Swelling-induced Ca2+ release from intracellular calcium stores in rat submandibular gland acinar cells

K. Park, S. Lee, A. C. Elliott, J. S. Kim, J. H. Lee

    Research output: Contribution to journalArticlepeer-review

    Abstract

    The effects of osmotically-induced cell swelling on cytoplasmic free Ca2+ concentration ([Ca2+]i) were studied in acinar cells from rat submandibular gland using microspectrofluorimetry. Video-imaging techniques were also used to measure cell volume. Hypotonic stress (78% control tonicity) caused rapid cell swelling reaching a maximum relative volume of 1.78 ± 0.05 (n = 5) compared to control. This swelling was followed by regulatory volume decrease, since relative cell volume decreased significantly to 1.61 ± 0.08 (n = 5) after 10 min exposure to hypotonic medium. Osmotically induced cell swelling evoked by medium of either 78% or 66% tonicity caused a biphasic increase of [Ca2+]i. The rapid phase of this increase in [Ca2+]i was due to release of Ca2+ from intracellular stores, since it was also observed in cells bathed in Ca2+-free solution. The peak increase of [Ca2+]i induced by cell swelling was 3.40 ± 0.49 (Fura-2 F340/F380 fluorescence ratio, n = 11) and 3.17 ± 0.43 (n = 17) in the presence and the absence of extracellular Ca2+, respectively, corresponding to an absolute [Ca2+]i of around 1 μM. We found that around two-thirds of cells tested still showed some swelling-induced Ca2+ release (SICR) even after maximal concentrations (10-5 M-10-4 M) of carbachol had been applied to empty agonist-sensitive intracellular Ca2+ stores. This result was confirmed and extended using thapsigargin to deplete intracellular Ca2+ pools. Hypotonic shock still raised [Ca2+]i in cells pretreated with thapsigargin, confirming that at least some SICR occurred from agonist-insensitive stores. Furthermore, SICR was largely inhibited by pretreatment of cells with carbonyl cyanide m-cholorophenyl hydrazone (CCCP) or ruthenium red, inhibitors of mitochondrial Ca2+ uptake. Our results suggest that the increase in [Ca2+]i, which underlies regulatory volume decrease in submandibular acinar cells, results from release of Ca2+ from both agonist-sensitive and mitochondrial Ca2+ stores.
    Original languageEnglish
    Pages (from-to)165-176
    Number of pages11
    JournalJournal of Membrane Biology
    Volume186
    Issue number3
    DOIs
    Publication statusPublished - 1 Apr 2002

    Keywords

    • Ca2+
    • Ca2+ stores
    • Carbachol
    • Cell swelling
    • Regulatory volume decrease
    • Submandibular gland

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