Effects of inhibitors of cyclic nucleotide phosphodiesterase on actions of cholecystokinin, bombesin, and carbachol on pancreatic acini

1983 ◽  
Vol 245 (5) ◽  
pp. G676-G680
Author(s):  
J. D. Gardner ◽  
V. E. Sutliff ◽  
M. D. Walker ◽  
R. T. Jensen
Keyword(s):  
Dose Response ◽  
Cyclic Nucleotide ◽  
Response Curve ◽  
Dose Response Curve ◽  
Cyclic Nucleotide Phosphodiesterase ◽  
Enzyme Secretion ◽  
Amylase Secretion ◽  
Pancreatic Acini ◽  
Rightward Shift ◽  
Stimulation Of

In dispersed acini from guinea pig pancreas two inhibitors of cyclic nucleotide phosphodiesterase, Ro 20-1724 and 3-isobutyl-1-methylxanthine (IBMX), augmented the increase in amylase secretion caused by supramaximal concentrations of cholecystokinin but did not alter the stimulation of enzyme secretion caused by bombesin. The augmentations of the action of cholecystokinin caused by Ro 20-1724 or IBMX could be reproduced by 8-bromo-cAMP. When tested alone or with theophylline, cholecystokinin did not alter cAMP in pancreatic acini; however, with Ro 20-1724 or IBMX, concentrations of cholecystokinin that were supramaximal for stimulating amylase secretion caused a significant increase in cellular cAMP. These findings indicate that Ro 20-1724 and IBMX augment the action of cholecystokinin on enzyme secretion by inhibiting cyclic nucleotide phosphodiesterase and allowing a significant cholecystokinin-induced increase in cellular cAMP. IBMX but not Ro 20-1724 caused a parallel rightward shift in the dose-response curve for the stimulation of amylase secretion caused by carbachol. IBMX also caused a parallel rightward shift in the dose-response curve for the stimulation of outflux of 45Ca caused by carbachol. These results indicate that IBMX, but not Ro 20-1724, can function as a muscarinic cholinergic antagonist.

Effects of inhibitors of cyclic nucleotide phosphodiesterase on the actions of vasoactive intestinal peptide and secretin on pancreatic acini

1982 ◽  
Vol 242 (6) ◽  
pp. G547-G551
Author(s):  
J. D. Gardner ◽  
L. Y. Korman ◽  
M. D. Walker ◽  
V. E. Sutliff
Keyword(s):  
Vasoactive Intestinal Peptide ◽  
Dose Response ◽  
Cyclic Nucleotide ◽  
Response Curve ◽  
Phosphodiesterase Inhibitor ◽  
Dose Response Curve ◽  
Cyclic Nucleotide Phosphodiesterase ◽  
Amylase Secretion ◽  
Pancreatic Acini ◽  
Stimulation Of

Theophylline, 3-isobutyl-1-methylxanthine (IBMX), and Ro 20-1724 each augmented the increase in cAMP and the stimulation of amylase secretion caused by vasoactive intestinal peptide (VIP) or secretin. With IBMX the dose-response curve for the stimulation of amylase secretion caused by VIP or secretin spanned a range of lower concentrations than did that obtained with Ro 20-1724, which in turn spanned a range of lower concentrations than did that obtained with theophylline. The configuration of the dose-response curve for the action of VIP on cAMP differed with each phosphodiesterase inhibitor tested. With Ro 20-1724 the dose-response curve was monophasic, whereas with the two methylxanthines the dose-response curve was biphasic. With theophylline the magnitude of the second component of the dose-response curve was larger than the first; with IBMX the magnitude of the first component was larger than the second. The configuration of the dose-response curve for the action of secretin on cAMP also differed with each phosphodiesterase inhibitor tested. With theophylline the dose-response curve was monophasic, whereas with Ro 20-1724 and IBMX the dose-response curve was biphasic. With Ro-20-1724 the magnitude of the second component of the dose-response curve was larger than the first; with IBMX the magnitude of the first component was larger than the second. These results indicate that cAMP is compartmentalized in pancreatic acinar cells and that the different compartments of cAMP are affected differently by various inhibitors of cyclic nucleotide phosphodiesterase. These findings also suggest that the different compartments of cAMP are acted on by phosphodiesterases with different sensitivities to various inhibitors.

