Prooxidant effects of ascorbate in rat brain slices

✍ Scribed by Jin H. Song; Seon H. Shin; Gregory M. Ross

• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 165 KB
• Volume: 58
• Category: Article
• ISSN: 0360-4012
• DOI: 10.1002/(sici)1097-4547(19991015)58:2<328::aid-jnr13>3.0.co;2-o

✦ Synopsis

Ascorbate is a well-known reducing agent, but it can generate oxidative potential under appropriate condition. In rat cerebral cortex homogenate, 1 mM ascorbate decreased thiobarbituric acid-reactive substances (TBARS) content to 86% Ϯ 4% of control values, confirming that ascorbate is a reducing agent. However, ascorbate increased TBARS, in a doserelated manner, in slices prepared from cerebral cortex. Ferrous ion (Fe 2ϩ ) had little effect on ascorbateinduced lipid oxidation in cortical slices, and EDTA did not have an influence on the ascorbate-induced oxidative action. Conversely, ascorbate plus Fe 2ϩ elevated TBARS content to more than threefold over ascorbate alone in tissue homogenates. In summary, ascorbate is a reducing agent in the brain tissue homogenate but has an oxidizing effect in brain slices. A hypothesis is proposed to explain the oxidative effects of ascorbate in cortical slices, wherein extracellular ascorbate is oxidized to dehydroascorbate, which is rapidly carried into the cells via a glucose transporter (GLUT). The dehydroascorbate in cytosol is then reduced back to ascorbate, and, during the reduction process, cellular components are oxidized.