Hep G2 cells were pretreated with control MEM or 3 μmmenadione for 45 min in the presence of the indicated additions. Final concentrations of the additions were 20 μg/ml cycloheximide, 10 mm NAC, 50 μm pyrrolidine dithiocarbamate, 5 mm thiourea, and 0.5 mm uric acid. The cells were then exposed to 18 μm menadione for 18 hr, and viability was determined as described in Materials and Methods. Results are mean ± standard deviation of three to five wells per experiment from three separate experiments.