Cloning serum ferritin from rat liver

Clones, specific for various size subunits of serum ferritin, were obtained by using N-terminal amino acid sequence from serum ferritin's subunits, and internal sequence conserved among intracellular ferritins from various mammalian species. The paired primers were used in reverse transcription-PCR and a partial cDNA clone for each subunit of serum ferritin was obtained. These clones were used to verify the presence of serum ferritin mRNA in hepatic cells and liver tissue, and to assess iron responsiveness. One cloned PCR product translated into a sequence of 61 amino acid residues, possibly representing a portion of the 57 kDa subunit of serum ferritin. Comparing amino acid sequences revealed no significant homology to immunoglobulin-G or intracellular ferritin. These results support the concept that serum ferritin is transcriptionally regulated by iron, and is not the product of the same genes as those encoding for intracellular ferritin or IgG.