A series of 3-(arylureido)-5-phenyl-1,4-benzodiazepines, nonpeptidal antagonists of the peptide hormone cholecystokinin (CCK), are described. Derived by reasoned modification of the CCK-A selective 3-carboxamido-1,4-benzodiazepine, MK-329, this paper chronicles the development of potent, orally effective compounds in which selectivity for the CCK-B receptor subtype was achieved. The principal lead structure that emerged from these studied is L-365,260, a compound which has been submitted for clinical evaluation. Details of the ability to modulate the receptor interactions of these benzodiazepines by appropriate structure modifications are discussed which imply the possibility of further refining the CCK-B receptor affinity and selectivity of this class of compounds.

The effects of cholecystokinin octapeptide (CCK(8)), the CCK-A receptor antagonist, MK-329, and the CCK-B receptor antagonist, L-365, 260, microinfused into the paraventricular nucleus of hypothalamus (PVN) on colonic motor function was investigated in awake rats, chronically implanted with a microinjection cannula into the PVN and a catheter into the proximal colon. In fasted rats, bilateral microinfusion of CCK(8) at doses of 1.5 and 3.0 microg/rat into the PVN stimulated colonic transit, as shown by a significant increase in the geometric center by 47 and 54%, respectively. This effect of CCK(8) was site-specific to the PVN, since microinjection of the peptide into sites outside of but adjacent to PVN had no effect. In non-fasted rats, L-365,260 bilaterally microinjected into the PVN at a dose of 1.5 microg/rat inhibited propulsive colonic motor function; colonic transit time significantly increased by 73% in comparison to the control condition. Microinfusion of the CCK-A antagonist into in the PVN did not affect colonic transit. These results show that the PVN is a responsive site for the central CCK(8)-induced modulation of colonic motility. The data suggest, that endogenous CCK in the paraventricular nucleus of the hypothalamus unfolds a stimulatory effect on colonic transit through action on CCK-B receptors.

In this study, a selective antagonist of cholecystokinin (CCK)-A receptors, loxiglumide, was used to evaluate the role of CCK in the control of the release of gastrin and pancreatic hormones (insulin, glucagon, pancreatic polypeptide (PP), and somatostatin) after stimulation with exogenous CCK and ingestion of a standard liquid mixed meal in healthy humans. Exogenous CCK-8, which induced a small but significant increase in gastric acid secretion, resulted in dose-dependent increments in plasma PP levels without significant changes in plasma levels of insulin, glucagon, or somatostatin. Pretreatment with loxiglumide resulted in a marked increase in CCK-induced gastric acid secretion and abolished the increments in plasma PP without alteration of plasma insulin, glucagon, or somatostatin levels. Ingestion of the liquid meal resulted in an immediate rise in intragastric pH from basal values of about 2 to pH6 lasting 90-120 min, and this was accompanied by significant increments in plasma gastrin, insulin, glucagon, PP, and somatostatin. Administration of loxiglumide (1200 mg orally) caused a reduction in the postprandial intragastric pH and the two- to three-fold increase in plasma gastrin. Plasma insulin and glucagon levels in tests with loxiglumide tended to increase, probably owing to accelerated gastric emptying, whereas plasma PP and somatostatin were significantly reduced. This study provides evidence that CCK exerts an inhibitory effect on gastric acid secretion and plasma gastrin release as well as a stimulatory influence on the release of PP and somatostatin via CCK-A receptors but does not influence directly insulin or glucagon secretion in man.

We have shown that systemic administration of interleukin-1beta (IL-1beta) excites gastric vagal afferent activity in part via stimulation of type A cholecystokinin (CCK-A) receptors in rats. The present study was undertaken to determine whether the response of the gastric vagal afferent nerve to systemic IL-1beta is altered in Otsuka Long-Evans Tokushima Fatty (OLETF) rats, which lack CCK-A receptors. The response was compared with that of the control strain, Long-Evans Tokushima Otsuka (LETO) rats. All animals were anesthetized with pentobarbital and artificially ventilated. Intravenous administration of 4 microg/kg of IL-1beta increased gastric vagal afferent activity in both LETO and OLETF rats, whereas a smaller dose of 2 microg/kg of IL-1beta increased activity only in the OLETF rats. The present results demonstrate that the response of the gastric vagal afferent activity in CCK-A receptor deficient OLETF rats was more sensitive to intravenous administration of IL-1beta than was in control LETO rats.

