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Published on: March 6, 2015
Nonionic diffusion of short-chain fatty acids across rat colon
A N Charney1, L Micic, R W Egnor
1Nephrology Section, Veterans Affairs Medical Center, New York University School of Medicine, New York 10010, USA.
The American Journal of Physiology
|April 8, 1998
Summary
Short-chain fatty acids (SCFAs) are primarily transported across the rat colon via nonionic diffusion. This study found that pH changes significantly influence SCFA transport, supporting diffusion as the main mechanism.
Area of Science:
- Gastroenterology
- Physiology
- Molecular Biology
Background:
- Short-chain fatty acids (SCFAs) play crucial roles in colon health.
- SCFA transport mechanisms across the colon epithelium are not fully understood.
- Potential transport pathways include nonionic diffusion and SCFA-/HCO3- exchange.
Purpose of the Study:
- To investigate the relative importance of nonionic diffusion versus SCFA-/HCO3- exchange in colonic SCFA transport.
- To elucidate the impact of pH gradients on SCFA fluxes in the rat colon.
Main Methods:
- Utilized Ussing chambers to study stripped segments of rat proximal and distal colon.
- Measured unidirectional fluxes of radiolabeled SCFAs (butyrate, propionate, isobutyrate).
- Manipulated extracellular pH, luminal Na+, luminal Cl-, and SCFA concentrations.
Main Results:
- Decreases in mucosal or serosal pH stimulated SCFA fluxes in a directional manner.
- SCFA transport was independent of luminal Na+ and ouabain.
- Luminal Cl- removal did not affect mucosal-to-serosal flux but reduced serosal-to-mucosal flux.
- SCFA flux increased linearly with SCFA concentration.
Conclusions:
- Nonionic diffusion is the predominant mechanism for SCFA transport across the rat colon.
- Extracellular pH gradients significantly influence SCFA transport rates.
- Apical membrane SCFA-/HCO3- exchange plays a minor role in SCFA absorption.
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