Comparison of chemical-induced transcriptional activation of fish and human estrogen receptors: Regulatory implications

Under the current EU chemical regulation REACH (Registration, Evaluation, Authorization and Restriction of Chemicals), revised plant protection products and biocides directives, evaluation of endocrine disrupting properties of chemicals becomes a regulatory need. Transcriptional activation (TA) testing of estrogen receptors (ERs) could be one important first step in the screening and testing of endocrine disrupting chemicals (EDCs) for regulatory purposes. However up to now there is no consensus on which species or subtype of ERs should be used for TA testing. This study collected data from publications on TA testing with fish and human ERs for 90 chemicals, covering strong, moderate, and weak or non-ER binders. Each chemical has been reported at least twice, with differential ER TA values that result from different cellular contexts, from intra-/inter-species and subtypes of ERs and from intra-/inter-laboratory differences. All assays could distinguish the differential transcriptional activity induced by chemicals of strong, moderate, and weak or non-ER binders. It is concluded that transactivation of ERs in one vertebrate species or one subtype of ERs could be extrapolated to other species or subtypes of ERs for the purpose of chemical screening. It is emphasized that results from ER TA assays can only be used in a weight-of-evidence approach for further testing in regulatory programs. These results are of importance for regulatory testing strategies and decision making for EDCs.