Distal convoluted tubule Cl- concentration is modulated via K+ channels an transporters

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 ix:T. Basal measurements indicated that the mean [Cl-](i) was similar to 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.