Palmer Lawrence G, Frindt Gustavo
Department of Physiology and Biophysics, Weill Medical College of Cornell University, New York, New York 10021, USA.
Curr Opin Nephrol Hypertens. 2007 Sep;16(5):477-83. doi: 10.1097/MNH.0b013e32820ac850.
The connecting tubule is emerging as a nephron segment critical to the regulation of Na+ and K+ excretion and the maintenance of homeostasis for these ions. The segment is difficult to study, however, and much of the available information we have concerning its functions is indirect. Here, we review the major transport mechanisms and transporters found in this segment and outline several unsolved problems in the field.
Recent electrophysiological and immunohistochemical measurements together with theoretical studies provide a more comprehensive view of ion transport in the connecting tubule. New signaling pathways governing Na+ and K+ transport have also been described.
Key questions about how Na+ and K+ transport are regulated remain unanswered. Is the connecting tubule the site of final regulation of both Na+ and K+ excretion? If so, how are the transport rates of these two ions independently controlled?
连接小管正成为肾单位中对钠和钾排泄调节以及这些离子内环境稳定维持至关重要的一个节段。然而，该节段难以研究，我们所掌握的关于其功能的大部分现有信息都是间接的。在此，我们综述该节段中发现的主要转运机制和转运体，并概述该领域几个未解决的问题。
近期的电生理学和免疫组织化学测量以及理论研究为连接小管中的离子转运提供了更全面的认识。还描述了调控钠和钾转运的新信号通路。
关于钠和钾转运如何被调节的关键问题仍未得到解答。连接小管是钠和钾排泄的最终调节部位吗？如果是，这两种离子的转运速率是如何独立控制的？
