devazepide and gastrin-17

Cholecystokinin and related peptides are involved in the control of intestinal motility and cholecystokinin receptor ligands might represent new pharmacological tools for the treatment of symptoms associated with functional bowel disorders. However, the respective roles played by cholecystokinin receptor subtypes and the mechanisms underlying these regulatory actions remain undetermined. This study was designed to examine the influence of cholecystokinin receptor subtypes on the motor activity of guinea-pig distal colon. The effects of drugs acting on CCK1 and CCK2 receptors were assessed in vitro on the contractile activity of longitudinal smooth muscle, both under basal conditions and in the presence of transmural electrical stimulation or KCl-induced contractions. The application of cholecystokinin octapeptide sulphate (cholecystokinin-8S) to colonic preparations induced concentration-dependent contractions which were prevented by devazepide (CCK1 receptor antagonist), enhanced by GV150013 (CCK2 receptor antagonist) or N(omega)-nitro-L-arginine methylester (L-NAME, nitric oxide synthase inhibitor), and unaffected by tetrodotoxin. The application of gastrin-17 to colonic preparations resulted in relaxant responses which were insensitive to devazepide, and prevented by GV150013, L-NAME or tetrodotoxin. L-NAME, N(omega)-propyl-L-arginine (NPA, neuronal nitric oxide synthase inhibitor) or GV150013 enhanced electrically evoked contractile responses, whereas devazepide did not. When tested in the presence of L-NAME or NPA the enhancing effect of GV150013 on electrically induced contractions no longer occurred. In the presence of KCl-induced pre-contractions, cholecystokinin-8S or gastrin-17 evoked concentration-dependent relaxations, which were unaffected by devazepide and were counteracted by GV150013, L-NAME, NPA or tetrodotoxin. In conclusion, the present results indicate that, at level of distal colon, CCK1 receptors mediate direct contractile effects on smooth muscle, whereas CCK2 receptors on enteric neurons mediate relaxant responses via nitric oxide release.

Topics: Adamantane; Animals; Cholecystokinin; Colon; Devazepide; Dose-Response Relationship, Drug; Drug Combinations; Drug Interactions; Electric Stimulation; Enzyme Inhibitors; Gastrins; Guinea Pigs; Hormone Antagonists; Male; Muscle Contraction; Muscle, Smooth; NG-Nitroarginine Methyl Ester; Nitric Oxide Synthase Type I; Nootropic Agents; Perfusion; Phenylurea Compounds; Potassium Chloride; Receptor, Cholecystokinin B; Sincalide

This report describes the molecular cloning and pharmacological characterization of a transiently expressed chicken brain cholecystokinin receptor (CCK-CHR) in COS-7 cells. A polymerase chain reaction (PCR)-based cloning strategy was applied using: (1) an initial PCR with deoxyinosine-containing primers designed to target conserved regions in CCK receptors, followed by (2) rapid amplification of cDNA ends (RACE), and (3) full-length PCR of the CCK-CHR cDNA. The full-length cloned bicistronic CCK-CHR cDNA contained a short upstream open reading frame (uORF) coding for a putative six-amino-acid-long peptide of unknown function, followed by a long open reading frame (lORF) encoding the 436-amino-acid-long CCK-CHR receptor protein. At the amino acid level, the CCK-CHR shared approximately 50% homology with mammalian and Xenopus laevis CCK receptors. The pharmacological profile of CCK-CHR resembled that of CCK-B receptors using agonists (CCK-8, CCK-4, gastrin-17), whereas CCK-CHR showed higher affinity for the CCK-A receptor antagonist, devazepide, than for the CCK-B receptor antagonist, L-365,260. To the best of our knowledge, this is the first description and functional expression study of a cloned chicken CCK receptor cDNA.

