Figure 4.

Pb²⁺ only perturbs total and labile heme after a recovery period following exposure to Pb²⁺. In cells expressing HS1-M7A, Pb²⁺ increases labile heme (A), decreases total heme (B), and diminishes cell viability (C) in a dose-dependent manner if cells are allowed to recover for 4 h in SCE medium following Pb²⁺ exposure in MES buffer. However, labile (D) and total heme (E) in cells expressing HS1-M7A immediately after the exposure to Pb²⁺ in MES buffer are not significantly affected. All data represent the mean ± S.D. (error bars) of triplicate cultures, and statistical significance was assessed using a two-sample t test. Black asterisks, statistical significance between the indicated pairwise comparisons of conditions; red asterisks, statistical significance relative to 0 μm Pb. *, p < 0.05; **, p < 0.005; ***, p < 0.001; n.s., not significant.