A new CCK analogue differentiates two functionally distinct CCK receptors in rat and mouse pancreatic acini

1989 ◽  
Vol 257 (4) ◽  
pp. G594-G600 ◽  
Author(s):  
T. Matozaki ◽  
J. Martinez ◽  
J. A. Williams
Keyword(s):  
Competitive Inhibition ◽  
Inhibitory Effect ◽  
Leucine Incorporation ◽  
Amylase Release ◽  
Pancreatic Acini ◽  
Cck Receptors ◽  
Partial Agonists ◽  
Low Concentrations ◽  
Phenylalanine Residue ◽  
Stimulation Of

Analysis of the competitive inhibition of 125I-labeled cholecystokinin octapeptide (CCK-8) binding to isolated rat or mouse pancreatic acini showed that in both species CCK-8 interacts with two different affinity sites. A newly synthesized CCK analogue modified at the COOH-terminal phenylalanine residue totally inhibited 125I-CCK binding. This interaction occurred with sites of a single affinity in rat acini but with two different affinity sites in mouse acini. When acini were incubated with increasing concentrations of CCK-8, a biphasic stimulation of amylase release was observed. By use of rat acini, the analogs stimulated amylase release but caused no inhibition at supramaximal concentrations. By contrast, in mouse pancreatic acini, analogues showed a biphasic stimulation of amylase release similar to CCK-8. Both CCK-8 and the analogue stimulated [3H]leucine incorporation into protein at low concentrations in rat pancreatic acini. Higher concentrations of CCK-8 profoundly inhibited [3H]leucine incorporation, whereas the analogue had no inhibitory effect. Moreover, the analogue at higher concentrations blocked the inhibition of [3H]leucine incorporation caused by CCK-8 but did not affect carbamylcholine-induced inhibition. In mouse acini, however, the CCK analogue inhibited [3H]leucine incorporation similar to the effect of CCK-8. The results support the concept that occupancy of distinct affinity sites or states of the CCK receptor is associated with specific biological actions. A model of the CCK receptor is proposed in which two interchangeable affinity states exist. By occupying all the receptors in only one state, the new CCK analogues serve as partial agonists of some and antagonists of other actions of CCK.

Relationship of cholecystokinin receptor binding to regulation of biological functions in pancreatic acini

1982 ◽  
Vol 242 (3) ◽  
pp. G250-G257 ◽  
Author(s):  
H. Sankaran ◽  
I. D. Goldfine ◽  
A. Bailey ◽  
V. Licko ◽  
J. A. Williams
Keyword(s):  
Binding Sites ◽  
Acid Uptake ◽  
Biological Functions ◽  
Amylase Release ◽  
Pancreatic Acini ◽  
Lower Affinity ◽  
Cck Receptors ◽  
Aminoisobutyric Acid ◽  
Stimulation Of ◽  
Binding Component

Cholecystokinin (CCK) was conjugated to 125I-Bolton-Hunter reagent (125I-BH-CCK), and the binding of this ligand to CCK receptors in isolated mouse pancreatic acini was correlated with the regulation by CCK of both amylase release and the transport of 2-deoxyglucose and alpha-aminoisobutyric acid. Stimulation of amylase release by CCK was biphasic. At low CCK concentrations (less than 200 pM), amylase release was progressively stimulated, whereas at higher CCK concentrations (greater than 200 pM), amylase release was progressively reduced. In contrast, stimulation of 2-[3H]deoxyglucose transport and inhibition of alpha-[3H]aminoisobutyric acid transport were monophasic, being one-half maximal at 0.85 and 0.44 nM, respectively. Under incubation conditions identical to those employed for measuring biological functions, the binding of 125I-BH-CCK to receptors in acini was rapid and reversible. Competition-inhibition curves and Scatchard plots of equilibrium binding were compatible with two orders of binding sites. Employing a computer program for analysis of multiple binding sites, a high-affinity, low-capacity binding component having a Kd of 26 pM and a lower-affinity, higher-capacity binding component having a component Kd of 2.2 nM were resolved. Regulation of 2-[3H]deoxyglucose and alpha-[3H]aminoisobutyric acid uptake appeared, therefore, to be the result of fractional occupancy of the lower-affinity CCK receptors. Regulation of amylase released was more complex and appeared to be due to the concomitant occupancy of both the high- and low-affinity CCK receptors.

