHG-I have an initially increasing effect on LES pressure but produce unphysiologically high gastrin blood levels. Physiological levels of gastrin were measured only using an infusion dose of 0.5 mug-kg-1-h-1, which was below the threshold for increasing LES pressure.

Animals↗
PubMed1993

Effect of Helicobacter pylori eradication on antral gastrin- and somatostatin-immunoreactive cell density and gastrin and somatostatin concentrations.

The density of antral gastrin (G)- and somatostatin (D)-immunoreactive cells and the contents of antral gastrin and somatostatin were investigated in endoscopic antral biopsy specimens from patients with duodenal ulcer before and after eradication of Helicobacter pylori. After H. pylori eradication both antral somatostatin concentration (p = 0.0002) and antral D-cell density (p = 0.01) increased significantly. Conversely, although the number of G-cells was unchanged, antral (p = 0.0002) and serum (p = 0.001) gastrin contents decreased significantly. The number of oxyntic D-cells did not change significantly. These results strongly suggest that the hypergastrinaemia observed in H. pylori-positive patients may be due to a deficiency in antral somatostatin, which normally inhibits the synthesis and release of gastrin.

Adult↗
PubMed1991

[Blood gastrin and ultrastructure of gastrin-producing cells in chronic gastritis with secretory insufficiency].

The content of basal gastrin and ultrastructure of gastrinproducing cells was studied in 81 patients showing chronic gastritis with secretory insufficiency. The highest level of gastrin was revealed in the blood of patients with diffuse atrophic gastritis, moderately increased--focal atrophic gastritis. The blood gastrin was reduced in patients with antral gastritis. A study of the ultrastructure of gastrinproducing cells revealed their high functional activity in diffuse atrophic gastritis and a moderate in focal atrophic gastritis. Changes of the gastrin level and ultrastructure of gastrinproducing cells should be considered in the choice of treatment methods.

Adult↗
PubMed1986

Synergistic interaction between an H2-receptor antagonist and enprostil on 24-hour intragastric pH, serum gastrin concentration, and tissue immunoperoxidase staining for gastrin, somatostatin, and serotonin in a patient with metastatic gastrinoma.

A 56-year-old woman newly diagnosed as having Zollinger-Ellison syndrome due to a metastatic gastrinoma underwent 24-hour intragastric pH monitoring, serum gastrin (total, G-17 and G-34) measurements, and immunoperoxidase staining of duodenal, antral, and gastric body biopsies for gastrin, somatostatin, and serotonin. Determinations were made while the patient was given different doses of ranitidine, enprostil (a synthetic orally administered prostaglandin E2), or ranitidine plus enprostil. Following are the findings from this single-patient study: Intragastric pH was persistently low but varied in response to food when the patient was given ranitidine. Immunocytochemical staining of antral biopsies obtained before the patient was treated revealed a reduced number of cells containing G-17 and G-34 but an increase in the antral somatostatin-containing D-cells. Treatment with 35 micrograms of enprostil BID plus 300 mg of ranitidine BID for two and 11 weeks was associated with an increased number of duodenal G-cells, a decrease in antral D-cells, and a decrease in the number of antral serotonin-containing cells. Enprostil in a dosage of 35 or 70 micrograms BID had no effect on intragastric pH, but when enprostil was given in combination with ranitidine, postprandial and nocturnal intragastric alkalinity was accentuated along with a return of duodenal and antral G-cells and a loss of the antral D-cell hyperplasia. Optimal pH control was achieved with 300 mg of ranitidine BID; more frequent dosing with ranitidine did not further increase intragastric pH. Both the total serum gastrin concentration and G-17 levels fluctuated in response to meals. The serum concentrations of total gastrin, G-17, and G-34 were reduced with enprostil and with ranitidine.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1984

Fasting and postprandial serum gastrin levels in obese and slim subjects, and the effects of surgical treatment for obesity on serum gastrin levels.

