Levels of plasma ceruloplasmin protein are markedly lower following dietary copper deficiency in rodents

Ceruloplasmin (Cp) is a multicopper oxidase and the most abundant copper binding protein in vertebrate plasma Loss of function mutations in humans or experimental deletion in mice result in iron overload consistent with a putative ferroxidase function Prior work suggested plasma may contain multiple ferroxidases Studies were conducted in Holtzman rats (Rattus norvegicus), albino mice (Mus musculus), Cp-/- mice, and adult humans (Homo sapiens) to investigate the copper-iron interaction Dietary copper-deficient (CuD) rats and mice were produced using a modified AIN-76A diet. Results confirmed that o-dianisidine is a better substrate than paraphenylene diamine (PPD) for assessing diamine oxidase activity of Cp Plasma from CuD rat dams and pups, and CuD and Cp-/- mice contained no detectable Cp diamine oxidase activity Importantly, no ferroxidase activity was detectable for CuD rats, mice, or Cp-/- mice compared to robust activity for copper-adequate (CuA) rodent controls using western membrane assay. Immunoblot protocols detected major reductions (60-90%) in Cp protein in plasma of CuD rodents but no alteration in liver mRNA levels by qRT-PCR. Data are consistent with apo-Cp being less stable than holo-Cp Further research is needed to explain normal plasma Iron in CuD mice Reduction in Cp is a sensitive biomarker for copper deficiency (C) 2010 Elsevier Inc All rights reserved