Action of theophylline on secretagogue-stimulated amylase release from dispersed pancreatic acini

1980 ◽  
Vol 239 (4) ◽  
pp. G324-G333
Author(s):  
L. Y. Korman ◽  
M. D. Walker ◽  
J. D. Gardner
Keyword(s):  
Guinea Pig ◽  
Vasoactive Intestinal Peptide ◽  
Enzyme Secretion ◽  
Amylase Release ◽  
Pancreatic Acini ◽  
Modes Of Action ◽  
Low Concentrations ◽  
High Concentrations ◽  
Stimulation Of

In dispersed acini from guinea pig pancreas, theophylline did not alter basal amylase release, but had three functionally distinct modes of action on the stimulation of amylase release caused by various secretagogues. 1) At relatively low concentrations (0.1-1.0 mM), theophylline augmented the increase in enzyme secretion caused by vasoactive intestinal peptide, secretin, or 8-bromoadenosine 3',5'-monophosphate, but did not alter the increase in amylase release caused by other secretagogues. 2) At intermediate concentrations (1-10 mM), theophylline selectively altered the increase in enzyme secretion caused by carbamylcholine, but did not alter the effects of cholecystokinin or bombesin, secretagogues whose modes of action are similar to that of cabamylcholine. 3) At high concentrations (greater than 10 mM), theophylline inhibited the increase in enzyme secretion caused by all secretagogues tested.

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

1989 ◽  
Vol 257 (2) ◽  
pp. G202-G209 ◽  
Author(s):  
S. Sato ◽  
H. A. Stark ◽  
J. Martinez ◽  
M. A. Beaven ◽  
R. T. Jensen ◽  
...  
Keyword(s):  
Response Curve ◽  
Cytosolic Calcium ◽  
Calcium Mobilization ◽  
Amylase Release ◽  
Pancreatic Acini ◽  
Rat Pancreas ◽  
Cck Receptors ◽  
High Affinity ◽  
Low Concentrations ◽  
The Relationship

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.

Structure-activity relationship studies on cholecystokinin: analogues with partial agonist activity

1988 ◽  
Vol 254 (2) ◽  
pp. G176-G182 ◽  
Author(s):  
M. C. Galas ◽  
M. F. Lignon ◽  
M. Rodriguez ◽  
C. Mendre ◽  
P. Fulcrand ◽  
...  
Keyword(s):  
Guinea Pig ◽  
Partial Agonist ◽  
Peptide Bond ◽  
Primary Amide ◽  
Amylase Release ◽  
Pancreatic Acini ◽  
Cck Receptors ◽  
Close Relationship ◽  
Guinea Pig Brain ◽  
Phenylalanine Residue

In the present study, hepta- and octapeptide analogues of the C-terminal part of cholecystokinin, modified on the C-terminal phenylalanine residue, were synthesized. CCK analogues were prepared in which the peptide bond between aspartic acid and phenylalanine had or had not been modified and were lacking the C-terminal primary amide function. These CCK derivatives were able to cause full stimulation of amylase release from rat pancreatic acini but without a decrease in amylase release at supramaximal concentrations. There was a close relationship between the abilities of these derivatives to stimulate amylase release and their abilities to inhibit binding of 125I-BH-CCK-9 to CCK receptors on rat and guinea pig pancreatic acini. These CCK analogues were also able to recognize the guinea pig brain CCK receptors, some of them being particularly potent. The findings indicate that the aromatic ring of phenylalanine is important for the binding to brain and pancreatic CCK receptors, whereas the C-terminal primary amide function is not essential for the binding to pancreatic CCK receptors but is crucial for biological activity of rat pancreatic acini.

