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Ascorbate uptake in pig coronary artery endothelial cells
Kelly A Best1, Melanie E Holmes, Sue E Samson
1Department of Biology, McMaster University, Hamilton Ontario, Canada.
Molecular and Cellular Biochemistry
|May 11, 2005
Summary
Pig coronary artery endothelial cells actively transport vitamin C (ascorbate) using sodium-dependent vitamin C transporters (SVCT2), similar to smooth muscle cells. This finding clarifies ascorbate uptake mechanisms in distinct vascular cell types.
Area of Science:
- Vascular Biology
- Cell Physiology
- Biochemistry
Background:
- Smooth muscle and endothelial cells in pig coronary arteries are distinct.
- Ascorbate uptake mechanisms were previously only studied in smooth muscle cells.
- Epithelial cell ascorbate transporters differ from those in smooth muscle.
Purpose of the Study:
- To investigate ascorbate transport in pig coronary artery endothelial cells.
- To determine the mRNA expression of sodium-dependent vitamin C transporters (SVCT) in these cells.
Main Methods:
- Utilized 14C-ascorbate uptake assays and High-Performance Liquid Chromatography (HPLC).
- Performed RT-PCR to analyze SVCT mRNA expression.
- Investigated Na(+)-dependence, stereoselectivity, and inhibitor effects on uptake.
Main Results:
- Endothelial cells exhibited Na(+)-dependent, stereoselective L-ascorbate uptake, inhibited by sulfinpyrazone.
- Kinetic analysis revealed Km values for ascorbate (27 ± 3 µM) and Na+ (73 ± 14 mM).
- Both endothelial and smooth muscle cells expressed SVCT2 mRNA, unlike epithelial cells (mainly SVCT1).
Conclusions:
- Pig coronary artery endothelial cells possess functional ascorbate transporters.
- Endothelial cells share similarities with smooth muscle cells in SVCT2 expression and kinetic parameters for ascorbate uptake.
- These findings highlight distinct ascorbate transport systems in vascular endothelial versus epithelial cells.