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J D Gardner

Publications and source records attributed to J D Gardner.

At least 91 records · Page 5Linked to original sources
PubMed1989

Short-chain pseudopeptide bombesin receptor antagonists with enhanced binding affinities for pancreatic acinar and Swiss 3T3 cells display strong antimitotic activity.

The high inhibitory potency of the previously developed bombesin antagonist [Leu13, psi CH2NHLeu14]bombesin (analogue I) (IC50 values of 30 and 18 nM for inhibition of bombesin-stimulated amylase secretion from guinea pig acinar cells and Swiss 3T3 cell growth, respectively) diminished considerably when shorter chain lengths were examined. For instance, [Leu13, psi CH2NHLeu14]bombesin-(5-14),[Leu13, psi CH2NHLeu14] bombesin-(6-14), and [Leu9, psi CH2NHLeu10]neuromedin C had IC50 values of 150, 150, and 280 nM, respectively. Incorporation of a D-Phe residue at position 6 of [Leu13, psi CH2NHLeu14] bombesin did not significantly change the various biological parameters. However, its presence in [Leu13, psi CH2NHLeu14]bombesin-(6-14) and at position 2 of psi-neuromedin C-(2-10) resulted in about 10-fold increases in potency up to and above that of the original antagonist. For instance, [D-Phe6,Leu13,psi CH2NHLeu14]bombesin-(6-14) and des-Gly1-[D-Phe2,Leu9,psi CH2NHLeu10]neuromedin C exhibited IC50 values of 5 and 28 nM, respectively. Analogues based on the litorin sequence which contains an NH2-terminal pyroglutamic acid residue at the bombesin position 6 equivalent were also quite potent. The ability of various analogues to interact with bombesin receptors on pancreatic acini correlated reasonably well with potencies derived from inhibition of bombesin-stimulated growth of Swiss 3T3 cells. Additional studies of NH2- and COOH-terminal structure-activity relationships resulted in the synthesis of [D-Phe6,Leu13,psi CH2NHPhe14]bombesin-(6-14), which was particularly effective in inhibiting 3T3 cell growth at high picomolar concentrations (IC50 = 0.72 nM and Ki = 3.1 nM for 3T3 cells; IC50 = 7.5 nM and Ki = 9.9 nM for acini). Detailed investigations with one of the most potent antagonists, [D-Phe6,Leu13,psi CH2NHLeu14]bombesin-(6-14) (Ki = 14 nM for acini cells and 7.1 for 3T3 cells), demonstrated that this analogue was a competitive inhibitor of bombesin and that this activity was specific for the bombesin receptor. Thus, inhibitory potencies have been improved generally up to 25 times over previously reported structures; and, given that bombesin itself has a Ki of 1.2 nM for 3T3 cell binding, some of these analogues are extraordinarily high affinity receptor antagonists. They can also be synthesized more readily and offer fewer proteolytic degradation sites than the original pseudopeptide and should be excellent candidates for in vivo studies aimed at inhibition of bombesin-dependent human small cell lung carcinoma growth.

Amino Acid Sequence↗
PubMed1989

CCK-JMV-180: a peptide that distinguishes high-affinity cholecystokinin receptors from low-affinity cholecystokinin receptors.

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 the low-affinity receptors.

Amylases↗
PubMed1989

Cyclic GMP does not inhibit protein kinase C-mediated enzyme secretion in rat pancreatic acini.

