Fig. (4). Erstressin does not cause reduced cell viability or significant apoptosis in A172 cells at 6 hr or 18 hr Panel A. Dose-response curves for cellular ATP levels (a measure of cell viability and metabolic activity) in cells treated with either Erstressin (Es) or Nostressin (Ns) at concentrations up to 33 µM. The positive control Toxoflavin (Tf) causes considerable reduction in ATP levels at concentrations at or above 10 µM (error bars represent SD, **p < 0.0001, *p < 0.001 as compared to vehicle-treated samples). Panel B. JC-1 staining (reduction in mitochondrial membrane potential (ΔΨm)) in cells treated with vehicle (Veh, DMSO), 10 µM Erstressin (Es), 10 µM Nostressin (Ns) or 10 µM Toxoflavin (Tf) for 6 hours and 18 hours. Ordinate represents percentage of cell population with positive JC-1 mitochondrial staining. Data are representative of three independent experiments.