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Developmental expression of ROMK in rat kidney
1Department of Pediatrics, Albert Einstein College of Medicine, Bronx New York 10461, USA.
The American Journal of Physiology
|June 11, 1999
Summary
Postnatal increases in renal potassium (SK) and sodium (ENaC) channel activity are linked to higher levels of ROMK and ENaC proteins in developing rat kidneys. This study tracks ROMK and ENaC expression during kidney maturation.
Area of Science:
- Nephrology
- Molecular Biology
- Physiology
Background:
- The apical secretory K+ (SK) channel in principal cells is crucial for K+ secretion in the cortical collecting duct (CCD).
- SK channel activity increases postnatally, following enhanced epithelial Na+ channel (ENaC) activity.
Purpose of the Study:
- To investigate the developmental expression of ROMK (Renal Outer Medullary Potassium channel), the molecular basis of the SK channel.
- To correlate postnatal increases in SK and ENaC channel activity with the expression of ROMK and ENaC subunit proteins in the developing rat kidney.
Main Methods:
- Used gene-specific probes to assess ROMK mRNA abundance.
- Employed ROMK-specific antibodies for nephron distribution and localization studies.
- Utilized antibodies for aquaporin-3 (AQP-3), Tamm-Horsfall protein (THP), and Dolichos biflorus agglutinin (DBA) for cell-specific identification.
- Performed immunoblot analysis for protein quantification.
- Examined alpha, beta, and gamma-ENaC subunit expression via immunolocalization.
Main Results:
- Demonstrated a developmental increase in renal ROMK mRNA and protein abundance.
- Showed ROMK expression along apical membranes of principal cells and thick ascending limbs of Henle (TALH).
- Identified ROMK in medullary TALH and collecting ducts by 1 week, and in CNTs and CCDs by 3 weeks postnatally.
- Observed a developmental increase in a ~40-kDa ROMK protein band.
- Found apical staining for alpha-ENaC in distal nephron segments after the first week.
- Detected beta- and gamma-ENaC subunits, with gamma-ENaC showing some apical polarization.
Conclusions:
- Postnatal increases in principal cell apical SK and Na+ channel activity are partly mediated by increased abundance of ROMK and ENaC subunit proteins.
- ROMK mRNA and protein expression increases during kidney development, correlating with functional channel maturation.
- ENaC subunit expression and localization also change postnatally, contributing to enhanced sodium transport.