Experimental pancreatitis is mediated by low-affinity cholecystokinin receptors that inhibit digestive enzyme secretion (original) (raw)
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Failure of a Potent Cholecystokinin Antagonist to Protect Against Diet-Induced Pancreatitis in Mice
Pancreas, 1989
The effects of a potent cholecystokinin (CCK) receptor antagonist, L-364,718, on two forms of experimental acute pancreatitis in mice were evaluated. The antagonist prevented the hyperamylasemia, pancreatic edema, and acinar cell vacuolization that followed administration of a supramaximally stimulating dose of the cholecystokinin analogue cerulein. In contrast, the same dose of L-364,718 (1 mg/kg/6 h) and an even higher dose (10 mglkg/6 h) failed to prevent the hyperamylasemia, acinar cell necrosis, and mortality that followed administration of a choline-deficient ethionine-supplemented diet. These observations are at variance with those previously reported to follow administration of the relatively weak cholecystokinin antagonist proglumide (Niederau C et al. J Clin Znvest 1986;78: 10.5643). The observations reported in this communication suggest that cholecystokinin does not play an important role in diet-induced pancreatitis and that CCK receptor antagonists are unlikely to be of benefit in the treatment of clinical acute pancreatitis.
Mechanism of Cholecystokinin-A- Receptor Antagonist on Human Pancreatic Exocrine Secretion
Digestion, 1999
Expressions of the cholecystokinin (CCK)-A and -B receptor genes in human duodenum, pancreas and gallbladder were examined by Northern blot analysis and reverse transcriptase polymerase chain reaction (RT-PCR) followed by Southern blot hybridization. The autoradiographic study of CCK-A and -B receptors in the human duodenum and pancreas was examined in vitro. To determine the subtypes to CCK receptors in the pancreas or duodenum, we studied the abilities of CCK-A and -B receptor agonists (CCK-8 and gastrin) and antagonists (loxiglumide, L-364,718 and L-365,260) to inhibit binding of 125I-CCK-8. CCK-A receptor mRNA was not expressed in the human pancreas, but was expressed in the gallbladder and duodenum, although it was expressed in the pancreas by RT-PCR. CCK-B receptor mRNA was expressed in the pancreas, but not in gallbladder and duodenum. Using autoradiography, high concentrations of CCK-A receptors were detected in the duodenal mucosa, although in the pancreas only CCK-B recept...
Pancreas, 1997
To determine the effect of long-term blockade of cholecystokinin (CCK) on both pancreatic storage and secretion processes, L 364,718 (a CCK receptor antagonist) was administered to rats at 0.1 mg/kg/day for 3, 7, and 15 days. Zymogen granules were analyzed by flow cytometry to determine their light scattering properties-forward scatter and side scatter-as well as their amylase content measured by a specific antiserum. The mean number of zymogen granules per cell was counted on pancreatic sections using electron microscopy. DNA content, pancreatic weight, and enzyme secretion were also studied under both basal conditions and CCK infusion at a dose of 1.25 p g k g h , which is able to displace the CCK receptor antagonist. Two subpopulations of zymogen granules (Z, and Z,) were identified on the basis of their light scattering parameters, in both control and L 364,718-treated rats. L 364,718 administered for 3, 7, and 15 days induced a significant reduction in the amylase content of individual zymogen granules, for both 2, and Z, zymogen granule subsets. In contrast, the number of zymogen granules per cell increased from It is well established that long-term administration of exogenous cholecystokinin (CCK) or its analogue cerulein increases the pancreatic content of both DNA and protein (1-3). Similar effects have been observed in experimental situations in which endogenous CCK was increased such as feeding with trypsin inhibitors (4) or bile-pancreatic juice diversion (5).
Biochimica Et Biophysica Acta-molecular Cell Research, 1989
When pancreatic acini are incubated with increasing concentrations of cholecystokinin octapeptide (CCK-8) the dose-response curve for stimulation of enzyme secretion increases, reaches a maximum and then decreases. The upstroke of the dose-response curve reflects occupation of high-affinity, stimulatory CCK receptors (Kd 69 pM), whereas the downstroke of the dose-response curve reflects occupation of low-affinity inhibitory CCK receptors (Kd 10 nM). In the present study, we used dispersed acini from rat pancreas to examine the effects of CCK-JMV-180, an analogue of the C-terminal heptapeptide of CCK (CCK-7) having the structure BOC-Tyr(SO3) Ahx-Gly-Trp-Ahx-Asp2 phenylethyl ester. CCK-JMV-180 inhibited binding of 125I-labelled CCK-8 to pancreatic acini. Computer analysis of the dose-inhibition curve indicated that CCK-JMV-180 interacted with both classes of CCK receptor and had a Kd of 2.2 nM for high-affinity CCK receptors and a Kd of 19 nM for low-affinity CCK receptors. Occupation of high-affinity CCK receptors by CCK-JMV-180 caused a 14-fold increase in amylase secretion, the same increase caused by occupation of these high-affinity receptors by CCK-7 or CCK-8. Occupation of low-affinity CCK receptors by CCK-JMV-180 did not alter amylase secretion, in contrast to occupation of these low-affinity receptors by CCK-7 or CCK-8, each of which caused inhibition of amylase secretion. Furthermore, occupation of the low-affinity CCK receptors by CCK-JMV-180 reversed the inhibition of amylase secretion caused by a supramaximal concentration of CCK-8. The present results indicate that CCK-JMV-180 interacts with high-affinity CCK receptors and with low-affinity CCK receptors, and has a functionally distinct action at each class of receptor: CCK-JMV-180 is an agonist at the high-affinity receptors and a competitive antagonist at low-affinity receptors.