scholarly journals Inhibition by somatostatin of amylase secretion induced by calcium and cyclic AMP in rat pancreatic acini

1994 ◽  
Vol 304 (2) ◽  
pp. 531-536 ◽  
Author(s):  
H Ohnishi ◽  
T Mine ◽  
I Kojima
Keyword(s):  
Cyclic Amp ◽  
G Protein ◽  
Pertussis Toxin ◽  
Dose Response ◽  
Response Curve ◽  
Dose Response Curve ◽  
Amylase Secretion ◽  
Ionophore A23187 ◽  
Dependent Manner ◽  
Pancreatic Acini

It has recently been shown that somatostatin inhibits amylase secretion from isolated pancreatic acini by reducing cyclic AMP (cAMP) production [Matsushita, Okabayashi, Hasegawa, Koide, Kido, Okutani, Sugimoto and Kasuga (1993) Gastroenterology 104, 1146-1152]. To date, however, little is known as to the other mechanism(s) by which somatostatin inhibits amylase secretion in exocrine pancreas. To investigate the action of somatostatin independent of cAMP generation, we examined the effect of somatostatin in isolated rat pancreatic acini stimulated by 1 microM calcium ionophore A23187 and 1 mM 8-bromo-cyclic AMP (8Br-cAMP). Somatostatin inhibited amylase secretion evoked by a combination of A23187 and 8Br-cAMP in a dose-dependent manner. The maximum inhibition was obtained by 10(-7) M somatostatin, and at this concentration somatostatin inhibited the effect of A23187 and 8Br-cAMP by approximately 30%. In electrically permeabilized acini, an elevation of free calcium concentration resulted in an increase in amylase secretion and cAMP enhanced the secretion evoked by calcium. cAMP shifted the dose-response curve for calcium-induced secretion leftwards and elevated the peak value of secretion. Somatostatin inhibited the effect of cAMP on calcium-induced amylase secretion by shifting the dose-response curve to the right. To determine the involvement of a G-protein(s), we examined the effect of somatostatin in acini pretreated with pertussis toxin. Pretreatment of acini with pertussis toxin completely blocked somatostatin-inhibition of amylase-secretion evoked by A23187 and 8Br-cAMP. These results indicate that somatostatin decreases amylase secretion induced by cAMP and calcium by reducing the calcium sensitivity of exocytosis. A pertussis toxin-sensitive G-protein is also involved in this step.

Cholecystokinin-induced restricted stimulation of pancreatic enzyme secretion

1982 ◽  
Vol 242 (5) ◽  
pp. G464-G469 ◽  
Author(s):  
N. Barlas ◽  
R. T. Jensen ◽  
J. D. Gardner
Keyword(s):  
Dose Response ◽  
Incubation Time ◽  
Response Curve ◽  
Pancreatic Enzyme ◽  
Enzyme Secretion ◽  
Enzyme Release ◽  
Pancreatic Acini ◽  
Basal Rate ◽  
Pancreatic Enzyme Secretion ◽  
Stimulation Of

