Oral Health Science Center, hrc7, Tokyo Dental College, Mihama-ku, Chiba 261-8502, Japan.
J Pharmacol Sci. 2010;112(2):223-30. doi: 10.1254/jphs.09267fp. Epub 2010 Jan 30.
Although the central role of ameloblasts in synthesis and resorption of enamel matrix proteins during amelogenesis is well documented, the Ca(2+)-transport/extrusion mechanism remains to be fully elucidated. To clarify Ca(2+)-transport in rat ameloblasts, we investigated expression and localization of Na(+)-Ca(2+) exchanger (NCX) isoforms and the functional characteristics of their ion transporting/pharmacological properties. RT-PCR and immunohistochemical analyses revealed expression of NCX1 and NCX3 in ameloblasts, localized in the apical membrane. In patch-clamp recordings, Ca(2+) efflux by Na(+)-Ca(2+) exchange showed dependence on external Na(+). Ca(2+) influx by Na(+)-Ca(2+) exchange, measured by fura-2 fluorescence, showed dependence on extracellular Ca(2+) concentration, and it was blocked by NCX inhibitors KB-R7943, SEA0400, and SN-6. These results showed significant expression of NCX1 and NCX3 in ameloblasts, indicating their involvement in the directional Ca(2+) extrusion pathway from cells to the enamel mineralizing front.
虽然成釉细胞在釉基质蛋白的合成和吸收过程中起核心作用已得到充分证实，但钙转运/外排机制仍有待充分阐明。为了阐明大鼠成釉细胞中的钙转运，我们研究了钠钙交换体（NCX）亚型的表达和定位及其离子转运/药理学特性的功能特征。RT-PCR 和免疫组织化学分析显示 NCX1 和 NCX3 在成釉细胞中表达，定位于顶膜。在膜片钳记录中，钠钙交换的钙外排依赖于细胞外的钠离子。通过荧光素-2 荧光测量的钠钙交换的钙内流依赖于细胞外钙离子浓度，并被 NCX 抑制剂 KB-R7943、SEA0400 和 SN-6 阻断。这些结果表明 NCX1 和 NCX3 在成釉细胞中有显著表达，表明它们参与了从细胞到釉质矿化前沿的定向钙外排途径。
