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Sodium-dependent nucleoside transport in mouse intestinal epithelial cells. Two transport systems with differing
1Department of Biochemical and Clinical Pharmacology, St. Jude Children's Research Hospital, Memphis, Tennessee 38101.
Mouse intestinal epithelial cells possess two distinct sodium-dependent nucleoside transport systems. Formycin B and thymidine serve as model substrates to differentiate these transporters, which are not inhibited by nitrobenzylmercaptopurine riboside.
Area of Science:
- Cellular Biology
- Biochemistry
- Physiology
Background:
- Nucleoside transporters are crucial for cellular uptake of essential nucleosides.
- Understanding these transporters is vital for drug delivery and metabolic studies.
- Specific transporters in the intestine play a key role in nutrient absorption.
Purpose of the Study:
- To investigate the mechanisms of nucleoside transport in mouse intestinal epithelial cells.
- To characterize the properties of sodium-dependent nucleoside transporters.
- To identify distinct transporters based on substrate specificity and inhibition patterns.
Main Methods:
- Isolation of primary mouse intestinal epithelial cells.
- Uptake assays using radiolabeled nucleoside analogs (formycin B, thymidine).
- Inhibition studies with various purine and pyrimidine nucleosides, and nitrobenzylmercaptopurine riboside.
Main Results:
- Two distinct sodium-dependent nucleoside transport systems were identified.
- Formycin B transport showed saturation kinetics (Km 45 +/- 3 microM) and was inhibited by purine nucleosides.
- Thymidine transport was also sodium-dependent and inhibited by pyrimidine nucleosides and adenosine, but not formycin B.
Conclusions:
- Mouse intestinal epithelial cells exhibit at least two different sodium-dependent nucleoside transporters.
- Formycin B and thymidine can be used as substrates to distinguish between these two transport systems.
- These transporters are distinct from the nitrobenzylmercaptopurine riboside-sensitive equilibrative nucleoside transporters.
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