Tanimura A, Tojyo Y, Matsumoto Y
Department of Dental Pharmacology, School of Dentistry, Health Sciences University of Hokkaido, Japan.
Cell Struct Funct. 1998 Jun;23(3):129-35. doi: 10.1247/csf.23.129.
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.
通过对通透的HSY细胞内钙库（[Ca2+]L）中的钙浓度进行成像，研究了1,4,5-三磷酸肌醇（IP3）诱导的量子化Ca2+释放的空间特征。双激发（344nm/360nm）下的mag-fura-2荧光比率图像显示，依次施加不同浓度的IP3（0.1、0.3、10μM）会导致细胞质所有区域的比率逐步下降。该比率的这种变化表明，[Ca2+]L的逐步下降与量子化Ca2+释放有关。为了监测单个细胞器内[Ca2+]L的变化，通过共聚焦显微镜研究了通透细胞中mag-fura-red荧光的IP3依赖性变化。增加IP3浓度的应用导致细胞质内质网样网状结构内的荧光逐步增加。这一发现表明，单个Ca2+库中的[Ca2+]L不会因亚最大浓度的IP3而耗尽，并支持量子化Ca2+释放的稳态模型。