During a 5-min incubation with increasing concentrations of cholecystokinin, enzyme secretion from pancreatic acini increased, became maximal at 1 nM cholecystokinin, and then decreased progressively to 65% of maximal with concentrations of cholecystokinin above 1 nM. During a 20-min incubation with increasing concentrations of cholecystokinin, enzyme secretion increased, became maximal at 0.3 nM cholecystokinin, and then decreased progressively to 40% of maximal with concentrations of cholecystokinin above 0.3 nM. The configuration of the dose-response curve for cholecystokinin-stimulated enzyme secretion did not change when the incubation time was increased from 20 to 30, 45, or 60 min. Concentrations of cholecystokinin that were supramaximal for stimulating enzyme secretion abolished the stimulation caused by other secretagogues that promote mobilization of cellular calcium (e.g., carbamylcholine, bombesin, physalaemin, or A23187), as well as that caused by secretagogues that elevate cellular cAMP (e.g., vasoactive intestinal peptide or secretin). The submaximal stimulation caused by supramaximal concentrations of cholecystokinin reflects what we have termed "restricted stimulation" of enzyme secretion. Secretion is than the basal rate of release and is "restricted" in the sense that enzyme release is submaximal and cannot be increased by adding another secretagogue.

Muscarinic receptor subtypes on rat pancreatic acini: secretion and binding studies

1986 ◽  
Vol 251 (2) ◽  
pp. G275-G279 ◽  
Author(s):  
D. S. Louie ◽  
C. Owyang
Keyword(s):  
Receptor Antagonist ◽  
Muscarinic Receptor ◽  
Dose Response ◽  
Response Curve ◽  
Dose Response Curve ◽  
Receptor Subtypes ◽  
Muscarinic Receptor Subtypes ◽  
Amylase Release ◽  
Pancreatic Acini ◽  
Rightward Shift

Characterization of muscarinic receptor subtypes on rat pancreatic acinar cells was examined by using specific muscarinic receptor antagonists to study amylase secretion and binding of [N-methyl-3H]scopolamine ([3H]NMS). Rat pancreatic acini were dispersed in HEPES-Ringer buffer and incubated with acetylcholine +/- 4-diphenylacetoxy-N-methylpiperadine-methiodide (4-DAMP, a specific M2 muscarinic receptor antagonist) or +/- pirenzepine (a specific M1 muscarinic receptor antagonist). 4-DAMP (10(-9) to 10(-6) M) caused a progressive parallel rightward shift in the acetylcholine dose-response curve without a change in maximal amylase release. Only high concentrations of pirenzepine (10(-6) to 10(-4) M) caused a rightward shift in the dose-response curve to acetylcholine. Schild analysis of the data indicated an inhibitory constant (Ki) of 200 pM for 4-DAMP and 183 nM for pirenzepine. The slope of the Schild regression lines was not different from unity, suggesting competitive inhibition. Binding of 50 pM [3H]NMS was specific, rapid, and saturable. [3H]NMS binding was displaced by increasing concentrations of 4-DAMP or pirenzepine with apparent Ki's of 102 pM and 330 nM, respectively, and similar maximal binding levels of 60 fmol/mg prot. We have demonstrated that 4-DAMP has an approximately 1,000-fold greater potency than pirenzepine to inhibit amylase release and binding, indicating that cholinergic-stimulated amylase release from pancreatic acini is mediated by M2 muscarinic receptors.

Effect of a Rab3A effector domain-related peptide, CCK, and EGF in permeabilized pancreatic acini

1994 ◽  
Vol 267 (3) ◽  
pp. G350-G356
Author(s):  
S. Zeuzem ◽  
D. Stryjek-Kaminska ◽  
W. F. Caspary ◽  
J. Stein ◽  
A. Piiper
Keyword(s):  
Dose Response ◽  
Response Curve ◽  
Dose Response Curve ◽  
Pancreatic Acinar Cells ◽  
Amylase Secretion ◽  
Small Molecular Weight ◽  
Amylase Release ◽  
Pancreatic Acini ◽  
Effector Domain ◽  
Domain Peptide