A new biological contribution of cyclo(His-Pro) to the peripheral inhibition of pancreatic secretion

1997 ◽  
Vol 273 (6) ◽  
pp. E1127-E1132 ◽  
Author(s):  
Pascal Fragner ◽  
Olivier Presset ◽  
Nicole Bernad ◽  
Jean Martinez ◽  
Claude Roze ◽  
...  
Keyword(s):  
Pancreatic Secretion ◽  
Biological Activities ◽  
Systemic Circulation ◽  
Inhibitory Effect ◽  
Pancreatic Acinar Cells ◽  
Exocrine Pancreatic Secretion ◽  
Amylase Release ◽  
Pancreatic Acini

The tripeptide pyro-Glu-His-Pro-NH2[thyrotropin-releasing hormone (TRH)] was isolated from the hypothalamus as a thyrotropin-releasing factor. It has a broad spectrum of central nervous system-mediated actions, including the stimulation of exocrine pancreatic secretion. TRH is also synthesized in the endocrine pancreas and found in the systemic circulation. Enzymatic degradation of TRH in vivo produces other bioactive peptides such as cyclo(His-Pro). Because of the short half-life of TRH and the stability of cyclo(His-Pro) in vivo, we postulated that at least part of the peripheral TRH effects on the exocrine pancreatic secretion may be attributed to cyclo(His-Pro), which has been shown to have other biological activities. This study determines in parallel the peripheral effects of TRH and cyclo(His-Pro) as well as the putative contribution of other TRH-related peptides on exocrine pancreatic secretion in rats. TRH and its metabolite cyclo(His-Pro) dose dependently inhibited 2-deoxy-d-glucose (2-DG)-stimulated pancreatic secretion. TRH and all the related peptides tested had no effect on the basal and cholecystokinin-stimulated amylase release from pancreatic acinar cells in vitro. These data indicate that cyclo(His-Pro) mimics the peripheral inhibitory effect of TRH on 2-DG-stimulated exocrine pancreatic secretion. This effect is not detected on isolated pancreatic acini. Our findings provide a new biological contribution for cyclo(His-Pro) with potential experimental and clinical applications.

scholarly journals Caerulein and carbamoylcholine stimulate pancreatic amylase release at resting cytosolic free Ca2+

1986 ◽  
Vol 235 (1) ◽  
pp. 139-143 ◽  
Author(s):  
R Bruzzone ◽  
T Pozzan ◽  
C B Wollheim
Keyword(s):  
Fold Increase ◽  
Free Calcium ◽  
Amylase Secretion ◽  
Rapid Phase ◽  
Secretory Rate ◽  
Amylase Release ◽  
Pancreatic Acini ◽  
Significant Stimulation ◽  
Phase 0 ◽  
Stimulation Of

Cytosolic free calcium concentrations ([Ca2+]i) and amylase secretion were measured in isolated rat pancreatic acini loaded with the intracellularly trapped fluorescent indicator quin2. Both caerulein and carbamoylcholine caused a rapid increase in [Ca2+]i, with a maximal 3-fold increase at 10(-9) M-caerulein and 10(-4) M-carbamoylcholine. However, caerulein (10(-12) M and 10(-11) M) as well as carbamoylcholine (10(-7) M) caused a significant stimulation of amylase release, while not inducing any detectable rise in [Ca2+]i. Changes in [Ca2+]i after addition of either secretagogue were transient and did not last more than 2-3 min. By contrast, when amylase secretion was monitored as a function of time, two distinct secretory phases could be observed upon addition of either carbamoylcholine (10(-5) M) or caerulein (10(-10) M). An initial, rapid phase (0-5 min) which caused a 6-7-fold increase above basal, followed by a sustained (5-30 min), but less marked, secretory rate (2-3-fold above basal). Addition of atropine (10(-4) M) 5 min after carbamoylcholine (10(-5) M) (i.e. after termination of the rise in [Ca2+]i and of the first secretory phase) did not cause any significant change in [Ca2+]i, while significantly inhibiting amylase secretion from 5 to 30 min to the same rate observed in the absence of the secretagogue. These results show that caerulein and carbamoylcholine, two agents thought to activate secretion mainly through mobilization of Ca2+ from intracellular stores, are capable of eliciting amylase secretion independently of a concomitant rise in [Ca2+]i. Furthermore, with both secretagogues the rise in [Ca2+]i, when observed, was only transient, while the stimulation of amylase release was sustained.

