Effects of a new proglumide analogue CR 1392 on pancreatic exocrine secretion in the rat

The effects of proglumide analogue. CR 1392, on pancreatic exocrine secretion were studied in the isolated pancreatic acini and the isolated perfused pancreata of rats. In the isolated acini, CR 1392 caused a parallel rightward shift of the dose-response curve for amylase secretion stimulated by cholecystokinin octapeptide (CCK-8). CR 1392 inhibited maximally stimulated amylase release by CCK-8 (100 pM) in a concentration-dependent manner, with a half maximal inhibition (ID50) at 8.0 +/- 0.6 microM. CR 1409, another proglumide analogue, also caused a concentration-dependent inhibition (ID50: 3.2 +/- 0.4 microM). Although CR 1409 was about 2.5-fold more potent than CR 1392 in inhibiting the stimulated amylase release, 1 mM CR 1409 caused 107.4 +/- 0.9% increase in amylase release, suggesting acinar cell damage. CR 1392 (1 mM) also caused 19.9 +/- 2.3% increase in amylase release, but was less toxic than CR 1409. The antagonism produced by CR 1392 was selective for CCK and had no effect on amylase release stimulated by other receptor secretagogues or by agents bypassing receptors. CR 1392 added 20 min after the CCK-8 stimulation rapidly abolished pancreatic exocrine secretion in both isolated acini and isolated perfused pancreas. Although the inhibitory effect of CR 1392 was fully reversible in the isolated acini, the pancreata perfused with 100 microM CR 1392 for 20 min did not respond to the subsequent stimulation with CCK-8 for more than 20 min. These results indicate that CR 1392 is a potent, competitive, specific and long acting antagonist of CCK in rat pancreas.

Comparative effects of CCK receptor antagonists on rat pancreatic secretion in vivo

The present experiments evaluate in vivo effects of recently described cholecystokinin (CCK) receptor antagonists on rat pancreatic secretion. Pancreaticobiliary secretion was studied after bile duct cannulation in anesthetized rats. After two basal 10-min fractions were selected, secretion was stimulated by intravenous caerulein (0.1-30.0 micrograms/kg) or secretin, and collected for seven further 10-min fractions. Peptide antagonists (CR 1409, CR 1392, and CR 1505) and nonpeptide antagonists (asperlicin and L364,718) were given intravenously 10 min before agonists. Increasing doses of antagonists gradually reduced secretion of protein and enzymes stimulated by submaximal and maximal doses of caerulein. The antagonists did not alter nonstimulated or secretin-stimulated secretion, indicating their specificity for the CCK receptor. Except for proglumide and asperlicin, all antagonists were able to abolish caerulein-stimulated pancreatic secretion, as evaluated by the mean integrated 1-h response to a near-maximal dose of caerulein. The caerulein dose-response curve was gradually shifted to the right by increasing doses of CR 1409, indicating competitive-like kinetics. Inhibition of secretion due to supramaximal doses of caerulein, however, could be reversed by doses of CR 1409 smaller than expected from extrapolating truely competitive kinetics from an in vitro situation to the in vivo situation. The rank order of potency of the compounds to antagonize caerulein-stimulated secretion in vivo agreed with their relative potencies to antagonize caerulein-stimulated amylase secretion from pancreatic acini in vitro as well as with their affinity to bind to peripheral CCK receptors in vitro.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Effects of the cholecystokinin receptor antagonist L-364,718 on experimental pancreatitis in mice

The effects of the cholecystokinin receptor antagonist L-364,718 was studied in a model of mild pancreatitis induced in mice by repeated injections of the secretagogue caerulein and in a lethal form of pancreatitis induced by feeding mice an ethionine-supplemented choline-deficient diet. L-364,718 prevented the caerulein-induced rise in serum amylase and pancreatic weight in a dose-dependent manner, the most effective dose being 0.1 mg/kg body wt. L-364,718 also prevented the caerulein-induced pancreatic inflammation as seen by light microscopy. L-364,718 offered no protective effects as determined by changes in serum amylase, pancreatic weight, histology, or mortality in the ethionine-supplemented choline-deficient diet model.

