Xenoestrogens,
phytoestrogens and
synthetic estrogens, are able to bind to
estrogen receptors, and to mimic estrogenic activities in a cell and tissue specific manner. For the characterization of environmental
estrogens mainly mammary derived and yeast based models have been used. The aim of this study was therefore to assess selected natural and synthetic compounds in an endometrial derived model. We measured the relative estrogenic potency of
phytoestrogens (
genistein,
daidzein,
coumestrol, some naringenins),
synthetic estrogens (
bisphenol A,
octylphenol,
nonylphenol,
o,p'-DDT), mycoestrogen (zearalanone) as well as extracts of Cimicifuga racemosa on
alkaline phosphatase (AlkP) activity in the endometrial derived
adenocarcinoma cell line Ishikawa. We used a modified multiwell plate in vitro bioassay based on the
estrogen-specific and dose-dependent enhancement of AlkP activity in this cell line.
Estradiol, which induced AlkP at levels as low as 10(-8)M, was used as positive control. Most of the compounds studied showed a clear dose-dependent
estrogenic effect. Compared to the vehicle control (
ethanol) all phyto- and mycoestrogens, stimulated the AlkP activity 2-4-fold at a concentration of 10(-6)M. The synthetic chemicals
bisphenol A and
nonylphenol showed an effect at 10(-6)M,
octylphenol at 10(-5)M. Effects of o,p'-DTT could not be measured.
ICI 182,780, a pure
estrogen receptor antagonist, significantly inhibited these effects. The latter result demonstrated the
estrogen receptor dependency of this process. In summary, most of the
phytoestrogens and industrial chemicals tested, behaved as
estrogen receptor agonists in terms of the stimulation of AlkP activity.