Calcium fluxes in isolated pancreatic acini: effects of secretagogues

1981 ◽  
Vol 240 (1) ◽  
pp. G38-G49 ◽  
Author(s):  
R. L. Dormer ◽  
J. H. Poulsen ◽  
V. Licko ◽  
J. A. Williams
Keyword(s):  
Time Course ◽  
Calcium Content ◽  
Total Calcium ◽  
Good Correspondence ◽  
Amylase Release ◽  
Pancreatic Acini ◽  
Kinetic Component ◽  
Rapid Drop ◽  
Single Exponential ◽  
Stimulation Of

45Ca2+ exchange and total calcium content were measured in isolated mouse pancreatic acini. 45Ca2+ uptake could be described as the sum of a constant and a single exponential kinetic component; about 60% of total acinar calcium was exchangeable. Stimulation by bethanechol increased 45Ca2+ uptake, but the time course of uptake could be fit only by the addition of a more rapid kinetic component without any change in the total exchangeable Ca2+. 45Ca2+ washout after 1-h loading could be fit as the sum of two exponential components. Stimulation increased the rate of 45Ca2+ washout with the appearance of a third and more rapid kinetic component. There was not, however, a good correspondence between the exponential constants measured in uptake and washout protocols in unstimulated acini. Exponential constants were also affected by the concentration of calcium in the medium, further indicating the presence of nonlinearities in 45Ca2+ exchange. The dose-response relationships were similar for bethanechol stimulation of 45Ca2+ uptake and amylase release, whereas stimulation of 45Ca2+ washout reached a maximum at a higher concentration of bethanechol. Both 45Ca2+ uptake and analytical measurement of total Ca2+ showed a rapid drop in acinar Ca2+ content followed by a gradual reuptake on stimulation by bethanechol. It is concluded that the initial primary effect of secretagogues is to increase Ca2+ efflux, which is interpreted to be the result of release of sequestered calcium into the cytosol.

New proglumide-analogue CCK receptor antagonists: very potent and selective for peripheral tissues

1986 ◽  
Vol 250 (6) ◽  
pp. G856-G860 ◽  
Author(s):  
C. Niederau ◽  
M. Niederau ◽  
J. A. Williams ◽  
J. H. Grendell
Keyword(s):  
Agonist Activity ◽  
Receptor Antagonists ◽  
Maximal Inhibition ◽  
Amylase Release ◽  
Peripheral Tissues ◽  
Pancreatic Acini ◽  
Cholecystokinin Receptor ◽  
Low Concentrations ◽  
Competitive Kinetics ◽  
Cck Receptor Antagonists

The present study evaluates the ability of two recently synthesized analogues of proglumide, both 4-benzamido-N,N-di-alkyl-glutaramic acid derivatives, to act as cholecystokinin receptor antagonists. Both new antagonists inhibited cholecystokinin-stimulated amylase release and, similarly, binding of 125I-cholecystokinin to isolated rat pancreatic acini. These effects displayed competitive kinetics; both antagonists showed no agonist activity and were specific in that only those secretagogues were inhibited that interact with the cholecystokinin receptor. Both antagonists also inhibited binding of 125I-cholecystokinin to mouse pancreatic membrane particles similarly to results with rat pancreatic acini. With the more potent of the two new antagonists, half-maximal inhibition of action and binding of cholecystokinin was observed with low concentrations of approximately 10(-7) M; compared with proglumide, the new antagonists were as much as 4,000 times more potent. Unlike proglumide, which inhibits binding of cholecystokinin to pancreas and brain tissue similarly, both antagonists inhibited binding of cholecystokinin to the pancreas at much lower concentrations compared with brain. The more potent of the inhibitors was 300 times more potent in inhibiting binding of cholecystokinin to pancreatic tissues compared with brain.

scholarly journals Control of amylase biosynthesis and release in the parotid gland of the rat

1978 ◽  
Vol 176 (3) ◽  
pp. 855-863 ◽  
Author(s):  
Margaret A. McPherson ◽  
C. Nicholas Hales
Keyword(s):  
Total Protein ◽  
Leucine Incorporation ◽  
Protein Synthesis Inhibitor ◽  
Pulse Labelling ◽  
Synthesis Inhibitor ◽  
Physiological Concentration ◽  
Amylase Release ◽  
Cholinergic Agents ◽  
Rat Parotid ◽  
Stimulation Of

