ABSTRACT
<p><b>OBJECTIVE</b>To study 17β-estradiol (E2), ethinylestradiol (EE2), estriol (E3), estrone (E1) on MCF-7 proliferation effects, and compare the effects of independent action (IA) model with concentration addition (CA) model in assessing the combined effects of estrogen.</p><p><b>METHODS</b>The combinations of E2 + EE2, E2 + E3 and E2 + E1 were chosen and the cellular proliferation effects were examined by MTT assay.</p><p><b>RESULTS</b>The maximum proliferation effects at dose of 10⁻⁹ mol/L was 325.48% for E2, 330.34% for EE2, 255.22% for E3, and 199.61% for E1. In the E2 + EE2, E2 + E3, E2 + E1 groups, the results of IA model analysis were very close to the experimental results. The IA model tend to overestimated the experimental results, while the CA model often underestimated the experimental results. In the EC (E2, 30) + C (EE2, 70) group, the results exceed the maximum estrogen effects of E2, while in other groups, the results were lower.</p><p><b>CONCLUSIONS</b>The estrogenic effects of the four tested substances from high to low efficiency were that: EE2 > E2 > E3 > E1. The effect of IA model in predicting the combined effects of binary mixture was better than CA model. A small proportion of binary mixture showed synergy.</p>