CGS 20625, a novel pyrazolopyridine anxiolytic

CGS 20625 (2-(4-methoxyphenyl)2,3,5,6,7,8,9,10-octa hydrocyclohepta[b]pyrazolo-[3,4-d]pyridin-3-one) is a potent and selective ligand for the central benzodiazepine receptor (IC50 = 1.3 nM), with little or no affinity to several other neurotransmitter receptor binding sites in vitro. CGS 20625 had a gamma-aminobutyric acid ratio of 0.9 and increased t-[35S]butylbicyclophosphorothionate binding by 20% in vitro, a profile indicative of a partial agonist or mixed agonist/antagonist. In vivo, CGS 20625 blocked a pentylenetetrazol discriminative cue with an ED50 = 1.7 mg/kg p.o. The compound selectively increased conflict responding in the Cook-Davidson paradigm with a minimal effective dose of 0.3 mg/kg p.o., as compared with 3.0 mg/kg p.o. for diazepam. At doses as high as 100 mg/kg p.o., CGS 20625 had no effect on variable interval responding, suggesting minimal sedation. Unlike diazepam, CGS 20625 had no effect on rotorod performance at doses up to 100 mg/kg p.o. indicating no overt muscle relaxation, and did not potentiate the action of ethanol in this behavioral paradigm. Also, CGS 20625 had no marked effect on locomotor behavior, did not potentiate hexobarbital sleep time and had no sedative activity at doses up to 300 mg/kg p.o. CGS 20625 was efficacious in preventing pentylenetetrazol-induced seizures (ED50 = 0.7 mg/kg p.o.), had less efficacy with no clear dose-response relationship against picrotoxin-induced seizures and had no effect on either strychnine or electroshock-induced convulsions at doses up to 300 mg/kg p.o.(ABSTRACT TRUNCATED AT 250 WORDS)

An analogue of substance P with broad receptor antagonist activity

[DPro4,DTrp7,9,10]Substance P-4-11 functions as a substance P receptor antagonist in several different systems. Because some analogues of substance P can function as receptor antagonists for bombesin as well as substance P, we tested [DPro4,DTrp7,9,10]substance P-4-11 for its ability to modify the interaction of various pancreatic secretagogues with their receptors in dispersed acini from guinea pig pancreas. [DPro4,DTrp7,9,19]Substance P-4-11 did not stimulate amylase secretion and did not alter the stimulation of amylase secretion caused by secretin, vasoactive intestinal peptide, calcitonin gene-related peptide or carbachol, but did inhibit the stimulation of amylase secretion caused by substance P, bombesin or cholecystokinin. With substance P, bombesin and cholecystokinin, [DPro4,DTrp7,9,10]substance P-4-11 caused a parallel rightward shift in the dose-response curve for stimulation of amylase secretion with no change in the maximal response. Schild plots of these results gave straight lines with slopes that were not significantly different from unity. [DPro4,DTrp7,9,10]Substance P-4-11 inhibited binding of 125I-labeled substance P, 125I-[Tyr4]bombesin and 125I-cholecystokinin octapeptide over the same range of concentrations as that in which it inhibited biologic activity of each of these peptides. Half-maximal inhibition of binding of 125I-substance P occurred with 4 microM, of 125I-[Tyr4]bombesin with 17 microM and of 125I-cholecystokinin octapeptide with 5 microM. With each radiolabeled peptide the value of Ki for inhibition of binding by [DPro4,DTrp7,9,10]substance P-4-11 was not significantly different from the corresponding value of Ki calculated from the appropriate Schild plot. The present results indicate that [DPro4,DTrp7,9,10]substance P-4-11 is a competitive antagonist at receptors for substance P, for bombesin and for cholecystokinin. Thus, these receptors must share a common peptide recognition mechanism even though they interact with agonists that have no obvious structural similarity.

