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Nucleoside transporter subtype expression and function in rat skeletal muscle microvascular endothelial cells
Richard G E Archer1, Václav Pitelka, James R Hammond
1Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada.
British Journal of Pharmacology
|August 4, 2004
Summary
Microvascular endothelial cells (MVECs) actively transport nucleosides via equilibrative and concentrative nucleoside transporters (NTs). Inhibiting these NTs significantly impacts adenosine
Area of Science:
- Endothelial cell biology
- Nucleoside transport mechanisms
- Microvascular physiology
Background:
- Microvascular endothelial cells (MVECs) regulate metabolite exchange, including adenosine.
- Nucleoside transporters (NTs) in MVECs are hypothesized to play a crucial role in adenosine's microvascular actions.
- Understanding NT function in MVECs is key to modulating adenosine signaling.
Purpose of the Study:
- To characterize nucleoside transporter (NT) binding and uptake in rat skeletal muscle MVECs.
- To determine the expression profile of equilibrative (ENT) and concentrative (CNT) NT subtypes in MVECs.
- To investigate the impact of NT inhibition on adenosine transport in the microvasculature.
Main Methods:
- Assessed [(3)H]nitrobenzylmercaptopurine riboside (NBMPR) binding and [(3)H]formycin B (FB) uptake in isolated rat skeletal muscle MVECs.
- Utilized qualitative and quantitative polymerase chain reaction (PCR) to determine ENT (ENT1, ENT2, ENT3) and CNT (CNT1, CNT2, CNT3) expression.
- Investigated Na(+)-dependent and independent transport mechanisms, including the effects of dipyridamole and NBMPR.
Main Results:
- MVECs exhibited significant Na(+)-independent [(3)H]FB uptake mediated by both inhibitor-sensitive (es) and inhibitor-insensitive (ei) equilibrative NTs.
- A minor component of Na(+)-dependent cif/CNT2-mediated [(3)H]FB uptake was observed.
- MVECs possess a high number of high-affinity [(3)H]NBMPR binding sites, indicative of abundant es transporters (ENT1), alongside ei (ENT2) and cif/CNT2 expression.
Conclusions:
- Rat skeletal muscle MVECs express functional es/ENT1, ei/ENT2, and cif/CNT2 nucleoside transporters.
- This primary cell culture model provides a valuable tool for studying NT regulation and adenosine bioactivity in the microvasculature.
- Findings highlight the significant role of endothelial NTs in microvascular adenosine homeostasis.