In pancreatic acini, cGMP can be increased by secretagogues such as cholecystokinin (CCK), cholinergic agents, and bombesin, whose actions on enzyme secretion are believed to be mediated by protein kinase C. However, the role of cGMP in acinar cell function has been unclear. A recent paper by Rogers et al. (Rogers, J., Hughes, R.G., and Matthews, E. K. (1988) J. Biol. Chem. 263, 3713-3719) reported that two analogues of cGMP, N2,O2-dibutyl guanosine 3':5'-monophosphate (Bt2cGMP) and 8-bromoguanosine 3':5'-monophosphate (8Br-cGMP), at concentrations in the nanomolar range, inhibited the stimulation of amylase secretion caused by CCK-8, bethanechol, bombesin, and 12-O-tetradecanoylphorbol-13-acetate (TPA). Rogers et al. also reported that sodium nitroprusside inhibited the stimulation of enzyme secretion caused by CCK-8 or TPA. These authors concluded that cGMP inhibits protein kinase C-mediated secretion in pancreatic acini. In the present study we attempted to confirm the findings of Rogers et al., We found, however, that Bt2cGMP inhibited CCK-8-stimulated amylase release only at concentrations of the nucleotide above 10 microM. Moreover, there was a close correlation between the ability of Bt2cGMP to inhibit CCK-8-stimulated amylase release and its ability to inhibit binding of 125I-CCK-8. Bt2cGMP, at concentrations as high as 3 mM, did not alter the stimulation of amylase release caused by carbachol, bombesin, TPA, or A23187. 8Br-cGMP, at concentrations up to 1 mM, did not inhibit the stimulation of amylase release caused by CCK-8 or TPA. At concentrations above 0.1 mM, 8Br-cGMP augmented the stimulation of amylase release caused by CCK-8, carbachol, bombesin, or TPA. Sodium nitroprusside, at a concentration that causes a 60-fold increase in cGMP, did not inhibit the stimulation of amylase release caused by CCK-8, carbachol, bombesin, or TPA. Our results do not confirm the findings of Rogers et al. and indicate that cGMP does not inhibit protein kinase C-mediated secretion in pancreatic acini.

Amylases↗
PubMed1989

Use of long-acting somatostatin analog SMS 201-995 in patients with pancreatic islet cell tumors.

Natural somatostatin reduces plasma concentrations of many peptides, and is of short term benefit in patients with islet cell tumors, but has to be given as a continuous intravenous infusion. We review the published experience with the long acting synthetic somatostatin analogue SMS 201-995 in patients with islet cell tumors. Fifteen of 18 patients with vasoactive intestinal peptide-producing tumors, 8 of 8 patients with glucagonomas, 7 of 7 patients with unresectable insulinomas, and 3 of 3 patients with growth hormone releasing factor-producing tumors had a good sustained symptomatic response to SMS 201-995. Patients with benign insulinomas responded variably and are best treated by surgery. Patients with gastrinomas are best treated by oral gastric antisecretory agents. In all these syndromes, the clinical response to SMS 201-995 did not necessarily parallel the change in plasma concentration of marker peptide, suggesting that SMS 201-995 may have actions at various sites. The effect of SMS 201-995 on tumor size has been assessed in 46 patients, less than 20% of whom showed a reduction in tumor size. Side effects have been mild, but include steatorrhea and gastrointestinal disturbances. More studies will be required to fully assess the effects of long-term administration of SMS 201-995.

Adenoma, Islet Cell↗
PubMed1989

Ovarian carcinoma as a cause of Zollinger-Ellison syndrome. Natural history, secretory products, and response to provocative tests.

Zollinger-Ellison syndrome is usually caused by a gastrin-secreting tumor in or near the pancreas. We describe a patient in whom an ovarian cystadenocarcinoma was the cause of the syndrome. The patient presented with a short history of peptic ulceration and development of a large pelvic mass. Investigations demonstrated a basal acid output of 37.8 mEq/h and a maximal acid output of 36.0 mEq/h, and the plasma concentration of gastrin was 830 pg/ml (normal less than 100). Secretin and calcium infusion tests were positive, and a meal test was compatible with Zollinger-Ellison syndrome. Imaging studies demonstrated a normal liver and pancreas but a large cystic right ovarian mass. Resection of the mass resulted in a marked reduction in gastric acid output, a fall in plasma gastrin concentration to normal, negative calcium and secretin tests, and a normal (positive) meal test. Histology of the mass showed it to be a mucinous cystadenocarcinoma. The tumor stained with immunoperoxidase technique was positive for gastrin, and the cyst fluid contained high concentrations of gastrin and calcitonin. One year later, the patient has no biochemical or imaging evidence of tumor. Ovarian, gastrin-producing tumors and pancreatic gastrinomas cannot be distinguished by provocative tests, and negative imaging studies do not exclude a pancreatic tumor. Patients with an ovarian mass and Zollinger-Ellison syndrome should have a bilateral oophorectomy and a careful exploration of the pancreatic area.

