Dual effects of daidzein on chicken hepatic vitellogenin II expression and estrogen receptor-mediated transactivation in vitro.

Two in vitro systems were employed to delineate the estrogenic activity of daidzein (Da), alone or in combination with high or low concentrations of estrogen in two cell types possessing different estrogen-receptor (ER) isoforms, ERalpha and/or ERbeta: (1) vitellogenin II (VTG), the egg yolk precursor protein and the endpoint biomarker for estrogenicity, in chicken primary hepatocytes, and (2) CHO-K1 cells transiently co-transfected with ERalpha or ERbeta and estrogen-response elements (ERE) linked to a luciferase reporter gene. Da (100 microM) alone induced VTG mRNA expression in chicken hepatocytes, albeit with much less potency compared to estradiol (E(2)). Da exhibited different effects in the presence of 1 microM and 10 microM E(2).