Characterization of an Estradiol-Induced Protein from Rainbow Trout Serum as Vitellogenin by the Composition and Radioimmunological Cross Reactivity to Ovarian Yolk Fractions1

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Abstract
An estrogen-induced protein has been isolated by a simple method from plasma of rainbow trout (Salmo gairdneri) and an antibody against it was raised in a rabbit. Three fractions were isolated from trout ovaries using the method for isolation of lipovitellin and phosvitin of Wallace et al. (1966). Two factors crossreacted with the antibody and could be displaced by serum from vitellogenic trout only, suggesting that the isolated serum fraction was trout vitellogenin. Biochemical analysis established similarities between vitellogenin, lipovitellin and phosvitin from trout and other oviparous species. A radioimmunoassay for vitellogenin has been developed for rainbow trout using vitellogenin as standard and gonad lipovitellin or β′ component as radioligand. In this system little cross reactivity was found with vitellogenin rich sera from closely related Salmo salar.