Kidney erythropoietin transcript levels are increased in IRP2^-/- and IRP1^+/- IRP2^-/- mice. RNA extracted from kidneys of WT, IRP2^-/-, and IRP1^+/- IRP2^-/- mice was assessed by relative quantitative PCR as described in “Materials and methods.” As a control, the 18S ribosomal subunit was amplified (top arrow) and erythropoietin mRNA (Epo) was amplified simultaneously (bottom arrow), indicating that erythropoietin mRNA levels increase significantly in kidneys of IRP2^-/- animals and more prominently in IRP1^+/- IRP2^-/- mice. bp indicates base pair.