We report here that a synthetic peptide of the effector domain of the small-molecular-weight GTP-binding protein Rab3A (EDRab3AL) is a potent stimulator of inositol 1,4,5-trisphosphate [Ins(1,4,5)P3] production and amylase secretion in digitonin-permeabilized pancreatic acini. Moreover, the Rab3A effector domain peptide caused phosphatidylinositol 4,5-bisphosphate breakdown, indicating that the observed increase in Ins(1,4,5)P3 is due to stimulation of a phosphoinositide-specific phospholipase C (PLC). The dose-response curve for EDRab3AL-induced amylase release was biphasic, showing a maximum at 0.3 nM EDRab3AL and a decline at higher peptide concentrations. By contrast, the dose-response curve for EDRab3AL-induced Ins(1,4,5)P3 production was monophasic, showing stimulation with increasing EDRab3AL concentrations. A peptide of the effector domain of Rab1A, EDRab1AL, had no effect, indicating that the response to EDRab3AL is specific. Cholecystokinin octapeptide (CCK-8) and EDRab3AL had additive effects on the acinar Ins(1,4,5)P3 level. Epidermal growth factor (EGF), which has recently been shown to inhibit CCK-8-induced Ins(1,4,5)P3 production in pancreatic acinar cells, also decreased EDRab3AL-induced Ins(1,4,5)P3 production. These results suggest that EDRab3AL and CCK-8 act on the same EGF-inhibitable PLC by independent mechanisms. CCK-8 increased and EGF decreased amylase release in response to submaximal EDRab3AL concentrations. By contrast, at supramaximal EDRab3AL concentrations EGF increased and CCK-8 decreased EDRab3AL-stimulated amylase release. EDRab3AL had no effect in intact acini, indicating that the site of action of EDRab3AL is intracellular. We conclude that EDRab3AL regulates phosphoinositide-specific PLC activity and thereby amylase secretion in an analogous fashion to CCK-8, but from within the cell.(ABSTRACT TRUNCATED AT 250 WORDS)

Cholecystokinin-induced persistent stimulation of enzyme secretion from pancreatic acini

1981 ◽  
Vol 240 (6) ◽  
pp. G459-G465 ◽  
Author(s):  
S. M. Collins ◽  
S. Abdelmoumene ◽  
R. T. Jensen ◽  
J. D. Gardner
Keyword(s):  
Enzyme Secretion ◽  
Amylase Secretion ◽  
Intermediate Step ◽  
Pancreatic Acini ◽  
Persistent Effect ◽  
Incubation Solution ◽  
Cholecystokinin Receptors ◽  
Incomplete Removal ◽  
High Concentrations ◽  
Stimulation Of

When pancreatic acini are first incubated with cholecystokinin, washed to remove free cholecystokinin and then reincubated in fresh incubation solution, there is significant residual stimulation of amylase secretion. This residual stimulation requires relatively high concentrations of the secretagogue, is reversible, and is specific for cholecystokinin. Induction of residual stimulation occurs more rapidly at 37 degrees C (maximal by 1 min) than at 4 degrees C (maximal by 10 min), and, once induced, residual stimulation persists for up to 75 min at 37 degrees C and for more than 90 min at 4 degrees C. The persistent effect of cholecystokinin on enzyme secretion cannot be accounted for by incomplete removal of the secretagogue by the wash procedure or by activation of some intermediate step in the mechanism of action of cholecystokinin that persists after the secretagogue dissociates from its receptors. Instead, cholecystokinin-induced residual stimulation of enzyme secretion appears to result from persistent occupation of cholecystokinin receptors by the secretagogue.

VIP stimulation of β-naphthylamidase activity in guinea-pig thyroid sections

1985 ◽  
Vol 109 (4) ◽  
pp. 505-510 ◽  
Author(s):  
P. A. Ealey ◽  
N.J. Marshall ◽  
R. P. Ekins
Keyword(s):  
Dose Response ◽  
Response Curve ◽  
Receptor Site ◽  
Dose Response Curve ◽  
Tsh Receptor ◽  
Maximal Response ◽  
Cytochemical Bioassay ◽  
Order Of Magnitude ◽  
Specific Receptors ◽  
Stimulation Of

