Mouse ferrochelatase and reporter gene expression in various nonerythroid and erythroid tissues. (A) Total RNA was isolated from liver (L), spleen (Sp), kidney (K), testis (T), brain (B), and skeletal muscle (Sk) from control (PBS-treated) or PHZ-treated mice. A total of 15 μg of total RNA was analyzed by Northern blot. RNA was probed for mouse ferrochelatase mRNA or EKLF mRNA with radiolabeled mouse ferrochelatase or human EKLF cDNA probes. Equal loading of RNA was assessed by ethidium bromide staining of 18S and 28S ribosomal RNA. (B) 3.0-mm³ fragments of various tissue described above plus marrow from control-treated (PHZ-, hatched bars) or PHZ-treated (solid bars) −4.0 TG mice were homogenized in luciferase assay buffer. Luciferase activity of tissue extracts was measured for 10 seconds in a luminometer and expressed as relative light units per μg of protein. Luciferase activity in erythroid tissues is expressed on a scale 100 times that of nonerythroid tissues. Each luciferase activity data point represents an average of two to three mice.