Test No. 493: Performance-Based Test Guideline for Human Recombinant Estrogen Receptor
(hrER) In Vitro Assays to Detect Chemicals with ER Binding Affinity
This Performance-Based Test Guideline (PBTG) describes in vitro assays, which provide
the methodology for human recombinant in vitro assays to detect substances with estrogen
receptor binding affinity (hrER binding assays). It comprises two mechanistically
and functionally similar test methods for the identification of estrogen receptor
(i.e. ERα) binders and should facilitate the development of new similar or modified
test methods. The two reference test methods that provide the basis for this PBTG
are: 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. This assay measures the ability of a radiolabeled ligand ([3H]17β-estradiol)
to bind with the ER in the presence of increasing concentrations of a test chemical
(i.e. competitor). Test chemicals that possess a high affinity for the ER compete
with the radiolabeled ligand at a lower concentration as compared with those chemicals
with lower affinity for the receptor. This assay consists of two major components:
a saturation binding experiment to characterise receptor-ligand interaction parameters
and document ER specificity, followed by a competitive binding experiment that characterises
the competition between a test chemical and a radiolabeled ligand for binding to the
ER. These test methods are being proposed for screening and prioritisation purposes,
but also provide mechanistic information that can be used in a weight of evidence
approach.
Published on July 28, 2015Also available in: French
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