1. Amylase biosynthesis and release in the rat parotid were studied under various conditions. Incorporation of [3H]leucine into amylase, extracted from the tissue by immunoadsorbent, was measured and found to be time-dependent and totally inhibited by the protein synthesis inhibitor puromycin. 2. Adrenaline, at a concentration (10μm) that gave maximum stimulation of release, inhibited [3H]leucine incorporation into both total protein and amylase. This effect was reversed by phentolamine. 3. Adrenaline (1μm) and isoproterenol (10μm) stimulated biosynthesis of total protein and amylase. These effects were blocked by propranolol, as were the effects on release. Dibutyryl cyclic AMP (2mm) mimicked the effects of isoproterenol and adrenaline (1μm) on both amylase biosynthesis and release. All the above stimulatory effects on amylase biosynthesis were only observed if the tissue was pretreated with effector before pulse-labelling with [3H]leucine. 4. Insulin (625μunits/ml initial concentration, 150μunits/ml final concentration) stimulated incorporation of [3H]leucine into total protein and amylase when added to the tissue at the same time as the leucine. 5. Carbamoylcholine (10μm) decreased [3H]leucine incorporation into total protein and amylase when both were added to the tissue simultaneously, but this effect was prevented by removal of effector and washing the tissue before addition of [3H]leucine. 6. Stimulation of β-adrenergic receptors increased both amylase release and biosynthesis, but stimulation of α-receptors can inhibit biosynthesis without inhibiting release. Cholinergic agents can also inhibit amylase biosynthesis, but stimulate release. Insulin at approximately physiological concentration can increase incorporation of leucine into amylase without stimulating release. The system described therefore provides an excellent model for the further investigation of the mechanisms of these diverse effects.

scholarly journals Physiological concentrations of cyanide stimulate mitochondrial Complex IV and enhance cellular bioenergetics

2021 ◽  
Vol 118 (20) ◽  
pp. e2026245118
Author(s):  
Elisa B. Randi ◽  
Karim Zuhra ◽  
Laszlo Pecze ◽  
Theodora Panagaki ◽  
Csaba Szabo
Keyword(s):  
Cell Proliferation ◽  
Mammalian Cells ◽  
Inhibitory Effect ◽  
Mitochondrial Complex ◽  
Metabolizing Enzymes ◽  
Complex Iv ◽  
Low Concentrations ◽  
Cellular Bioenergetics ◽  
Current Report ◽  
Stimulation Of

In mammalian cells, cyanide is viewed as a cytotoxic agent, which exerts its effects through inhibition of mitochondrial Complex IV (Cytochrome C oxidase [CCOx]). However, the current report demonstrates that cyanide’s effect on CCOx is biphasic; low (nanomolar to low-micromolar) concentrations stimulate CCOx activity, while higher (high-micromolar) concentrations produce the “classic” inhibitory effect. Low concentrations of cyanide stimulated mitochondrial electron transport and elevated intracellular adenosine triphosphate (ATP), resulting in the stimulation of cell proliferation. The stimulatory effect of cyanide on CCOx was associated with the removal of the constitutive, inhibitory glutathionylation on its catalytic 30- and 57-kDa subunits. Transfer of diluted Pseudomonas aeruginosa (a cyanide-producing bacterium) supernatants to mammalian cells stimulated cellular bioenergetics, while concentrated supernatants were inhibitory. These effects were absent with supernatants from mutant Pseudomonas lacking its cyanide-producing enzyme. These results raise the possibility that cyanide at low, endogenous levels serves regulatory purposes in mammals. Indeed, the expression of six putative mammalian cyanide-producing and/or -metabolizing enzymes was confirmed in HepG2 cells; one of them (myeloperoxidase) showed a biphasic regulation after cyanide exposure. Cyanide shares features with “classical” mammalian gasotransmitters NO, CO, and H2S and may be considered the fourth mammalian gasotransmitter.

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