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Osmotic swelling stimulates ascorbate efflux from cerebral astrocytes
R Siushansian1, S J Dixon, J X Wilson
1Department of Physiology, University of Western Ontario, London, Canada.
Journal of Neurochemistry
|March 1, 1996
Summary
Brain cell swelling triggers rapid release of ascorbate (vitamin C) from astrocytes. This release may aid in osmoregulation and combat oxidative stress during conditions like ischemia.
Area of Science:
- Neuroscience
- Cell Biology
- Biochemistry
Background:
- Ascorbate (vitamin C) is vital for brain function, acting as a cofactor, neuromodulator, and antioxidant.
- Cerebral astrocytes store high concentrations of ascorbate and are prone to swelling during pathological conditions.
Purpose of the Study:
- To investigate the impact of osmotic stress and cell swelling on ascorbate transport in astrocytes.
- To identify the mechanisms and pathways involved in swelling-induced ascorbate efflux.
Main Methods:
- Primary rat astrocyte cultures were subjected to hypotonic and hypertonic stress to induce swelling.
- Ascorbate efflux and uptake were measured using HPLC with electrochemical detection.
- The effects of anion-transport inhibitors (DIDS, DNDS) on efflux were evaluated.
Main Results:
- Hypotonic stress rapidly increased ascorbate efflux from astrocytes within 1 minute.
- Swelling-induced efflux was significantly inhibited by DIDS and DNDS, suggesting involvement of anion transporters.
- The efflux pathway was selective, retaining larger anions like BCECF.
- Na(+)-dependent ascorbate uptake was only slightly inhibited, indicating it does not mediate swelling-induced efflux.
Conclusions:
- Astrocytic swelling triggers a rapid, selective efflux of ascorbate, potentially mediated by anion channels.
- This ascorbate release may play a role in cellular osmoregulation and antioxidant defense during brain injury.
- Understanding this mechanism is crucial for developing therapeutic strategies for neurological conditions involving cell swelling and oxidative stress.