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Evidence for electrogenic sodium-dependent ascorbate transport in rat astroglia
J X Wilson1, E M Jaworski, S J Dixon
1Department of Physiology, Faculty of Dentistry, University of Western Ontario, London, Canada.
Neurochemical Research
|January 1, 1991
Summary
Rat brain astrocytes utilize a sodium-ascorbate cotransport system for vitamin C uptake. This process is influenced by external cations like sodium and potassium, affecting cellular vitamin C levels.
Area of Science:
- Neuroscience
- Cell Biology
- Biochemistry
Background:
- Ascorbate (vitamin C) is crucial for brain function.
- Astrocytes play vital roles in neuronal support and brain homeostasis.
- Understanding nutrient transport in astrocytes is key to brain health.
Purpose of the Study:
- To investigate the role of external cations in ascorbate uptake by rat cerebral astrocytes.
- To elucidate the mechanism and stoichiometry of the ascorbate transport system.
Main Methods:
- Primary cultures of rat cerebral astrocytes were used.
- Ascorbate uptake rates were measured under varying concentrations of external cations (Na+, Ca2+, K+).
- The effects of ionophores (gramicidin, nystatin, valinomycin) on uptake were assessed.
Main Results:
- Ascorbate uptake was dependent on external Na+ and Ca2+ concentrations.
- A Na(+)-ascorbate cotransport system with a stoichiometry of 2 Na+:1 ascorbate anion was identified.
- Increased external K+ (depolarization) inhibited ascorbate uptake, an effect modulated by membrane potential.
Conclusions:
- Rat astrocytes possess an electrogenic Na(+)-ascorbate cotransport system.
- Astroglial membrane potential, influenced by ions like K+, regulates ascorbate uptake.
- This transport system is essential for maintaining adequate vitamin C levels in the brain.