August 4, 2023 by Grace Panter

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Hot off the press! Grace and Becky, with colleagues from CropLife Europe, have just had a review paper on the sensitivity of fish testing guidelines to detect the anti-androgenic activity of substances, published in Critical Reviews in Toxicology. In part, this review addresses regulatory uncertainties regarding the sensitivity of fish tests, such as the fish short-term reproduction assay (FSTRA), a recommended study design in ECHA/EFSA (2018) endocrine disrupter guidance document, to detect this endocrine modality. The review looks at the existing evidence on the sensitivity of fish to detect anti-androgens, starting with the homology of the fish androgen receptor (AR) and ending with the diagnostic endpoints used in fish test guidelines.

Highlights of the paper include:

• The use of the United States Environmental Protection Agency’s (US EPA’s) Sequence Alignment to Predict Across Species Susceptibility (SeqAPASS) database to demonstrate the similarity of the AR between mammals (humans) and fish species; and between four recommended test guideline fish species (Pimephales promelas, Danio rerio, Oryzias latipes, Gasterosteus aculeatus).
• Fish in vitro data for model anti-androgenic substances to demonstrate similar competitive binding affinities between fish ARs and the human AR; and the inhibition AR transactivation.
• Fish in vivo data for model anti-androgenic substances to demonstrate inhibition of androgen induced spiggin production, and the comparability of findings between the rapid androgen disruption activity reporter (RADAR) assay and the androgenic female stickleback screen (AFSS). If an anti-androgenic mechanism of action is suspected from the mammalian dataset, this review suggests that the most reliable way to confirm this would be the undertaking of a RADAR assay, or in vitro spiggin assay (no standard test guideline available), which involves co-exposure with an androgen.
• Based on the results from other chronic in vivo fish studies (FSTRA, fish sexual development test [FSDT], partial and full life-cycles, Medaka Extended One Generation Reproduction Test [MEOGRT]) the response of endpoints (vitellogenin, secondary sexual characteristics, gonadal histopathology, sex ratio) to the anti-androgen modality was inconsistent within, and across, the various fish studies and in most cases no response was found for the potent anti-androgens. However, test designs incorporating male secondary sexual characteristics and gonadal histopathology are considered to be most predictive (i.e., FSTRA, partial and full life-cycles, or MEOGRT).
• Overall, the FSTRA does not under perform for detecting anti-androgenic substances when compared to the test designs without co-exposure to an androgen.

Find out more about this Open Access publication here: https://doi.org/10.1080/10408444.2023.2232398