Abstract. Subsequent to the discovery of vasoactive intestinal peptide (VIP) in the thyroid gland, VIP has been shown to stimulate various thyroid functions. The site of interaction of VIP with the thyroid follicular cell is at present not known, and this study has used the ultrasensitive cytochemical bioassay (CBA) for thyroid stimulators to investigate this further. Exposure of thyroid sections for 3 min to VIP resulted in increased naphthylamidase activity, with half-maximal response observed at 3 × 10−13 m VIP. This response to such low doses of VIP is consistent with the CBA being ultrasensitive to other thyroid stimulators e.g. TSH, thyroid stimulating antibodies and forskolin. The response to VIP was abolished by rabbit anti-VIP antiserum. The dose-response curve to VIP was bell-shaped (as with the other stimulators), maximal stimulation occurring at 10−12 m VIP. In contrast, however, to other thyroid stimulators, namely TSH, LATS-B and 3 monoclonal stimulating antibodies, whose ascending limbs of the doseresponse curves extended over 3-4 orders of magnitude, the VIP curve rose rapidly from basal to maximal tissue stimulation from 10−13 to 10−12m VIP, i.e. one order of magnitude. This unusual dose-response curve to VIP was parallel to that produced by forskolin. 11E8, a monoclonal 'blocking' antibody which is a potent inhibitor of TSH stimulation, did not 'block' forskolin stimulation, consistent with the belief that forskolin acts at a post-receptor site. However, unlike forskolin, VIP was inhibited by monoclonal 11E8, which may imply a hitherto unexpected involvement of the TSH receptor in VIP stimulation of the thyroid or, alternatively, steric inhibition by 11E8 when bound to the TSH receptor of VIP interaction with adjacent VIP-specific receptors.

Forskolin stimulation of naphthylamidase in guinea pig thyroid sections detected with a cytochemical bioassay

1985 ◽  
Vol 108 (3) ◽  
pp. 367-371 ◽  
Author(s):  
Patricia A. Ealey ◽  
Leonard D. Kohn ◽  
Nicholas J. Marshall ◽  
Roger P. Ekins
Keyword(s):  
Guinea Pig ◽  
Dose Response ◽  
Response Curve ◽  
Thyroid Tissue ◽  
Receptor Site ◽  
Dose Response Curve ◽  
Cytochemical Bioassay ◽  
Surface Receptor ◽  
Stimulation Of ◽  
Endocrine Tissues

Abstract. Forskolin, from the roots of the Indian medicinal plant Coleus forskohlii, has recently been shown to be a potent stimulator of adenylate cyclase in many systems, including endocrine tissues such as the thyroid gland. We describe forskolin activation of β-naphthylamidase activity in guinea pig thyroid tissue using the cytochemical bioassay (CBA) for thyroid stimulators. This CBA is the most sensitive bioassay for TSH and LATS-B currently available, being able to detect stimulation by doses as low as 10−5 mU TSH/l and 10−9 mU LATS-B/l. The dose-response curve to forskolin was bell-shaped (as is seen with TSH and LATS-B) with the ascending limb of the curve produced by 10−13 m to 10−12 m forskolin after a 3 min exposure time. Maximal stimulation was observed with 10−12m forskolin. However, the dose-response curve to forskolin was not parallel to that given by TSH, the slope of the ascending limb being much greater. It has been suggested that stimulation of β-naphthylamidase activity in the CBA is via cAMP. We report that dibutyryl cAMP at doses from 10−16m to 10−11 m produces a bell-shaped dose-response curve with a very broad peak response, again not parallel to that produced by TSH. Forskolin activation of β-naphthylamidase in the CBA is unaffected by a 1:106 dilution of 11E8, a monoclonal antibody raised against solubilised TSH receptors, which binds to the TSH receptor and inhibits TSH stimulation. Although the precise location of forskolin action is not known, this is further evidence that forskolin acts at a post-surface receptor site.

Role of Endothelial K + Channels in NO-Dependent Vasorelaxant Responses to Acetylcholine in Rat Aorta.