23 obese and 17 control subjects were studied after ingestion of a heavy breakfast, and 11 obese and 11 control subjects were studied after ingestion of a mixed liquid test meal. Five subjects from the latter group were also studied two and six weeks after a jejuno-ileal bypass operation and the remaining six subjects from this group were studied twelve weeks after a stapled gastric partitioning. No significant differences in fasting or postprandial serum gastrin levels were found between the obese and the lean subjects, neither when studied with the breakfast meal nor when studied with the mixed liquid test meal. After the jejuno-ileal bypass operation the serum gastrin levels were not significantly different from the preoperative ones, whereas both the fasting and the postprandial serum gastrin levels were significantly augmented after the stapled gastric partitioning procedure. The group operated on with the latter method was also studied with an insulin test before and after the operation. Similar to that seen after ingestion of the mixed liquid test meal, the serum gastrin levels after the insulin-induced hypoglycemia were significantly higher postoperatively.

Adult↗
PubMed1995

Alteration in gastric nerve fibers containing gastrin-releasing peptide in relation to the gastrin-producing cell population after truncal vagotomy in a rat model.

The fine structural alteration in the gastric nerve fibers containing gastrin-releasing peptide (GRP) was studied in relation to the dynamics of gastrin-producing cells (G-cells) after truncal vagotomy in a rat model. The circulating gastrin levels were markedly elevated from the 1st day after vagotomy and the number of G-cells with positive immunoreaction for G17 and G34(1-15) was significantly increased in the vagotomized group. On the 3rd day after vagotomy, the G-cells showed conspicuous ultrastructural changes characterized by hypertrophy of the Golgi complexes and increased numbers of secretory granules. The GRP-positive nerve fibers formed a fine network in the gastric wall and were densely distributed in the oxyntic mucosa close to the blood vessels and showing varicosities composed of either small clear or GRP-positive large vesicles containing an electron-dense core. In the oxyntic mucosa of the vagotomized rats, axonal swelling of the nerves occurred on the 3rd day, and a depletion of GRP immunoreactivity was evidenced by a markedly decreased number of large-cored vesicles on the 7th day, when the serum GRP levels were also found to be markedly elevated. These findings indicate that the alteration in gastric nerve fibers containing GRP after truncal vagotomy may be related to hypergastrinemia and antral G-cell hyperplasia in the rat gastric mucosa.

Animals↗
PubMed1986

Paradoxical effects of gastrin releasing peptide on gastrin release and gastric secretion in the rat.

The effects of gastrin releasing peptide (GRP) on gastrin release and gastric secretion were studied in anesthetized rats. Intravenous infusion of GRP (1-16 micrograms/kg/hr) caused a dose-dependent increase in serum gastrin level, however, it had no effect on basal gastric secretion in the lumen-perfused stomach preparation. Furthermore, GRP inhibited gastric secretion stimulated by pentagastrin or histamine dose-dependently, but not by carbachol. Simultaneous infusion of GRP and a beta adrenergic blocking agent, propranolol, an inhibitor of somatostatin release, did not alter the inhibitory effect of GRP on pentagastrin-stimulated gastric secretion. These results suggest that the inhibitory effect of GRP on gastric secretion in a stimulated condition is mediated via peptide hormones coreleased by GRP, and not via beta-adrenergic pathways.

Animals↗
PubMedDate not supplied

Effect of synthetic porcine gastrin-releasing peptide on plasma levels of immunoreactive cholecystokinin pancreatic polypeptide and gastrin in dogs.

This study was conducted to determine if synthetic porcine gastrin-releasing peptide (GRP) stimulates the release of immunoreactive cholecystokinin (CCK), pancreatic polypeptide (PP) and gastrin in dogs. Three doses (0.01, 0.1 and 0.5 micrograms/kg-hr) of synthetic porcine GRP were administered intravenously to six conscious dogs. Synthetic porcine GRP stimulated the release of each hormone in a dose-related manner. The effect of GRP on the response of gastrin was greater than its effect on CCK and PP responses. This study indicates that the biological action of synthetic porcine GRP is similar to the bombesin, an amphibian peptide shown previously to stimulate the release of gastrointestinal peptides.