Topics: Amino Acid Sequence; Animals; Benzodiazepinones; Brain; Chickens; Cloning, Molecular; COS Cells; Devazepide; DNA, Complementary; Gastrins; Inosine; Molecular Sequence Data; Phenylurea Compounds; Polymerase Chain Reaction; Radioligand Assay; Receptors, Cholecystokinin; RNA, Messenger; Sequence Homology, Amino Acid; Sincalide; Tetragastrin

1. Cholecystokinin (CCK) and gastrin both stimulate gastric somatostatin (SOM) secretion in vitro and thus have the potential to modulate their direct effects on the parietal cell. However, the relative potencies and the mechanisms of action of CCK and gastrin on SOM secretion in vivo have not been determined. 2. The objectives of the present study were to compare the in vivo potencies of the sulphated(s) and non-sulphated (ns) forms of gastrin heptadecapeptide (G-17) and CCK octapeptide (CCK-8) on SOM secretion, and to determine the nature of the receptors involved by repeating the studies in the presence of the CCK-A and CCK-B/gastrin receptor antagonists L-364,718 and L-365,260, respectively. All experiments were performed in the chronically cannulated sheep. 3. Dose-response experiments revealed the following potencies for SOM secretion: G-17s = CCK-8s > G-17 ns >> CCK-8ns. However, based on the plasma levels achieved and a higher metabolic clearance rate (MCR) for CCK, CCK-8s was the most potent. 4. Both the CCK-A and CCK-B/gastrin receptor antagonists suppressed CCK-8s-stimulated SOM output. In contrast, G-17s-stimulated SOM output was inhibited by only the CCK-B/gastrin receptor antagonist. 5. Both receptor antagonists increased basal plasma gastrin and CCK levels. 6. The predominant circulating SOM molecular form after both gastrin and CCK stimulation was SOM-14. 7. In conclusion, the sulphated forms of CCK and gastrin are more potent than the non-sulphated forms. Despite sharing a common biologically active carboxy terminus, CCK stimulates SOM secretion by both the CCK-A and CCK-B/gastrin receptors, while gastrin acts via the CCK-B/gastrin receptor alone. These findings explain in part why CCK is a net inhibitor of gastric acid secretion in vivo.

Topics: Animals; Benzodiazepinones; Cholecystokinin; Chromatography, High Pressure Liquid; Devazepide; Drug Interactions; Gastric Mucosa; Gastrins; Hormone Antagonists; Infusions, Intravenous; Phenylurea Compounds; Receptor, Cholecystokinin A; Receptor, Cholecystokinin B; Receptors, Cholecystokinin; Sheep; Sincalide; Somatostatin

The effect of gastrin on the enterochromaffin-like cells in the rat stomach is mediated by cholecystokinin (CCK)-B receptors and manifested as activation of histidine decarboxylase (HDC). The dipeptoids PD 136450, PD 135158, and PD 134308 are thought to be selective CCK-B receptor antagonists. The effects of the dipeptoids and of gastrin-17 and sulfated CCK-8 on rat stomach HDC activity were examined.. Drugs were infused intravenously or subcutaneously to fasted rats, and the HDC activity was determined.. The dipeptoids activated HDC with maximal responses (50%-60% of the maximal response to gastrin) at 1 mumol.kg-1.h-1. Rat gastrin-17 activated HDC maximally at 3 nmol.kg-1.h-1, and sulfated CCK-8 produced maximal response at 20 nmol.kg-1.h-1. The CCK-B receptor antagonist L-365,260 inhibited the HDC activation induced by gastrin, sulfated CCK-8, or the dipeptoids. The dipeptoids did not inhibit the gastrin-induced HDC activation.. Gastrin, sulfated CCK-8, and the dipeptoids activated rat stomach HDC. L-365,260 but not devazepide inhibited the HDC activation. Thus, the dipeptoids, which failed to inhibit the gastrin-induced HDC activation, act as CCK-B receptor agonists and not as antagonists. It is important to recognize this to ensure appropriate interpretation of data obtained with these drugs.

