Figure 3: Preincubation of astrocytes with Pi infusion is a prerequisite for the protective effect against H2O2 cytotoxicity. Pi infusion (12.5 μg/mL) was added to astrocytes before (−2 h, −1 h) or after (1 h, 2 h) the addition of H2O2. Cytotoxicity was measured 20 h later. The results are means ± SEM of one experiment ( ) out of three independent experiments. .