A new test to identify endocrine disruptors using sex hormone-binding globulins from human serum

Abstract

Based on the concept in clinical diagnostics that the principal binding protein in blood for estrogens and androgens, sex hormone-binding globulin (SHBG), determines the estrogenic/androgenic status of humans, a new assay was developed. The format of this assay was similar to a competitive radioimmuno assay, wherein SBHG as capture protein was coupled to microtiter plates coated with anti-SHBG antibody and tritiated estradiol was used as a tracer. Due to its affinity for SHBG relative to estradiol, testosterone was selected as sensitive reference compound to assess any estrogenic activity of environmental contaminants and a reference curve was established. Test compounds included endogenous steroids, pharmaceutical substances, pesticides and industrial pollutants. For each test compound a competition curve of similar shape was obtained and compared to that of testosterone. Displacement of tritiated estradiol indicated an affinity of a certain substance for SHBG and, consequently, an estrogenic activity. Among the compounds tested, strong displacement was demonstrated for estradiol, diethylstilbestrol (DES), norgestrel, permithrin, nonylphenol and bisphenol-A; followed by dehydro-isoandrosterone, 6a-methylprednisolone, androsterone, 2,4-D, dichlofluanid, vinclozolin, and malathion. No affinity could be observed for atrazin, simazin, hexaconazole, tebuconazole, glyphosate, and aldicarb. Further, combinations of some of the compounds tested showed no additive or synergistic effects. Our data are discussed in relation to those reported in the literature. Other hormone-binding proteins from human blood are proposed for further research on hormone-disrupting xenobiotics.