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Aldosterone reduces crypt colon permeability during low-sodium adaptation
M Moretó1, E Cristià, A Pérez-Bosque
1Departament de Fisiologia, Facultat de Farmàcia, Universitat de Barcelona, Barcelona, Spain. mmoreto@ub.edu
The Journal of Membrane Biology
|January 28, 2006
Summary
Aldosterone, not angiotensin II, enhances sodium absorption in rat colonic crypts. It reduces permeability and increases epithelial sodium channel (ENaC) expression, crucial for electrolyte balance.
Area of Science:
- Physiology
- Gastroenterology
- Endocrinology
Background:
- Colonic fluid and electrolyte absorption is vital for homeostasis.
- Aldosterone and angiotensin II are key hormones regulating sodium balance.
- Their specific roles in colonic crypt absorption require elucidation.
Purpose of the Study:
- To investigate the distinct roles of aldosterone and angiotensin II in regulating colonic crypt absorption.
- To determine the impact of these hormones on crypt permeability and sodium transport.
Main Methods:
- Used adrenalectomized (ADX) rats on high-NaCl (HS) and low-NaCl (LS) diets.
- Administered aldosterone or angiotensin II via osmotic mini-pumps.
- Measured extracellular Na+ concentration, crypt permeability to dextran, transepithelial electrical resistance (TER), and ENaC expression.
Main Results:
- Low-NaCl diet decreased crypt wall permeability and increased TER.
- Aldosterone administration in ADX rats reduced dextran permeability, increased TER, enhanced pericryptal Na+ accumulation, and upregulated ENaC expression.
- Angiotensin II infusion in ADX rats did not reverse aldosterone deprivation effects.
Conclusions:
- Aldosterone is the primary hormone responsible for increased Na+ absorption in colonic crypts.
- Aldosterone reduces paracellular and pericryptal sheath permeability.
- Aldosterone upregulates epithelial sodium channel (ENaC) expression in the colon.