Distal convoluted tubule Cl<sup>−</sup>concentration is modulated via K<sup>+</sup>channels and transporters
Xiao‐Tong Su, Nathan J. Klett, Avika Sharma, Charles N. Allen, Wen-Hui Wang, Chao-Ling Yang, David H. Ellison
Abstract
Cl − -sensitive with-no-lysine kinase (WNK) plays a key role in regulating the thiazide-sensitive Na + -Cl − cotransporter (NCC) in the distal convoluted tubule (DCT). Cl − enters DCT cells through NCC and leaves the cell across the basolateral membrane via the Cl − channel ClC-K2 or K + -Cl − cotransporter (KCC). While KCC is electroneutral, Cl − exit via ClC-K2 is electrogenic. Therefore, an alteration in DCT basolateral K + channel activity is expected to influence Cl − movement across the basolateral membrane. Although a role for intracellular Cl − in the regulation of WNK and NCC has been established, intracellular Cl − concentrations ([Cl − ] i ) have not been directly measured in the mammalian DCT. Therefore, to measure [Cl − ] i in DCT cells, we generated a transgenic mouse model expressing an optogenetic kidney-specific Cl-Sensor and measured Cl − fluorescent imaging in the isolated DCT. Basal measurements indicated that the mean [Cl − ] i was ~7 mM. Stimulation of Cl − exit with low-Cl − hypotonic solutions decreased [Cl − ] i , whereas inhibition of KCC by DIOA or inhibition of ClC-K2 by NPPB increased [Cl − ] i , suggesting roles for both KCC and ClC-K2 in the modulation of [Cl − ] i . Blockade of basolateral K + channels (Kir4.1/5.1) with barium significantly increased [Cl − ] i . Finally, a decrease in extracellular K + concentration transiently decreased [Cl − ] i , whereas raising extracellular K + transiently increased [Cl − ] i , further suggesting a role for Kir4.1/5.1 in the regulation of [Cl − ] i . We conclude that the alteration in ClC-K2, KCC, and Kir4.1/5.1 activity influences [Cl − ] i in the DCT.