Estrogen receptor competitive binding assay of bisphenol A and para-nonylphenol

  Objective   The estrogen-like activity of bisphenol A and p-nonylphenol was examined with the estrogen receptor competitive binding assay.

  Methods   Adulthealthy female SD rat were ovarietomized and sacrificed 2 weeks later. Cytosol estrogen receptor were abstracted from the uteri. Aliquots of 150μg cytosol protein were added with 1μCi/mol 3 HE2 50μl and increasing concentrations of unlabeled E2, BPA and p-NP, the total volume of reponse was 200μl. The mixtures were incubated at 4℃ 16-18 hours. DCC methods removed free labeled-ligand. At last, the radioactivity was measured.

  Results   The percent inhibitory values(IC₅₀)of E2 was 1×10^-9 mol/L. BPA and p-NP can inhibit of 3 H-E2 binding to rat uterine cycotol estrogen receptor with an IC₅₀ of 2.08×10^-5 mol/L and 2.66×10^-5 mol/L, respectively. The relative binding affinity(RBA)of BPA and p-NP were 0.004 8 and 0.003 8, respectively. The binding capacity of BPA to ER was bigger than that of p-NP.

  Conclusion   Binding to ER maybe was the mechanism that BPA and p-N P mimicked estrogen-like activity.