Related Experiment Video
Updated: Aug 2, 2026

11:27
Methods to Study Epithelial Transport Protein Function and Expression in Native Intestine and Caco-2 Cells Grown in 3D
Published on: March 16, 2017
Uptake pathways for amino acids in mouse intestine
The American Journal of Physiology
|October 1, 1986
Summary
This study identifies multiple amino acid (AA) uptake pathways in mouse jejunum, revealing distinct Na+-dependent and Na+-independent systems for various AAs. These findings enhance our understanding of nutrient absorption mechanisms.
Area of Science:
- Physiology
- Gastroenterology
- Molecular Biology
Background:
- Understanding amino acid (AA) transport is crucial for nutrient absorption.
- Previous research has indicated complex transport mechanisms in the intestine.
- Characterizing specific AA uptake pathways in the mouse jejunum remains an active area of investigation.
Purpose of the Study:
- To characterize the amino acid (AA) uptake pathways in an everted-sleeve preparation of mouse jejunum.
- To determine the kinetic properties and identify distinct transport systems for various AAs.
- To compare AA uptake mechanisms across different species.
Main Methods:
- Utilized an everted-sleeve preparation of mouse jejunum for in vitro studies.
- Measured amino acid (AA) uptake over time and at varying concentrations.
- Employed kinetic analysis (saturable kinetics, Km values) and cross-inhibition studies to differentiate transport pathways.
Main Results:
- Amino acid (AA) uptake showed linear kinetics initially, becoming saturable at higher concentrations (Km 1-4 mM).
- Distinct uptake plateau behaviors were observed for different AAs, suggesting multiple transport systems.
- Na+-dependent transport was significant, averaging 83% at low concentrations and 54% at high concentrations, with evidence for at least five or six distinct AA uptake pathways.
Conclusions:
- Mouse jejunum possesses multiple, distinct amino acid (AA) uptake pathways, including Na+-dependent systems for acidic, basic, neutral, and imino AAs, and Na+-independent systems.
- Cross-inhibition studies suggest shared and specific pathways for different AA classes.
- These findings provide detailed insights into intestinal AA transport and highlight interspecies similarities and differences.
More Related Videos
Related Concept Videos
Glucose Absorption Into the Small Intestine
Complex carbohydrates consumed cannot be absorbed into the small intestine in their original form. First, they must be hydrolyzed to a monosaccharide form such as glucose or galactose. These monosaccharides are then transported across the intestinal membrane and into the blood via transcellular transport. The intestinal epithelial cells allow the movement of these monosaccharides with a defined 'entry' through membrane transporter proteins present on their apical membrane and 'exit' via the...
Protein Absorption
Proteins in the gastrointestinal tract typically come from food, but they can also originate from disintegrated cells or secreted enzymes. In the stomach, the enzyme pepsin breaks down these proteins into polypeptides. The fragments then move into the duodenum as a semi-fluid mass called chyme. Pancreatic proteases, such as trypsin and chymotrypsin, and intestinal brush border enzymes like carboxypeptidases further dismantle the polypeptides into tripeptides, dipeptides, and free amino acids.
Carrier-Mediated Transport
Carrier-mediated transport is a pivotal process in drug absorption, particularly for lipid-insoluble drugs, and encompasses facilitated diffusion and active transport. Facilitated diffusion allows drugs to move along their concentration gradient without energy expenditure, while active transport utilizes ATP to drive drug movement against this gradient.
Active transport involves two types of membrane-spanning transporters: uptake and efflux. Uptake transporters are expressed in the small...
Active transport involves two types of membrane-spanning transporters: uptake and efflux. Uptake transporters are expressed in the small...
Methods 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,...
Absorption of Nutrients
Absorption refers to taking dietary nutrients from the intestinal lumen for transportation throughout the body. After digestion in the small intestine, carbohydrates, proteins, and fats are broken down into simpler forms. These essential macronutrients and other vital substances, such as vitamins, minerals, and water, are then prepared for absorption into the bloodstream.
Enterocytes, which are specialized polar epithelial cells, line the mucosa of the small intestinal walls. These cells...
Enterocytes, which are specialized polar epithelial cells, line the mucosa of the small intestinal walls. These cells...
Amino Acid Biosynthetic Pathways
Amino acid biosynthesis is essential for cell growth, protein synthesis, and metabolic regulation. Cells generate essential and non-essential amino acids from metabolic intermediates to sustain vital biological functions. These intermediates originate from key metabolic pathways: glycolysis, the tricarboxylic acid (TCA) cycle, and the pentose phosphate pathway. Important precursors include α-ketoglutarate, pyruvate, oxaloacetate, phosphoenolpyruvate, and erythrose-4-phosphate, which provide...