Animals↗
PubMed1983

The effect of atropine on bombesin and gastrin releasing peptide stimulated gastrin, pancreatic polypeptide and neurotensin release in man.

The effects of 1-h infusions of bombesin and gastrin releasing peptide (GRP) at 50 pmol/kg per h and neurotensin at 100 pmol/kg per h on gastrin, pancreatic polypeptide (PP) and neurotensin release in man were determined following either saline or atropine infusion (20 micrograms/kg). Bombesin produced a rise in plasma neurotensin from 32 +/- 6 to 61 +/- 19 pmol/l and of PP from 26 +/- 8 to 36 +/- 7 pmol/l. There was a further rise of plasma PP to 50 +/- 13 pmol/l after cessation of the infusion. GRP had no significant effect on plasma neurotensin, but compared to bombesin, produced a significantly greater rise in plasma PP from 34 +/- 6 to 66 +/- 19 pmol/l during infusion. There was no post-infusional increase. At this dose, GRP was as effective as bombesin in releasing gastrin, although unlike bombesin its effect was enhanced by atropine. Neurotensin produced a rise in plasma PP from 17 +/- 4 to 38 +/- 8 pmol/l. Atropine blocked the release of PP during GRP and neurotensin infusion. Atropine had no effect on neurotensin or PP release during bombesin infusion, but did block the rise in plasma PP following bombesin infusion. We conclude that, in contrast to meal-stimulated neurotensin release, bombesin-stimulated neurotensin release is cholinergic independent. Despite structural homology, bombesin and GRP at the dose used are dissimilar in man in their actions and sensitivity to cholinergic blockade.

Adolescent↗
PubMed1989

Synthesis of gastrin antagonists, analogues of the C-terminal tetrapeptide of gastrin, by introduction of a beta-homo residue.

A series of analogues of Boc-Trp-Leu-Asp-Phe-NH2, a potent gastrin agonist, were synthesized by introducing a beta-homo residue in the sequence. These compounds were tested in vivo on acid secretion, in the anesthetized rat, and for their ability to inhibit binding of labeled gastrin to its receptors on gastric mucosal cells. These analogues behaved as gastrin antagonists. The most potent compounds in this series were Boc-Trp-Leu-beta-homo-Asp-NHCH2C6H5 (10) (IC50 = 1 microM, ED50 = 0.2 mg/kg), Boc-Trp-Leu-beta-homo-Asp-NHCH2CH2C6H5 (11) (IC50 = 0.75 microM, ED50 = 0.5 mg/kg), Boc-Trp-Leu-beta-homo-Asp-Phe-NH2 (12) (IC50 = 1.5 microM, ED50 = 0.1 mg/kg), and Boc-Trp-Leu-beta-homo-Asp-D-Phe-NH2 (13) (IC50 = 2 microM, ED50 = 0.1 mg/kg). We could demonstrate the importance of the region of the peptide bond between leucine and aspartic acid and of the structure of the C-terminal dipeptide Asp-Phe-NH2, for exhibiting biological activity on acid secretion.

Animals↗
PubMed1983

The effect of a gastrin-receptor antagonist on gastric acid secretion and serum gastrin in the Zollinger-Ellison syndrome.

We studied the effect of intravenous administration of a gastrin-receptor antagonist (proglumide) on gastric acid secretion and serum gastrin in three patients with Zollinger-Ellison syndrome. Proglumide administered as a bolus injection (50 mg/kg) or as an infusion (50 mg/kg hour and 100 mg/kg hour) or as a combination of bolus injection and infusion (50 mg/kg I.V. followed by 50 mg/kg hour) inhibited gastric acid secretion by 13-62%. Cimetidine (2 mg/kg I.V. followed by 2 mg/kg hour) inhibited gastric acid secretion by 83-86%. Neither proglumide nor cimetidine significantly influenced serum gastrin concentrations. We conclude that proglumide is a relatively weak inhibitor of gastric acid secretion in patients with the Zollinger-Ellison syndrome.

Adult↗