In vitro study of vitellogenesis in the blue crab (Callinectes sapidus): Site and control of vitellin synthesis

The determine the site of vitellin (Vn) synthesis in the blue crab, Callinectes sapidus, tissues (ovary, hepatopancreas, and gill) from adult female crabs were incubated in vitro with [³⁵S]methionine. Tissue extracts were separated by sodium dodecyl sulfate‐polyacrylamide gel electrophoresis and radiolabeled proteins were visualized by autoradiography: Four radiolabeled ovarian proteins (188, 168, 109, and 86 kDa) comigrated with the subunits of Vn. A Western blot analysis confirmed that these ovarian proteins were the Vn subunits. Proteins in the hepatopancreas and gill were also radiolabeled but were not Vn‐immunoreactive. In vitro incorporation of [³⁵S] methionine into ovarian proteins was inhibited by an extract of eyestalks; the inhibition was dose‐dependent and specific. Autoradiography of the electrophoretically separated ovarian proteins revealed that the eyestalk extract inhibited incorporation of [³⁵S] methionine into numerous proteins, including the Vn subunits. These results suggest that the ovary is a site of Vn synthesis and that the eyestalks contain a factor or factors that directly inhibit the synthesis of Vn and other ovarian proteins. It is anticipated that the suppression of ovarian protein synthesis will be a useful bioassay for blue crab vitellogenesis‐inhibiting hormone. © 1995 Wiley‐Liss, Inc.