Identification of vitellogenin receptors in the ovary of a teleost fish, the Mediterranean sea bass (Dicentrarchus labrax)

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 (I-125-VTG) after SDS-electrophoresis showed specific binding of (125)1-VTG to a protein band of 100 kDa. Filter binding assays showed that binding of I-125-VTG to membrane receptors was saturable with increasing amounts of I-125-VTG. Scatchard analysis of the saturation data revealed a single class of binding sites with an apparent KD Of 1.04.10(-8) M. The specificity of the VTG receptors was tested in competition assays; binding of I-125-VTG to ovarian membranes was completely abolished with an excess of purified sea bass VTG (cold VTG, VTG degrees) or plasma from estradiol (E2)-treated fish, while the addition of control male plasma (without VTG) caused negligible effect.