Topics: Animals; Benzodiazepinones; Devazepide; Enzyme Activation; Gastrins; Histidine Decarboxylase; Indoles; Ligands; Male; Meglumine; Phenethylamines; Phenylurea Compounds; Rats; Rats, Sprague-Dawley; Receptor, Cholecystokinin B; Receptors, Cholecystokinin; Sincalide; Stomach

1. The cardiovascular actions of cholecystokinin and related peptides were investigated in the pithed rat. The receptors and the mechanisms involved in these experiments were characterized. 2. Sulphated cholecystokinin octapeptide (sCCK-8, 0.1-100 nmol kg-1, i.v.) elicited a dose-dependent bradycardia and increase in mean arterial blood pressure. Neither gastrin-17 nor pentagastrin had any effect at concentrations up to 100 nmol kg-1. 3. Both the pressor response and bradycardia elicited by sCCK-8 were reduced by the selective CCKA receptor antagonists, devazepide (0.5-50 nmol kg-1) and lorglumide (1-7 mumol kg-1). The selective CCKB receptor antagonists, CI-988 (1 mumol kg-1) and L-365,260 (15 mumol kg-1) did not inhibit the effects of sCCK-8. 4. The pressor response induced with sCCK-8 was reduced by treatment with either phentolamine (3 mumol kg-1) or guanethidine (2 mumol kg-1) and was unaffected by treatment with propranolol, atropine or hexamethonium. The pressor response also persisted following bilateral adrenalectomy. 5. The bradycardia induced with sCCK-8 was unaffected by treatment with phentolamine, propranolol, guanethidine, atropine, hexamethonium or bilateral adrenalectomy. 6. The tetrapeptide of cholecystokinin (CCK-4) elicited a dose-dependent pressor response but did not induce bradycardia. The pressor response was unaffected by devazepide (50 nmol kg-1), L-365260 (15 mumol kg-1) or phentolamine (3 mumol kg-1). 7. In the pithed rat, sCCK-8 acted via CCKA receptors to increase arterial blood pressure indirectly, at least in part, through activation of alpha-adrenoceptors. The observed bradycardia was also mediated byCCKA receptors but possibly through a direct action on the heart.

Topics: Adrenalectomy; Adrenergic Agents; Animals; Benzodiazepinones; Blood Pressure; Bradycardia; Cholecystokinin; Decerebrate State; Devazepide; Dose-Response Relationship, Drug; Gastrins; Guanethidine; Heart Rate; Hormone Antagonists; Hormones; Hypertension; Indoles; Male; Meglumine; Pentagastrin; Phentolamine; Proglumide; Rats; Receptors, Cholecystokinin; Sincalide; Tetragastrin

Functional studies suggest that guinea pig chief cells have both cholecystokinin-A (CCK-A) and CCK-B receptors (CCK-A-R and CCK-B-R, respectively). However, all efforts to directly characterize the specific CCK-A-R using binding have been unsuccessful. Recent studies describe specific CCK-A-R agonists such as A-71378 ([desamino-Nle28,31-(N-methyl)Asp32]CCK heptapeptide]. In the present study, [D-Tyr-Gly]A-71378 was synthesized, which has > 300-fold selectivity for CCK-A-R and can be iodinated. [D-Tyr-Gly]A-71378 was equipotent to A-71378 in stimulating pepsinogen release from purified guinea pig chief cells. Binding of 125I-labeled [D-Tyr-Gly]A-71378 was saturable and specific. Potencies for inhibiting binding were as follows: [D-Tyr-Gly]A-71378 = A-71378 = 4x CCK octapeptide (CCK-8) > 1,000x des(SO4)-CCK-8, gastrin. In contrast, for 125I-gastrin binding they were CCK-8 > gastrin-17-I > des(SO4)-CCK-8 >> A-71378 or [D-Tyr-Gly]A-71378. Binding of [D-Tyr-Gly]A-71378 was best fitted by a two-site model. In contrast, 125I-gastrin binding was fitted with a single-site model. For inhibiting binding of 125I-[D-Tyr-Gly]A-71378, the CCK antagonists had relative affinities of L-364,718 >> L-365,260, and the reverse was true with 125I-gastrin. Correlation of binding with changes in biological activity suggested low-affinity CCK-A-R were mediating these changes. These results demonstrate directly for the first time that guinea pig chief cells possess CCK-A-R and CCK-B-R. The pharmacology of these CCK-A-R resembles those on other tissues. This novel, highly selective CCK-A ligand should be useful because it will identify CCK-A-R when they make up as little as 0.2% of the total CCK receptor number.

