ENaC inhibition stimulates HCl secretion in the mouse cortical collecting duct. I. Stilbene-sensitive Cl⁻secretion

Abstract

Inhibition of the epithelial Na+ channel (ENaC) reduces Cl− absorption in cortical collecting ducts (CCDs) from aldosterone-treated rats and mice. Since ENaC does not transport Cl−, the purpose of the present study was to explore how ENaC modulates Cl− absorption in mouse CCDs perfused in vitro. Therefore, we measured transepithelial Cl− flux and transepithelial voltage in CCDs perfused in vitro taken from mice that consumed a NaCl-replete diet alone or the diet with aldosterone administered by minipump. We observed that application of an ENaC inhibitor [benzamil (3 μM)] to the luminal fluid unmasks conductive Cl− secretion. During ENaC blockade, this Cl− secretion fell with the application of a nonselective Cl− channel blocker [DIDS (100 μM)] to the perfusate. While single channel recordings of intercalated cell apical membranes in split-open CCDs demonstrated a Cl− channel with properties that resemble the ClC family of Cl− channels, ClC-5 is not the primary pathway for benzamil-sensitive Cl− flux. In conclusion, first, in CCDs from aldosterone-treated mice, most Cl− absorption is benzamil sensitive, and, second, benzamil application stimulates stilbene-sensitive conductive Cl− secretion, which occurs through a ClC-5-independent pathway.

Barttin Regulates the Subcellular Localization and Posttranslational Modification of Human Cl-/H+ Antiporter ClC-5

“…Because of the prominent effects of ClC-5 in the PT, the physiological role of this transporter in the TAL and ICCD seems to be underrated. However, expression of ClC-5 in these segments is well documented ( Günther et al, 1998 ; Luyckx et al, 1998 ; Devuyst, 1999 ; Sakamoto et al, 1999 ; Nanami et al, 2015 ; Ogawa et al, 2017 ; see Figure 1 ). Several studies demonstrate that this expression has a physiological impact.…”

“…Based on the homology between proteins of the CLC family, we hypothesized that barttin might be also able to regulate the function and localization of ClC-5. Remarkably, expression of ClC-5 has been detected not only in the PT, which is devoid of barttin, but also in kidney segments with significant barttin expression such as the thick ascending limb of the Henle’s loop (TAL), and in intercalated cells of the collecting duct (ICCD) ( Günther et al, 1998 ; Luyckx et al, 1998 ; Devuyst, 1999 ; Sakamoto et al, 1999 ; Nanami et al, 2015 ; Ogawa et al, 2017 ;Figure 1A ).…”

The role of pendrin in blood pressure regulation

“…As such, ENaC blockade must alter Cl Ϫ exchange or channel activity either by changing the release of a signaling molecule that regulates this transporter/channel or by modulating the driving force for Cl Ϫ movement mediated by another Cl Ϫ transport mechanism. While the Cl Ϫ transport mechanism targeted by ENaC inhibition is unknown, it does not appear to be mediated by pendrin, ClC-5, or CFTR (46,51,52). Amiloride-sensitive Cl Ϫ absorption may occur instead through paracellular Cl Ϫ transport or through transcellular Cl Ϫ transport mediated by an electrogenic Cl Ϫ exchanger or a Cl Ϫ channel.…”

Renal intercalated cells and blood pressure regulation

“…1 ), which is expressed on the apical plasma membrane and is upregulated in models of metabolic acidosis [ 24 , 25 ]. In the type A intercalated cell, this active H + secretion occurs in parallel with secretion of Cl − , although the mechanism for Cl − secretion is not well understood [ 26 – 29 ].…”

“…ENaC blockade changes Cl − transport or channel activity either through paracrine signaling or by altering the driving force of Cl − movement. While the mechanism by which ENaC inhibition changes Cl − transport is not known, recent studies have shown that it does not involve pendrin, ClC-5, or CFTR [ 5 , 26 , 48 ]. Amiloride-sensitive Cl − absorption may involve paracellular Cl − transport or transcellular transport mediated by an electrogenic Cl − exchanger.…”