Effect of ionophore A23187 on cytosolic Ca2+ and enzyme secretion

1982 ◽  
Vol 243 (3) ◽  
pp. C196-C199 ◽  
Author(s):  
R. J. Stark ◽  
J. O'Doherty
Keyword(s):  
Cell Activation ◽  
Narrow Range ◽  
Acinar Cells ◽  
Enzyme Secretion ◽  
Free Calcium ◽  
Ionophore A23187 ◽  
Amylase Release ◽  
Intracellular Ca ◽  
The Mean

As the ionophore A23187 is believed to act by increasing cytosolic Ca2+ ([Ca]i), it offers a mechanism for experimentally controlling [Ca]i. Ca2+-selective microelectrodes were employed to examine the effect of A23187 on [Ca]i and the role of [Ca]i in acinar secretion. The mean [Ca]i in acinar cells of the mouse pancreas was determined to be 0.43 +/- 0.03 microM. When the ionophore was added to the saline bathing the acinar cells, 10(-6) M A23187 depolarized the membrane potential (Em) by 5.2 +/- 0.3 mM and the intracellular Ca-electrode potential (ECs) by 9.8 +/- 0.6 while 10(-5) M A23187 depolarized Em by 7.4 +/- 0.3 mV and ECs by 14.1 +/- 0.8. These changes in potentials reflect an increase in [Ca]i to 0.62 +/- 0.03 microM with 10(-6) M and 0.73 +/- 0.05 microM with 10(-5) M A23187. The increase in [Ca]i observed with 10(-6) M A23187 was similar to that found with concentrations of acetylcholine (Ach) that produced maximal enzyme secretion, whereas the increase in [Ca]i with 10(-5) M was similar in magnitude to that observed with ACh concentration that inhibited or reduced secretion. Measurements of amylase release during 30 min exposure of A23187 produced an 88.4% increase in amylase activity over basal levels with 10(-6) M and little or no change with (10(-5) M, indicating that the ionophore influences secretion through changes in [Ca]i in a manner analogous to the natural secretagogue ACh. This report establishes that acinar secretion occurs only within a narrow range of [Ca]i activities and suggests intracellular increases in both "bound" and "free" calcium may occur during cell activation.

Intracellular calcium levels in the Plasmodium berghei ookinete

Parasitology ◽  
2008 ◽  
Vol 135 (12) ◽  
pp. 1355-1362 ◽  
Author(s):  
I. SIDÉN-KIAMOS ◽  
C. LOUIS
Keyword(s):  
Intracellular Calcium ◽  
Plasmodium Berghei ◽  
Calcium Concentration ◽  
Insect Cells ◽  
Ionophore A23187 ◽  
Rodent Malaria Parasite ◽  
Calcium Indicators ◽  
Intracellular Ca

SUMMARYOokinetes are the motile and invasive stages of Plasmodium parasites in the mosquito host. Here we explore the role of intracellular Ca2+ in ookinete survival and motility as well as in the formation of oocysts in vitro in the rodent malaria parasite Plasmodium berghei. Treatment with the Ca2+ ionophore A23187 induced death of the parasite, an effect that could be prevented if the ookinetes were co-incubated with insect cells before incubation with the ionophore. Treatment with the intracellular calcium chelator BAPTA/AM resulted in increased formation of oocysts in vitro. Calcium imaging in the ookinete using fluorescent calcium indicators revealed that the purified ookinetes have an intracellular calcium concentration in the range of 100 nm. Intracellular calcium levels decreased substantially when the ookinetes were incubated with insect cells and their motility was concomitantly increased. Our results suggest a pleiotropic role for intracellular calcium in the ookinete.

Messenger role of calcium in function of pancreatic acinar cells

1980 ◽  
Vol 239 (5) ◽  
pp. G335-G347
Author(s):  
I. Schulz
Keyword(s):  
Plasma Membrane ◽  
Acinar Cells ◽  
Enzyme Secretion ◽  
Pancreatic Acinar Cells ◽  
Free Calcium ◽  
Plasma Membrane Permeability ◽  
Cyclic Monophosphate ◽  
Free Calcium Concentration ◽  
Cytosolic Free Calcium Concentration ◽  
Group D

