scholarly journals Spatial characterisation of ryanodine-induced calcium release in mouse pancreatic acinar cells

2003 ◽  
Vol 369 (3) ◽  
pp. 441-445 ◽  
Author(s):  
Michael C. ASHBY ◽  
Ole H. PETERSEN ◽  
Alexei V. TEPIKIN
Keyword(s):  
Experimental Data ◽  
Calcium Release ◽  
Ryanodine Receptors ◽  
Acinar Cells ◽  
Pancreatic Acinar Cells ◽  
Apical Region ◽  
Low Doses ◽  
Polarized Cells ◽  
Inositol 1,4,5 Trisphosphate ◽  
Increased Sensitivity

In pancreatic acinar cells, agonists evoke intracellular Ca2+ transients which are initiated in the apical region of these polarized cells. There are contradictory experimental data concerning Ca2+ release from ryanodine receptors (RyRs) in the apical region. In the present study, we have used low doses of ryanodine to open RyRs leading to the release of Ca2+ from intracellular stores. Ryanodine causes Ca2+ release that is initiated in the apical region of the cell but is dependent upon functional inositol 1,4,5-trisphosphate receptors (IP3Rs). These results suggests that co-ordinated release from co-localized RyRs and IP3Rs underlies the increased sensitivity of the apical region to initiation of intracellular Ca2+ transients.

scholarly journals Localized Ca2+ uncaging reveals polarized distribution of Ca2+-sensitive Ca2+ release sites

2002 ◽  
Vol 158 (2) ◽  
pp. 283-292 ◽  
Author(s):  
Michael C. Ashby ◽  
Madeleine Craske ◽  
Myoung Kyu Park ◽  
Oleg V. Gerasimenko ◽  
Robert D. Burgoyne ◽  
...  
Keyword(s):  
Ryanodine Receptors ◽  
Acinar Cells ◽  
Cell Types ◽  
Pancreatic Acinar Cells ◽  
Apical Region ◽  
Basal Region ◽  
Activation Pattern ◽  
Inositol Trisphosphate Receptors ◽  
Agonist Stimulation ◽  
Major Process

Ca2+-induced Ca2+ release (CICR) plays an important role in the generation of cytosolic Ca2+ signals in many cell types. However, it is inherently difficult to distinguish experimentally between the contributions of messenger-induced Ca2+ release and CICR. We have directly tested the CICR sensitivity of different regions of intact pancreatic acinar cells using local uncaging of caged Ca2+. In the apical region, local uncaging of Ca2+ was able to trigger a CICR wave, which propagated toward the base. CICR could not be triggered in the basal region, despite the known presence of ryanodine receptors. The triggering of CICR from the apical region was inhibited by a pharmacological block of ryanodine or inositol trisphosphate receptors, indicating that global signals require coordinated Ca2+ release. Subthreshold agonist stimulation increased the probability of triggering CICR by apical uncaging, and uncaging-induced CICR could activate long-lasting Ca2+ oscillations. However, with subthreshold stimulation, CICR could still not be initiated in the basal region. CICR is the major process responsible for global Ca2+ transients, and intracellular variations in sensitivity to CICR predetermine the activation pattern of Ca2+ waves.

Calcium release by cholecystokinin analogue OPE is IP3 dependent in single rat pancreatic acinar cells

1994 ◽  
Vol 267 (1) ◽  
pp. C220-C228 ◽  
Author(s):  
H. Y. Gaisano ◽  
D. Wong ◽  
L. Sheu ◽  
J. K. Foskett
Keyword(s):  
Molecular Weight ◽  
Low Molecular Weight Heparin ◽  
Calcium Release ◽  
Acinar Cells ◽  
Pancreatic Acinar Cells ◽  
Low Molecular Weight ◽  
Ip3 Receptor ◽  
Intact Cells ◽  
Inositol 1,4,5 Trisphosphate ◽  
Low Levels

