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Cholecystokinin stimulates growth of human pancreatic adenocarcinoma SW-1990.

The effect of a synthetic analogue of CCK (Thr4,Nle7CCK-9) on growth of SW-1990 human pancreatic cancer was examined in two experimental models. Nude mice bearing SW-1990 pancreatic cancer xenografts were injected with CCK (5, 15, or 25 micrograms/kg) or vehicle twice daily for 20 days. Animals were then sacrificed and tumor volume, weight, protein, and deoxyribonucleic acid (DNA) content were evaluated. SW-1990 cells were grown in vitro and the effects of CCK, secretin, vasoactive intestinal peptide (VIP), and proglumide (a CCK-receptor antagonist) on cell number and DNA synthesis were determined. The highest dose of CCK, 25 micrograms/kg, significantly increased tumor weight, protein content, and DNA content (P less than 0.005). In vitro, CCK caused significant increases in cell counts of up to 47% at six days and 66% at 12 days compared to control. Graded concentrations of CCK had a biphasic effect on DNA synthesis with significant increases of up to 65% (P less than 0.005). CCK-induced cell proliferation was inhibited by proglumide. Secretin slightly increased cancer cell growth, although not as potently as CCK, VIP or secretin in combination with CCK did not show potentiation. These results indicate that growth of some human pancreatic cancers may be influenced by gastrointestinal peptides, of which CCK is the most potent.

Adenocarcinoma↗

Role of cholecystokinin in canine pancreatic exocrine response to bombesin stimulation.

The role of cholecystokinin in bombesin-stimulated pancreatic secretion in dogs was examined by the use of a specific cholecystokinin antagonist, proglumide. The primary component of bombesin-stimulated pancreatic secretion at the lowest tested dose was due to cholecystokinin, with only 25 percent of bombesin-stimulated protein output preserved during proglumide infusion. Maximal stimulation of cholecystokinin release was achieved by even the lowest dose of bombesin, whereas dose-related increases in bombesin-stimulated protein secretion were observed. This increase in exocrine secretion is probably explained by increased direct bombesin stimulation. Our findings suggest that the maximal dose of bombesin is lower for cholecystokinin release than its effective dose for enzyme secretion. We conclude that, in all probability, postprandial release of bombesin (or its analogue, gastrin-releasing peptide) affects pancreatic function primarily through release of cholecystokinin.

Animals↗

Do antagonists of pancreatic cholecystokinin receptors interact with central nervous system cholecystokinin receptors?

The abilities of the pancreatic cholecystokinin (CCK) receptor antagonists dibutyryl cyclic GMP, proglumide, benzotript, CBZ-tryptophan, CBZ-cysteine and CCK-27-32-amide to inhibit CCK binding to its receptor in the pancreas and brain of mice and guinea pigs was examined. In both species, the same relative potencies of the antagonists in brain and pancreas was seen except that dibutyryl cyclic GMP was considerably more potent on pancreas than on cerebral cortex CCK receptors. CCK-27-32-amide was the most potent inhibitor for both brain and pancreas but was more potent in the guinea pig than in the mouse. Proglumide, a relatively weak antagonist, was a more potent inhibitor of the guinea pig than of the mouse pancreas receptor. Thus, these data suggest that there are both tissue-specific and species-specific differences in CCK antagonist interactions with the CCK receptor.

Animals↗

The effects of cholecystokinin and cholecystokinin antagonists on synaptic function in the CA1 region of the rat hippocampal slice.

The effects of two CCK antagonists, benzotript and proglumide, and of sulfated and non-sulfated cholecystokinin octapeptide (CCK-8-S and CCK-8-NS), were studied in the CA1 region of the rat hippocampal slice. Both benzotript and proglumide shifted presynaptic volley (prevolley) vs population spike input/output (I/O) curves for Schaffer collateral-commissural synaptic transmission to the right. This result indicates that the antagonists had a net depressant effect on synaptic transmission. CCK-8-S shifted prevolley vs population spike I/O curves to the left, indicating a net excitatory effect. Analysis of component I/O curves indicated that CCK-8-S and the CCK antagonists were acting postsynaptically by changing CA1 pyramidal cell threshold. CCK-8-NS had no significant effect on overall or component I/O functions. These findings suggest that endogenous CCK is released, directly or indirectly, upon stimulation of the Schaffer collateral-commissural fibers and increases the excitability of CA1 pyramidal cells.