Cystadenocarcinoma↗
PubMed1989

Parenteral antisecretory drug therapy in patients with Zollinger-Ellison syndrome.

Forty-six patients with Zollinger-Ellison syndrome were studied prospectively to determine a safe and effective method and criterion for controlling gastric acid hypersecretion during periods when oral antisecretory agents could not be used. In each patient it was possible to reduce acid secretion to less than or equal to 10 mEq/h after an i.v. bolus of 150 or 300 mg of cimetidine and a stepwise titration of cimetidine given by continuous infusion. The mean dose given by i.v. infusion was 2.9 mg/kg body wt.h but there was a wide range (0.5-7.0 mg/kg body wt.h) and the minimal dose had to be determined individually for each patient. The minimal i.v. cimetidine dose did not correlate with basal or maximal acid output or fasting gastrin concentration, but correlated closely with either the previous oral dose of cimetidine (r = 0.96, p less than 0.001) or the previous oral dose of ranitidine or famotidine (r = 0.95, p less than 0.001). To study the efficacy and safety of an i.v. infusion of cimetidine, 34 patients undergoing surgery were maintained on i.v. cimetidine for a mean of 12 days (range 1-83 days). One-half of the patients did not require dose adjustment, whereas the remainder required an average of 2 adjustments, usually in the first 3 postoperative days. No patient developed complications attributable to gastric acid hypersecretion in the postoperative period, and there was no detectable neurologic, hematologic, or hepatic toxicity. This study demonstrates that a continuous i.v. infusion of cimetidine adequately inhibits gastric acid hypersecretion in patients with Zollinger-Ellison syndrome. However, high doses were frequently required, the dose had to be determined in a stepwise fashion individually for each patient, and the i.v. dose correlated with the previous oral dose. Reducing acid secretion to less than or equal to 10 mEq/h was a safe criterion during surgery and continuous i.v. cimetidine was safe and effective in achieving this degree of control for up to 83 days.

Administration, Oral↗
PubMed1989

Long-term efficacy and safety of omeprazole in patients with Zollinger-Ellison syndrome: a prospective study.

To determine the long-term efficacy, safety, and toxicity of omeprazole, we studied 40 patients with Zollinger-Ellison syndrome given omeprazole for 6-51 mo (median 29). The mean daily dose of omeprazole required to control gastric acid secretion was 82 +/- 31 mg. Thirty-one patients required omeprazole once per day. In 9 patients acid output was not controlled by 120 mg once per day, but was controlled by 60 mg every 12 h. The daily dose of omeprazole correlated with the previous dose of histamine H2-receptor antagonist (r = 0.89, p less than 0.001), basal acid output (r = 0.43, p less than 0.01), and maximal acid output (r = 0.39, p less than 0.02) but not with serum concentration of gastrin (r = -0.32). Increases in the dose of omeprazole were required in 9 patients. Twenty-nine patients had mild peptic symptoms with acid outputs less than 10 mEq/h while taking histamine H2-receptor antagonists. Symptoms resolved completely in 23 patients and partially in 3 when taking omeprazole. Omeprazole prevented mucosal disease in all patients including 17 in whom histamine H2-receptor antagonists had produced only partial resolution despite acid output being less than 10 mEq/h and in those with symptoms during omeprazole therapy. Omeprazole therapy was not associated with any significant side effects, nor with any evidence of hematologic or biochemical toxicity. Serum concentrations of gastrin did not change significantly during therapy. In 6 patients treated with omeprazole for 1 yr there was no change in basal or maximal acid output. In all patients, gastric morphology and histopathology demonstrated no evidence of gastric carcinoid formation. These results demonstrate that with long-term treatment of up to 4 yr, omeprazole is safe, with no evidence of hematologic, biochemical, or gastric toxicity. Furthermore, omeprazole remained effective, with only 23% of patients requiring an increase in dose, and continued to control symptoms in patients who had not been entirely symptom-free despite high doses of histamine H2-receptor antagonists. Omeprazole is now the drug of choice in patients with Zollinger-Ellison syndrome.

Adult↗
PubMed1989

Interaction of CCK with pancreatic acinar cells.