Cholecystokinin (CCK) and carbachol raise intracellular Ca2+ concentration ([Ca2+]i) in pancreatic acinar cells by elevating inositol 1,4,5-trisphosphate (IP3). CCK analogues JMV-180 and OPE stimulate fully efficacious enzyme secretion and [Ca2+]i oscillations but release Ca2+ from intracellular stores by apparently IP3-independent mechanisms in permeabilized acinar cells. In the present study, we investigated whether OPE mobilizes Ca2+ from IP3-sensitive Ca2+ stores and whether IP3 mediates such responses in single intact cells. OPE and JMV-180 similarly elevated IP3 to low levels compared with those elicited by 10 nM CCK. Depletion of IP3-sensitive stores by elevation of intracellular IP3 using carbachol, microinjection of a nonmetabolizable IP3 analogue, or exposure to thapsigargin, in the absence of extracellular Ca2+, depleted the same Ca2+ stores that were sensitive to OPE. In converse experiments, OPE depleted carbachol- or thapsigargin-sensitive stores, indicating that carbachol-, thapsigargin-, IP3-, and OPE-sensitive Ca2+ stores overlap completely and that stores mobilized by OPE are IP3 sensitive. To determine whether IP3 mediates responses to OPE, cells were microinjected with low-molecular-weight heparin, a competitive inhibited the rise of [Ca2+]i in response to carbachol, OPE, or JMV-180, whereas de-N-sulfated heparin, an inactive heparin, was without effect. These results indicate that CCK analogues release Ca2+ from IP3-sensitive Ca2+ stores by mechanisms involving the IP3 receptor.

BILE SENSITIZES INOSITOL TRISPHOSPHATE AND RYANODINE RECEPTORS TO EXCESSIVE CALCIUM RELEASE IN MOUSE PANCREATIC ACINAR CELLS

Pancreas ◽  
2005 ◽  
Vol 31 (4) ◽  
pp. 457-458
Author(s):  
J A Murphy ◽  
D N Criddle ◽  
M G. T Raraty ◽  
J P Neoptolemos ◽  
A V Tepikin ◽  
...  
Keyword(s):  
Calcium Release ◽  
Inositol Trisphosphate ◽  
Ryanodine Receptors ◽  
Acinar Cells ◽  
Pancreatic Acinar Cells

Effect of intracellular pH on acetylcholine-induced Ca2+ waves in mouse pancreatic acinar cells

1998 ◽  
Vol 275 (3) ◽  
pp. C810-C817 ◽  
Author(s):  
Antonio González ◽  
Fatima Pfeiffer ◽  
Andreas Schmid ◽  
Irene Schulz
Keyword(s):  
Intracellular Ph ◽  
Acinar Cells ◽  
Propagation Rate ◽  
Spreading Speed ◽  
Pancreatic Acinar Cells ◽  
Acidic Ph ◽  
Basolateral Side ◽  
Inositol 1,4,5 Trisphosphate ◽  
The Relationship ◽  
Cytosolic Acidification

We have used fluo 3-loaded mouse pancreatic acinar cells to investigate the relationship between Ca2+ mobilization and intracellular pH (pHi). The Ca2+-mobilizing agonist ACh (500 nM) induced a Ca2+ release in the luminal cell pole followed by spreading of the Ca2+ signal toward the basolateral side with a mean speed of 16.1 ± 0.3 μm/s. In the presence of an acidic pHi, achieved by blockade of the Na+/H+exchanger or by incubation of the cells in a Na+-free buffer, a slower spreading of ACh-evoked Ca2+ waves was observed (7.2 ± 0.6 μm/s and 7.5 ± 0.3 μm/s, respectively). The effects of cytosolic acidification on the propagation rate of ACh-evoked Ca2+ waves were largely reversible and were not dependent on the presence of extracellular Ca2+. A reduction in the spreading speed of Ca2+ waves could also be observed by inhibition of the vacuolar H+-ATPase with bafilomycin A1 (11.1 ± 0.6 μm/s), which did not lead to cytosolic acidification. In contrast, inhibition of the endoplasmic reticulum Ca2+-ATPase by 2,5-di- tert-butylhydroquinone led to faster spreading of the ACh-evoked Ca2+ signals (25.6 ± 1.8 μm/s), which was also reduced by cytosolic acidification or treatment of the cells with bafilomycin A1. Cytosolic alkalinization had no effect on the spreading speed of the Ca2+ signals. The data suggest that the propagation rate of ACh-induced Ca2+ waves is decreased by inhibition of Ca2+ release from intracellular stores due to cytosolic acidification or to Ca2+ pool alkalinization and/or to a decrease in the proton gradient directed from the inositol 1,4,5-trisphosphate-sensitive Ca2+ pool to the cytosol.

scholarly journals Inositol 1,4,5-trisphosphate and inositol 1,3,4-trisphosphate formation in Ca2+-mobilizing-hormone-activated cells

1985 ◽  
Vol 232 (1) ◽  
pp. 237-243 ◽  
Author(s):  
G M Burgess ◽  
J S McKinney ◽  
R F Irvine ◽  
J W Putney
Keyword(s):  
Guinea Pig ◽  
Inositol Trisphosphate ◽  
Acinar Cells ◽  
Temporal Correlation ◽  
Dimethyl Sulphoxide ◽  
Pancreatic Acinar Cells ◽  
Hormone Stimulation ◽  
Inositol 1,4,5 Trisphosphate ◽  
Intracellular Messenger ◽  
Stimulation Of