Action Potentials↗

Cholecystokinin-octapeptide antagonizes morphine analgesia in periaqueductal gray of the rat.

The analgesic effect of systemic morphine (5 mg/kg, s.c.) was dose-dependently antagonized by CCK-8 administered to the periaqueductal gray (PAG) of the rat. This effect could be reversed by proglumide, a CCK-receptor antagonist. The effect of morphine analgesia was potentiated by proglumide administered to PAG. These results are compatible with the notion that PAG is a strategic site where CCK-8 exerts an antiopioid activity.

Analgesia↗

Participation of central descending nociceptive facilitatory systems in secondary hyperalgesia produced by mustard oil.

The present series of experiments were designed to examine a potential role for central descending pain facilitatory systems in mediating secondary hyperalgesia produced by topical application of mustard oil and measuring the nociceptive tail-flick reflex in awake rats. Topical application of mustard oil (100%) to the lateral surface of the hind leg produced a facilitation of the tail-flick reflex that was significantly reduced in spinal transected animals. Mustard oil hyperalgesia was also inhibited in animals that had received electrolytic lesions in the rostral ventromedial medulla (RVM). Intrathecal (i.t.) administration of the non-selective cholecystokinin (CCK) receptor antagonist proglumide (10 micrograms) prior to mustard oil application completely blocked both the lesser and greater hyperalgesic responses observed in spinal transected and normal animals, respectively, and produced an inhibition of the tail-flick reflex in normal animals. Administration of the selective CCKB receptor antagonist L-365260 i.t. dose-dependently inhibited mustard oil hyperalgesia (ID50 = 364 ng) at doses approximately 5-fold less than the CCKA receptor antagonist devazepide (ID50 = 1760 ng). Similar to spinal proglumide, microinjection of the neurotensin antagonist SR48692 (3.5 micrograms) into the RVM blocked mustard oil hyperalgesia and inhibited the tail-flick reflex. These data suggest that secondary hyperalgesia produced by mustard oil is mediated largely by a central, centrifugal descending pain facilitatory system which involves neurotensin in the RVM and spinal CCK (via CCKB receptors). The inhibition of the tail-flick reflex produced by mustard oil following spinal or supraspinal administration of receptor antagonists suggests concurrent activation of central descending facilitatory and inhibitory systems.

Animals↗

Evidence for dopaminomimetic effect of intrastriatally injected cholecystokinin octapeptide in mice.

The behavioural effect of intrastriatally injected cholecystokinin sulphated octapeptide (CCK-8S), and its interactions with the antagonists Z-CCK-(27-32)NH2 and proglumide, were investigated in mice. When injected into the right striatum, CCK-8S (0.05-1 ng) induced contralateral rotations, as did the dopamine agonist apomorphine. Non-sulphated CCK-8 was inactive and sulphated desamino-CCK-7 was only weakly active in this respect. CCK-8S-induced turning was antagonized by co-injected Z-CCK-(27-32)NH2 (0.01-10 ng) or proglumide (0.1-1 micrograms), as well as by intraperitoneal injection of the neuroleptic drug haloperidol. These data suggest that CCK-8S may, in these conditions, stimulate dopamine-mediated neurotransmission, and that Z-CCK-(27-32)NH2, in addition to its peripheral effect, is also a very potent CCK antagonist at the striatal level.

Animals↗

Cholecystokinin and gastrin induce cell contraction in pig ileum by interacting with different receptor subtypes.