To investigate the impact of hypoxia on the expression of receptor activator of NF-kB ligand (RANKL) and osteoprotegerin (OPG) in human periodontal ligament cells (hPDLCs) in vitro. hPDLCs were incubated in a hypoxic atmosphere of 2% O2, 5% CO2, 94% N2 at 37°C for 6, 12, 24 and 48 h. After that, cell proliferation assay was determined using CCK-8 technique. SP immunocytochemistry method was performed to trace the expression of hypoxia-inducible factor 1 alpha (HIF-1α) in hPDLCs. The expression levels of RANKL and OPG were investigated using real-time PCR and ELISA. As a control, the cells were incubated at normoxic conditions of 20% O2, 5% CO2, 75% N2. All results were analyzed using one-way ANOVA at a significant level of P=0.05. OPG mRNA and protein levels were down-regulated meanwhile RANKL mRNA and soluble RANKL (sRANKL) protein levels were up-regulated after stimulated by hypoxia. The relative RANKL/OPG expression ratios were increased in both mRNA and protein levels. The expression of RANKL mRNA and sRANKL protein levels was enhanced significantly (P<0.05) under the hypoxia conditions at 12 h, 24 h and 48 h while OPG mRNA and protein were reduced significantly (P<0.05) at 12 h, 24 h and 48 h. Hypoxia can affect the expression of RANKL and OPG in hPDLCs, which constitute an important pathogenic event in the alveolar bone resorption. Lack of oxygen in periodontal tissue may accelerate the development of periodontitis.

The observation that systemic administration of the peptide cholecystokinin (CCK) inhibits food intake in mammalian species has led to the hypothesis that endogenous peripheral CCK released from the small intestine during a meal acts as a satiety factor. It was predicted that if CCK does play an important role in satiety, then systemic administration of a specific CCK receptor antagonist should block the effects of the endogenous peptide released during a meal and increase food intake. The present study was undertaken to test the hypothesis by investigating the effects of the cholecystokinin(1) (CCK(1)) receptor antagonist N-alpha-3'-quinolinoyl-D-Glu-N,N-dipentylamide dicyclohexylammonium (A70104), which is unlikely to cross the blood-brain barrier, on food intake in rats. A70104 (20-200 microg/kg, i.p.) had no any significant effect on the intake of a test meal in rats under different experimental conditions. However, pretreatment of rats with A70104 (50 microg/kg, i.p.) abolished the inhibitory effects of exogenous peripheral CCK (5 microg/kg, i.p.) on food intake. The findings that A70104 had no effect on food intake when administered on its own, but abolishes the suppressant effect of exogenous peripheral CCK, suggest that endogenously released peripheral CCK does not play an important role as a satiety factor in rats.

OBJECTIVE

The present study evaluates whether endogenous gastrin regulates pancreatic growth in the mouse.

METHODS

Male NMRI mice weighing 12-15 g were assigned to six groups (10 mice/group) which were treated with different combinations of 0.9% NaCl, omeprazole, a CCK-A antagonist, a CCK-B antagonist, loxiglumide, and L365, 260 for 10 days each according to different protocols.

RESULTS

Omeprazole caused a marked, 10-fold increase in serum gastrin which was not affected by the gastrin antagonist, but markedly reduced by the CCK-A antagonist. The marked increase in endogenous gastrin caused by omeprazole did not promote pancreatic growth in any way. Similarly, the gastrin antagonist did not inhibit pancreatic growth. In contrast, the CCK-A antagonist significantly decreased pancreatic weight and protein content.