Topics: Animals; Benzodiazepinones; Devazepide; Gastric Mucosa; Gastrins; Guinea Pigs; Ligands; Male; Oligopeptides; Pancreas; Pepsinogens; Phenylurea Compounds; Receptors, Cholecystokinin; Sincalide; Stomach

Several studies examined in vivo and in vitro biologic activity of the human gallbladder in response to cholecystokinin (CCK). However, few studies have demonstrated directly the interaction of CCK with receptors on the human gallbladder, which is responsible for this biologic activity.. To characterize CCK receptors on human gallbladder tissue, gallbladders were removed from human donor grafts that were being used for liver transplantation. The gallbladders were rapidly frozen and sectioned for measurement of binding of 125I-Bolton-Hunter-labeled-CCK-8 and were cut into strips for in vitro bioassay.. Binding of 125I-BH-CCK-8 to human gallbladder was saturable, specific, and dependent on time, pH, and temperature. The binding was inhibited only by cholecystokinin-related peptides including CCK-8 (IC50 10 +/- 1.0 nmol/L) (mean +/- SD), des(SO3) CCK-8 (IC50 0.9 +/- 0.2 mumol/L), and gastrin-17-I (IC50 9.0 +/- 2.0 mumol/L) or specific CCK receptor antagonist L-364,718. Computer analysis of binding of 125I-BH-CCK-8 to gallbladder tissue showed a single class of binding sites with high affinity for CCK-8. Autoradiography localized binding of 125I-BH-CCK-8 only to the smooth muscle layer of the gallbladder. In the bioassay des(SO3) CCK-8 (EC50 1.2 +/- 0.7 mumol/L) and gastrin-17-I (EC50 4.5 +/- 2.4 mumol/L) were 150- and 563-fold less potent than CCK-8 (EC50 8.0 +/- 2.2 nmol/L). The relative potencies of CCK agonists for inhibiting binding of 125I-BH-CCK-8 agreed closely with their relative potencies for causing gallbladder contraction. The dose-response curve for CCK-8 alone to induce gallbladder contraction was not significantly different from those caused by CCK-8 plus 1 mumol/L tetrodotoxin or 1 mumol/L atropine.. These results characterized the CCK receptors on smooth muscle of human gallbladder as sulfate dependent and causing gallbladder contraction.

Topics: Autoradiography; Benzodiazepinones; Binding Sites; Carbachol; Devazepide; Dose-Response Relationship, Drug; Gallbladder; Gastrins; Hormones; Humans; Hydrogen-Ion Concentration; In Vitro Techniques; Iodine Radioisotopes; Muscle Contraction; Muscle, Smooth; Receptors, Cholecystokinin; Reference Values; Secretin; Serotonin; Sincalide; Substance P; Temperature; Vasoactive Intestinal Peptide

With the availability of selective gastrin/CCKB (L365,260) and CCKA (L364,718) receptor antagonists the present study was designed to investigate the role of gastrin and cholecystokinin (CCK) receptors in meal-stimulated gastric acid secretion. Gastric acid output was measured by continuous intragastric titration in conscious rats. Vehicle (dimethylsulfoxide/saline, 3:1), L365,260 (3 or 9 mg/kg), or L364,718 (1 mg/kg) was given by i.v. bolus injection. Basal acid output was strongly inhibited by both doses of L365,260 while L364,718 had no effect. Intragastric peptone (4%, w/v) increased acid secretion 40-65% of the response to a maximal dose (2.5 nmol/kg per h) of gastrin-17. L365,260 completely abolished gastrin-17 stimulated acid secretion and partially inhibited peptone-induced acid secretion. Blockade of CCKA receptors by L364,718 did not affect peptone-stimulated acid output. This study demonstrates that gastrin/CCKB receptors are important in regulating basal acid secretion in the conscious rat while CCKA receptors do not appear to influence basal or peptone-stimulated gastric acid secretion. Blockade of gastrin/CCKB receptors partially inhibits intragastric meal-stimulated acid secretion indicating that the gastrin/CCKB receptor has a physiological role as mediator of food-stimulated acid secretory response in conscious rats.

