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Micromolar and submicromolar Ca 2+ spikes regulating distinct cellular functions in pancreatic acinar cells
Author(s) -
Ito Koichi,
Miyashita Yasushi,
Kasai Haruo
Publication year - 1997
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1093/emboj/16.2.242
Subject(s) - exocytosis , biology , biophysics , intracellular , agonist , microbiology and biotechnology , secretion , biochemistry , receptor
Agonists induce Ca 2+ spikes, waves and oscillations initiating at a trigger zone in exocrine acinar cells via Ca 2+ release from intracellular Ca 2+ stores. Using a low affinity ratiometric Ca 2+ indicator dye, benzothiazole coumarin (BTC), we found that high concentrations of agonists transiently increased Ca 2+ concentrations to the micromolar range (>10 μM) in the trigger zone. Comparison with results obtained with a high affinity Ca 2+ indicator dye, fura‐2, indicated that fura‐2 was in fact saturated with Ca 2+ during the agonist‐induced Ca 2+ spikes in the trigger zone. We further revealed that the micromolar Ca 2+ spikes were necessary for inducing exocytosis of zymogen granules investigated using capacitance measurements. In contrast, submicromolar Ca 2+ spikes selectively gave rise to sequential activation of luminal and basal ion channels. These results suggest new functional diversity in Ca 2+ spikes and a critical role for the micromolar Ca 2+ spikes in exocytotic secretion from exocrine acinar cells. Our data also emphasize the value of investigating the Ca 2+ signalling using low affinity Ca 2+ indicators.