RESUMO
The characterization of vitellogenin (VTG) receptors in ovarian membranes from vitellogenic female sea bass (Dicentrarchus labrax) is described. Incubation of membrane proteins with radiolabeled VTG (125I-VTG) after SDS-electrophoresis showed specific binding of 125I-VTG to a protein band of 100 kDa. Filter binding assays showed that binding of 125I-VTG to membrane receptors was saturable with increasing amounts of 125I-VTG. Scatchard analysis of the saturation data revealed a single class of binding sites with an apparent KD of 1.04 x 10(-8) M. The specificity of the VTG receptors was tested in competition assays; binding of 125I-VTG to ovarian membranes was completely abolished with an excess of purified sea bass VTG (cold VTG, VTG degree) or plasma from estradiol (E2)-treated fish, while the addition of control male plasma (without VTG) caused negligible effect.
