Abstract: ObjectiveTo examine the estrogenic-like activity of the pesticide prochloraz by tests in vitro and study the possible mechanism.MethodsMCF-7 cells were maintained in RPMI 1640 medium containing 10% bovine serum.Two weeks before the addition of the test compound the cells were transformed into phenol red-free RPMI 1640 medium containing 10% charcoal/dextran treated bovine serum.There are seven cell groups deal with different treatments:a vehicle control group,a positive group and five proliferation test,MTT test and growth curve were used to assess the effect on the proliferation of MCF-7 cells by pr ochloraz,and estrogen receptor(ER)binding test was used to analyze the binding ability of prochloraz with ER.ResultsProchloraz can induce the proliferation of MCF-7 cells at 10^-7~10^-5 mol/Lwith dose-effect relationship,and this effect is significantly different from vehicle control(P<0.05 or P<0.01).Our study also show that prochloraz can bind with ER and inhibit the bind of ¹²⁵I-E₂ with ER.ConclusionsProchloraz has estrogenic activity which caused by its bind with ER.