Sarah Broadley, BSc (Hons), MSc, PGCE, Research Scientist IV, Specialty Pathology Services; Dr. Catherine Ross, DVM, MSc, MRCVS, Pathologist, Department of Pathology Covance Laboratories Ltd., Harrogate, UK
‘An endocrine disruptor is an exogenous substance or mixture that alters function(s) of the endocrine system and consequently causes adverse health effects in an intact organism, or its progeny, or (sub) populations’ WHO-ICPS, 2002.
The Endocrine Disruptor Screening Program (EDSP) is intended to determine if a pesticide, chemical or other substance may pose a risk to human health or environment due to disruption of the endocrine system. The short-term reproduction assay (Test guideline 229) is validated using the fathead minnow (Pimephales promelas) and with a subset of endpoints on the Japanese medaka and zebrafish. The assay considers the reproductive fitness as an integrated measure of toxicant effects using a suite of histological and biochemical endpoints which reflect effects associated with disturbance of the hypothalamus-pituitary-gonadal (HPG) endocrine axis.
In 2018, the OECD issued a revised Conceptual Framework for the Testing and Assessment of Endocrine Disrupting Chemicals. The Conceptual Framework consists of five levels of tests and is designed to be used as a toolbox.
Level 1 – Sorting and prioritisation based on existing information.
Level 2 – In vitro assays providing mechanistic data.
Level 3 – In vivo assays providing data about selected endocrine mechanisms and effects.
Level 4 – In vivo assays providing data about adverse effects on endocrine mechanisms.
Level 5 – In vivo assays providing comprehensive data on effects from endocrine and other mechanisms.
The Fish Short-Term Reproduction Assay falls into Level 3 along with the Amphibian Metamorphosis Assay, Uterotrophic Assay and Hershberger’s Assay.
Currently, in the EU there are no statutory requirements to use specific tests for endocrine disruption unless requested to do so.
In the U.S. however, testing is mandatory and the U.S. EPA have developed a two-tiered strategy.
Tier 1 Assays – A selection of in vitro and in vivo assays. The Fish Short-Term Reproduction Assay and the Amphibian Metamorphosis Assay fall into this range of tests.
Tier 2 Assays – In vivo apical assays including Mammalian 2-generation toxicity, Amphibian Growth/Reproduction, Avian 2-generation, Fish 2-generation and Mysid 2-generation.
Fish Short-Term Reproduction Assay