Hay-Schmidt Anders, Grunnet Morten, Abrahamse Salomon L, Knaus Hans-Günther, Klaerke Dan A
Department of Anatomy, The Panum Institute, University of Copenhagen, Blegdamsvej 3, 2200 Copenhagen N, Denmark.
Pflugers Arch. 2003 Apr;446(1):61-8. doi: 10.1007/s00424-002-0983-x. Epub 2003 Feb 15.
Big-conductance Ca(2+)-activated K(+) channels (BK channels) may play an important role in the regulation of epithelial salt and water transport, but little is known about the expression level and the precise localization of BK channels in epithelia. The aim of the present study was to quantify and localize the BK channels in the distal colon epithelium by iberiotoxin (IbTX) binding using the radiolabeled iberiotoxin analogue (125)I-IbTX-D19Y/Y36F, by autoradiography and by immunohistochemical studies. The results showed that the surface cells, responsible for Na(+) absorption, contained a high number of BK channels, whereas the abundance of the channels in the Cl(-)-secreting crypt cells was very low or absent. Surprisingly, the (125)I-IbTX-D19Y/Y36F binding and immunohistochemical studies showed expression of BK channels in the apical as well as in the basolateral membranes of the surface cells. In conclusion, the significant and distinct expression of BK channels in epithelia, combined with their strict regulation, indicate that these channels may play an important role in the overall regulation of salt and water transport.
大电导钙激活钾通道（BK通道）可能在上皮盐和水转运的调节中发挥重要作用，但关于BK通道在上皮中的表达水平和精确定位知之甚少。本研究的目的是通过使用放射性标记的埃博毒素类似物（125）I-埃博毒素-D19Y/Y36F、放射自显影和免疫组织化学研究，通过埃博毒素（IbTX）结合来定量和定位远端结肠上皮中的BK通道。结果表明，负责Na（+）吸收的表面细胞含有大量的BK通道，而Cl（-）分泌隐窝细胞中的通道丰度非常低或不存在。令人惊讶的是，（125）I-埃博毒素-D19Y/Y36F结合和免疫组织化学研究表明，表面细胞的顶端和基底外侧膜中均有BK通道表达。总之，BK通道在上皮中的显著且独特的表达，以及它们的严格调节，表明这些通道可能在盐和水转运的整体调节中发挥重要作用。
