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Thiazide-sensitive NaCl absorption in rat cortical collecting duct
1Laboratory of Kidney and Electrolyte Metabolism, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892.
The American Journal of Physiology
|September 1, 1990
Summary
This study reveals two key sodium (Na) and chloride (Cl) transport pathways in rat kidney collecting ducts. Amiloride-sensitive and thiazide-sensitive pathways contribute to Na absorption, with thiazide-sensitive transport also involving active Cl absorption.
Area of Science:
- Nephrology
- Renal Physiology
- Molecular Biology
Background:
- The cortical collecting duct (CCD) plays a crucial role in regulating kidney function and maintaining electrolyte balance.
- Understanding the mechanisms of sodium and chloride transport in the CCD is essential for comprehending renal physiology and treating related disorders.
Purpose of the Study:
- To elucidate the distinct pathways involved in transepithelial sodium (Na) and chloride (Cl) transport in the rat kidney's cortical collecting duct.
- To investigate the roles of specific inhibitors, such as hydrochlorothiazide and amiloride, in modulating these transport mechanisms.
Main Methods:
- Isolated perfused cortical collecting ducts from deoxycorticosterone-treated rats were utilized.
- The effects of hydrochlorothiazide, amiloride, and bumetanide on net Na absorption, Cl absorption, fluid absorption, and transepithelial voltage were measured.
Main Results:
- Hydrochlorothiazide significantly reduced Na and Cl absorption, indicating a thiazide-sensitive pathway.
- Amiloride abolished the lumen-negative voltage and partially inhibited Na absorption, suggesting an electrogenic pathway involving an apical Na channel.
- In the presence of amiloride, active Cl absorption was observed, pointing to a Na-Cl cotransport system.
Conclusions:
- Two parallel Na transport pathways exist in the CCD of mineralocorticoid-replete rats: an amiloride-sensitive electrogenic pathway and a thiazide-inhibitable electroneutral pathway.
- The thiazide-inhibitable pathway likely involves apical Na-Cl cotransport, mediating secondary active chloride transport.