Mineralocorticoid Receptor Antagonists Cause Natriuresis in the Absence of Aldosterone
MR (mineralocorticoid receptor) antagonists are recommended for patients with resistant hypertension even when circulating aldosterone levels are not high. Although aldosterone activates MR to increase epithelial sodium channel (ENaC) activity, glucocorticoids also activate MR but are metabolized by...
Saved in:
Published in | Hypertension (Dallas, Tex. 1979) Vol. 79; no. 7; pp. 1423 - 1434 |
---|---|
Main Authors | , , , , , , , , |
Format | Journal Article |
Language | English |
Published |
United States
01.07.2022
|
Subjects | |
Online Access | Get full text |
Cover
Loading…
Summary: | MR (mineralocorticoid receptor) antagonists are recommended for patients with resistant hypertension even when circulating aldosterone levels are not high. Although aldosterone activates MR to increase epithelial sodium channel (ENaC) activity, glucocorticoids also activate MR but are metabolized by 11βHSD2 (11β-hydroxysteroid dehydrogenase type 2). 11βHSD2 is expressed at increasing levels from distal convoluted tubule (DCT) through collecting duct. Here, we hypothesized that MR maintains ENaC activity in the DCT2 and early connecting tubule in the absence of aldosterone.
We studied AS (aldosterone synthase)-deficient (AS
) mice, which were backcrossed onto the same C57BL6/J strain as kidney-specific MR knockout (KS-MR
) mice. KS-MR
mice were used to compare MR expression and ENaC localization and cleavage with AS
mice.
MR was highly expressed along DCT2 through the cortical collecting duct (CCD), whereas no 11βHSD2 expression was observed along DCT2. MR signal and apical ENaC localization were clearly reduced along both DCT2 and CCD in KS-MR
mice but were fully preserved along DCT2 and were partially reduced along CCD in AS
mice. Apical ENaC localization and ENaC currents were fully preserved along DCT2 in AS
mice and were not increased along CCD after low salt. AS
mice exhibited transient Na
wasting under low-salt diet, but administration of the MR antagonist eplerenone to AS
mice led to hyperkalemia and decreased body weight with higher Na
excretion, mimicking the phenotype of MR
mice.
Our results provide evidence that MR is activated in the absence of aldosterone along DCT2 and partially CCD, suggesting glucocorticoid binding to MR preserves sodium homeostasis along DCT2 in AS
mice. |
---|---|
ISSN: | 0194-911X 1524-4563 |
DOI: | 10.1161/hypertensionaha.122.19159 |