Figure 6.

Nonheme ⁵⁷Fe concentrations in nuclear and mitochondrial fractions, cell iron, and ferritin concentrations after exposure to humic acid. Cells were incubated with ⁵⁷Fe FAC and exposed to humic acid for 15 min. Collected fractions were hydrolyzed, and ICPMS was employed to measure ⁵⁷Fe concentrations, which were decreased in the mitochondrial fraction following humic acid exposure (A). In (A), * indicates a significant decrease relative to the same fraction collected from BEAS-2B cells exposed to PBS. With exposure to 200 μM FAC, cells imported iron (B). Inclusion of both FAC and 100 μg/mL of humic acid increased metal levels further. Exposures were repeated for 24 h, and ferritin was measured in cell lysate using an immunoturbidimetric assay. Exposures to FAC and both FAC and humic acid increased cell ferritin concentration (C). Co-exposure to both FAC and humic acid resulted in the highest levels of cell ferritin. In (B) and (C), * indicates a significant increase relative to BEAS-2B cells exposed to PBS, and ** indicates a significant increase relative to BEAS-2B cells exposed to either FAC alone or humic acid alone.