K+ and Rb+ transport by the rabbit CCD: Rb+ reduces K+ conductance and Na+ transport.
K+ and Rb+ transport by the rabbit CCD: Rb+ reduces K+ conductance and Na+ transport.
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兔子 CCD 的 K 和 Rb 传输：Rb 降低 K 电导和 Na 传输。
DOI：
10.1152/ajprenal.1989.257.1.f43
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发表时间：
1989
期刊：
影响因子：
--
通讯作者：
Stokes,JB
中科院分区：
文献类型：
--
作者：
Warden,DH;Hayashi,M;Schuster,VL;Stokes,JB
我们比较了K+和Rb+跨兔皮质集合管的转运，以了解K+分泌的机制。被动示踪剂通量，主动分泌率，电生理行为，和每个离子的能力，以支持Na+-K+-ATP酶活性进行了测定。当主动转运被阿米洛利抑制时，K+渗透性是Rb+渗透性的两倍。在5 mM Rb+取代5 mM K+的溶液中，跨上皮电导（GT）为一半。当4 mM Ba 2+加入到管腔中时，Rb+和K+的渗透性都下降到与预期的细胞旁扩散没有不同的值。Ba 2+诱导的K+和Rb+渗透性的变化之间的关系，并在同时测量的GT提供了强有力的证据表明，K+跨顶膜运输是很大程度上，如果不是唯一的，导电。我们还确定，净K+分泌大于净Rb+分泌（当每个都是丰富的离子）。这种差异的原因可能涉及K+分泌过程中的几个步骤，包括：1）与K+相比，Rb+存在时ATP酶活性降低（约80%），2）Na+吸收减少，3）顶端（可能还有基底外侧）K+传导的部分阻断。虽然K+和Rb+运输之间存在定量差异，但我们没有发现任何证据表明这些离子是通过不同的机制运输的。
We compared transport of K+ and Rb+ across the rabbit cortical collecting duct to gain insight into the mechanisms of K+ secretion. Passive tracer fluxes, active secretory rates, electrophysiological behavior, and the ability of each ion to support Na+-K+-ATPase activity were determined. When active transport was inhibited by amiloride, K+ permeability was twice the Rb+ permeability. Transepithelial conductance (GT) was half as great in solutions where 5 mM Rb+ replaced 5 mM K+. When 4 mM Ba2+ was added to the lumen, both Rb+ and K+ permeability fell to values not different from that expected for paracellular diffusion. The relationship between Ba2+-induced changes in the K+ and Rb+ permeabilities and in the simultaneously measured GT provides strong evidence that K+ transport across the apical membrane is largely, if not exclusively, conductive. We also determined that net K+ secretion is greater than net Rb+ secretion (when each is the abundant ion). The reasons for this difference probably involve several steps in the K+ secretory process and include the following: 1) reduced ATPase activity in the presence of Rb+ (approximately 80%) compared with K+, 2) reduction of Na+ absorption, and 3) partial blockade of the apical (and perhaps basolateral) K+ conductance. Although there were quantitative differences between K+ and Rb+ transport, we found no evidence suggesting that these ions are transported by different mechanisms.