Direct demonstration of increases in cytosolic free Ca2+ during stimulation of pancreatic enzyme secretion

1983 ◽  
Vol 3 (3) ◽  
pp. 233-240 ◽  
Author(s):  
R. L. Dormer
Keyword(s):  
Divalent Cation ◽  
Pancreatic Enzyme ◽  
Enzyme Secretion ◽  
Ionophore A23187 ◽  
Pancreatic Acini ◽  
Direct Demonstration ◽  
Pancreatic Enzyme Secretion ◽  
Hypotonic Swelling ◽  
Isolated Rat ◽  
Stimulation Of

The Ca2+-activated photoprotein aequorin has been incorporated into intact, isolated rat pancreatic acini by a hypotonic swelling method. The isolated acini retained normal secretory responses after loading with aequorin. Increases in cytosolic Ca2+ concentration in response to a physiological secretagogue, carbamylcholine, and to divalent-cation ionophore A23187 have been demonstrated. Simultaneous measurement of the dynamics of enzyme secretion and changes in cytosolic Ca2+ concentration has been achieved using a newly developed apparatus.

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.

Intracellular Ca2+ in pancreatic acinar cells: Regulation and role in stimulation of enzyme secretion

1987 ◽  
Vol 7 (4) ◽  
pp. 333-344 ◽  
Author(s):  
Robert L. Dormer ◽  
Graham R. Brown ◽  
Claire Doughney ◽  
Margaret A. McPherson
Keyword(s):  
Endoplasmic Reticulum ◽  
Pancreatic Enzyme ◽  
Acinar Cells ◽  
Enzyme Secretion ◽  
Pancreatic Acinar Cells ◽  
Current Evidence ◽  
Primary Role ◽  
Direct Demonstration ◽  
Pancreatic Enzyme Secretion ◽  
Stimulation Of

Evidence for a primary role for intracellular Ca2+ in the stimulation of pancreatic enzyme secretion is reviewed. Measurements of cytoplasmic free Ca2+ concentration have allowed direct demonstration of its importance in triggering enzyme secretion and defined the concentration range over which membrane Ca2+ pumps must work to regulate intracellular Ca2+. Current evidence suggests a key role for the Ca2+ Mg-ATPase of rough endoplasmic reticulum in regulating intracellular Ca2+ and accumulating a Ca2+ store which is released by the action of inositol-l,4,5 trisphosphate following stimulation of secretion.

Selective modification of the ability of cholecystokinin to cause residual stimulation of pancreatic enzyme secretion

1982 ◽  
Vol 243 (3) ◽  
pp. G214-G217
Author(s):  
M. L. Villanueva ◽  
J. Martinez ◽  
M. Bodanszky ◽  
S. M. Collins ◽  
R. T. Jensen ◽  
...  
Keyword(s):  
Aspartic Acid ◽  
Pancreatic Enzyme ◽  
Terminal Region ◽  
Enzyme Secretion ◽  
Aspartic Acid Residue ◽  
Pancreatic Acini ◽  
Pancreatic Enzyme Secretion ◽  
Stimulation Of

In the C-terminal heptapeptide of cholecystokinin (-Tyr(SO3H)-Met-Gly-Trp-Met-Asp-Phe-NH2), replacing the aspartic acid residue by beta-aspartic acid did not alter the ability of the peptide to cause stimulation, desensitization, or residual stimulation of enzyme secretion from dispersed pancreatic acini. Replacing the tyrosine sulfate residue by hydroxynorleucine sulfate did not alter the ability of the heptapeptide to cause stimulation or desensitization, but caused a 50-fold decrease in the potency with which the peptide caused residual stimulation of enzyme secretion. These findings suggest that a modification of the N-terminal region of cholecystokinin heptapeptide, which does not alter the ability of the peptide to bind to its receptor on pancreatic acini and by so doing cause stimulation and desensitization of enzyme secretion, can increase the rate at which the bound peptide dissociates when the acini are washed and reincubated. This increased dissociation is reflected by a reduction in the potency with which the peptide causes residual stimulation of enzyme secretion.

