Basolateral K-Cl cotransporter regulates colonic potassium absorption in potassium depletion
P Sangan1, S R Brill, S Sangan
1Departments of Internal Medicine and Cellular and Molecular Physiology, Yale University, New Haven, Connecticut 06520, USA.
The Journal of Biological Chemistry
|July 6, 2000
Summary
Dietary potassium depletion increases active potassium absorption in the rat colon by up-regulating both H,K-ATPase and K-Cl cotransporter 1 (KCC1) expression, suggesting coordinated regulation for enhanced nutrient uptake.
Area of Science:
- Physiology
- Molecular Biology
- Renal and Electrolyte Physiology
Background:
- Active potassium absorption in the rat distal colon is electroneutral and relies on apical H,K-ATPase.
- Dietary sodium and potassium depletion significantly enhance potassium absorption.
- Previous studies linked sodium depletion to H,K-ATPase alpha-subunit upregulation and potassium depletion to beta-subunit upregulation.
Purpose of the Study:
- To investigate the role of K-Cl cotransporter 1 (KCC1) in the rat distal colon.
- To determine if KCC1 expression is altered by dietary sodium or potassium depletion.
- To elucidate the coordinated mechanisms of active potassium absorption.
Main Methods:
- Northern blot analysis using rabbit kidney KCC1 cDNA probe to detect rat colon mRNA.
- Western blot analysis using KCC1-specific antibody to identify protein expression in basolateral membranes.
- Comparison of KCC1 expression under normal, sodium-depleted, and potassium-depleted dietary conditions.
Main Results:
- KCC1 mRNA was detected in the rat colon and significantly increased with potassium depletion, but not sodium depletion.
- A 155-kDa KCC1 protein was identified in the rat colonic basolateral membrane.
- Potassium depletion, but not sodium depletion, increased KCC1 protein expression in the basolateral membrane.
Conclusions:
- K-Cl cotransporter 1 (KCC1) is involved in transepithelial potassium absorption in the rat distal colon.
- KCC1 expression is regulated by dietary potassium levels, contributing to increased potassium absorption during depletion.
- Active potassium absorption involves coordinated regulation of apical H,K-ATPase and basolateral KCC1.
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