The inositol trisphosphate liberated on stimulation of guinea-pig hepatocytes, pancreatic acinar cells and dimethyl sulphoxide-differentiated human myelomonocytic HL-60 leukaemia cells is composed of two isomers, the 1,4,5-trisphosphate and the 1,3,4-trisphosphate. Inositol 1,4,5-trisphosphate was released rapidly, with no measurable latency on hormone stimulation, and, consistent with its proposed role as an intracellular messenger for Ca2+ mobilization, there was good temporal correlation between its formation and Ca2+-mediated events in these tissues. There was a definite latency before an increase in the formation of inositol 1,3,4-trisphosphate could be detected. In all of these tissues, however, it formed a substantial proportion of the total inositol trisphosphate by 1 min of stimulation. In guinea-pig hepatocytes, where inositol trisphosphate increases for at least 30 min after hormone application, inositol 1,3,4-trisphosphate made up about 90% of the total inositol trisphosphate by 5-10 min. In pancreatic acinar cells, pretreatment with 20 mM-Li+ caused an increase in hormone-induced inositol trisphosphate accumulation. This increase was accounted for by a rise in inositol 1,3,4-trisphosphate; inositol 1,4,5-trisphosphate was unaffected. This finding is consistent with the observation that Li+ has no effect on Ca2+-mediated responses in these cells. The role, if any, of inositol 1,3,4-trisphosphate in cellular function is unknown.

scholarly journals Ca2+-sensitivity of inositol 1,4,5-trisphosphate-mediated Ca2+ release in permeabilized pancreatic acinar cells

1990 ◽  
Vol 265 (3) ◽  
pp. 681-687 ◽  
Author(s):  
P H G M Willems ◽  
M D De Jong ◽  
J J H H M De Pont ◽  
C H Van Os
Keyword(s):  
Acinar Cells ◽  
Inhibitory Effect ◽  
Feedback Mechanism ◽  
Pancreatic Acinar Cells ◽  
Release Mechanism ◽  
Concomitant Increase ◽  
Permeabilized Cells ◽  
Negative Feedback Mechanism ◽  
Inositol 1,4,5 Trisphosphate ◽  
Energy Dependent

Hormonal and phorbol ester pretreatment of pancreatic acinar cells markedly decreases the Ins(1,4,5)P3-induced release of actively stored Ca2+ [Willems, Van Den Broek, Van Os & De Pont (1989) J. Biol. Chem. 264, 9762-9767]. Inhibition occurred at an ambient free Ca2+ concentration of 0.1 microM, suggesting a receptor-mediated increase in Ca2(+)-sensitivity of the Ins(1,4,5)P3-operated Ca2+ channel. To test this hypothesis, the Ca2(+)-dependence of Ins(1,4,5)P3-induced Ca2+ release was investigated. In the presence of 0.2 microM free Ca2+, permeabilized cells accumulated 0.9 nmol of Ca2+/mg of acinar protein in an energy-dependent pool. Uptake into this pool increased 2.2- and 3.3-fold with 1.0 and 2.0 microM free Ca2+ respectively. At 0.2, 1.0 and 2.0 microM free Ca2+, Ins(1,4,5)P3 maximally released 0.53 (56%), 0.90 (44%) and 0.62 (20%) nmol of Ca2+/mg of acinar protein respectively. Corresponding half-maximal stimulatory Ins(1,4,5)P3 concentrations were calculated to be 0.5, 0.6 and 1.4 microM, suggesting that the affinity of Ins(1,4,5)P3 for its receptor decreases beyond 1.0 microM free Ca2+. The possibility that an inhibitory effect of sub-micromolar Ca2+ is being masked by the concomitant increase in size of the releasable store is excluded, since Ca2+ release from cells loaded in the presence of 0.1 or 0.2 microM free Ca2+ and stimulated at higher ambient free Ca2+ was not inhibited below 1.0 microM free Ca2+. At 2.0 and 10.0 microM free Ca2+, Ca2+, Ca2+ release was inhibited by approx. 30% and 75% respectively. The results presented show that hormonal pretreatment does not lead to an increase in Ca2(+)-sensitivity of the release mechanism. Such an increase in Ca2(+)-sensitivity to sub-micromolar Ca2+ is required to explain sub-micromolar oscillatory changes in cytosolic free Ca2+ by a Ca2(+)-dependent negative-feedback mechanism.

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