CONCLUSIONS

The present results strongly suggest that endogenous gastrin--in contrast to CCK--does not regulate pancreatic growth in the mouse. The inhibitory effect of loxiglumide on omeprazole-induced increase in serum gastrin might be explained by recent findings which showed that CCK-A antagonists can stimulate gastric acid secretion probably due to a reduction of the inhibitory effect of basal CCK on the D-cell and its somatostatin release. Probably such a slight stimulation of gastric acid secretion caused by the CCK-A antagonist might reduce the gastrin increase caused by omeprazole's abolishment of acid secretion.

Operant feeding was recorded in 18 h deprived pigs after peripheral (IV) or central (ICV) administration of saline, the CCK A agonist A-71378, the CCK B agonist pentagastrin, or pentagastrin vehicle. In Experiment 1 (n = 10), A-71378 (0.5, 1.0, and 2.0 micrograms/kg) given IV produced a sustained dose-related reduction in food intake (p < 0.02), whereas the same doses of pentagastrin were without effect. In Experiment 2 (n = 10), neither agonist given ICV (1 microgram) had consistent effects on operant responding. A higher ICV dose of A-71378 (5 micrograms) was also ineffective, whereas 1 microgram CCK octapeptide given ICV inhibited feeding (p < 0.03). These findings suggest that A receptors outside the blood-brain barrier mediate the suppressant effect of IV CCK on feeding in the pig and that neither peripheral nor central B receptors influence food intake in this species.

Sulfated cholecystokinin octapeptide (CCK-8) was administered either intraperitoneally or into the cerebral ventricle of fully conscious mice, and locomotor activity was quantified. CCK-8 administered by either route suppressed locomotor activity. Subcutaneously administered selective CCK-A receptor antagonist, L-364,718 (1 mg/kg), reversed the inhibitory effect of centrally as well as peripherally administered CCK-8, but the selective CCK-B receptor antagonist, L-365,260 (1 mg/kg), did not. These results demonstrate that centrally as well as peripherally administered CCK-8 suppresses locomotor activity in mice through an interaction with CCK-A, but not CCK-B, receptors.

This review shows that numerous neuropeptides and hormones are involved in the regulation of intestinal transit. Many gastrointestinal hormones known to act on smooth muscle to influence muscle contractility also play a role in the genesis of abrupt changes associated with alimentary behaviour. In many monogastrics and ruminants, the cyclic occurrence of the migrating motor complex (MMC) is linked to peripheral hormonal factors only slightly influenced by the nature of food. Motilin is the major hormone involved in triggering the gastric migrating motor complex while somatostatine and enkephalins are implicated in the propagation along the small intestine. Other hormones, like CCKCCK released at the central nervous system ventromedial hypothalamus is involved in maintaining the postprandial type of activity. Gastrointestinal transit may be altered in physiopathological situations in which CRF, TRH and some cytokines (IL1 beta, TNF alpha) play an important role.

OBJECTIVE

Ingestion of a meal frequently induces an urge to defaecate, the so-called gastro-colonic or gastro-rectal reflex. In patients with irritable bowel syndrome (IBS), symptoms are often provoked by meals. Cholecystokinin (CCK), a proximal gut peptide released after ingestion of a meal, may mediate these postprandial changes. The potential role of CCK in rectal sensory and motor function was evaluated by a rectal barostat study in healthy controls and patients with IBS. METHOD ; The sensory effects on serosal and mucosal receptors were studied. Twelve healthy controls and 12 patients with IBS underwent a ramp distension procedure of the rectum during infusion of CCK and placebo in random order. In 10 other healthy controls and 10 IBS patients an intermittent distension procedure was performed during infusion of CCK and placebo in random order.

RESULTS

No differences were found in rectal compliance during ramp distensions between IBS patients and controls. CCK did not affect perception of urge and pain in controls or in IBS patients. Similar results were obtained during the intermittent distensions, but at higher distension pressures CCK significantly increased rectal sensitivity in IBS patients.

CONCLUSIONS

Infusion of exogenous CCK to plasma levels normally seen in the postprandial state did not influence rectal motor function or sensations during ramp distension but it did significantly increase pain sensation in IBS patients during rapid intermittent distension.