A pseudopeptide that is a potent cholecystokinin agonist in the peripheral system is able to inhibit the dopamine-like effects of cholecystokinin in the striatum

There are no known specific effective cholecystokinin (CCK) receptor antagonists of both peripheral and central nervous systems. Here, we describe experiments which demonstrate that a synthetic pseudopeptide analogue of CCK-7 is a potent agonist in the peripheral system and behaves as a selective and highly potent inhibitor of the dopamine-like effects of CCK in the striatum. This compound, t-butyloxycarbonyl-Tyr (SO3H)-Nle psi (COCH2)Gly-Trp-Nle-Asp-Phe-NH2, is able to stimulate enzyme secretion from rat pancreatic acini, with high efficacy and potency. It is also very potent in inhibiting the binding of labeled CCK-8 to rat pancreatic acini (IC50 = 5 nM) and to guinea pig and mouse brain membranes (IC50 = 0.7 nM). However, this compound is able to antagonize the effects of intrastriatally injected t-butyloxycarbonyl-[Nle28,31] CCK-8 in mice, with high potency.

Functional expression of brain cholecystokinin and bombesin receptors in Xenopus oocytes

Total RNA was extracted from 15-day-old whole rat brains. Microinjection of the RNA into Xenopus laevis oocytes induced electrophysiological responsiveness to cholecystokinin-8 (CCK) and bombesin (BBS) but not to corticotropin-releasing factor (CRF) or somatostatin. The responses to CCK and BBS were similar in shape, time course, and reversal potential to that induced by receptor mediated phospholipid breakdown and that which is induced by intracellular injection of IP3. These responses were not blocked by atropine or by mianserin, did not require extracellular Ca2+ and were completely suppressed by intracellular injection of EGTA.

Influence of "calcium2+-channel blockers" on exocrine pancreatic secretion by isolated rat acini

Cytoplasmic Ca2+ is regarded as an intracellular messenger for acetylcholine- and cholecystokinin (CCK)-stimulated pancreatic enzyme secretion. We investigated in the in vitro model of isolated rat pancreatic acini whether or not Ca2+-channel blockers are able to inhibit Ca2+-mediated enzyme secretion. Isolated rat pancreatic acini were prepared via collagenase digestion. The effect of various Ca2+-channel blockers on amylase secretion stimulated by various secretagogues was monitored. Verapamil, but not nitrendipine, dose-dependently reduced CCK8- and carbachol-stimulated enzyme secretion. Higher doses of either CCK8 or carbachol could not reverse the inhibition caused by verapamil. Amylase secretion stimulated by the ionophore A23817 was not altered by verapamil. Verapamil augmented enzyme secretion stimulated by secretagogues which work through cAMP as second messenger. 3H-N-methylscopolamine- and 125I-Bolton-Hunter-CCK8-binding to pancreatic acini was dose-dependently inhibited by verapamil, but the inhibition curves did not parallel the inhibition curves with unlabeled receptor agonists. Thus, the impairment of exocrine pancreatic amylase secretion by verapamil is probably not due to its known "Ca2+-channel" blocking abilities in other tissues but is rather caused by noncompetitive effects on the level of muscarinic receptors and receptors for CCK.

Differential regulation of cholecystokinin- and muscarinic-receptor-mediated phosphoinositide turnover in Flow 9000 cells

