FIGURE 2.

Effects of heme on ALAS-1 protein expression in mitochondria from human hepatocytes and cell lines. A, mitochondrial fractions (75 μg of protein) were incubated at 30 °C with heme (1 μm) for indicated time period to examine the time course of the heme effect. MW, molecular weight. B, mitochondria from various liver cell lines were incubated with buffer, DMSO, or heme for 8 h, and ALAS-1 protein levels were assessed by Western immunoblotting analysis. C, ALAS-1 protein half-life was determined by quantifying band intensities of remaining ALAS-1 protein normalized to VDAC1/porin and plotted on semi-logarithmic graph. Half-lives were 8.7, 3.4, or 51.7 h following exposure of cells to DMSO, heme, or 4,6-dioxoheptanoic acid (DHA), respectively. D, the effect of heme (1 μm) on ALAS-1 was examined in mitochondria from human liver biopsies. Results of bar graphs are mean ± SE.