Out of seven human carcinoma cell lines (M7609, CCK-81, FCC-1, RPMI#4788, QGP-1, HLC-1, and KNS-62), 4 cell lines were found to produce immunoreactive calcitonin (ICT), a potential tumor marker for various malignancies. During a 7-day culture, 1.4 X 10(5) QGP-1, RPMI#4788, HLC-1, and KNS-62 cells secreted 7,000 pg, 500 pg, 400 pg, and 400 pg of ICT in the medium, respectively. The production of ICT by QGP-1 cells was increased by addition of pentagastrin or calcium gluconate. Three different components of ICT (peak I, molecular weight greater than 40,000; peak II, 14,000-18,000; peak III, 3,400) were detected by gel filtration of the QGP-1 spent medium. In a competitive inhibition-type radioimmunoassay of serial dilutions of each ICT component, peak III component showed very similar immunoreactivity to synthetic calcitonin. However, the other two components gave clearly different immunoreactivities from the peak III component and showed very similar immunoreactivities to each other. All the cell lines were further screened for synthesis of 7 other tumor markers, carcinoembryonic antigen, nonspecific cross-reacting antigen, CA19-9, tissue polypeptide antigen, alpha-fetoprotein, beta 2-microglobulin and ferritin. Every cell line produced 2 to 6 markers concomitantly, and various combinations of positive markers were found among the cell lines.

White-crowned sparrows maintained on short days (9:15-h light-dark cycle) were peripherally injected with 1.0, 4.0, and 16 micrograms/kg ip of cholecystokinin octapeptide (CCK-8). Meal size over the subsequent 30 min was significantly depressed in a dose-dependent fashion. Water intake was not affected. The anorexic effect caused by 4.0 micrograms/kg was attenuated by 100 micrograms/kg of the type-A CCK receptor antagonist MK-329 but not by 300 micrograms/kg of the type-B CCK receptor antagonist L 365,260, suggesting that CCK-induced suppression of food intake in this species is mediated by a CCK-A receptor. Administration of both CCK-A and CCK-B receptor antagonists alone resulted in no change in meal size. These experiments suggest that white-crowned sparrows, when weight stable, respond to CCK-8 in a manner comparable with several mammalian species.

A group of the 24-26 paraldehyde fuchsin-positive median neurosecretory cells (MNC) in the pars intercerebralis of the brain of the blowfly, Calliphora vomitoria, has shown immunoreactivity towards three different antibodies to alpha-endorphin, a peptide that corresponds to the amino acid sequence present between residues 61 and 76 of the precursor molecule, beta-lipotropin (beta-LPH). The immunoreactive material could be followed in axons within the median bundle, the tract through which neurosecretory material from the MNC is passed down to the corpus cardiacum (CC). The alpha-endorphin-immunoreactive material was observed leaving the CC in the cardiac-recurrent nerve, dorsal to the proventriculus, in the direction of the abdomen. The cells that contain the alpha-endorphin-like material are different from those of the MNC that contain insulin-, pancreatic polypeptide-, and gastrin/CCK-like peptides. This finding demonstrates the considerable complexity and peptidergic nature of the MNC and constitutes further evidence that morphinomimetic-like peptides are present in the nervous system of invertebrates.

These studies investigated whether endogenous activation of CCK(A) receptors mediates the expression of amphetamine (AMP)-induced locomotor activity. In Experiment 1, locomotor activity was assessed in rats pretreated with the CCK(A) antagonist devazepide (0.001, 0.01, and 0.1 mg/kg) and subsequently injected with AMP (1.5 mg/kg). In Experiment 2, rats were administered AMP (1.5 mg/kg) once daily for 7 days. Following a 10-day withdrawal, locomotor activity was assessed following treatment with devazepide (0.001, 0.01, and 0.1 mg/kg) and AMP (0.75 mg/kg). In both studies, rats were classified as low (LR) or high (HR) responders based upon a median split of their locomotor response to a novel environment. Results from Experiment 1 showed that AMP potentiated the expression of locomotor activity, and this effect was most pronounced in HR rats. However, devazepide did not affect AMP-induced locomotion. Results from Experiment 2 demonstrated that chronic AMP pretreatment augmented the locomotor response to subsequent AMP challenge, and this effect was most pronounced in the HR group. Further, this augmented response was blocked by devazepide in HR rats. These findings constitute the first demonstration that endogenous CCK(A) receptor activation is an important substrate mediating AMP-induced locomotor activity in animals with a previous history of AMP treatment.