We have explored the hypothesis that the apparent greater efficiency of cholecystokinin (CCK-8) receptor-second messenger coupling compared with that of muscarinic receptor in Flow 9000 cells is due to differential feedback inhibitory control mechanisms. Pretreatment of Flow 9000 cells with the tumour-promoting protein kinase C (PKC)-activating agent 12-O-tetradecanoylphorbol 13-acetate (TPA) produced a time- and dose-dependent inhibition of CCK-8 and acetylcholine (ACh) stimulation of inositol phosphate production. The inhibition by TPA of ACh-induced PI (phosphoinositide) response involved reduction of the maximal response, but no change in the concentration of ACh required to evoke a half-maximal response. In contrast, TPA inhibition of CCK-8 responses could be overcome by increasing the CCK-8 concentrations. Flow 9000 cells pretreated with TPA exhibited a 52-68% reduction in [3H]quinuclidinyl benzilate ([3H]QNB) binding capacity, whereas [125I]CCK-8 binding was unchanged. In saponin-permeabilized Flow 9000 cells, TPA pretreatment had no effect on guanosine 5'-[gamma-thio]triphosphate (GTP[S])-induced inositol phosphate formation, indicating that G-protein linkage to phosphoinositidase C (PIC) was not affected. However, TPA significantly inhibited the potentiating effect of GTP[S] on CCK-8 and ACh activation of PI response, suggesting that the coupling between the receptors and the G-protein was impaired. The PKC-activator 1-oleoyl-2-acetylglycerol (OAG), a diacylglycerol analogue, also significantly reduced CCK-8 and ACh stimulation of inositol phosphate accumulation in these cells. Our results are consistent with the hypothesis that muscarinic activation of PI hydrolysis is subjected to rapid feedback inhibition via the 1,2-diacylglycerol-PKC pathway. CCK-receptor activation of PI turnover is modulated to a lesser extent, and this may partially explain apparent differences in the efficiency of receptor-second messenger coupling. It is proposed that TPA acting through PKC exerts its inhibitory action on muscarinic-agonist-mediated PI response mainly at the receptor level, whereas the inhibitory effect on CCK-8 response is at a site close to the receptor-G-protein coupling step.

Effect of cholecystokinin receptor antagonist on pancreatic responses to exogenous gastrin and cholecystokinin and to meal stimuli

Exocrine pancreatic response to food is believed to result from the interaction of neural and hormonal factors, but their contribution in the net postprandial secretion is unknown. Recent description of a highly specific and potent cholecystokinin (CCK)-receptor antagonist permitted the evaluation of the physiologic role of CCK in postprandial pancreatic secretion. In dogs with chronic pancreatic fistula, CCK antagonism caused little alteration in sham feeding- or urecholine-induced pancreatic protein secretion, but reduced by approximately 60% the pancreatic protein response to a gastrointestinal meal and virtually abolished the pancreatic responses to duodenal perfusion with amino acids or oleate and to exogenous CCK, but not to secretin or neurotensin. The pancreatic protein responses, particularly to lower doses of gastrin, were also reduced by CCK-receptor antagonist, but no changes in the responses to secretin or neurotensin were detected. Cholecystokinin antagonism also significantly reduced the pancreatic polypeptide responses to CCK, gastrin, and the gastrointestinal meal, possibly due to removal of the CCK-mediated release of pancreatic polypeptide. We conclude that CCK plays a crucial role in the mediation of the gastrointestinal phase, but not the cephalic phase, of pancreatic secretion.

Effect of metoclopramide, bethanechol and the cholecystokinin receptor antagonist, L-364,718, on gastric emptying in the rat

The prokinetic effects of metoclopramide, bethanechol and L-364,718 on a semisolid meal and solid pellet gastric emptying were evaluated and compared. Each compound increased the rate of meal emptying as measured 90 min post-dose. L-364,718, a non-peptide CCK antagonist, was the most potent of these three agents with statistically significant activity observed at 0.03, 0.1 and 0.3 mg/kg p.o. Only metoclopramide significantly enhanced pellet emptying in a dose-dependent manner (3-30 mg/kg p.o.). The effects of each test agent and the potential physiologic role of cholecystokinin in regulating gastric emptying are discussed.

Binding of gastrin(17) to human gastric carcinoma cell lines

The hormone gastrin stimulates acid secretion by gastric parietal cells and acts as a growth factor for the gastric mucosa. Gastrin receptors with dissociation constants of approximately 0.5 nM have been detected on isolated gastric parietal cells, and on some cell lines derived from colon carcinomas. We now report that gastrin is also bound by five cell lines derived from human gastric carcinomas, but that the affinities of these lines for gastrin range from 0.2 to 1.3 microM. Cholecystokinin8 binds to the cell line Okajima with an affinity similar to gastrin17, while shorter gastrin analogues bind with reduced affinity. Binding of gastrin is unaffected by acetylcholine, histamine, or a number of other hormones with the exception of insulin which inhibits binding with an IC50 value of 0.5 microM. The ability to bind gastrin with affinities in the microM range appears to be a property widespread among other tumor cell lines.

