Evaluation of copper metabolism in neonatal rats by speciation analysis using liquid chromatography hyphenated to ICP mass spectrometry†
It is known that copper (Cu) is highly accumulated in several organs in the perinatal period, suggesting changes in Cu metabolism with development, although the precise mechanisms are still unclear. To elucidate the mechanisms underlying Cu accumulation in the organs of neonatal rats, we performed speciation analysis using high-performance liquid chromatography hyphenated to inductively coupled plasma mass spectrometry. In the neonatal rat liver immediately after birth, the Cu concentration was elevated 10-fold compared to that in the juvenile rat liver. Most of the accumulated Cu was bound to metallothionein, although Cu in Cu, zinc-superoxide dismutase (SOD) was reduced. Contrary to the hepatic Cu accumulation, the serum Cu concentrations in the neonatal rats were low due to the decreased amount of Cu bound to ceruloplasmin. The mRNA expression of antioxidant protein 1 (Atox1), a Cu chaperone that transports Cu to Atp7b, remained low up to two weeks after birth. These results suggest that Cu accumulation in the neonatal rat liver is caused by the low expression of Atox1, and the accumulation is useful to distribute Cu to Cu-containing anti-oxidative enzymes (e.g., SOD and Atox1) after respiration starts.