Determination of apoceruloplasmin by radioimmunoassay in nutritional copper deficiency, Menkes’ kinky hair syndrome, Wilson’s disease, and umbilical cord blood

Abstract

Radioimmunoassay can detect as little as 10 ng apoceruloplasmin. Interference by holoceruloplasmin is overcome by using an antiapoceruloplasmin antibody absorbed with holoceruloplasmin and by correcting for the relatively small inhibition of binding of apoceruloplasmin to absorbed antibody caused by holoceruloplasmin. The apoceruloplasmin concentration in infants with nutritional copper deficiency (2.9 ± 0.9 mg/100 ml), Menkes’ kinky hair syndrome (1.4 ± 0.5 mg/100 ml), and Wilson’s disease (2.7 ± 2.0 mg/100 ml) did not differ significantly from normal (3.3 ± 3.1 mg/100 ml) despite significant reductions (P < 0.01) in the concentration of holoceruloplasmin in each of these conditions. In umbilical cord blood from normal neonates, however, the concentration of apoceruloplasmin (0.7 ±0.5 mg/100 ml) was significantly lower than normal (P < 0.01), as was the concentration of holoceruloplasmin. Speculation in Wilson's disease the incorporation of copper into nascent apoceruloplasmin, which is probably synthesized at a normal rate and is of normal structure, is reduced. There could be a defect in an enzyme required to catalyze the incorporation or a failure of copper to reach the nascent protein. In normal neonates the rate of apoceruloplasmin synthesis is probably reduced. This reduction may be responsible for the lower concentrations of both holo- and apoceruloplasmin observed in sera of neonates compared with that of older subjects. © 1974 International Pediatric Research Foundation, Inc.