Figure 4.

Effects of exogenous hydrogen peroxide on LoVo cell viability in comparison with the effects induced by purified ZmPAO and spermine. LoVo WT (squares) and LoVo DX (circles) cells were incubated with various concentrations of either exogenous hydrogen peroxide (open symbols) or exogenous spermine plus ZmPAO (solid symbols) for 60 min at 37°C. Each point represents the means ± SEM of 2 independent experiments, with 2 to 5 plates per experiment. Where not shown, error bars lie within symbols. Data are shown on a logarithmic scale. Data were analyzed by one-way ANOVA, followed by Tukey’s post hoc test. ^*P<0.05 and ^**P<0.01 vs. LoVo WT cells incubated with ZmPAO and spermine; ^†P<0.05 vs. LoVo WT cells incubated with H₂O₂. ZmPAO, maize polyamine oxidase; LoVo WT cells, LoVo wild-type cells; LoVo DX cells, LoVo multidrug-resistant cells.