FIG. 5.

Dose dependence of Aβ on the extracellular cysteine/cystine redox couple. Astrocytes were either untreated (white bar), or treated acutely (gray bar) or repeatedly (black bar) with 1, 10, and 50 μM of Aβ (25–35). At the indicated time, an aliquot of culture supernatant was collected and extracellular cysteine (Cys) (a), cystine (Cys₂) (b), and GSH (d) were measured, and the redox potential (c) was calculated as described in Fig. 4 legend. Data are mean±SD from two independent experiments each performed in triplicate on different batches of cells. Asterisks (*p≤0.05, **p≤0.01, ***p≤0.001) denote level of significance and are shown only if there was a statistically significant difference and represent the comparison between untreated controls and treated conditions.