The aim of this study was to determine the cholecystokinin (CCK) receptor subtype involved in the direct myogenic effect of CCK on pig ileum. Smooth muscle cells were dispersed from pig ileum circular muscle layer and incubated in the presence of various concentrations of CCK agonists and antagonists. Contraction was assessed by measuring the length of 50 cells and expressed as the percentage decrease in cell length from control. Maximal contraction varied between 19% +/- 3% (gastrin II, 10 nmol/L) and 26% +/- 3% [CCK octapeptide (CCK-8), 10 nmol/L]. EC50 for CCK tetrapeptide (CCK-4) was the same than for pentagastrin (30 pmol/L), which were more potent than CCK-8 (100 pmol/L) and unsulfated gastrin 17 (100 pmol/L), which in turn were more potent than unsulfated CCK heptapeptide (CCK-7; 300 pmol/L) and sulfated gastrin II (300 pmol/L). The maximal contraction induced by synthetic analogs of CCK was 22% +/- 1% for 1 nmol/L JMV 170 and 23% +/- 1% for 10 nmol/L JMV 180. EC50 was 10 pmol/L for JMV 170 and 800 pmol/L for JMV 180. Contraction induced by 10 nmol/L CCK was inhibited as follows: L 365,260 half maximal inhibition (IC50) = 1 nmol/L greater than L 364,718 (IC50 = 90 nmol/L) greater than proglumide (IC50 = 1 mumol/L). Contraction induced by 10 nmol/L unsulfated gastrin 17 was inhibited as follows: L 365,260 (IC50 = 1 pmol/L) greater than L 364,718 (IC50 = 60 nmol/L) greater than proglumide (IC50 = 4 mumol/L). Removal of Ca2+ from the extracellular medium did not alter the contraction induced by CCK-8 (10 nmol/L) but impaired the contraction induced by unsulfated gastrin 17 (10 nmol/L) -56% in Ca(2+)-free medium, -77% in Ca(2+)-free medium plus 2 mmol/L EGTA, and -70% in the presence of 1 mumol/L nifedipine. These results show that the CCK receptor of pig ileum smooth muscle cells is closely similar to the B receptor and is not dependent on an influx of extracellular Ca2+ to induce cell contraction. By contrast, gastrin could act through a specific receptor subtype, the "gastrin receptor," triggering a Ca2+ influx into the cell to induce cell contraction.

Animals↗

A new simple mouse model for the in vivo evaluation of cholecystokinin (CCK) antagonists: comparative potencies and durations of action of nonpeptide antagonists.

A new simple mouse assay for the in vivo evaluation of CCK antagonists which is based upon visual determination of the gastric emptying of a charcoal meal is described. CCK-8 (24 micrograms/kg s.c.) but not various other peptide and nonpeptide agents effectively inhibited gastric emptying in this test system. The effect of CCK-8 was antagonized by established peripheral CCK antagonists but not representative agents of various other pharmacological classes. The rank order of potency of the CCK antagonists were: L-364,718 (ED50 = 0.01 mg/kg, i.v.; 0.04 mg/kg, p.o.) greater than Compound 16 (ED50 = 1.5 mg/kg, i.v.; 2.0 mg/kg p.o.) greater than asperlicin (ED50 = 14.8 mg/kg i.v.) greater than proglumide (ED50 = 184 mg/kg i.v.; 890 mg/kg, p.o.). Duration of action studies based upon ED50 values determined at various time intervals after oral administration showed that L-364,718 and proglumide are considerably longer acting than Compound 16. Asperlicin (ED50 greater than 300 mg/kg, p.o.) was ineffective as a CCK antagonist when administered orally. These data provide the first direct comparisons of the in vivo potencies of current CCK antagonists and demonstrate the utility of a new simple mouse assay for the in vivo characterization of peripheral CCK antagonists.

Administration, Oral↗

Cholecystokinin stimulates neuronal receptors to produce contraction of the canine colon.