Hypertension ◽  
2000 ◽  
Vol 36 (suppl_1) ◽  
pp. 698-698
Author(s):  
John Quilley ◽  
Yue Qiu
Keyword(s):  
Dose Response ◽  
Response Curve ◽  
Rat Aorta ◽  
Dose Response Curve ◽  
Response Curves ◽  
K Channels ◽  
Voltage Dependent ◽  
The Right ◽  
Stimulation Of

P30 Endothelium-dependent vasorelaxant responses to acetylcholine (Ach) in rat aorta are mediated solely by NO. Rings precontracted with U46619 were used to investigate the role of endothelial K + channels. Thus, any effect of K + channel inhibitors on Ach responses in the absence of an effect on those to nitroprusside (NP) can be attributed to interference with Ach-induced stimulation of NO. Vasorelaxant responses to Ach (log EC 50 -7.29M) were abolished by removal of the endothelium or inhibition of NO synthesis with nitroarginine (100μM) which potentiated responses to NP (log EC 50 -9.41M vs -8.47M for control). In the presence of TEA (10mM) to inhibit K + channels, the dose-response curve for Ach, but not NP, was shifted to the right (log EC 50 -6.06). Elevation of extracellular K + (25mM KCl)also shifted the dose-response curve for Ach to the right. Inhibitors of specific types of K + channels: BaCl 2 (30μM), apamin (100nM), glibenclamide (10μM), charybdotoxin (50nM) and iberiotoxin (100nM) were without effect on dose-response curves to either Ach or NP. However, the combination of apamin (100nM) and charybdotoxin (50nM) but not apamin plus iberiotoxin, reduced relaxant responses to Ach (log EC 50 -6.95M) without affecting those to NP.These results confirm that Ach-induced relaxation of rat aorta is mediated entirely by endothelium-derived NO, the release of which apparently involves hyperpolarization of the endothelium. This effect is dependent on activation of a K + channel that is blocked by a combination of apamin/charybdotoxin but neither agent alone, possibly indicating characteristics of both Ca 2+ - activated and voltage-dependent K + channels.

scholarly journals The involvement of protein phosphorylation in stimulus-secretion coupling in the mouse exocrine pancreas

1983 ◽  
Vol 210 (2) ◽  
pp. 353-359 ◽  
Author(s):  
M L Roberts ◽  
F R Butcher
Keyword(s):  
Cyclic Amp ◽  
Protein Phosphorylation ◽  
Dose Response ◽  
Exocrine Pancreas ◽  
Response Curve ◽  
Dose Response Curve ◽  
Amylase Secretion ◽  
Ionophore A23187 ◽  
Muscarinic Agonist ◽  
Derivatives Of

Secretagogue-induced protein phosphorylation was studied in the mouse pancreas in vitro, by using polyacrylamide-gel electrophoresis to separate the labelled proteins. Muscarinic cholinergic agonists increased the phosphorylation of a single band, which corresponded to Mr 32000, when the tissue was incubated with Ca2+ present in the extracellular medium, but not in Ca2+-free Krebs solution. In the presence of Ca2+, ionophore A23187 stimulated phosphorylation of the same band. The dose-response curve for carbachol-induced phosphorylation was biphasic, with maximum response at 1.0 microM-carbachol, and lesser responses when greater concentrations were used. This resembles the dose-response curve for carbachol-induced amylase secretion. The data suggest that the muscarinic-agonist-induced protein phosphorylation is stimulated secondarily to elevation of cytosol [Ca2+] and do not support the idea that diacylglycerol formed from hydrolysis of phosphatidylinositol is the activator of the protein kinase. Derivatives of cyclic AMP stimulated phosphorylation of bands corresponding to Mr 95500, 32000 and 20000. The effects of dibutyryl cyclic AMP and bethanechol on the protein of Mr 32000 were not additive, suggesting that the two agents produced phosphorylation of the same site(s) on this protein. Since derivatives of cyclic AMP, which are not very effective secretagogues in the exocrine pancreas, stimulate phosphorylation of the protein of Mr 32000, it is difficult to argue that phosphorylation of this particular protein leads to protein secretion.

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