Enzyme secretion from the exocrine pancreas is elicited by a) cholinergic stimulants, b) hormones belonging to the family of pancreozymin, c) some amphibian peptides such as bombesin, eledoisin, and physalaemin, and d) secretin and vasoactive intestinal polypeptide. Whereas the mechanism of the group d hormones in stimulating enzyme secretion involves adenosine 3',5'-cyclic monophosphate, the others seem to use a common pathway involving Ca2+ as intracellular messenger and probably guanosine 3',5'-cyclic monophosphate as modulator of their action. Their effects can be ascribed to two processes. One pathway involves release of Ca2+ from an intracellular store that is most likely located in the plasma membrane. This phase is independent of extracellular Ca2+ and leads to a rise of guanosine 3',5'-cyclic monophosphate. The other pathway is characterized by an increased permeability of the plasma membrane for Ca2+ and is necessary for sustained secretion. Both pathways lead to an increase cytosolic-free Ca2+ concentration. Ca2+ is either directly involved in fusion of zymogen granules with the luminal cell membrane or triggers events that lead to exocytosis. Furthermore, augmented cytosolic-free calcium concentration a) increased the plasma membrane permeability for Na+, Cl-, and K+, which leads to depolarization of the cell, and b) induces uncoupling of neighboring acinar cells.

scholarly journals Ca2+Signaling in B Cells

2010 ◽  
Vol 10 ◽  
pp. 2254-2264 ◽  
Author(s):  
Taras Lyubchenko
Keyword(s):  
B Cells ◽  
B Cell ◽  
Cell Activation ◽  
Molecular Mechanisms ◽  
B Cell Activation ◽  
B Cell Tolerance ◽  
Immune Synapse ◽  
Intracellular Ca ◽  
Dependent Protein

An increase in intracellular Ca2+concentration is one of the major initial steps in B-cell activation that occurs within minutes after antigen receptor (BCR) engagement. In recent years, significant advances have been made in characterizing molecular mechanisms of Ca2+signaling in lymphocytes, although the majority of work was done on T cells. This mini-review discusses several underexplored areas of Ca2+signaling in B cells: (1) Ca2+signaling in immune synapse and multifaceted Ca2+responses within a single cell, (2) source of Ca2+involved in Ca2+-dependent protein phosphorylation events and the role of store-operated influx, (3) role of BCR coreceptors in Ca2+signaling, and (4) Ca2+signaling and maintenance of B-cell tolerance and clinical significance of Ca2+signaling alterations.

Potentiation of carbachol-induced amylase release by propionate in guinea pig and vole pancreatic acini

1999 ◽  
Vol 277 (3) ◽  
pp. R767-R775
Author(s):  
Etsumori Harada ◽  
Megumi Mitani ◽  
Takashi Takeuchi
Keyword(s):  
Guinea Pig ◽  
Secretory Pathway ◽  
Direct Action ◽  
Camp Level ◽  
Amylase Secretion ◽  
Ionophore A23187 ◽  
Camp Content ◽  
Amylase Release ◽  
Pancreatic Acini ◽  
Intracellular Ca

The action of propionate, one of the major end products of microbial fermentation in herbivores was investigated in isolated, perifused pancreatic acini of guinea pigs, voles, and mice. With the use of guinea pig acini, 100 μM propionate had no effect, whereas 300 and 600 μM increased amylase release by six- and ninefold, respectively. Simultaneous perifusion of carbachol (CCh) 10 μM plus propionate 100 μM in guinea pig acini produced a potentiated secretory response that was 130% higher than the summated value obtained with CCh and propionate alone. The potentiation by propionate (100 μM) of CCh (10 μM)-induced amylase release was also obtained in vole pancreatic acini, but the mouse pancreatic preparation did not exhibit a similar potentiation. In contrast to CCh, propionate (100–600 μM) alone had no significant effect on intracellular Ca2+ concentration ([Ca2+]i) and did not alter [Ca2+]ielicited by CCh. Ca ionophore A23187 (5 μM)-induced amylase release in guinea pig acini was enhanced twofold by the addition of propionate. Cellular cAMP content was increased slightly by propionate, but did not alter dose dependently. The cAMP level with combinations of CCh and propionate was almost same as that with CCh alone and propionate alone. Staurosporine did not modify amylase secretion induced by a combination of CCh and propionate. These results suggest that propionate, in addition to a direct action on amylase release, potentiates CCh-induced amylase release in guinea pig and vole acini via a secretory pathway not associated with an increase in [Ca2+]iand cellular cAMP.

scholarly journals Regulation of macrophage lysosomal enzyme secretion: role of arachidonate metabolites, divalent cations and cyclic AMP

1980 ◽  
Vol 44 (1) ◽  
pp. 299-315
Author(s):  
R.M. McMillan ◽  
D.E. Macintyre ◽  
J.E. Beesley ◽  
J.L. Gordon
Keyword(s):  
Cyclic Amp ◽  
Lysosomal Enzyme ◽  
Lysosomal Enzymes ◽  
Divalent Cations ◽  
Cell Types ◽  
Enzyme Secretion ◽  
Ionophore A23187 ◽  
Enzyme Release ◽  
Arachidonate Metabolites

