Immunochemical Properties of Vitellogenins and Egg Yolk Proteins in Female Fusilier, Caesio diagramma

This study was conducted to compare the immunochemical properties of female-specific serum proteins (vitellogenin, VTG) and egg yolk proteins in female fusilier, Caesio diagramma. VTG of fusilier was identified and characterized by using immunochemical analysis. Two types of VTG (VTG1 and VTG2) reacted clearly with antiserum against egg proteins, were confirmed in the serum of mature female. The results of sephacryl S-300 showed that the molecular weights of VTG1 and VTG2 were 560,000 and 410,000, respectively. Yolk proteins, E2 and E3, were isolated from egg extracts, and molecular weights of them were estimated 410,000 and 170,000, respectively. The treatment of 17β-estradiol (E₂) to males has induced the synthesis of VTG of which immunological characteristics seems to be similar to the yolk proteins. The results suggest that VTG can be synthesized in the liver by the action of E₂ stimulation, and incorporated into the oocytes through the blood circulation. The level of serum E₂ was moderately high throughout the spawning period of June. The level of serum VTG was also sustained at high in May and June. The concentration changes of serum E₂ and VTG were corelated to the ovarian development in female fusilier. The results indicated that E₂ may have some important roles for the vitellogenesis in female fusilier. Also, the VTG can be a precursor protein of yolk not only because it could be synthesized in the liver then incorporated into the oocytes but also because an egg yolk protein had the similiar molecular weights and antigenecity with VTG.