Purification of the pancreatic cholecystokinin receptor
Regulatory Peptides, 1989
We have previously shown that the pancreatic cholecystokinin (CCK) receptor can be solubilized in 1% digitonin. In this study, digitonin-solubilized CCK receptors from rat pancreas were purified using sequential affinity chromatography on ricin-II agarose and on AffiGeI-CCK. Electrophoresis of the radioiodinated purified receptors on SDS-polyacrylamide gels followed by autoradiography revealed two proteins: a major band of Mr = 80,000-90,000, and a minor band of Mr = 55,000. Through the purification procedure, the receptors preserved their agonist specificity (CCK-8 < CCK-33 < desulfated CCK-8 < CCK-4) and binding affinity. Scatchard transformations of binding data for the purified receptor preparation were best fit by linear plots compatible with a single class of binding sites with Ka = 9.4 nM. The estimated purification was about 80,000 fold and consistent with the expected Bmax for a pure Mr = 80,000 protein binding one CCK molecule. This two-step purification procedure opens the possibility for molecular studies of the CCK receptor.
British Journal of Pharmacology, 1997
1In the pig, the secretory response of the pancreas is not inhibited by the antagonist MK329 suggesting that cholecystokininA (CCKA) receptors are not involved.2Membranes were isolated from the pancreas of 6 Large White pigs to characterize their CCK receptors.3The binding of [M125I]-BH-[Thr, Nle]CCK-9 was dependent on pH, maximal after a 90 min incubation period, saturable and reversible. Saturation analysis of the binding demonstrated a single class of high affinity sites (Kd = 0.22 ± 0.02 nM) and a binding capacity, Bmax= 110.64±12.50 fmol mg−1 protein.4Competition binding by agonists and antagonists of CCKA and CCKB/gastrin receptors demonstrated the presence of two distinct binding components, sites presenting a high affinity for [Thr, Nle]CCK-9, gastrin, PD 135158, L-365,260 and a low affinity for MK329, SR 27897, and sites presenting a high affinity for [Thr, Nle]CCK-9, MK329, SR 27897 and a low affinity for gastrin, PD 135158, L-365,260.5These pharmacological data demonstrate the presence of both CCKA and CCKB/gastrin receptors in the pig pancreas, the latter being predominant.6Two distinct membrane proteins (50 and 85–100 kDa, respectively) display pharmacological features of CCKB/gastrin and CCKA receptors.7In pigs, as in calves and humans, CCKB/gastrin receptors are predominant in the pancreas.In the pig, the secretory response of the pancreas is not inhibited by the antagonist MK329 suggesting that cholecystokininA (CCKA) receptors are not involved.Membranes were isolated from the pancreas of 6 Large White pigs to characterize their CCK receptors.The binding of [M125I]-BH-[Thr, Nle]CCK-9 was dependent on pH, maximal after a 90 min incubation period, saturable and reversible. Saturation analysis of the binding demonstrated a single class of high affinity sites (Kd = 0.22 ± 0.02 nM) and a binding capacity, Bmax= 110.64±12.50 fmol mg−1 protein.Competition binding by agonists and antagonists of CCKA and CCKB/gastrin receptors demonstrated the presence of two distinct binding components, sites presenting a high affinity for [Thr, Nle]CCK-9, gastrin, PD 135158, L-365,260 and a low affinity for MK329, SR 27897, and sites presenting a high affinity for [Thr, Nle]CCK-9, MK329, SR 27897 and a low affinity for gastrin, PD 135158, L-365,260.These pharmacological data demonstrate the presence of both CCKA and CCKB/gastrin receptors in the pig pancreas, the latter being predominant.Two distinct membrane proteins (50 and 85–100 kDa, respectively) display pharmacological features of CCKB/gastrin and CCKA receptors.In pigs, as in calves and humans, CCKB/gastrin receptors are predominant in the pancreas.
