4.6. Quantitation of Intracellular Heme

Intracellular heme was quantified in MEFs using a heme assay kit (Sigma-Aldrich, St. Louis, MO, USA) according to the manufacturer’s instructions. Briefly, 200 μL of heme reagent was added to 50 μL of sample. Subsequently, the samples were vortexed to mix. The plate containing the mixtures was incubated for 5 min at room temperature (about 22 °C), and absorbance was measured at 400 nm.