Topics: Animals; Benzodiazepinones; Cholecystokinin; Devazepide; Eating; Gastric Acid; Gastrins; Hormones; Injections, Intravenous; Male; Peptones; Phenylurea Compounds; Rats; Rats, Sprague-Dawley; Receptors, Cholecystokinin

In this investigation we studied the influence of two gastrin fragments, pentagastrin and nonsulfated heptadecagastrin, and two cholecystokinin fragments, sulfated and desulfated cholecystokinin 26-33, on intracellular and secreted triacylglycerol in isolated hepatocyte cultures. Both gastrin fragments inhibited triacylglycerol release in a biphasic manner, exhibiting maximal effect at 0.1 nmol/L (nonsulfated heptadecagastrin) and 0.3 nmol/L (pentagastrin). At these concentrations triacylglycerol secretion was 42% (nonsulfated heptadecagastrin, p < 0.001) and 62% (pentagastrin, p < 0.001) lower than in cells untreated with gastrin. Sulfated cholecystokinin 26-33 caused a 35% decrease in triacylglycerol secretion at 0.1 nmol/L (p < 0.01), and desulfated cholecystokinin 26-33 caused a 53% decrease at 0.2 nmol/L (p < 0.001). In all experiments, the hormone-induced decrease in triacylglycerol secretion was accompanied by an increase in intracellular triacylglycerol content. The cholecystokinin-A receptor antagonist L-364, 718 did not affect the decrease in triacylglycerol secretion induced by 0.3 nmol/L pentagastrin, whereas the cholecystokinin-B receptor antagonist L-365, 260 inhibited the pentagastrin effect at concentrations above 50 nmol/L. These results suggest that gastrin, cholecystokinin or some other gastrinlike hormone (or all three) may play a previously unrecognized regulatory role with respect to hepatic very low density lipoprotein secretion.

Topics: Animals; Benzodiazepinones; Cells, Cultured; Depression, Chemical; Devazepide; Gastrins; Liver; Male; Pentagastrin; Peptide Fragments; Phenylurea Compounds; Rats; Rats, Sprague-Dawley; Receptors, Cholecystokinin; Sincalide; Triglycerides

Isolated gastric glands from rabbit were used to characterize the functional cholecystokinin (CCK)-like peptide receptors that mediate pepsinogen secretion. Pepsinogen secretion was stimulated by both CCK octapeptide sulfate (CCK-8) and A-71378, a selective CCK-A-type receptor agonist, with similar mean effective doses (1.0 and 0.8 nM, respectively). Compared with CCK-8, gastrin-17 (G-17-I) showed reduced potency and only partial efficacy for stimulation of pepsinogen secretion while inhibiting the maximal CCK-8-stimulated response. The nonpeptide inhibitors, asperlicin and L-364,718, inhibited pepsinogen secretion with identical pA2 values for antagonism of both CCK and gastrin, indicating that both peptides interact with the same functional receptor. Specific binding of [3H]CCK-8 to isolated chief cell membranes was displaced fully by both CCK and gastrin, indicating full receptor occupancy by both peptides. A novel synthetic peptide analogue, pseudogastrin [(Glu)5-Ala-Tyr-Nle-Gly-Trp-Nle-Asp-Phe-NH2], was used to investigate the structural basis for the lower potency and efficacy of G-17-I. The potency of CCK and gastrin analogues for pepsinogen secretion was found to be dependent on both sulfation of a tyrosine residue and the position of the tyrosine residue relative to the COOH-terminal phenylalanine amide. The efficacy appears to be determined partially by the extended NH2-terminal sequence of G-17-I. The results of the present study are interpreted to show that pepsinogen secretion is mediated by a CCK-A-type receptor and gastrin acts at the same receptor as a partial agonist.

Topics: Amino Acid Sequence; Animals; Benzodiazepinones; Cell Membrane; Cholecystokinin; Devazepide; Gastric Mucosa; Gastrins; Hormones; In Vitro Techniques; Kinetics; Molecular Sequence Data; Oligopeptides; Pepsinogens; Rabbits; Receptors, Cholecystokinin; Sequence Homology, Amino Acid; Sincalide