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Updated: Aug 10, 2026

Using Multi-fluorinated Bile Acids and In Vivo Magnetic Resonance Imaging to Measure Bile Acid Transport
Published on: November 27, 2016
Acid-base effects on intestinal Na(+) absorption and vesicular trafficking
Alan N Charney1, Richard W Egnor, Jesline Alexander-Chacko
1Nephrology Section, Veterans Affairs Medical Center, New York University School of Medicine, New York 10010, USA. alan.charney@med.va.gov
Vesicular trafficking is not involved in pH-stimulated ileal sodium (Na(+)) absorption. However, CO(2)-stimulated colonic Na(+) absorption relies on the trafficking of the Na(+)/H(+) exchanger (NHE) protein.
Area of Science:
- Physiology
- Cell Biology
- Gastroenterology
Background:
- The Na(+)/H(+) exchanger (NHE) plays a crucial role in regulating intracellular pH and sodium absorption in the gastrointestinal tract.
- Understanding the mechanisms of NHE regulation, particularly vesicular trafficking, is essential for comprehending intestinal electrolyte balance.
Purpose of the Study:
- To investigate the role of vesicular trafficking in pH-stimulated ileal sodium (Na(+)) absorption.
- To determine the involvement of vesicular trafficking in carbon dioxide (CO(2))-stimulated colonic Na(+) absorption.
Main Methods:
- Quantification of subapical vesicles using transmission electron microscopy.
- Assessment of membrane protein internalization via confocal microscopy and FITC-labeled apical membranes.
- Measurement of Na(+) absorption and Western blot analysis of NHE isoforms (NHE2 and NHE3) following specific stimuli.
Main Results:
- pH stimulation did not alter subapical vesicle number, NHE2/NHE3 abundance, or apical membrane fluorescence in ileal cells.
- Wortmannin, an inhibitor of vesicular trafficking, did not affect pH-stimulated ileal Na(+) absorption.
- Colonic NHE3 protein content increased with elevated PCO(2), and its trafficking (internalization/exocytosis) was modulated by changes in PCO(2).
Conclusions:
- Vesicular trafficking plays no role in pH-stimulated ileal Na(+) absorption.
- Vesicular trafficking is a critical mechanism for CO(2)-stimulated colonic Na(+) absorption, involving the regulation of NHE3.
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