Recent studies demonstrate that cholecystokinin-like peptides are widely distributed in the CNS as well as in the peripheral nervous system and gastrointestinal tract. Studies with agonists have demonstrated multiple classes of receptors and recently potent receptor antagonists have been described which will distinguish these classes and should allow a better understanding of the role of CCK in various physiological processes. One of the known peripheral physiological functions of CCK is the stimulation of digestive enzymes from pancreatic acinar cells. In recent years the interaction of CCK with pancreatic acinar cells has been extensively studied and significant advances have been made in understanding its cellular basis of action. Robert Jensen and colleagues report on each of these areas.

Animals↗
PubMed1989

Prospective study of the standard meal provocative test in Zollinger-Ellison syndrome.

PURPOSE: The purpose of this work was to evaluate the proposed usefulness of a standard meal-stimulated gastrin provocative test in: (1) distinguishing Zollinger-Ellison syndrome (ZES) from antral syndromes; (2) localizing duodenal gastrinomas; or (3) suggesting that patients with multiple endocrine neoplasia type I (MEN-I) may have an increased incidence of antral syndromes. PATIENTS AND METHODS: Seventy-four consecutive patients with ZES referred to the National Institutes of Health were studied prospectively. The extent and location of gastrinomas, acid secretory studies, and the presence or absence of MEN-I were determined and correlated with the results of the gastrin response to standard meal provocative testing. RESULTS: For patients with fasting serum gastrin levels less than 1,000 pg/mL (n = 43), only 44% had a less than 50% increase over the pre-meal value, which is reported to be the typical response in ZES, and 40% had a 50% to 99% increase. Furthermore 16% had a 100% or greater increase, 9% a 150% or greater increase, and 5% a 200% or greater increase, which overlaps with values reported to be characteristic of 98%, 92%, and 46% of patients with antral syndromes. Results did not differ for patients with or without MEN-I, depend on the extent of the gastrinoma (duodenal versus pancreatic gastrinomas), the presence of previous gastric surgery or type of gastric surgery, or for patients with fasting serum gastrin concentrations greater than or equal to 1,000 pg/mL or less than 1,000 pg/mL. studies of four patients before and after resection of the gastrinoma, who prior to surgery had a greater than 100% increase in gastrin secretion after the meal, demonstrated that all patients had a less than 100% increase postoperatively even though no gastric resection was done. CONCLUSIONS: Approximately half of the patients with ZES have a greater than 50% increase in serum gastrin concentration following a standard test meal and one fifth have a 100% or greater increase. Therefore, they cannot be distinguished on this basis from patients with antral syndromes. The increased serum gastrin level after the meal in these patients with ZES appears to be due to the gastrinoma. Furthermore, the current study provides no evidence for the proposals that antral syndromes are more common in patients with MEN-I, that gastric surgery affects the meal response in patients with gastrinomas, or that the meal test is useful in localizing duodenal gastrinomas.

Adolescent↗
PubMed1989

Interaction of peptides related to VIP and secretin with guinea pig pancreatic acini.

The abilities of human and rat growth hormone-releasing factors (hGHRF, rGHRF), peptide histidine isoleucine or methionine (PHI, PHM) and the Gila monster venom peptides (helospectin I, helospectin II, and helodermin) to interact with guinea pig pancreatic acini were characterized and compared with vasoactive intestinal peptide (VIP) and secretin. Each peptide caused a sevenfold stimulation of amylase release, and the relative potencies were: VIP greater than helospectin I = helospectin II = helodermin = rGHRF greater than PHI = PHM greater than hGHRF greater than secretin. Each peptide inhibited 125I-labeled VIP binding, and the relative potencies agreed closely with those for stimulating enzyme secretion. Each peptide inhibited 125I-labeled secretin binding with the potencies: secretin greater than helospectin I = helospectin II = helodermin greater than rGHRF = PHI = VIP greater than PHM greater than hGHRF. Each peptide caused a 78-fold increase in adenosine 3',5'-cyclic monophosphate cAMP. VIP or rGHRF and PHI or PHM demonstrated high and low selectivity, respectively, for VIP receptors, secretin high selectivity for the secretin receptor, and helospectin I or II and helodermin a relatively high affinity for both VIP and secretin receptors. Correlation of the ability of each peptide to increase cAMP or amylase release and inhibit binding of 125I-VIP or 125I-secretin suggested all the actions of these peptides could be explained by the occupation of VIP or secretin receptors. To investigate this further, 125I-labeled helodermin was prepared, and binding was saturable, specific, and could be accounted for by the binding to VIP or secretin receptors.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1989

Regulation of bombesin receptors on pancreatic acini by cholecystokinin.