Cholecystokinin (CCK) has been suggested to mediate satiety in a number of non-primate species via its peripheral actions as well as a possible central mechanism involving magnocellular and parvocellular oxytocin release. Quantitative in vitro autoradiography employing [125I]-Bolton-Hunter labelled CCK-8S ([125I]-CCK-8S) was used to examine the distribution and density of CCK receptors in sections of brain from normal rats and rats deprived of food, water or both food and water for 4 days. In food-deprived rats, specific [125I]-CCK-8S binding was reduced by 64 +/- 5% in the hypothalamic supraoptic nucleus (SON) and by 44 +/- 13% in the paraventricular nucleus of the hypothalamus (PVN). In contrast, water deprivation increased binding of [125I]-CCK-8S by 128 +/- 15% in the SON and by 196% +/- 24% in the PVN, while combined food and water deprivation produced smaller increases in both nuclei (30 +/- 5% and 98 +/- 26% in SON and PVN respectively). Changes in receptor density in the PVN appeared to be most prominent in the magnocellular (especially oxytocin-rich) subdivisions. None of the treatments employed produced changes in [125I]-CCK-8S binding in the ventromedial hypothalamic nucleus or the reticular thalamic nucleus. Both CCK-A and CCK-B receptor subtypes were visualized in the nucleus of the solitary tract and the area postrema of normal rats, but levels of binding to both of these subtypes were unaffected by the experimental treatments. These selective alterations demonstrate the plasticity of CCK receptors in the SON and PBN, and are probably associated with changes in the level of neurochemical activity of magnocellular oxytocinergic neurones in these areas. These results, together with reports of changes in the level of CCK synthesis in cells of the SON and PVN after hyperosmotic stimuli, suggest that CCK may act in an autocrine fashion on these neurones and that both CCK receptors and peptide levels are altered in the same direction following cellular activation or inhibition.

In male rats anesthetized with urethane (600 mg/kg) and alpha-chloralose (60 mg/kg), extracellular recordings were made from tuberoinfundibular (TI) neurons in the paraventricular nucleus (PVN) identified by antidromic stimulation of the median eminence. Electrical stimulation of the gastric branches of the vagus nerve excited 26 (72%) of 36 TI neurons tested. I.v. (0.5-1 microgram/rat) or i.p. (5 micrograms/rat) administration of cholecystokinin (CCK-8) excited 10 (63%) of 16 TI neurons tested. The excitatory responses induced by CCK-8 were abolished by bilateral cervical vagotomy. These results suggest that TI neurons in the PVN receive excitatory inputs from gastric afferents via vagus nerves.

Mediation of mother-infant interactions by the brain-gut peptide cholecystokinin (CCK) was examined by observing behavior of Otsuka Long-Evans Tokushima Fatty (OLETF) rats, which lack functional CCKA receptors because of a genetic abnormality. OLETF (n = 10) and control (Long-Evans Tokushima Otsuka [LETO] n = 10) dams interacted with 1 pup of each line on Postpartum Days 6-9. OLETF pups received more body and anogenital licking and emitted substantially more ultrasonic vocalizations than LETO pups. OLETF dams carried pups less frequently and showed a nursing position more frequently than LETO dams. No significant Pup X Dam Line interactions or line differences in dams' activity were detected. The results provide convergent validity to previous pharmacological studies implicating CCK mediation of both infant and maternal behavior.