Interaction of memantine with cholecystokinin receptors in mouse brain

The effect of memantine on CCK receptors in mouse brain has been investigated using particles of dissected cortex and striatum. Total binding of radio-labelled CCK33 was one-half maximal within 10 min of incubation and reached a maximum after 30 to 60 min when either cortex or striatum was used. Non-specific binding (presence of 100 microM unlabelled CCK8) was 50 to 80% of total binding at steady state conditions. CCK8 inhibited specific binding of radiolabelled CCK33 in a dose-dependent manner; the IC50 (half-maximal inhibitory concentration) was in the range 3 to 4 nM. Memantine increased CCK binding in a concentration-dependent manner, though at high concentrations. The EC50 (half-maximal effective concentration) of this effect was less than 100 microM. The memantine effect is not due to an inhibition of labelled CCK degradation in the medium. The effect of memantine on CCK binding is unique for brain since it was not observed in pancreatic acinar membranes. These data, therefore, suggest a modulatory effect of memantine on CCK receptors in mouse brain (cortex and striatum) particles.

[Species differences in the behavioral effects of cerulein--an agonist of the receptors of the octapeptide cholecystokinin--in white mice and rats]

It has been shown in the behavioural experiments that combined pretreatment with haloperidol (0.25 mg/kg) and caerulein (40 micrograms/kg), and to a lesser extent pretreatment with caerulein alone caused long-term reversal of amphetamine (2 mg/kg) induced hyperexcitability in rats. Administration of proglumide (50 mg/kg), an antagonist of CCK-8 receptors, did not reverse long-term antiamphetamine effect of caerulein. In mice pretreatment with caerulein (50 and 100 micrograms/kg) alone or in combination with haloperidol (0.25 mg/kg) caused hypersensitivity to the behavioural effect of amphetamine (3 mg/kg). Intraventricular (I ng), but not systemic (100-500 micrograms/kg) administration of caerulein selectively antagonized seizures in mice induced by intraventricular administration of quinolinic acid (5 micrograms) and N-methyl-D-aspartate (0.2 microgram). Pretreatment with proglumide (50 mg/kg) reversed the anticonvulsive effect of caerulein in mice. In rats, caerulein failed to affect the seizures caused by intraventricular administration of quinolinic acid. The results of the present study demonstrate the existence of obvious interspecies differences in the behavioural effects of caerulein, the agonist of CCK-8 receptors, in mice and rats.

[Antagonism of caerulein, a CCK-8 receptor agonist, to the behavioral effects of ketamine in mice and rats]

It has been established in experiments on male mice and rats that caerulein antagonized the behavioural effects of ketamine, an agonist of phencyclidine receptors. Caerulein (75-375 micrograms/kg) and haloperidol (0.1-1.5 mg/kg) suppressed the stereotyped behaviour and motor excitation induced by ketamine (30 mg/kg) in mice. Caerulein and haloperidol failed to affect ketamine-induced ataxia. Caerulein (10 micrograms/kg) and the opioid antagonist naloxone (5 mg/kg) completely blocked the amnestic action of ketamine (30 mg/kg) in passive avoidance experiments on rats. It seems likely that the suppression of the behavioural effects of ketamine by caerulein is related to its functional antagonism with dopamine and opioid receptors.

The cholecystokinin receptor antagonist L364,718 increases food intake in the rat by attenuation of the action of endogenous cholecystokinin

1. To determine the role of endogenous cholecystokinin (CCK) in the regulation of food intake, the effects of the potent CCK receptor antagonist L364,718 were investigated on the intake of a palatable diet in non-deprived rats. The effect of a single dose of proglumide was also investigated for comparative purposes. In addition, the ability of L364,718 to antagonize the reduction in food intake produced by exogenous cholecystokinin-octapeptide (CCK8) or bombesin in food-deprived rats was determined. 2. L364,718 (10-100 micrograms kg-1, i.p.) increased the intake of palatable diet during the 30 min test period. Proglumide (300 mg kg-1, i.p.) also increased the intake of palatable diet. Conversely, CCK8 (0.5-5 micrograms kg-1, i.p.) produced a reduction in the intake of the diet. 3. In fasted rats, L364,718 (100 micrograms kg-1, i.p.) antagonized the reduction in food intake produced by CCK8 (10 micrograms kg-1, i.p.) but not that produced by bombesin (50 micrograms kg-1, i.p.). L364,718 did not increase food intake in these animals when measured over a 6 h period. 4. It is concluded that L364,718 is a potent, selective antagonist of the effects of CCK8 on food intake. The observation that L364,718 and proglumide increase the intake of a palatable diet provides some evidence that endogenous CCK is involved in the control of food intake in this model.

