Lopes A G, Amzel L M, Markakis D, Guggino W B
Department of Physiology, Johns Hopkins University, Baltimore, MD 21205.
Proc Natl Acad Sci U S A. 1988 Apr;85(8):2873-7. doi: 10.1073/pnas.85.8.2873.
Thin descending limb cells from Henle's loop (from the inner strip of the outer medulla of long loops) were studied with optical and video techniques to identify the mechanisms of ion transport and cell volume regulation. Increasing the K+ concentration in the basolateral solution from 5 to 90 mM caused the cells to swell. This K+-induced swelling was inhibited by exposure of the basolateral membrane to 9 mM Ba2+ and was abolished by removing Cl- from the perfusion solutions. Decreasing the perfusion osmolality caused an increase in cell volume followed by a return to the preexposure volume. The latter regulatory decrease in hypoosmolality was slowed by basolateral Ba2+ and the removal of HCO-3 from the solutions. Further slowing occurred when both HCO-3 and Cl- were removed. Exposure of cells to ouabain abolished volume regulation. These data suggest that the basolateral cell membrane of the thin descending limb has a Cl- -dependent K+ permeability, which is important in cell volume regulation. The cells also possess Cl- and HCO-3 transport pathways that participate in volume regulation. Finally, volume regulation is dependent upon the operation of the Na/K pump.
利用光学和视频技术研究了来自亨氏袢细降支（来自长袢外髓质内带）的细胞，以确定离子转运和细胞体积调节的机制。将基底外侧溶液中的K⁺浓度从5 mM增加到90 mM会导致细胞肿胀。这种K⁺诱导的肿胀可通过将基底外侧膜暴露于9 mM Ba²⁺而受到抑制，并通过从灌注溶液中去除Cl⁻而消除。降低灌注渗透压会导致细胞体积增加，随后恢复到暴露前的体积。基底外侧Ba²⁺以及从溶液中去除HCO₃⁻会减缓低渗状态下细胞体积的后期调节性减小。当同时去除HCO₃⁻和Cl⁻时，细胞体积减小进一步减缓。将细胞暴露于哇巴因会消除体积调节。这些数据表明，细降支的基底外侧细胞膜具有Cl⁻依赖性K⁺通透性，这在细胞体积调节中很重要。细胞还具有参与体积调节的Cl⁻和HCO₃⁻转运途径。最后，体积调节依赖于Na/K泵的运作。