When guinea pig pancreatic acini are first incubated with the COOH-terminal octapeptide of cholecystokinin (CCK-8), washed, and then reincubated with 125I-[Tyr4]bombesin (125I-[Tyr4]BN) there is a significant decrease in binding of 125I-[Tyr4]BN compared with that observed with pancreatic acini that have been first incubated with no additions. The CCK-8-induced decrease in binding is maximal after 90 min of first incubation is abolished by reducing the temperature of the first incubation from 37 to 4 degrees C or by adding L364,718 to the first incubation and cannot be reproduced by first incubating acini with A23187, 8-bromoadenosine 3',5'-cyclic monophosphate (8Br-cAMP), 8-bromoadenosine 3',5'-cyclic monophosphate (8Br-cGMP), or 12-O-tetradecanoylphorbol 13-acetate. 125I-[Tyr4]BN interacts with a single class of receptors on pancreatic acini, and first incubating acini with CCK-8 decreases the affinity of BN receptors for BN with no change in the maximal binding capacity. CCK-8 does not alter the rate at which bound 125I-[Tyr4]BN dissociates from pancreatic acini; therefore, CCK-8 must alter the rate at which the radiolabeled BN analogue associates with its receptor. Pancreatic acini possess two classes of CCK receptors: one has a high affinity for CCK-8; the other has a low affinity for CCK-8. The dose-response curve for CCK-8-induced inhibition of binding of 125I-[Tyr4]BN appears to to reflect occupation of low-affinity CCK receptors by CCK-8.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetates↗
PubMed1989

Neuromedin B receptor in esophagus: evidence for subtypes of bombesin receptors.

To identify receptors for bombesin-related peptides in the rat esophagus, we measured binding of 125I-Bolton-Hunter neuromedin B (125I-BH-neuromedin B) and 125I-[Tyr4]bombesin to tissue sections from the rat esophagus and compared the results with those for rat pancreas. Esophagus bound both tracers, whereas pancreas bound only 125I-[Tyr4]bombesin. In each tissue binding was saturable, dependent on pH, on time, and on temperature, reversible, and specific. Autoradiography demonstrated binding of both tracers only to the muscularis mucosae of the esophagus and binding of 125I-[Tyr4]bombesin diffusely over pancreatic acini. In the esophagus, the relative potencies for inhibition of binding of both tracers were as follows: neuromedin B greater than bombesin greater than GRP = neuromedin C; similar relative potencies were found for causing contraction of muscle strips from whole esophagus and from the isolated muscularis mucosae. In pancreas tissue sections and dispersed acini, the relative potencies for inhibition of binding of 125I-[Tyr4]bombesin were as follows: bombesin greater than GRP = neuromedin C much greater than neuromedin B. Similar relative potencies were found for stimulation of enzyme secretion from dispersed pancreatic acini. Computer analysis in both tissues demonstrated only a single binding site. The present study demonstrates that rat esophagus muscle possesses specific receptors for bombesin-related peptides. Furthermore, this study shows that the esophageal bombesin receptors represent a previously unidentified class of bombesin receptors in that they have a higher affinity for neuromedin B than for bombesin. In contrast, the pancreatic bombesin receptors have, like all other bombesin receptors described to date, a high affinity for bombesin, but low affinity for neuromedin B.

Animals↗
PubMed1989

Benzodiazepine analogues L365,260 and L364,718 as gastrin and pancreatic CCK receptor antagonists.

