Related Experiment Video
Updated: Jun 14, 2026
09:04
DNBS/TNBS Colitis Models: Providing Insights Into Inflammatory Bowel Disease and Effects of Dietary Fat
Published on: February 27, 2014
Carbon dioxide affects rat colonic Na+ absorption by modulating vesicular traffic.
Alan N Charney1, Richard W Egnor, Nicholas Cassai
1Nephrology Section, Veterans Affairs Medical Center, New York University School of Medicine, New York, New York 10010, USA. alan.charney@med.va.gov
Gastroenterology
|February 8, 2002
Summary
Carbon dioxide (CO2) influences sodium (Na+) absorption in the colon by regulating the movement of the Na+/H+ exchanger NHE3 via endosome recycling. This process impacts vesicle trafficking to the apical membrane.
Area of Science:
- Physiology
- Cell Biology
- Gastroenterology
Background:
- Carbon dioxide (CO2) plays a role in regulating colonic sodium (Na+) absorption.
- The Na+/H+ exchanger NHE3 is a key protein involved in this process.
Purpose of the Study:
- To investigate how CO2 affects colonic Na+ absorption.
- To determine the role of endosome recycling of the Na+/H+ exchanger NHE3 in this process.
Main Methods:
- Rat distal colon segments were studied under various acid-base conditions.
- Transmission electron microscopy and immunocytochemistry were used to visualize and quantify NHE3 and vesicles.
- Confocal microscopy assessed endocytosis and vesicle movement.
- Ussing chamber experiments measured Na+ absorption with inhibitors.
Main Results:
- Subapical vesicle numbers inversely correlated with Na+ absorption and PCO2.
- NHE3 was localized to microvilli and vesicle membranes.
- CO2 stimulation altered NHE3 distribution from apical to subapical regions.
- Inhibitors confirmed NHE3's role in CO2-stimulated Na+ absorption and wortmannin affected vesicle movement.
Conclusions:
- CO2 modulates Na+ absorption in the rat distal colon.
- This modulation occurs partly through regulating the trafficking of NHE3-containing vesicles to the apical membrane.
Related Concept Videos
01:23Transcellular Transport of Solutes
Transcellular transport of solutes is the movement of substances like monosaccharides and amino acids through polarized cells. This transport mechanism is primarily seen in epithelial and endothelial cells aided by membrane transport proteins such as channels and transporters. The tight junctions between these cells confine the membrane proteins to the two sides of the cell. The epithelial cells have distinct apical and basolateral domains. In contrast, the endothelial cells show the luminal...
01:19Drug Absorption: Factors Affecting GI Absorption
The process of oral drug absorption can be influenced by several factors. Weakly acidic drugs tend to be absorbed more readily from the stomach due to their nonionized state. However, absorption may be less efficient in the upper intestine, where drugs are often ionized. Interestingly, despite the stomach's apparent advantage for drug absorption, its mucous layer can hinder diffusion. Its surface area is also smaller than the intestine's, which can further slow down the absorption rate.
In...
In...
01:23Factors Influencing Drug Absorption: Anatomical Parameters
Drug absorption involves the movement of drugs from the point of administration into the systemic circulation. Initially, Gastrointestinal (GI) motility propels the drug through the digestive tract and into the stomach. However, the stomach's high acidity and limited surface area restrict its role in drug absorption for most drugs. The drug then moves from the stomach to the small intestine via gastric emptying, which can be slowed by various factors, including interactions with other...
01:25Factors Influencing Drug Absorption: Disease States and Pharmacology
Multiple disease states can significantly influence the oral drug absorption process by affecting blood flow and the functionality of the gastrointestinal (GI) system. Various GI diseases, including conditions that alter GI motility, such as diarrhea, decreased acid secretions (achlorhydria), and infections, have been associated with reduced drug absorption.
Substances such as alcohol and specific drugs, including antineoplastics, can also negatively impact drug absorption. For instance,...
Substances such as alcohol and specific drugs, including antineoplastics, can also negatively impact drug absorption. For instance,...
01:16Methods for Studying Drug Absorption: In vitro
In vitro experiments are crucial for understanding the transport and absorption of drugs through biological materials. These studies employ varied methods such as the diffusion cell method, the everted sac technique, and the everted ring technique.
The diffusion cell method uses a two-compartment cell, including a donor compartment with the drug solution, which simulates the environment where the drug is applied, and a receptor compartment with a buffer solution, which simulates the environment...
The diffusion cell method uses a two-compartment cell, including a donor compartment with the drug solution, which simulates the environment where the drug is applied, and a receptor compartment with a buffer solution, which simulates the environment...
01:09Methods for Studying Drug Absorption: In situ
In situ experiments, such as the Doluisio method and Single-Pass Perfusion technique, provide critical insights into drug uptake by simulating in vivo conditions for drug absorption.
The Doluisio method involves perfusing a prepared segment of a rat's small intestine with a solution of radiolabeled drug and a non-absorbable marker. This helps to differentiate between absorbed and non-absorbed drug concentrations. The intestinal segment is connected at both ends using tubing and syringes,...
The Doluisio method involves perfusing a prepared segment of a rat's small intestine with a solution of radiolabeled drug and a non-absorbable marker. This helps to differentiate between absorbed and non-absorbed drug concentrations. The intestinal segment is connected at both ends using tubing and syringes,...