Cholecystokinin antagonists. Synthesis and biological evaluation of 4-substituted 4H-[1,2,4]triazolo[4,3-a][1,4]benzodiazepines

A series of 4-substituted 4H-[1,2,4]triazolo[4,3-a][1,4]benzodiazepines was prepared by standard methodology. These compounds were tested in vitro as antagonists of the binding of [125I]cholecystokinin (CCK) to rat pancreas and guinea pig brain receptors and of the binding of [125I]gastrin to guinea pig gastric glands. All compounds proved to have greater affinity for the peripheral CCK receptor with some analogues having IC50's in the subnanomolar range. In vivo activity of selected compounds in mice is presented and the structure/activity profile of this class of benzodiazepines as CCK antagonists is discussed.

Mechanism of action of the anti-shock effect of CCK-8: influence of CCK antagonists and of sympatholytic drugs

In an experimental model of haemorrhagic shock that causes 100% mortality in rats within 30 min, the intravenous bolus injection (20 micrograms/kg) of sulfated cholecystokinin octapeptide (CCK-8) induces a prompt and sustained rise in blood pressure and pulse amplitude, all treated animals still surviving at the end of the experiment (2 h). This effect of CCK-8 is completely blocked by reserpine (5 mg/kg i.p.), significantly antagonized by prazosin (0.1 mg/kg i.v.) and yohimbine (1 mg/kg i.v.), and unaffected by practolol (15 mg/kg i.v.) and proglumide (0.2 mg/kg i.v.); it is completely antagonized by the intravenous (0.01-0.05 mg/kg), but not by the intracerebroventricular (0.002 mg/kg) injection of the 'peripheral' CCK antagonist, L-364,718. The present data indicate that the cardiovascular effects of CCK-8 in haemorrhagic shock involve peripheral CCK receptors, and require the functional integrity of the sympathetic nervous system.

Characterization of gastrin receptors on guinea pig pancreatic acini

Recent studies have demonstrated gastrin receptors in some pancreatic tumors and that gastrin is a potent stimulant of pancreatic Na+-H+ exchange. In the present study we used 125I-labeled gastrin (125I-gastrin) to characterize gastrin receptors on guinea pig pancreatic acini. Binding of 125I-gastrin was temperature dependent, saturable, and specific for gastrin-related peptides. Analysis demonstrated a single class of receptors with high affinity for gastrin (Kd = 1.5 nM) and a binding capacity of 1 fmol/mg protein. Binding of 125I-gastrin was inhibited with the following relative potencies (Kd): cholecystokinin octapeptide (CCK-8) (0.35 nM) greater than gastrin-17-I = gastrin-34-I (1.5 nM) greater than pentagastrin (7 nM) greater than desulfated [des(SO3)]CCK-8 (28 nM) greater than CCK-4 (508 nM) and by the receptor antagonists CBZ-CCK-27-32-NH2 (3.5 microM) greater than proglumide analogue 10 (30 microM) greater than asperlicin (265 microM) greater than Bt2-guanosine 3',5'-cyclic monophosphate (828 micron). In contrast, for both stimulation of enzyme secretion and inhibition of binding of 125I-CCK-8 the relative potencies were CCK-8 much greater than des(SO3)CCK-8 greater than gastrin-17-I = gastrin-34-I greater than pentagastrin greater than CCK-4. For each receptor antagonist the dose-inhibition curve for gastrin-stimulated amylase release was superimpossible with that for CCK-8-stimulated amylase release. Gastrin-17-I at concentrations less than 0.1 microM did not potentiate carbachol or vasoactive intestinal peptide-stimulated amylase secretion and did not affect basal or stimulated adenosine 3',5'-cyclic monophosphate or 45Ca outflux.(ABSTRACT TRUNCATED AT 250 WORDS)

