Binding of metals to red drum vitellogenin and incorporation into oocytes

Gel filtration analysis of plasma from estradiol-treated male red drum (Sciaenops ocellatus) revealed a large protein-bound phosphorous peak with an apparent molecular weight of 225 000 which co-eluted with calcium, magnesium and zinc. A second metal-containing protein peak eluted after vitellogenin with an apparent molecular weight of 62 000. Vitellogenin purified by ion exchange chromatography contained calcium, magnesium, zinc, iron and copper. Equilibrium dialysis showed that cadmium can bind to vitellogenin in vitro and displace endogenous metals from their binding sites. Two days after injection of the cadmium-vitellogenin complex into Atlantic croaker (Micropogonias undulatus), most of the cadmium had been incorporated in the ovaries which suggests that this is an important route for metal accumulation by ovarian tissues.