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Evolution of the Medaka Extended One Generation Reproduction Test (MEOGRT)
Citation:
Flynn, K., D. Lothenbach, F. Whiteman, D. Hammermeister, L. Touart, J. Swintek, N. Tatarazako, Y. Onishi, T. Iguchi, AND R. Johnson. Evolution of the Medaka Extended One Generation Reproduction Test (MEOGRT). SETAC North America, Minneapolis, MN, November 12 - 16, 2017.
Impact/Purpose:
The presentation is a summary of nine medaka multigenerational tests conducted both by the USEPA and Japan Ministry of the Environment. The data from these tests were used to iteratively modify test protocols that eventually became the Medaka Extended One Generation Test (MEOGRT), a Tier 2 test in the USEPA’s Endocrine Disruption Screening Program and an accepted test in the OECD Test Guideline Program. The rationale for key decisions in the development of the MEOGRT protocol are discussed along with the data supporting these decisions.
Description:
In response to various legislative mandates, the United States Environmental Protection Agency (USEPA) formed its Endocrine Disruptor Screening Program (EDSP), which in turn, implemented a tiered testing strategy to determine the potential of pesticides, commercial chemicals, and environmental contaminants to disrupt the endocrine system. The second tier of this testing strategy is intended to further characterize the effects on these pathways and to establish a dose-response relationship for adverse effects. The Medaka Extended One Generation Reproduction Test (MEOGRT) was developed by the USEPA’s Office of Research and Development to fulfill the requirements of a Tier 2 test within the EDSP and published as the Office of Chemical Safety and Pollution Prevention Test Guideline 890.2200. In addition, a harmonized protocol was published by the Organisation for Economic Co-operation and Development (OECD) through collaboration between the USEPA and the Japanese Ministry of the Environment as OECD TG 240. The MEOGRT protocol was iteratively modified from a much longer research protocol based upon knowledge gained after successfully completing nine tests with variations in test protocols. After completion of these tests, both major modifications (e.g. increased replication) and minor modifications (e.g. choice of temperature) were incorporated into a final standardized MEOGRT protocol. The final protocol consists of continuously exposing parts of two generations of Japanese medaka (Oryzias latipes), starting with adult medaka (F0) exposed for 3 weeks and continuing into the F1 generation for 15 weeks post fertilization. Measurements of population-relevant parameters (i.e. survival, growth, and reproduction) are the primary emphasis of the MEOGRT protocol. However, these measurements are supplemented with measurements of liver vitellogenin levels, the number of papillae on the anal fin (an external sexual phenotype marker), and the histological evaluation of gonadal sex to help differentiate endocrine-mediated effects from systemic toxicity. These protocol iterations and the data associated with them provided valuable insights into nuances of the protocol. The various tests include exposure to 17â-estradiol, 4-t-octylphenol, o,p’- dichlorodiphenyltrichloroethane, 4-chloro-3-methylphenol, tamoxifen, 17â-trenbolone, vinclozolin, and prochloraz. The contents of this abstract neither constitute nor necessarily reflect USEPA policy.