A universal assay for vitellogenin in fish mucus and plasma

Expression of vitellogenin (VTG) in male fish has become a widely used biomarker of exposure to environmental estrogens. Vitellogenin is usually measured in blood by immunoassays that require species-specific antibodies. In this paper, we describe a universal assay that is based on the high-molecular weight and extensive phosphoserine content of all VTGs. Plasma and mucosal proteins from Pimephales promelas and Fundulus heteroclitus and mucosal proteins from Gambusia holbrooki were separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, stained with a commercially available fluropore dye (Pro-Q Diamond), and visualized by ultraviolet transillumination. The method allowed sensitive detection of VTG in females and estradiol-treated males in all species tested. Quantitative analysis indicated that the phosphoprotein assay is at least as sensitive as antibody-based methods but is universal, offering the advantage of VTG measurement in multiple species.