Reversal of cholecystokinin-induced persistent stimulation of pancreatic enzyme secretion by dibutyryl cyclic GMP

1981 ◽  
Vol 240 (6) ◽  
pp. G466-G471 ◽  
Author(s):  
S. M. Collins ◽  
S. Abdelmoumene ◽  
R. T. Jensen ◽  
J. D. Gardner
Keyword(s):  
Cyclic Gmp ◽  
Pancreatic Enzyme ◽  
Enzyme Secretion ◽  
Amylase Secretion ◽  
Pancreatic Acini ◽  
Incubation Solution ◽  
Complete Reversal ◽  
Pancreatic Enzyme Secretion ◽  
Derivatives Of ◽  
Stimulation Of

When pancreatic acini are first incubated with cholecystokinin, washed to remove free cholecystokinin, and then reincubated in fresh incubation solution, there is a significant residual stimulation of amylase secretion. Butyryl derivatives of cyclic GMP can prevent as well as reverse this cholecystokinin-induced residual stimulation. At 37 degrees C the nucleotide-induced reversal is complete within a few minutes, but at 4 degrees C complete reversal requires 90 min of incubation. The ability of butyryl cyclic GMP to reverse cholecystokinin-induced residual stimulation is itself fully reversible, and the nucleotide-induced reversal is accompanied by restoration of full responsiveness to cholecystokinin. The ability of dibutyryl cyclic GMP to reverse cholecystokinin-induced residual stimulation appears to result from the ability of the nucleotide to displace cholecystokinin from its receptors in pancreatic acini.

Stimulation of Pancreatic Enzyme Secretion by a Peptide Purified from Rat Bile-Pancreatic Juice

1986 ◽  
Vol 116 (8) ◽  
pp. 1540-1546 ◽  
Author(s):  
Shin-Ichi Fukuoka ◽  
Masahiro Tsujikawa ◽  
Tohru Fushiki ◽  
Kazuo Iwai
Keyword(s):  
Pancreatic Juice ◽  
Pancreatic Enzyme ◽  
Enzyme Secretion ◽  
Pancreatic Enzyme Secretion ◽  
Rat Bile ◽  
Stimulation Of

Prostaglandin E2 inhibits secretagogue-induced enzyme secretion from rat pancreatic acini

1991 ◽  
Vol 260 (5) ◽  
pp. G711-G719
Author(s):  
J. Mossner ◽  
R. Secknus ◽  
G. M. Spiekermann ◽  
C. Sommer ◽  
M. Biernat ◽  
...  
Keyword(s):  
Prostaglandin E2 ◽  
Pancreatic Enzyme ◽  
Enzyme Secretion ◽  
Amylase Secretion ◽  
Binding Studies ◽  
Pancreatic Acini ◽  
Inositol 1,4,5 Trisphosphate ◽  
Pancreatic Enzyme Secretion ◽  
Hcl Secretion ◽  
Specific Receptors

Prostaglandins of the E type may have a potential role in pancreatic physiology and pathophysiology. Because prostaglandins of the E type inhibit HCl secretion in parietal cells via a specific receptor by inhibition of adenylylcyclase, we studied whether a similar mechanism exists in the exocrine pancreas. Isolated rat pancreatic acini were incubated with various concentrations of secretagogues, such as cholecystokinin-octapeptide (CCK-8), bombesin, carbachol, and vasoactive intestinal peptide (VIP), in the absence or presence of prostaglandin E2 (PGE2), and amylase secretion was measured. For receptor binding studies, acini and pancreatic membranes were incubated with [3H]PGE2 and either unlabeled PGE2 or other types of prostaglandins. PGE2 (10(-13) to 10(-5) M) did not inhibit basal amylase secretion. However, CCK-8-stimulated secretion was significantly inhibited. Stimulation of secretion by bombesin, carbachol, VIP, and secretin was also inhibited by PGE2, but not as pronounced as CCK-8-stimulated secretion. The formation of inositol 1,4,5-trisphosphate induced by CCK-8 was markedly inhibited by simultaneous incubation with PGE2. Furthermore, PGE2 slightly but significantly reduced the CCK-8-induced efflux of 45Ca2+ from prelabeled acini. Intact acini and a membrane fraction bound [3H]PGE2 and this function could be equally competed by either unlabeled PGE2 or PGE1 in contrast to less-related prostaglandins such as PGF2 alpha, PGD2, and prostacyclin. We conclude that prostaglandins of the E type inhibit pancreatic enzyme secretion stimulated by various secretagogues. This function is mediated via specific receptors for PGE. With regard to CCK-8-stimulated secretion this function may be mediated by an inhibition of formation of inositol 1,4,5-trisphosphate.

