Measurement of intracellular GSH content. Intracellular GSH content was measured by flow cytometric analysis using MBB and PI after a 5-hour exposure to MGd and ascorbate in the (A) dexamethasone-sensitive cell line, C2E3, the (B) dexamethasone-resistant cell line, 1-310, the (C) highly dexamethasone-resistant cell line, 1-414, the (D) chemotherapy-sensitive cell line, 8226-RPMI, and the (E) highly chemotherapy-resistant line, DOX-10V. The mean fluorescence intensity of MBB represents the cellular GSH level of the live cells, and data are expressed as a percentage of cells staining for GSH. Results show GSH content with mannitol control, 100 μM ascorbate alone, 100 μM MGd alone, concurrent 50 μM MGd and 100 μM ascorbate, or concurrent 100 μM MGd and 100 μM ascorbate exposure. Dead cells were gated out with PI. Data are expressed as percentage of cells staining for GSH, with lower percentages indicating decreased intracellular GSH. N-ethylmaleimide at 100 μM was used as a positive control for each experiment (see “Materials and methods”). Results shown (means and SD) were averaged from 3 or more independent experiments performed in triplicate for each data point.