It has been previously demonstrated that guinea pig pancreas possesses both cholecystokinin-A (CCK-A) receptors and CCK-B (gastrin) receptors. In contrast to guinea pig pancreas, it is not known whether CCK receptors in rat pancreas are CCK-A receptors, CCK-B (gastrin) receptors, or both. Thus, in the present study, we characterized CCK receptors in rat pancreas at the receptor and mRNA level. 125I-Bolton-Hunter-labeled CCK octapeptide (125I-BH-CCK-8), the specific CCK-A and CCK-B (gastrin) receptor antagonists L364,718 and L365,260, and 125I-labeled gastrin-I were utilized to characterize CCK receptors in normal rat pancreas. Additionally, we utilized 32P-labeled cDNA probes of the CCK-A receptor and CCK-B (gastrin) receptor coding regions in order to examine the expression of CCK receptor subtypes in normal rat pancreas at the mRNA level. The dose-inhibition curve of CCK-8 inhibiting binding of 125I-BH-CCK-8 was significantly best fit by a two-site model with a high-affinity site (Kd = 0.68 +/- 0.13 nM) and a low-affinity site (Kd = 656 +/- 289 nM). L364,718 inhibited binding of 125I-BH-CCK-8 with high affinity, whereas no high-affinity inhibition for L365,260 to inhibit binding of 125I-BH-CCK-8 was detected. L364,718 was 627 times as potent as L365,260 in inhibiting binding of 125I-BH-CCK-8. No saturable binding was present for 125I-labeled gastrin-I. Gastrin-17-I did not inhibit binding of 125I-BH-CCK-8.(ABSTRACT TRUNCATED AT 250 WORDS)

By mapping the distribution of cholecystokinin (CCK) receptor types onto an established phylogenetic hypothesis of vertebrate relationships, we tested two hypothesis about the evolution of CCK receptors: (1) A single CCK receptor type, CCK-X, is the ancestral receptor, while CCK-A and CCK-B receptors represent derived receptor types; (2) the evolution of two separate CCK receptors is functionally related to the evolution of endothermy. Specifically, we localized and characterized 125I-CCK-binding sites in the gut and brain of mako shark (Isurus oxyrinchus), a warm-blooded chondrichthyean fish. Competitive inhibition studies of 125I-CCK binding showed that the CCK receptor in the mako shark brain, gallbladder, pyloric stomach, and intestine binds sulfated CCK-8 and sulfated gastrin-17 (gastrin-17-II) with much higher affinity (K(i) ranging from 0.05 to 2.02 nM) than unsulfated gastrin-17 (gastrin-17-I, K(i) ranging from 4.63 to 62.17 nM). These results indicate that the mako shark expresses a single CCK-X receptor in all tissues. Additional competitive inhibition studies showed that the mako CCK-X receptor has very low affinities for the following nonpeptide agonist and antagonists: AAACCK-A receptors) and L365,260 and CI-988 (specific for some mammalian CCK-B receptors), confirming the pharmacological differences between the CCK-X receptor and the CCK-A and -B receptors. Based on the mapped phylogenetic distribution of CCK receptor types, we conclude that CCK-X is the ancestral receptor type and that two receptor types, e.g. CCK-A and CCK-B, are not part of the suite of characters necessary for evolution of endothermy in fishes.

We summarize the discovery of luminal feedback regulation of pancreatic secretion in rats and its history. In rats, removal of proteolytic activity from the intestine produced a significant increase in pancreatic protein (enzyme) output. This increase was confirmed to be mediated by circulating cholecystokinin (CCK). Subsequently, two CCK-releasing peptides, monitor peptide and luminal CCK-releasing factor (LCRF), were purified from the rat pancreatic juice and small intestine, respectively, to elicit CCK release in luminal feedback regulation. Furthermore, we emphasize the important physiologic roles of CCK and CCK receptors by the discovery of disrupted CCK-A-receptor gene in rats. These findings should help to determine the regulation of pancreatic secretion and CCK functions in humans.

