VITELLOGENIN RECEPTORS DURING VITELLOGENESIS RAINBOW-TROUT ONCORHYNCHUS-MYKISS

Rainbow trout vitellogenin receptors have been characterized by ligand blotting and Scatchard analysis. Their evolution has been studied ove r a reproductive cycle in a broodstock of 2-year-old females. The rece ptors were prepared from ovarian membrane homogenates and were solubil ized using n-actyl-beta-D-glucopyranoside. The visualization of the re ceptor by ligand blotting using (125)iodine-vitellogenin after sodium dodecyl sulfate electrophoresis revealed the existence of one major bi nding component corresponding to a protein of 113 kDa. The Scatchard t ransformation of the binding data revealed a single class of binding s ites with an apparent K-d of 1.8 . 10(-8) M/L. The variations of the b inding characteristics (K-d and maximum binding) were investigated dur ing vitellogenesis. This study revealed that the K-d was not affected by oocyte growth during vitellogenesis, but was highly decreased in ov ulated eggs. The receptor number increased during the same period from 35 to 860 fM per oocyte, while the receptor number per mm(2) Of oocyt e membrane surface was doubled during the same period. (C) 1996 Wiley- Liss, Inc.