The motor effects of cholecystokinin 26-33-amide (CCK octapeptide; CCK-OP) and several purported CCK receptor antagonists on canine colonic circular muscle were determined in pentobarbital anesthetized dogs. Intravenous injections of CCK-OP had no effect on colonic motility at doses that contracted the gallbladder, stomach and duodenum. CCK-OP delivered by intraarterial injection to a small segment of the proximal colon produced a dose related increase in colonic motility with one-half maximum response at 12 ng/Kg and maximum response at 50 ng/Kg. The effects of intraarterial injections of several established CCK-receptor antagonists on proximal colonic responses to intraarterial injections of CCK-OP were determined. Proglumide, 10 mg/Kg, did not produce colonic contractions itself, but antagonized CCK-OP-induced responses. Carbobenzyloxy (CBZ)-CCK27-32-amide antagonized CCK-OP-induced colonic responses and also had no effect on basal colonic motility (0.1-1 and 5 micrograms/Kg). Neither compound antagonized acetylcholine- induced colonic responses. Butoxycarbonyl (BOC)-CCK31-33-amide increased basal colonic motility, but did not alter CCK-OP-induced responses at doses of 0.1 and 0.2 mg/Kg. Dibutyryl-cGMP at a dose of 0.1 mg/Kg did not affect basal motility or CCK-OP-induced contractions. At a dose of 1.0 mg/kg it increased basal colonic motility but did not affect CCK-OP-induced contractions. Pentagastrin increased colonic motor activity only at a dose of 5 micrograms/Kg, i.a., a much higher dose than effective doses of CCK-OP. The mechanism of CCK-OP-induced colonic motor effects also was determined. Atropine sulfate, 100 micrograms/Kg, i.v. significantly reduced both intraarterial acetylcholine-and CCK-OP-induced maximum colonic contractions. Tetrodotoxin, at intravenous doses that completely block neuronal activity, did not affect maximum acetylcholine-induced contractions but practically eliminated maximum CCK-OP-induced maximum colonic responses. In conclusion, intraarterial CCK-OP produces circular muscle contraction of the canine proximal colon that is mediated by stimulation of specific CCK receptors which produce the release of acetylcholine from cholinergic enteric neurons. Proglumide and CBZ-CCK27-32-amide are effective CCK receptor antagonists at these colonic neuronal receptors.

Acetylcholine↗

Evidence for potentiation by CCK antagonists of the effect of cholecystokinin octapeptide in the elevated plus-maze.

Systemic treatment with cholecystokinin octapeptide (CCK-8, 2.5-10 micrograms/kg, s.c.), a non-selective CCK agonist, decreased the exploratory activity of mice in an elevated plus-maze. At higher doses (5-10 micrograms/kg) CCK-8 reduced the frequency of rearing, but only 10 micrograms/kg of CCK-8 significantly inhibited the number of line crossings in the open-field test. A preferential CCKB antagonist L-365,260 (1 and 100 micrograms/kg, i.p.) and a non-selective CCK antagonist proglumide (0.1-1 microgram/kg, i.p.) potentiated the anti-exploratory effect of CCK-8 (2.5 micrograms/kg). Devazepide, a preferential CCKA antagonist, only at a high dose (100 micrograms/kg) tended to increase the action of CCK-8 in the plus-maze. However, the concomitant treatment of CCK-8 with L-365,260 and proglumide, differently from devazepide, also suppressed the locomotor activity in the open-field test. Therefore, it is likely that the potentiation by CCK antagonists of the anti-exploratory effect of CCK-8 is related to the suppression of motor activity. This peculiar interaction between CCK-8 and CCK antagonists could be explained in the light of the opposite role of CCKA and CCKB receptors in the regulation of motor activity in mice.

Animals↗

Antispasmodic activity on the gallbladder of the mouse of CR 1409 (lorglumide) a potent antagonist of peripheral CCK.

Cholecystokinin (CCK) is a hormonal regulator of the motility of the gallbladder. CCK-8, i.e. the biologically active C-terminal octapeptide of the hormone, elicits contraction and emptying of the gallbladder. Endogenous CCK released by egg yolk or fatty acids in the duodenum gives the same results. CR 1409 (lorglumide), a glutaramic acid derivative with peripheric competitive CCK-antagonistic activity, was evaluated in comparison with proglumide (the model CCK-receptor antagonist) and other conventional antispasmodic drugs, for their ability to inhibit the emptying of the gallbladder induced in mice by CCK-8 or by lyophylized egg yolk. CR 1409 (1-10 mg/kg) prevented dose-dependently the emptying of the gallbladder in both experimental models; proglumide exhibited a comparable activity at much higher doses (200-800 mg/kg). On the contrary the anticholinergic drug atropine, the calcium-antagonist nifedipine, and the phosphodiesterase inhibitor papaverine were almost ineffective. The present data support the hypothesis that the effects of CCK on gallbladder motility are mediated by a CCK-dependent specific mechanism.

