Cellular iron metabolism is altered during chronic inflammatory states leading to reticuloendothelial iron sequestration and an associated anemia. Nitric oxide may play a significant role in the anemia of chronic disease as demonstrated in a murine model of trypanosome infection whereby mice generate large amounts of nitric oxide (NO) and develop an associated severe anemia. This anemia is abrogated by administration of nitric oxide synthase inhibitor. To study the effects of NO on the expression of three genes important in cellular iron homeostasis- transferrin receptor (TfR), ferritin, and globin, we developed a human erythroleukemic (K562) cell line stably transduced with inducible nitric oxide synthase (iNOS). iNOS cDNA was subcloned into the retroviral plasmid pMFGS, then used to transfect the packaging cell lineΨ-crip. Viral supernatant from high titer clones was used to transduce K562 cells. Several K562 clones that constituitively express iNOS were expanded. FACS analysis demonstrated that TfR expression increased 62% in NO producing clones when compared to the same cells growing in the presence of the NOS inhibitor N-methyl-L-arginine (NMA). TfR mRNA was likewise increased in NO producing cells. Conversely, ferritin and globin protein expression were reduced 3-fold and 16-fold respectively in NO producing cells compared to cells grown in the presence of NMA. The amounts of mRNA for these proteins was the same whether or not NO was being produced suggesting regulation at the post-transcriptional level. These results demonstrate that NO can regulate gene expression for three proteins involved in iron metabolism, decreasing ferritin and globin expression, and increasing TfR expression. These interactions suggest a mechanism for the effect of NO on hemoglobin regulation that could relate to the anemia associated with chronic infections and inflammation.