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Updated: Jul 13, 2026

Functional Assessment of Intestinal Tight Junction Barrier and Ion Permeability in Native Tissue by Ussing Chamber Technique
Published on: May 26, 2021
Developmental changes in proximal tubule NaCl transport
1Department of Pediatrics, U.T. Southwestern Medical Center, 5323 Harry Hines Blvd, Dallas, TX, 75235-9063, USA, Michael. Baum@UTSouthwestern.edu
Neonatal kidneys exhibit distinct sodium and chloride transport mechanisms compared to adults, with different protein isoforms influencing these crucial functions during development.
Area of Science:
- Nephrology
- Molecular Biology
- Physiology
Background:
- The proximal tubule is responsible for reabsorbing a significant portion of filtered NaCl.
- Active NaCl transport in adult proximal tubules involves Na+/H+ exchangers (NHE3) and Cl-/base exchangers.
- Passive chloride transport occurs via the paracellular pathway in adult proximal tubules.
Purpose of the Study:
- To investigate the unexpected differences in proximal tubule transport between neonatal and adult rats.
- To identify the molecular basis for developmental changes in sodium and chloride handling.
- To understand the role of specific protein isoforms in neonatal kidney function.
Main Methods:
- Analysis of Na+/H+ exchanger isoform expression (NHE3 and NHE8) in neonatal and adult rat kidneys.
- Assessment of chloride permeability in neonatal and adult proximal tubules.
- Examination of tight junction protein (claudin) expression during development.
Main Results:
- NHE3 is largely absent, while NHE8 is abundant in neonatal proximal tubules, contrasting with adult expression patterns.
- Neonatal proximal tubules show significantly reduced chloride permeability compared to adult tubules.
- Specific claudin isoforms (claudins 6 and 9) are highly expressed in neonatal kidneys, correlating with low chloride permeability, but are absent in adults.
Conclusions:
- Developmental changes in proximal tubule transport are driven by distinct expression patterns of sodium and chloride transporters.
- The expression of specific Na+/H+ exchanger isoforms (NHE8 vs. NHE3) and tight junction proteins (claudins 6 and 9) underlies the functional differences observed in neonatal and adult kidneys.
- These isoform switches are critical for adapting kidney function during postnatal development.
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