Animals↗

Brain cholecystokinin octopeptide (CCK-8) concentrations: effect of tryptophan and other serotonergic agents.

The effects of 1-week drug treatment on the brain contents of neuropeptides were investigated. The cholecystokinin (CCK) concentrations in the hypothalamus were significantly decreased by tryptophan treatment but not by imipramine and cyproheptadine, which changed the serotonergic function. Proglumide, the CCK antagonist, induced in the hypothalamic and hippocampal-striatal areas an increase in CCK concentration, which was not reversed in the presence of tryptophan. Dynorphin and substance P(SP) concentrations were also modified by proglumide treatment.

Animals↗

The effect of pentagastrin on the somatostatin receptor/effector system in rat pancreatic acinar membranes.

An intraperitoneal (i.p.) injection of pentagastrin (250 micrograms/kg, three times daily) for 1 week increased somatostatin like-immunoreactivity (SSLI) content in the pancreas and the number of somatostatin (SS) receptors in pancreatic acinar membranes without influencing their apparent affinity as compared with control animals. No significant differences were seen in basal or forskolin (FK)-stimulated adenylate cyclase (AC) enzyme activities in the control and pentagastrin treated rats. In spite of the increase in the number of SS receptors, SS caused a significantly lower inhibition in AC activity in these membranes. This finding is related to the fact that the stable GTP analogue, 5'-guanylylimidodiphosphate (Gpp[NH]p) was a much less potent inhibitor of binding in the pancreatic acinar cell membranes from pentagastrin-treated animals than in those from controls. In addition the ability of Gpp(NH)p to inhibit FK-stimulated AC activity was also decreased in pancreatic acinar cell membranes from pentagastrin-treated rats. Pretreatment with proglumide, (20 mg/kg i.p.) a gastrin/cholecystokinin (CCK) receptor antagonist, prevented the pentagastrin-induced changes in SS level and binding as well as the inhibitory effect of SS on AC activity in pancreatic acinar cell membranes. Proglumide alone had no observable effect on the somatostatinergic system. These data suggest a SS receptor/G protein uncoupling as a result of binding of pentagastrin to gastrin receptors present in pancreatic acinar cell membranes.

Adenylyl Cyclases↗

Protective effect of CR 1409 (cholecystokinin antagonist) on experimental pancreatitis in rats and mice.

CR 1409, a glutaramic acid derivative with competitive cholecystokinin-antagonistic activity, was administered IP and evaluated in comparison with proglumide (the model CCK-receptor antagonist), gabexate (protease inhibitor) and PGE2 (cytoprotective) on two different models of experimental pancreatitis. Acute pancreatitis was induced in mice by six IP injections of 50 micrograms/kg caerulein at hourly intervals. The drugs were administered 30 minutes before each caerulein administration. Blood samples and pancreata were collected 3 hours after the last caerulein injection. In the second experiment, pancreatitis was induced in rats by injecting 0.3 ml 6% sodium taurocholate interstitially into the pancreas. The drugs were administered twice, 30 minutes before and 3 hours after taurocholate. The animals were killed 6 hours after laparotomy and blood samples and pancreata were collected. CR 1409 exhibited on both pancreatitis models a protective effect in a dose range of 0.3-10 mg/kg. Proglumide exhibited a protective activity at higher doses (200-400 mg/kg). Gabexate and PGE2 were effective only in pancreatitis induced by taurocholate in a dose range of 30-60 mg/kg and 60-130 micrograms/kg respectively. These results, showing a high protective effect of CR 1409 on different models of acute pancreatitis, suggest an important role of CCK in the pathogenesis of pancreatitis.

