Selective estrogenicity in orally exposed transgenic male mice of compounds known to be estrogenic in vitro

Transgenic reporter gene mice carrying a 3xERE-tataluc- insulated construct were exposed to compounds found to be estrogenic in vitro. Transgenic male mice, chosen for their relative low background levels of circulating estrogens, were fed a phyto-estrogen free diet. They were housed individually and exposed orally via custard (0.5 ml/day) to either 0.3 and 1 mg/kg 17- estradiol dipropionate (EP), 10 and 50 mg/kg bisphenol A (BPA), 10 and 50 mg/kg nonylphenol (NP), 30 and 100 mg/kg di-isoheptyl phthalate (DIHP), 30 and 100 mg/kg di (2-ethylhexyl) phthalate (DEHP), 30 and 100 mg/kg di (2-ethylhexyl) adipate (DEHA), 5 and 50 mg/kg p,p -dichlorodiphenyl-dichloroethylene (DDE) and 1.6 and 16.6 mg/kg quercetin or solvent control. Fourteen hours later the mice were sacrificed and tissues including liver, pituitary, brain, testes and bone were isolated and frozen immediately at -80 ¿C. Maximal luciferase activity, normalized for protein, was induced by 1 mg/kg EP in the liver (5400-fold), while this was 2-times lower at 0.3 mg EP/kg. Several compounds that were estrogenic in vitro were not estrogenic in vivo. However, tissue specific modulation of luciferase expression was found for some compounds, especially BPA induced luciferase in the liver and kidneys. Nonylphenol slightly induced luciferase in the liver and kidneys. Relative few compounds were estrogenic in vivo. In vitro the studied compounds are at least 104 less estrogenic than E2, this might explain the relative small amount of estrogenic compounds in vivo, as relative low concentrations were tested compared to our in vitro study