TABLE 2

EC50 for toxicity in the MTT assay of H2O2, HX/XO, and menadione in insulin-producing RINm5F cells overexpressing catalase in cytoplasm (cyto) or mitochondria (mito 1 and 2)

Cell clonesH2O2 (μmol/l)Menadione (μmol/l)HX/XO (mU/ml)
Control52 ± 8 (5)13.1 ± 0.6 (4)1.8 ± 0.2 (4)
Cyto346 ± 27 (5)13.6 ± 0.8 (4)4.0 ± 0.3 (4)*
Mito 1129 ± 18 (5)*15.8 ± 1.1 (4)3.0 ± 0.4 (4)
Mito 2231 ± 18 (5)20.0 ± 1.0 (4)5.8 ± 0.5 (4)
  • Data are means ± SE (no. experiments). Insulin-producing RINm5F cell clones overexpressing catalase in the cytoplasm (cyto) or mitochondria (mito 1 and 2), and control cells were exposed to serial concentrations of H2O2, HX/XO, and menadione, as indicated in Fig. 2. HX/XO (expressed in mU/ml) is a mixture containing a fixed ratio of 20 parts xanthine oxidase (mU/ml) and 1 part hypoxanthine (mmol/l). Viability of the cells was determined by the MTT assay. The EC50 values were calculated by nonlinear regression analyses from the curves in Fig. 2AC.

  • *

    * P < 0.01,

  • P < 0.001 vs. control cells.