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Spotlight on Endocrine Disruptor Testing
Dr. Malekani spoke with Joseph Marini, Senior Research Biologist, about his upcoming poster and platform presentation at the SETAC Europe 33rd Annual Meeting.
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SETAC Europe Platform Presentation: An Amphibian Metamorphosis Assay Dietary Restriction Study
The Amphibian Metamorphosis Assay (AMA) is a key in vivo endocrine screen to identify potential thyroid active chemicals. The Test Guidelines and associated guidance consider treatment-related effects on thyroid gland histomorphology to automatically result in the assay being considered positive for thyroid activity, independent of the direction of change or conflicting results in the other biological endpoints. EU guidance for assessing endocrine disrupting properties of pesticides and biocides classifies the endpoints from the TGs as those that provide direct (so called “T-mediated”) and indirect (“sensitive to but not diagnostic of T”) endpoints for the evaluation of T-activity. Here, it is assumed that accelerated and asynchronous development, as well as histopathologic effects are specific for a chemical-induced thyroid hormone interaction in the absence of clear toxicity (mortality). This is also reflected in the TGs, which provide an in-study decision logic suggesting that any kind of treatment-related effects involving thyroid gland histomorphology would automatically result in the assay being considered positive for thyroid activity.
The goal of this study was to evaluate how a non-chemical stressor, dietary restriction, might affect the outcome of the AMA, and in particular, developmental effects that are currently considered to be mediated specifically through the thyroid endocrine axis. To this end, an AMA was conducted with 5 different feeding regimes equivalent to 50, 30, 20, 10 and 5% of the TGs recommended feeding ration. Biological endpoints relating to growth and development, including thyroid gland histopathology, were evaluated and the specificity of these endpoints for the determination of thyroid activity was assessed.
Joseph Marini, Senior Research Biologist, presented this research at the SETAC Europe 33rd Annual Meeting, 30 April – 4 May 2023, in Dublin, Ireland.
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