OECD 493: Human recombinant estrogen receptor (hrER)
OECD 493: Human recombinant estrogen receptor (hrER) assay guidelines cover two methods to detect hrER binding affinity: the Freyberger-Wilson (FW) in vitro estrogen receptor (ER) binding assay using a full length human recombinant ERα, and the Chemical Evaluation and Research Institute (CERI) in vitro estrogen receptor binding assay using a human recombinant ligand binding domain protein. Similar test methods can also be developed from these guidelines. The assay measures the ER binding affinity of a radiolabeled ligand ([3H]17β-estradiol) at varying concentrations of a test substance. Two factors are assessed: saturation binding and competitive binding to the ER.