We examined the ability of the recently described 3-(benzoylamino)benzodiazepine analogue L365,260 and the 3-(acylamino)benzodiazepine analogue L364,718 to distinguish gastrin from pancreatic cholecystokinin (CCK) receptors. Neither L365,260 nor L364,718 when present alone (1 microM) caused stimulation of amylase release from guinea pig pancreatic acini or caused contraction of smooth muscle cells from guinea pig stomach. Each analogue inhibited CCK-stimulated amylase release, gastrin-17-I-stimulated smooth muscle contraction, binding of 125I-Bolton-Hunter-cholecystokinin octapeptide (125I-BH-CCK-8) to pancreatic CCK receptors, and binding of 125I-gastrin-17-I to gastrin receptors on pancreatic acini. L365,260, (Ki, 7.3 +/- 0.8 nM) was 50-70 times more potent than L364,718 at inhibiting binding of 125I-gastrin to pancreatic acini or gastrin-stimulated smooth muscle contraction. In contrast, L364,718 (Ki, 4 +/- 1 nM) was 145-200 times more potent than L365,260 at inhibiting binding of 125I-BH-CCK-8 to pancreatic acini or CCK-stimulated amylase release. Neither L364,718 nor L365,260 distinguished between high- and low-affinity CCK binding sites. L365,260 and L364,718 did not inhibit binding of radiolabeled vasoactive intestinal peptide, secretin, bombesin, substance P, or N-methylscopolamine to pancreatic acini. These results demonstrate that, in contrast to other gastrin-CCK receptor antagonists described, L365,260 is a selective gastrin receptor antagonist having an 80-fold higher affinity for gastrin than pancreatic CCK receptor, whereas L364,718 has a 125-fold higher affinity for pancreatic CCK receptors. Because of the selectivity of these two antagonists the involvement of CCK and gastrin in various physiological processes can be differentiated even when both receptors occur on the same cell.

Amylases↗
PubMed1989

Properties of receptors for gastrin and CCK on gastric smooth muscle cells.

Previous studies have demonstrated that cholecystokinin (CCK), gastrin, and structurally related peptides can interact with various types of receptors that can be distinguished by their relative affinities for agonists and antagonists. In the present study we examined the effect of gastrin, the COOH-terminal octapeptide of CCK (CCK-8), and the tetrapeptide of CCK (CG-4) on contraction of dispersed gastric smooth muscle cells from guinea pig and tested the ability of various CCK receptor antagonists to affect agonist-induced muscle cell contraction. For purposes of comparison we tested the effect of each antagonist on CCK-stimulated amylase secretion by pancreatic acini from guinea pig. On gastric smooth muscle cells, CCK-8, gastrin, and CG-4 were all full agonists. CCK-8 and gastrin were equipotent and CG-4 was 6,000-fold less potent. Each antagonist caused inhibition of CCK-stimulated contraction with relative potencies (IC50): L364,718 (4 microM) = CBZ-CCK-(27-32)-NH2 (3 microM) greater than proglumide analogue 10 (90 microM). Inhibition by each of the antagonists was competitive in nature, specific for CCK peptides, and each had the same IC50 whether contraction was stimulated by CCK-8, gastrin, or CG-4. Relative potencies (IC50) of the three antagonists for inhibiting CCK-stimulated amylase release from pancreatic acini were L364,718 (3 nM) greater than proglumide analogue 10 (200 nM) greater than CBZ-CCK-(27-32)-NH2 (3 microM). These results demonstrate that gastric smooth muscle cells possess receptors that differ from CCK receptors on pancreatic acini in terms of affinities for both agonists and certain antagonists.(ABSTRACT TRUNCATED AT 250 WORDS)

Amylases↗
PubMed1989

Receptor occupation, calcium mobilization, and amylase release in pancreatic acini: effect of CCK-JMV-180.

