Cells growth curves as affected by various concentrations of H
and tBHP. The exponentially growing SK-N-SH cells or Bβ1 and Bβ2 clones were seeded at a total of 2 × 105 cells per 6-cm plate and treated with different concentrations of H2O2 (0, 50 and 100 μM, respectively) (A) or tBHP (0, 50 and 100 nM, respectively) (B). After 48 h of treatment, the cells were trypsinized and counted by trypan blue exclusion assay. The result represented mean values of three individual determinations; the bars standard errors in three independent experiments as conducted. *P < 0.05, significance of difference as compared with the control group.