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Published on: August 9, 2014
Developmental changes in rabbit juxtamedullary proximal convoluted tubule acidification
1Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas 75235-9063.
Neonatal proximal convoluted tubules (PCT) show increased reliance on the Na+/H+ antiporter for proton secretion compared to adults. Maturation of PCT involves enhanced activity of the sodium-independent H+-ATPase.
Area of Science:
- Nephrology
- Physiology
- Cell Biology
Background:
- Apical proton secretion is crucial for proximal convoluted tubule (PCT) function.
- Understanding the maturation of proton transporters in the kidney is essential for pediatric nephrology.
Purpose of the Study:
- To investigate the developmental changes in apical proton secretion mechanisms in neonatal versus adult PCT.
- To differentiate the roles of the Na+/H+ antiporter and H+-ATPase in PCT acid-base homeostasis.
Main Methods:
- Utilized in vitro perfused neonatal and adult rat PCT.
- Monitored intracellular pH recovery from acid load using a pH-sensitive dye (BCECF).
- Assessed transporter activity by measuring pH recovery rates in the presence/absence of sodium and using specific inhibitors (N-ethylmaleimide, amiloride).
Main Results:
- Adult PCT exhibited significant sodium-dependent and sodium-independent pH recovery.
- Neonatal PCT showed predominantly sodium-dependent pH recovery, with limited sodium-independent activity.
- N-ethylmaleimide inhibited sodium-independent recovery in adults, implicating the H+-ATPase.
- Amiloride studies suggested a greater contribution of the Na+/H+ antiporter in neonatal PCT compared to adults.
Conclusions:
- The activity of the sodium-independent proton secretory mechanism, likely the H+-ATPase, increases during PCT maturation.
- Neonatal PCT relies more heavily on the Na+/H+ antiporter for apical proton secretion than adult PCT.
- These findings highlight developmental adaptations in renal acid-base transport mechanisms.
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