Abstract
In the renal cortical collecting duct (CCD), mineralocorticoid hormones, like aldosterone, augment the abundance of Na/K-ATPase molecules. It has been postulated that this response involves an isoform switch of the Na/K-ATPase catalytic subunit, α, as the molecular basis for the differential regulation of mineralocorticoid-induced and constitutively expressed Na/K-ATPase pools. In opposition to this attractive hypothesis, three lines of independent evidence are presented which demonstrate that the CCD exclusively expresses the α1 form despite mineralocorticoid-mediated changes in functional Na/K pump density. First, aldosterone increased [3H]ouabain binding in CCD 2.5- fold without changing the ouabain dissociation constant. Second, an electrophysiological assay for pump activity revealed that aldosterone increased maximum Na/K pump current in parallel with the change in ouabain binding without altering the apparent sodium affinity. Third, Western blot analysis with α isoform-specific, antipeptide antibodies demonstrated that aldosterone exclusively increased the total chemical pool of the α1 form of the pump without inducing other α subunit isoforms. In summary, aldosterone increases the abundance of Na/K-ATPase molecules in the CCD which are pharmacologically, physiologically, and chemically indistinguishable from those that are normally expressed.
Original language | English (US) |
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Pages (from-to) | 23469-23476 |
Number of pages | 8 |
Journal | Journal of Biological Chemistry |
Volume | 268 |
Issue number | 31 |
State | Published - 1993 |
Externally published | Yes |
ASJC Scopus subject areas
- Biochemistry
- Molecular Biology
- Cell Biology