Cholecystokinin at physiological levels evokes pancreatic enzyme secretion via a cholinergic pathway

1992 ◽  
Vol 263 (1) ◽  
pp. G102-G107 ◽  
Author(s):  
H. C. Soudah ◽  
Y. Lu ◽  
W. L. Hasler ◽  
C. Owyang
Keyword(s):  
Acetylcholine Release ◽  
Pancreatic Enzyme ◽  
Exocrine Secretion ◽  
Cholinergic Innervation ◽  
Enzyme Secretion ◽  
Healthy Humans ◽  
Cholinergic Pathway ◽  
Pancreatic Enzyme Secretion ◽  
Stimulation Of

The mechanism by which physiological concentrations of cholecystokinin (CCK) evoke pancreatic exocrine secretion in humans was investigated. CCK octapeptide (CCK-8) dose dependently increased trypsin and lipase output in healthy humans. Atropine inhibited CCK-8 (10 ng.kg-1.h-1)-stimulated trypsin output by 84.0 +/- 7.7% and lipase output by 78.6 +/- 9.2%. The inhibition with atropine was much less with a CCK-8 dose of 40 ng.kg-1.h-1 (41.8 +/- 6.6% for trypsin and 46.3 +/- 7.3% for lipase). CCK-8 at 10 ng.kg-1.h-1 produced plasma CCK levels similar to postprandial levels (6.0 +/- 1.3 vs. 6.9 +/- 0.8 pM), whereas the 40-ng.kg-1.h-1 dose produced supraphysiological levels (18.4 +/- 3.1 pM). To evaluate if CCK might act via stimulation of cholinergic nerves, in vitro studies were performed using rat pancreas. CCK-8 (10 nM-10 microM) stimulated [3H]acetylcholine release from pancreatic lobules that was blocked by tetrodotoxin, a calcium-free medium, and the CCK antagonist L364,718. In conclusion, CCK-stimulated pancreatic enzyme secretion is dependent on cholinergic neural and noncholinergic pathways. In humans, CCK infusions, which produce plasma CCK levels similar to those seen postprandially, stimulate the pancreas predominantly via a pathway dependent on cholinergic innervation. Correlative in vitro experiments suggest that CCK may act by stimulation of neural acetylcholine release. In contrast, supraphysiological CCK infusions act in part via noncholinergic pathways.

Postreceptor modulation of action of VIP and secretin on pancreatic enzyme secretion by secretagogues that mobilize cellular calcium

1982 ◽  
Vol 242 (4) ◽  
pp. G423-G428 ◽  
Author(s):  
M. J. Collen ◽  
V. E. Sutliff ◽  
G. Z. Pan ◽  
J. D. Gardner
Keyword(s):  
Vasoactive Intestinal Peptide ◽  
Pancreatic Enzyme ◽  
Enzyme Secretion ◽  
Secretory Process ◽  
Amylase Secretion ◽  
Pancreatic Acini ◽  
Rat Pancreas ◽  
Cellular Calcium ◽  
Twofold Increase ◽  
Pancreatic Enzyme Secretion

In dispersed acini from rat pancreas, secretagogues that act through or mimic the action of AMP [vasoactive intestinal peptide (VIP), secretin, or 8-bromo-AMP] caused a twofold increase in amylase secretion. Secretagogues that mobilize cellular calcium (carbamylcholine, C-terminal octapeptide of cholecystokinin, bombesin, or A23187) caused a sevenfold augmentation of the actions of VIP, secretin, or 8-bromo-cAMP on enzyme secretion. Carbamylcholine and the C-terminal octapeptide of cholecystokinin also augmented the action of VIP on amylase secretion from mouse pancreatic acini. Secretagogues that mobilize cellular calcium did not alter binding of 125I-VIP, cellular cAMP, or the increase in cellular cAMP caused by VIP or secretin. Similarly, secretagogues that increase cellular cAMP did not alter 45Ca outflux or the increase in 45Ca outflux caused by carbamylcholine, C-terminal octapeptide of cholecystokinin, bombesin, or A23187. These results indicate that in dispersed acini from rat pancreas there is postreceptor modulation of the actions of VIP and secretin on enzyme secretion by secretagogues that mobilize cellular calcium and that this modulation is a major determinant of the magnitude of the effect of VIP and secretin on enzyme secretion. This modulation, in turn, reflects the ability of cellular calcium, mobilized from intracellular stores, to amplify the action of cellular cAMP on the enzyme secretory process.

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