CALCIUM-TRANSPORT DURING MINERALIZATION
CALCIUM-TRANSPORT DURING MINERALIZATION
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DOI：
10.1002/ar.1092240212
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发表时间：
1989-06-01
影响因子：
--
通讯作者：
BAWDEN, JW
中科院分区：
文献类型：
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作者：
BAWDEN, JW
在硬组织形成过程中，钙从细胞外液室转运到矿化基质的机制尚不清楚。钙离子的移动通常有两种方式：(1)通过细胞周围空间的扩散，或(2)跨细胞运输。骨水泥和骨是难以研究的组织，对其机制知之甚少。牙本质为研究提供了一定的优势，并且钙进入矿化基质是通过跨细胞运输的。关于运输机制的信息很少。牙釉质更容易被发现。在釉质形成的各个阶段，成釉细胞层中明显存在与钙紧密相连的细胞间连接，这表明钙的运动是通过细胞间运输发生的。根据已发表的研究结果，可以提出关于跨细胞转运机制的假设。有人提出，在没有钙结合蛋白直接参与的情况下，通过分泌性成釉细胞进行相对低水平的钙运输。在成熟阶段，当钙流入基质大大增加时，钙结合蛋白（9kd）出现并促进运输，同时防止胞质游离钙离子浓度的非生理性增加。细胞外液和牙釉质基质液钙离子浓度的差异似乎对钙跨近端细胞膜的流入和跨远端细胞膜的流出至关重要。
The translocation of calcium from the extracellular fluid compartment into the mineralizing matrix during hard tissue formation is not well understood. There are two general means by which such calcium movement may occur: (1) diffusion through the pericellular space, or (2) transcellular transport. Cementum and bone are difficult tissues in which to study the system and little is known about the mechanisms involved. Dentin offers certain advantages for study and it appears that calcium movement into the mineralizing matrix is by trans‐cellular transport. Information concerning the transport mechanism is meager. Enamel is more easily explored. The apparent existence of intercellular junctions tight to calcium in the ameloblast layer at all stages of enamel formation indicates that calcium movement occurs by transcellular transport. Based on published findings, a hypothesis concerning mechanisms of transcellular transport may be advanced. It is proposed that the relatively low level of calcium transport through secretory ameloblasts occurs without direct involvement of a calcium binding protein. During the maturation stage, when calcium influx to the matrix is greatly increased, a calcium binding protein (9 kd) appears and facilitates transport while preventing unphysiologic increases in the cytosolic free calcium ion concentration. Differences in the calcium ion concentrations of extracellular fluid and enamel matrix fluid appear to be critical to the influx of calcium across the proximal cell membrane and the efflux of calcium across the distal cell membrane.