Induction of caspase-3 and caspase-9 activity by MRP8/MRP14. HMECs were treated for the indicated time points with either the medium control (□), 200 μg/mL MRP8/MRP14 (▪), or 200 nM STS (⊡). Cell lysates were then prepared and incubated with the caspase-8 substrate Ac-IETD-AMC (A), the caspase-3 substrate Ac-DEVD-AMC (B), and the caspase-9 substrate Ac-LEHD-AMC (C). The fluorometric determination of AMC release was expressed as fluorescence increase (delta F) per microgram of cell protein. *Significant differences compared with the control cells of the respective time period (n = 5; P < .05). Error bars indicate the standard error of the mean.