PERMEABILITY OF CELL JUNCTION DEPENDS ON LOCAL CYTOPLASMIC CALCIUM ACTIVITY
PERMEABILITY OF CELL JUNCTION DEPENDS ON LOCAL CYTOPLASMIC CALCIUM ACTIVITY
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DOI：
10.1038/254250a0
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发表时间：
1975-01-01
期刊：
影响因子：
64.8
通讯作者：
LOEWENSTEIN, WR
中科院分区：
文献类型：
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作者：
ROSE, B;LOEWENSTEIN, WR
许多种类的细胞通过由膜通道组成的连接处连接，一定大小范围的分子可以通过膜通道从一个细胞内部自由流动到另一个细胞内部。有人提出，连接通道的渗透性取决于细胞质中游离离子化钙的浓度（[Ca 2 +]i）（参考文献2）。这一假设得到了两类实验的支持。在一个例子中，耦合细胞系统的内部可以通过（非连接）膜上的一个孔与外部的已知[Ca 2 +]自由交换;当[Ca 2 +] i高于5-8 × 10− 5 M时，连接电导降低（解耦合）（参考文献3）。在另一类中，当（封闭）细胞系统用能量代谢抑制剂或Ca 2+离子载体5处理，或长时间暴露于无Ca、Mg培养基或Li培养基6时，解偶联增强;在这些条件下，由于细胞Ca代谢的已知特性，[Ca 2 +]i可能会升高7，8。在这里，我们展示了在这些条件下的三个耦合中的[Ca 2 +]itogether的变化，使用水母发光蛋白来显示细胞中的Ca 2+的分布。这将表明，解偶联，的确，在每一种情况下，与[Ca 2 +]的上升。此外，通过向细胞内局部注入Ca ~（2+），将表明当[Ca ~（2+）] i的升高发生在连接处时，解偶联增强，而当它发生在细胞的其它区域时，解偶联增强不明显。
MANY kinds of cells are coupled by junctions consisting of membrane channels through which molecules of a certain size range can flow freely from one cell interior to another1. It has been proposed that the permeability of the junctional channels depends on the concentration of free ionised calcium in cytoplasm ([Ca2+]i) (ref. 2). This hypothesis is supported by two classes of experiments. In one, the interior of a coupled cell system is allowed ito exchange freely with a known [Ca2+] in the exterior, through a hole in the (non-junctional) membrane; junctional conductance is reduced (uncoupling) when the [Ca2+]iis above 5–8 × 10−5M (ref. 3). In the other class, uncoupling ensues when the (closed) cell system is treated with inhibitors of energy metabolism or with Ca2+ionophores5, or on exposure for long periods to Ca,Mg-free medium or to Li medium6; in these conditions a rise in [Ca2+]i, may be expected because of known properties of cellular Ca metabolism7,8. Here, we demonstrate the changes in [Ca2+]itogether with those in coupling in three of these conditions, using aequorin to display the distribution of Ca2+in the cell. It will be shown that the uncoupling is, indeed, in each case associated with a rise in [Ca2+]. Furthermore, by local injection of Ca2+into the cells, it will be shown that uncoupling ensues when the rise in [Ca2+]ioccurs at the junction, but not when it occurs at other regions in the cell.