Pharmacological properties of lorglumide as a member of a new class of cholecystokinin antagonists

Derivatives of 5-(dipentylamino)-5-oxo-pentanoic acid are a new class of non-peptide cholecystokinin (CCK) antagonists. The most potent compound, D,L-4-(3,4-dichlorobenzoylamino)-5-(dipentylamino)-5-oxo-pen tanoic acid (lorglumide, CR 1409), has a great affinity for the pancreatic CCK receptors and is a competitive, specific and potent CCK antagonist on the smooth muscles of the gall bladder and ileum of the guinea pig and on the CCK-induced amylase secretion of isolated pancreatic acini. In vivo lorglumide antagonizes the contraction of the gall bladder of the guinea pig and of the dog provoked by i.v. CCK-8 or ceruletide (caerulein). It antagonizes the satiety effect of CCK-8 in the rat and is protective against ceruletide-, taurocholate- and diet-induced pancreatitis. Lorglumide is therefore a useful pharmacological tool to study the functions of CCK. For its pharmacological properties, its relatively low toxicity and because it is active also after oral administration, lorglumide is a candidate for diagnostic or therapeutic use in man when an involvement of CCK is suspected.

The chronic administration of dopamine antagonists and methamphetamine changed the [3H]-cholecystokinin-8 binding sites in the rat frontal cortex

The specific cholecystokinin (CCK) binding in the slide-mounted tissue sections of the rat frontal cortex was measured with [3H]-CCK-8. The binding was saturable, reversible, high in affinity, and inhibited by caerulein. The chronic administration of dopamine (DA) antagonists and methamphetamine (MAP) showed a tendency to increase the [3H]-CCK-8 binding sites (Bmax) in the frontal cortex. Long-term treatments with DA antagonists led to the depletion of CCK-8 and may have caused an observed proliferation of CCK-8 receptors in the frontal cortex.

Inhibition of pentagastrin-stimulated up-regulation of gastrin receptors and growth of mouse colon tumor in vivo by proglumide, a gastrin receptor antagonist

We have recently demonstrated that gastrin stimulates growth of mouse colon cancer (MC-26) in vivo by regulation of gastrin receptors (GR). In the present study, we have tested the effect of proglumide (PGL), a GR antagonist, on the trophic and GR-regulatory effects of gastrin on MC-26 tumors. Four groups of 12 mice each were inoculated with 5 X 10(4) MC-26 cells and given injections of either normal saline (control), pentagastrin (PG), PGL, or both PG + PGL for 21 days. At the end of the treatment period, body, tumor, fundic, and colon weights were noted and GR measured. Two types of specific gastrin-binding sites were found on tumor cell membranes of control mice, one with high binding affinity (Kd = less than 1.0 nM) and low capacity (GR), and the other with a very high capacity and a low affinity (Kd = greater than 0.1 microM) (type 2 gastrin-binding sites). Only the type 1 GR were observed on the fundic mucosal and colon membranes. PG treatment resulted in a significant weight increase of the tumors with an up-regulation of only type 1 GR. On the other hand, PG had no significant effect on fundic mucosal and colonic GR levels, but caused a significant increase in fundic mucosal weights. PGL completely inhibited both the trophic and GR up-regulatory effects of PG on tumors, but incompletely reduced the PG-stimulated fundic mucosal weight gain, indicating differential sensitivity of tumor and normal tissues to PGL. PGL, in the absence of PG, was slightly trophic for normal fundic mucosa, but had no effect on MC-26 tumors and normal colon. The one striking effect of PGL, in the presence of PG, was the significant lowering of the binding affinity of type 1 GR for gastrin on both the tumor and normal gastrointestinal tissues. This effect may be another mechanism by which PGL interferes with the actions of PG on MC-26 tumors and fundic mucosa of mice.