Journal of Pediatric Gastroenterology and Nutrition, 1992
This study used a cholecystokinin (CCK) antagonist to evaluate whether CCK that is released after regular meals regulates meal-stimulated insulin secretion. Several experiments were performed in eight to 10 healthy male volunteers, each in duplicate. The subjects received different meals either with or without i.v. infusion of 5 mgikgih of the CCK antagonist loxiglumide (Rotta, Italy). The mixed solid-liquid meals of 600, 800, or 1,OOO kcal consisting of regular German food were given orally. In addition, studies were camed out in which a liquid test meal of 750 kcal was infused into the duodenum over a 2-hour period to exclude effects of the CCK antagonist on gastric emptying. Finally, the subjects received an oral load of 100 g glucose either with or without i.v. infusion of loxiglumide. Loxiglumide at the dose used completely abolishes the actions of endogenous CCK and of exogenous CCK when given at doses that mimic postprandial circulating concentrations of this peptide at various target organs such as gallbladder, pancreas, stomach, and intestine. Loxiglumide also markedly reduced the increase in pancreatic polypeptide seen after the intraduodenal infusion of nutrients. However, loxiglumide at this dose did not alter the increase in circulating concentrations of glucose, insulin, and C-peptide after any of the various oral meals, after the intraduodenal administration of nutrients, and after the oral load of glucose. Although the present study does not rule out that in some conditions CCK may increase insulin secretion in humans, the results do rule out that CCK acts as a major physiologic incretin in healthy humans. Key Words: Cholecystokinin-Receptor-antagonist-Insulin-C-peptide-Incretin-Glucose metabolism. Insulin release after ingestion of nutrients is thought to be facilitated by the release of various gut factors that have been termed insulinotropic factors or incretins (1-3).
British Journal of Pharmacology, 1998
It is now well established that cholecystokinin (CCK) has a major physiological role in the regulation of pancreatic secretion and gastro-intestinal (GI) motility. Both these actions are mediated by stimulation of CCK A-receptors located on pancreatic acini and GI smooth muscle cells. While chronic administration of CCK-like peptides invariably causes pancreatic hypertrophy and hyperplasia, their action on gastric growth remains controversial. 2 In the present investigation the action of exogenous and endogenous CCK on both pancreatic and gastric growth was studied in the same animal. In addition, the ability of dexloxiglumide, a new potent and selective CCK A-receptor antagonist, to counteract CCK-mediated eects was evaluated. 3 The amphibian peptide caerulein (1 mg kg 71 intraperitoneally three times daily) was used as a CCK agonist, while camostate (200 mg kg 71 intragastrically once daily), a synthetic protease inhibitor, was used to release endogenous CCK. They were administered to rats for seven days with or without dexloxiglumide (25 mg kg 71 subcutaneously 15 min before the stimulus). On the eighth day, animals were killed, the pancreas and stomach excised, weighed, homogenized and their protein and DNA content measured. 4 Both exogenous and endogenous CCK increased the weight of the pancreas as well as the total pancreatic protein and DNA content. Dexloxiglumide, which alone did not aect pancreatic size and composition, was able to counteract both caerulein-and camostate-induced pancreatic changes. Neither stimuli aected gastric growth in respect of weight and composition of the oxyntic gland area and the antrum. 5 These results show dierent eects of CCK on pancreatic and gastric growth. The CCK-induced pancreatic hypertrophy and hyperplasia are blocked by the potent and speci®c CCK A-receptor antagonist, dexloxiglumide. This compound therefore represents a useful tool to investigate CCKreceptor interactions in peripheral organs.
Effects of cholecystokinin-58 on type 1 cholecystokinin receptor function and regulation
AJP: Gastrointestinal and Liver Physiology, 2008
Cholecystokinin, like many peptide hormones, is present as multiple molecular forms. CCK-58 has been identified as the dominant form in the circulation, whereas most of the studies of CCK-receptor interactions have been performed with CCK-8. Despite both sharing the pharmacophoric region of CCK, representing its carboxy terminal heptapeptide amide, studies in vivo have demonstrated biological diversity of action of the two peptides, with CCK-58, but not CCK-8, stimulating pancreatic fluid secretion and lengthening the interval between meals. Here, we have directly studied the ability of these two CCK peptides to bind to the type 1 CCK receptor and to stimulate it to elicit an intracellular calcium response. The calcium response relative to receptor occupation was identical for CCK-58 and CCK-8, with the longer peptide binding with approximately fivefold lower affinity. We also examined the ability of the two peptides to elicit receptor internalization using morphological techniques ...