Acute Disease↗

Mechanism of actions of cholecystokinin octapeptide on food intake and insulin and pancreatic polypeptide release in the dog.

We investigated the mechanism by which CCK-8 injected into the third cerebral ventricle (ITV administration) inhibits food intake and stimulates insulin and pancreatic polypeptide (PP) secretion in the dog. ITV administration of CCK-8 (4.08 micrograms/5 min) resulted in a significant elevation of plasma insulin and PP concentrations. This effect was abolished by truncal vagotomy and promptly inhibited by ITV administration of atropine (20 micrograms) and proglumide (10 mg). CCK-8 was less effective in increasing insulin and PP concentrations than in reducing feeding. Thus, 1.36 micrograms of ITV CCK-8 markedly reduced food intake to 14, 15, 29 and 31% of control values at 10, 30, 60 and 120 min, respectively. Atropine and naloxone (50 micrograms) had no blocking effect on CCK-8-induced satiety, whereas proglumide antagonized it. These results indicate that ITV CCK-8 effects the endocrine pancreas and food intake through atropine-sensitive and atropine-insensitive mechanisms, respectively, both of which are likely to be mediated by CNS CCK receptors. Intravenous CCK-8 also stimulated PP and insulin release, through mechanisms that were atropine-sensitive and atropine-insensitive, respectively. However, its mode of action, especially on insulin secretion, was quite different from that of ITV CCK-8. Therefore, exogenous CCK appears to act in the brain and the periphery in concert with and independently from cholinergic systems.

Animals↗

Peripheral factors in the mediation of cholecystokinin-induced satiety as assessed by comparative potencies of cholecystokinin antagonists.

Cholecystokinin COOH-terminal octapeptide (CCK-8) produces a satiating effect in the rat and other animals upon peripheral administration. Although it has been demonstrated that the receptors which mediate this action are located in the periphery and are of the CCK-A subtype, their anatomical location has not been firmly established. A dense population of CCK receptors in the pyloric sphincter has been suggested as a candidate. We here quantify the potency of several CCK antagonists to inhibit the contractile effect of CCK-8 on the rat pyloric sphincter in vitro. The potent and selective antagonist MK-329 has a Schild pK of 8.85; the less potent but selective antagonist lorglumide (CR-1409) a pK of 6.37; the related antagonist phenoxyacetylproglumide (phi oAc proglumide) a pK of 5.1; and the weak parent compound proglumide a pK of about 3.3. These data can be compared with the potencies of these compounds to inhibit the actions of CCK-8 to produce satiety in the rat; this comparison supports the contention that CCK receptors of the rat pyloric sphincter could in part mediate the satiety effect produced by exogenous CCK-8.

Animals↗

Somatostatin binding capacity, guanylate cyclase and tyrosine phosphatase activities during pancreatic proliferation in the rat induced by gastrectomy.

Gastrectomy increased pancreatic growth and this effect was associated with an increase in the number of somatostatin-14 (SS) receptors (146% of control) without altering their affinity. SS increased guanylate cyclase activity twofold in pancreatic acinar membranes from gastrectomized rats. The gastrectomy decreased pancreatic SS-like immunoreactivity (SS-LI) content (55% of control levels) and tyrosine phosphatase activity (74% of control levels). Administration of proglumide (20 mg/kg, IP), a gastrin/cholecystokinin (CCK) receptor antagonist, suppressed the inhibitory effect of gastrectomy on basal tyrosine phosphatase activity and SS-LI content, which returned to control levels. Furthermore, proglumide suppressed the increase of the number of SS receptors and of SS-stimulated guanylate cyclase activity induced by gastrectomy. All this suggests that pancreatic acinar cell growth is associated with upregulation of SS receptors, which could represent a mechanism promoted by the cell to negatively regulate the mitogenic activity of pancreatic growth factors such as CCK. In addition, the results also suggest that the negative regulation of tyrosine phosphatase activity may be important in the events involved in the pancreatic hyperplasia observed after gastrectomy.

Animals↗