We have investigated the role in macrophage lysosomal enzyme release of arachidonate metabolites, extracellular divalent cations and cyclic AMP (cAMP) which modulate secretion in other cell types. Lysosomal enzyme secretion induced by zymosan was accompanied by release of malondialdehyde (MDA), which is derived from arachidonic acid via prostaglandin synthase. Blockade of MDA formation, by aspirin or indomethacin, was associated with only a small inhibitory effect on lysosomal enzyme release by zymosan: arachidonate metabolites thus play only a minor role in mediating macrophage lysosomal enzyme release. Zymosan-induced secretion of lysosomal enzymes from macrophages did not require extracellular magnesium or calcium although release was enhanced by magnesium and inhibited by calcium. These effects may be related to an influence of the ions on phagocytosis. Elevation of intracellular divalent cation concentrations, by ionophore A23187, induced release of lysosomal enzymes but this was a result of cell lysis. Adenylate cyclase stimulants and dibutyryl cAMP produced slight inhibition of zymosan-induced lysosomal enzyme release. Aminophylline and papaverine caused more marked inhibition but their effects may be due to actions independent of phosphodiesterase inhibition. Our data indicate that arachidonate metabolites and cAMP do not play a major role in regulating zymosan-induced enzyme release from macrophages. Extracellular calcium and magnesium may modulate secretion but the role of intracellular divalent cations remains to be established. We conclude that macrophage lysosomal enzyme secretion is controlled by regulatory mechanisms different from those which control similar degranulation processes in other cell types.

Role of tobacco vs alcohol, in intracellular calcium levels and enzyme secretion in pancreatic acinar cells

Pancreatology ◽  
2013 ◽  
Vol 13 (4) ◽  
pp. e14-e15
Author(s):  
M. Luaces-Regueira ◽  
M. Castiñeira-Alvariño ◽  
M. Castro-Manzanares ◽  
A. Carrascal-Miniño ◽  
M. Campos-Toimil ◽  
...  
Keyword(s):  
Intracellular Calcium ◽  
Acinar Cells ◽  
Enzyme Secretion ◽  
Pancreatic Acinar Cells

Relation between free cytosolic calcium and amylase release by pancreatic acini

1985 ◽  
Vol 249 (3) ◽  
pp. G389-G398 ◽  
Author(s):  
D. L. Ochs ◽  
J. I. Korenbrot ◽  
J. A. Williams
Keyword(s):  
Acinar Cells ◽  
Cytosolic Calcium ◽  
Pancreatic Acinar Cells ◽  
Amylase Release ◽  
Pancreatic Acini ◽  
Intracellular Ca ◽  
Free Media ◽  
Induced Changes ◽  
Stoichiometric Relation ◽  
Stimulation Of

Pancreatic acini were loaded with the Ca-selective fluorescent indicator quin-2 by incubation with its acetyoxymethyl ester. Loading acini with 844 +/- 133 microM quin-2 altered neither their ultrastructure nor their viability. The rate of amylase release from quin-2-loaded acini in response to the secretagogue carbachol, however, was significantly smaller than that of control acini. Studies in which acini were loaded with both quin-2 and a similar Ca-chelating compound, BAPTA, indicated that this reduced amylase release was related to the Ca buffering properties of quin-2. The concentration of free intracellular Ca calculated from the fluorescence of quin-2 was 90 +/- 18 nM. Stimulation by carbachol of acini suspended in media containing 1.25 mM Ca caused a rapid, transient enhancement of this value. After stimulation amylase release, the onset of the rise in free cytosolic Ca levels was observed in 1.1 +/- 0.1 s following the addition of agonist, and peak Ca levels (545 +/- 112 nM) were obtained within 5.3 +/- 0.3 s. For concentrations of carbachol less than or equal to 10(-6) M, a stoichiometric relation was found between stimulated amylase release and the peak concentration of free cytosolic Ca achieved. At higher concentrations of carbachol, however, the peak free cytosolic Ca remained constant while amylase release declined. The latency of the rise in intracellular Ca following stimulation of acini suspended in Ca-free media was not different from that observed for acini suspended in normal media, but the rise time was significantly prolonged. In the presence of extracellular Ca, the intracellular level of Ca remained elevated 2.8-fold above basal levels for at least 15 min following stimulation with 10(-6) M carbachol, whereas it had returned to near resting levels by 15 min when either 3 X 10(-7) or 3 X 10(-5) M carbachol was the stimulus. The Ca ionophore ionomycin (10–6 M) induced changes in the level of free cytosolic Ca similar to those caused by 10(-6) M carbachol. Ionomycin, however, stimulated only approximately one-third as much amylase release. These data suggest that factors in addition to changes in free cytosolic Ca may be important in regulating enzyme secretion by pancreatic acinar cells.

