Representative example of cytofluorimetric analysis showing the effect of vitamin C alone or in combination with FAC, on the mitochondrial membrane potential of SH-SY5Y (panel A) and HTLA-230 (panel B) stained with JC-1 probe. In abscissa FL-1 (green fluorescence); in ordinate FL-2 (red fluorescence). Numbers represent the percentage of non-apoptotic red fluorescent cells (R1, R3) and that of apoptotic green fluorescent cells (R2, R4). Sodium ascorbate induces a marked increase in apoptosis which is fully prevented by treatment with FAC. SH-SY5Y and HTLA-230 were incubate in complete medium in the absence (A1, B1) or in presence of 1 mM sodium ascorbate (A2, B2) and 2 mM sodium ascorbate (A4, B4) for 16 hours. Cells were pretreated (A3, A5, B3, B5) with 70 μg/ml of FAC for 3 hours. Comparable results were obtained in three independent experiments.