Imaging of quantal calcium release in the inositol 1,4,5-trisphosphate-sensitive organelles of permeabilized HSY cells.
The spatial characteristics of inositol 1,4,5-trisphosphate (IP3)-induced quantal Ca2+ release were examined by imaging Ca2+ concentrations within Ca2+ stores ([Ca2+]L) in permeabilized HSY cells. The image of mag-fura-2 fluorescent ratio with dual excitation (344 nm/360 nm) demonstrated that a sequential application of different concentrations of IP3 (0.1, 0.3, 10 microM) resulted in a stepwise decrease in the ratio at all regions of the cytoplasm. This change in the ratio suggests that the stepwise decrease in [Ca2+]L is associated with the quantal Ca2+ release. To monitor the change in [Ca2+]L within a single organelle, IP3-dependent changes in the mag-fura-red fluorescence of permeabilized cells were studied by confocal microscopy. Applications of increasing concentrations of IP3 caused a stepwise increase in fluorescence within ER-like reticulum structures of the cytoplasm. This finding suggests that the [Ca2+]L in a single Ca2+ store was not depleted by submaximal concentrations of IP3, and supports the steady-state model of quantal Ca2+ release.
Department of Dental Pharmacology, School of Dentistry, Health Sciences University of Hokkaido, Japan. tanimura@hoku-iryo-u.ac.jp
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Tanimura
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Tojyo
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Matsumoto
D000230:Adenocarcinoma; D001572:Benzofurans / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D002463:Cell Membrane Permeability; D003952:Diagnostic Imaging; D004305:Dose-Response Relationship, Drug; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism; D005456:Fluorescent Dyes / Q000378:metabolism; D016257:Fura-2 / Q000031:analogs & derivatives / Q000378:metabolism; D006801:Humans; D007093:Imidazoles / Q000378:metabolism; D015544:Inositol 1,4,5-Trisphosphate / Q000494:pharmacology*; D018613:Microscopy, Confocal; D015388:Organelles / Q000378:metabolism*; D012468:Salivary Gland Neoplasms; D012503:Saponins / Q000494:pharmacology; D014407:Tumor Cells, Cultured
D001572:Benzofurans; D005456:Fluorescent Dyes; D007093:Imidazoles; D012503:Saponins; C058776:2-(2-(5-carboxy)oxazole)-5-hydroxy-6-aminobenzofuran-N,N,O-triacetic acid; C082877:fura red; D015544:Inositol 1,4,5-Trisphosphate; D002118:Calcium; D016257:Fura-2