We examined the relationships between receptor occupation, calcium mobilization, and stimulated amylase release for cholecystokinin octapeptide (CCK-8) and for CCK-JMV-180, an analogue of the COOH-terminal heptapeptide of CCK having the structure Boc-Tyr(SO3)-Nle-Gly-Trp-Nle-Asp-2-phenylethyl ester using dispersed acini from rat pancreas. CCK-8 and CCK-JMV-180 each bind to two classes of CCK receptors: one class has a high affinity for CCK-8 and CCK-JMV-180 and the other class has a low affinity for CCK-8 and CCK-JMV-180. Mobilization of cellular calcium was assessed by measuring cytosolic calcium with a fluorescent indicator and by measuring outflux of radioactive calcium from preloaded cells. In terms of causing an increase in cytosolic calcium or an increase in calcium outflux, CCK-JMV-180 was 50-60% as efficacious as CCK-8. Analysis of the relationship between receptor occupation and calcium mobilization caused by CCK-8 and CCK-JMV-180 in combination indicates that calcium mobilization is caused by occupation of low-affinity CCK receptors. Comparison of the dose-response curve for calcium mobilization and amylase release stimulated by CCK-8 or CCK-JMV-180 indicates that very low concentrations of each peptide stimulate amylase release without causing detectable calcium mobilization. At these very low concentrations, CCK-8 or CCK-JMV-180 do not cause potentiation of amylase release when combined with vasoactive intestinal peptide.

Amylases↗
PubMed1989

Characterization of cholinergic receptors mediating pepsinogen secretion from chief cells.

By use of a highly enriched preparation of chief cells (greater than 90% pure) prepared from guinea pig stomach, the cholinergic receptors regulating pepsinogen secretion were studied. Each of five different muscarinic cholinergic agonists, but not the nicotinic cholinergic agonist nicotine, stimulated pepsinogen release. Carbamylcholine-stimulated pepsinogen release was inhibited by each of seven different cholinergic receptor antagonists with relative potencies of N-methylscopolamine greater than scopolamine = 4-diphenylacetoxy-N-methylpiperidine methiodide = atropine much greater than pirenzepine greater than AF-DX-116 much greater than tetraethylammonium. Binding of [N-methyl-3H]scopolamine ([3H]NMS) was time and temperature dependent, reversible, saturable, and specific. Analysis of [3H]NMS binding demonstrated a Kd of 1.3 nM for NMS with a binding capacity of 61 fmol/mg protein or 5,920 sites/chief cell. With the agonists carbamylcholine, acetylcholine, or muscarine, the receptor population could be divided into two classes of receptor sites: a class with high affinity (Kd, 12-53 microM) representing 73% of the binding sites and a class with low affinity (Kd, 2-5 mM) representing 27% of the binding sites. Each of the antagonists had equal affinity for both receptor populations. There was a close correlation between the ability of antagonists to inhibit [3H]NMS binding and carbamylcholine-stimulated pepsinogen release. Each agonist was 29- to 63-fold more potent at stimulating pepsinogen release than interacting with high-affinity receptors and 2,000- to 11,000-fold more potent than interacting with low-affinity receptors, suggesting spare receptors. Studies with the alkylating agent, propylbenzilylcholine mustard, demonstrated that there was a receptor reserve of 50-80%.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholine↗
PubMed1989

Carbachol-induced down-regulation of high-affinity receptors for vasoactive intestinal peptide.

When dispersed acini from guinea pig pancreas are first incubated with carbachol, the subsequent binding of 125I-vasoactive intestinal peptide (VIP) is inhibited during a second incubation. This inhibitory action of carbachol on binding of 125I-VIP depends on time, temperature, and the concentration of carbachol in the first incubation and can be blocked by atropine. First incubating acini with A23187, ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA), cholecystokinin octapeptide, bombesin, or 12-O-tetradecanoylphorbol-13-acetate does not alter binding of 125I-VIP. Adding EGTA to the first incubation medium abolishes the effect of carbachol on binding of 125I-VIP. In control acini or acini first incubated with carbachol, approximately half of the bound 125I-VIP can be stripped by acetic acid. 125I-VIP interacts with two distinct classes of receptors on pancreatic acini. One has a high affinity for VIP (Kd, 1 nM); the other has a low affinity for VIP (Kd, 2 microM). First incubating acini with carbachol decreases the number but not the affinity of high-affinity VIP receptors with no change in the number or affinity of low-affinity VIP receptors. Pancreatic acini possess two classes of muscarinic cholinergic receptors: one has a high affinity (Kd, 4 microM) and the other has a low affinity (Kd, 698 microM) for carbachol. The dose-response curve for carbachol-induced inhibition of binding of 125I-VIP and that for occupation of low-affinity muscarinic cholinergic receptors by carbachol are similar.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