Critical role of the mineralocorticoid receptor in aldosterone-dependent and aldosterone-independent regulation of ENaC in the distal nephron.

Details

Serval ID
serval:BIB_971F2AD35014
Type
Article: article from journal or magazin.
Collection
Publications
Institution
Title
Critical role of the mineralocorticoid receptor in aldosterone-dependent and aldosterone-independent regulation of ENaC in the distal nephron.
Journal
American journal of physiology. Renal physiology
Author(s)
Nesterov V., Bertog M., Canonica J., Hummler E., Coleman R., Welling P.A., Korbmacher C.
ISSN
1522-1466 (Electronic)
ISSN-L
1522-1466
Publication state
Published
Issued date
01/09/2021
Peer-reviewed
Oui
Volume
321
Number
3
Pages
F257-F268
Language
english
Notes
Publication types: Journal Article ; Research Support, Non-U.S. Gov't
Publication Status: ppublish
Abstract
The epithelial Na <sup>+</sup> channel (ENaC) constitutes the rate-limiting step for Na <sup>+</sup> absorption in the aldosterone-sensitive distal nephron (ASDN) comprising the late distal convoluted tubule (DCT2), connecting tubule (CNT), and collecting duct (CD). Previously, we demonstrated that ENaC activity in the DCT2/CNT transition zone is constitutively high and independent of aldosterone, in contrast to its aldosterone dependence in the late CNT/initial cortical CD (CCD). The mineralocorticoid receptor (MR) is expressed in the entire ASDN. Its activation by glucocorticoids is prevented through 11β-hydroxysteroid dehydrogenase 2 (11β-HSD2) abundantly expressed in the late but probably not early part of the ASDN. We hypothesized that ENaC function in the early part of the ASDN is aldosterone independent but may depend on MR activated by glucocorticoids due to low 11β-HSD2 abundance. To test this hypothesis, we used doxycycline-inducible nephron-specific MR-deficient [MR knockout (KO)] mice. Whole cell ENaC currents were investigated in isolated nephron fragments from the DCT2/CNT or CNT/CCD transition zones using the patch-clamp technique. ENaC activity was detectable in the CNT/CCD of control mice but absent or barely detectable in the majority of CNT/CCD preparations from MR KO mice. Importantly, ENaC currents in the DCT2/CNT were greatly reduced in MR KO mice compared with ENaC currents in the DCT2/CNT of control mice. Immunofluorescence for 11β-HSD2 was abundant in the CCD, less prominent in the CNT, and very low in the DCT2. We conclude that MR is critically important for maintaining aldosterone-independent ENaC activity in the DCT2/CNT. Aldosterone-independent MR activation is probably mediated by glucocorticoids due to low expression of 11β-HSD2.NEW & NOTEWORTHY Using a mouse model with inducible nephron-specific mineralocorticoid receptor (MR) deficiency, we demonstrated that MR is not only critical for maintaining aldosterone-dependent ENaC activity in CNT/CCD but also for aldosterone-independent ENaC activity in DCT2/CNT. Furthermore, we demonstrated that cells of this latter nephron segment express little 11β-HSD2, which probably allows glucocorticoids to stimulate MR, resulting in aldosterone-independent ENaC activity in DCT2/CNT. This site-specific ENaC regulation has physiologically relevant implications for renal sodium and potassium homeostasis.
Keywords
Aldosterone/metabolism, Aldosterone/pharmacokinetics, Animals, Epithelial Sodium Channels/metabolism, Kidney Tubules, Collecting/metabolism, Mice, Nephrons/metabolism, Potassium/metabolism, Receptors, Mineralocorticoid/drug effects, Receptors, Mineralocorticoid/metabolism, Sodium/metabolism, Sodium, Dietary/metabolism, 11β-hydroxysteroid dehydrogenase 2, aldosterone, aldosterone-sensitive distal nephron, epithelial Na+ channel, mineralocorticoid receptor
Pubmed
Web of science
Open Access
Yes
Create date
28/07/2021 11:28
Last modification date
23/01/2024 8:18
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