Effects of ions on amylase release by dissociated pancreatic acinar cells

1976 ◽  
Vol 231 (5) ◽  
pp. 1562-1567 ◽  
Author(s):  
JA Williams ◽  
P Cary ◽  
B Moffat
Keyword(s):  
Guinea Pig ◽  
Calcium Ionophore ◽  
Acinar Cells ◽  
Calcium Ionophore A23187 ◽  
Pancreatic Acinar Cells ◽  
Ionophore A23187 ◽  
Ion Content ◽  
Bathing Medium ◽  
Amylase Release ◽  
Mouse Cells

Dissociated acinar cells prepared from guinea pig and mouse pancreas were intact on the basis of structure, ion content, and their ability to increase release of amylase in response to bethanechol and the calcium ionophore A23187. Guinea pig but not mouse acinar cells increased amylase release in response to caerulein. An increase in the concentration of K+ in the medium, which increases amylase release from whole pancreas, did not increase release. The effect of varying the ionic content of the medium on basal and stimulated amylase release was studied. Bethanechol and caerulein were still able to stimulate amylase release when Ca2+ was omitted from the medium, whereas stimulation induced by A23187 was abolished. Elevation of the concentration of Mg2+ did not affect basal or stimulated amylase release. Removal of Na+ from the medium initially had no effect on amylase release although bethanechol-stimulated release by mouse cells was inion of the HCO3- or Cl- content of the medium did not affect cholinergic stimulation of secretion. It is concluded that stimulated amylase release by isolated acinar cells is relatively independent of the ionic constituency of the bathing medium.

scholarly journals Calcium metabolism and amylase release in rat parotid acinar cells

1976 ◽  
Vol 160 (3) ◽  
pp. 547-564 ◽  
Author(s):  
P Kanagasuntheram ◽  
P J Randle
Keyword(s):  
Cyclic Amp ◽  
Molecular Mechanisms ◽  
Acinar Cells ◽  
Ionophore A23187 ◽  
Free Medium ◽  
Dibutyryl Cyclic Amp ◽  
Trypan Blue Exclusion ◽  
Amylase Release ◽  
Parotid Acinar Cells ◽  
Rat Parotid

1. A method is described for the isolation of rat parotid acinar cells by controlled digestion of the gland with trypsin followed by collagenase. As judged by Trypan Blue exclusion, electron microscopy, water, electrolyte and ATP concentrations and release of amylase and lactate dehydrogenase, the cells are morphologically and functionally intact. 2. A method was developed for perifusion of acinar cells by embedding them in Sephadex G-10. Release of amylase was stimulated by adrenaline (0.1-10μM), isoproternol (1 or 10 μM), phenylephrine (1 μM), carbamoylcholine (0.1 or 1 μM), dibutyryl cycle AMP (2 MM), 3-isobutyl-1-methylxanthine (1mM) and ionophore A23187. The effects of phenylephrine, carbamoylcholine and ionophore A23187 required extracellular Ca2+, whereas the effects of adrenaline and isoproterenol did not. 3. The incorporation of 45Ca into parotid cells showed a rapidly equilibrating pool (1-2 min) corresponding to 15% of total Ca2+ and a slowly equilibrating pool (> 3h) of probably a similar dimension. Cholinergic and α-adrenergic effectors and ionophore A23187 and 2,4-dinitrophenol increased the rate of incorporation of 45Ca into a slowly equilibrating pool, whereas β-adrenergic effectors and dibutyryl cyclic AMP were inactive. 4. The efflux of 45Ca from cells into Ca2+-free medium was inhibited by phenylephrine and carbamoylcholine and accelerated by isoproterenol, adrenaline (β-adrenergic effect), dibutyryl cyclic AMP and ionophore A23187. 5. A method was developed for the measurement of exchangeable 45Ca in mitochondria in parotid pieces. Incorporation of 45Ca into mitochondria was decreased by isoproterenol, dibutyryl cyclic AMP or 2,4-dinitrophenol, increased by adrenaline, and not changed significantly by phenylephrine or carbamoylcholine. Release of 45Ca from mitochondria in parotid pieced incubated in a Ca2+-free medium was increased by isoproterenol, adrenaline, dibutyryl cyclic AMP or 2,4-dinitrophenol and unaffected by phenylephrine or carbamoylcholine. 6. These findings are compatible with a role for Ca2+ as a mediator of amylase-secretory responses in rat parotid acinar cells, but no definite conclusions about its role can be drawn in the absence of knowledge of the molecular mechanisms involved, their location, and free Ca2+ concentration in appropriate cell compartment(s).

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