MetHb- and heme-induced cell death and caspase activity in choroid plexus epithelial cell cultures. Cell death (leakage of lactate dehydrogenase (LDH)) in HCPEpiC cells, exposed to 1 to 30 μM metHb (A), 1 to 30 μM heme (B) or 10 μM metHb with +1.0 mg/ml Hp (C), was evaluated in cell culture medium at 1 to 24 hours as described in Materials and Methods. Caspase activity (activation of caspase-3 and -7) in HCPEpiC following exposure to 10 μM metHb (□), 10 μM heme (●) or 10 μM metHb +1.0 mg/ml Hp (■) was determined (D). Results are from triplicate experiments and presented as mean ± SEM. Baseline in respective graph corresponds to LDH leakage and caspase activity of control cells (exposed to culture medium only) for respective time point. Statistical differences between 10 μM metHb +1.0 mg/ml Hp versus 10 μM metHb were analyzed using ANOVA post hoc Bonferroni. *P < 0.05, **P < 0.01.