Despite the high impact of the antimicrobial peptide hepcidin in iron homeostasis, the regulation of this hormone is still not completely understood. Studies concerning hepcidin regulation are performed at the mRNA level. For the first time we analyzed the regulation of hepcidin not only at mRNA, but also at protein level in a hepatoma and a pancreatic beta cell line using quantitative RT-PCR and immunoblot analysis. Our data show, that hepcidin is present in HepG2 and RINm5F cells. A significant up-regulation of hepcidin was observed in both cell lines by the inflammatory cytokine interleukin-6, lipopolysaccharide, and a slight upregulation by deferoxamine. A down-regulation was detected after stimulation with erythropoietin. Hepcidin was regulated by iron in a dose dependent manner: low doses up to 3 microM increased hepcidin expression, high doses of iron (65 microM) revealed a switch-over to down-regulation of hepcidin expression. Regulation of hepcidin in HepG2 and RINm5F cells at mRNA and protein level by these substances indicates its involvement in inflammation and iron metabolism.