Effect of triptolide on caspase activity in RSF. RSF were cultured without agents for 24 h, or were incubated with 100 nM triptolide or 100 nM triptolide plus 10 μM Z-VAD-FMK, and then caspase activity was measured by the CaspACE™ assay system (Promega) as the absorbance at 405 nm. Data are the mean ± S.D. for 3 independent experiments. *, p < 0.01 versus untreated control cells and versus cells treated with triptolide plus Z-VAD-FMK. Significance was evaluated by Student's t-test with a Bonferroni's correction.