Recently, the involvement of the MAP kinase ERK in mitogenic signaling of cholecystokininB (CCK(B)) receptors has been shown. However, the intracellular effector systems involved in this signaling pathway are poorly defined. In this study, we used COS-7 cells transiently transfected with the human CCK(B) receptor to investigate cholecystokinin-induced MAP kinase activation. CCK-8 induced activation of ERK2 which is associated with its phosphorylation and localization in the nucleus. The CCK-8-dependent ERK stimulation is sensitive to wortmannin an inhibitor of phosphoinositide 3-kinases (PI3Ks) indicating the involvement of PI3K activity. To identify the PI3K species involved in mitogenic signaling of the CCK(B) receptor several dominant-negative mutants of PI3K regulatory and catalytic subunits were transiently expressed. Surprisingly, different catalytically inactive mutants of the G protein-sensitive PI3Kgamma did not affect ERK stimulation induced by CCK, whereas a dominant-negative mutant of the regulatory p85 subunit induced significant inhibition of CCK-dependent ERK activity. These results indicate an involvement of PI3K class 1A species alpha, beta or/and delta in signal transduction via CCK(B) receptors. In addition, protein kinase C (PKC)-dependent signaling pathways contribute to CCK(B)-mediated MAP kinase signaling as shown by inhibition of CCK-8-induced ERK activation by the PKC inhibitor bisindolylmaleimide.

CONCLUSIONS

Intermittent injections of sulfated cholecystokinin-8 (CCK-8S) or devazepide caused long-lasting effects on cell proliferation in exocrine pancreas in contrast to continuous infusion. The acinar cells responded to both treatments with changes in the labeling index (LI) during the whole study period. When studying the influence of stimulation and inhibition of the CCK-A receptor on cell proliferation in the exocrine pancreas, not only are the drugs and doses of importance but also the mode of administration.

BACKGROUND

Continuous infusion of CCK-8S or the CCK-A receptor antagonist devazepide induces transient changes in acinar cell proliferation in rat pancreas. The aim of the present experiments was to study whether intermittent administration of CCK-8S or devazepide prevents receptor desensitization and thereby affects exocrine pancreatic cell proliferation persistently.

METHODS

Male Sprague-Dawley rats were injected subcutaneously twice daily with CCK-8S (6 micrograms), devazepide (240 micrograms) or bovine serum albumin (BSA). The rats were sacrificed after 18 and 36 h and 3 and 7 d. One hour before sacrifice, the rats were injected intraperitoneally with 1 mCi/kg of tritiated thymidine. The pancreatic weight and the contents of water, protein, and DNA were determined. The LI (number of labeled cells/100 cells) of exocrine pancreatic cells was determined microscopically after autoradiography.

RESULTS

The concentration of plasma CCK was slightly increased by devazepide, but the increase was more pronounced by CCK-8S. The pancreatic wet weight was transiently increased 18 h after the start of CCK-8S injections (+14%), whereas devazepide caused a reduction after 7 d (-22%). The protein content was uninfluenced and the DNA content was decreased at 36 h with either treatment. CCK-8S increased the LI in acinar and centroacinar cells throughout the study period, but the ductal cell LI was increased only after 18 and 36 h. Injection of devazepide was followed by decreased LI of acinar cells throughout the study period. Also, the centroacinar and ductal cell LI decreased initially but returned to control values after 7 d.

Fat in small intestine decreases meal-stimulated gastric acid secretion and slows gastric emptying. CCK is a mediator of this inhibitory effect (an enterogastrone). Because intravenously administered peptide YY (PYY) inhibits acid secretion, endogenous PYY released by fat may also be an enterogastrone. Four dogs were equipped with gastric, duodenal, and midgut fistulas. PYY antibody (anti-PYY) at a dose of 0.5 mg/kg or CCK-A receptor antagonist (devazepide) at a dose of 0.1 mg/kg was administered alone or in combination 10 min before the proximal half of the gut was perfused with 60 mM oleate or buffer. Acid secretion and gastric emptying were measured. We found that 1) peptone-induced gastric acid secretion was inhibited by intestinal fat (P < 0.0001), 2) inhibition of acid secretion by intestinal fat was reversed by CCK-A receptor antagonist (P < 0.0001) but not by anti-PYY, and 3) slowing of gastric emptying by fat was reversed by CCK-A antagonist (P < 0. 05) but not by anti-PYY. We concluded that inhibition of peptone meal-induced gastric acid secretion and slowing of gastric emptying by intestinal fat depended on CCK but not on circulating PYY.