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Lagadic L, Coady KK, Körner O, Miller TJ, Mingo V, Salinas ER, Sauer UG, Schopfer CR, Weltje L, Wheeler JR. Endocrine disruption assessment in aquatic vertebrates - Identification of substance-induced thyroid-mediated effect patterns. ENVIRONMENT INTERNATIONAL 2024; 191:108918. [PMID: 39270431 DOI: 10.1016/j.envint.2024.108918] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/13/2024] [Revised: 07/12/2024] [Accepted: 07/26/2024] [Indexed: 09/15/2024]
Abstract
According to the World Health Organisation and European Commission definitions, substances shall be considered as having endocrine disrupting properties if they show adverse effects, have endocrine activity and the adverse effects are a consequence of the endocrine activity (using a weight-of-evidence approach based on biological plausibility), unless the adverse effects are not relevant to humans or non-target organisms at the (sub)population level. To date, there is no decision logic on how to establish endocrine disruption via the thyroid modality in non-mammalian vertebrates. This paper describes an evidence-based decision logic compliant with the integrated approach to testing and assessment (IATA) concept, to identify thyroid-mediated effect patterns in aquatic vertebrates using amphibians as relevant models for thyroid disruption assessment. The decision logic includes existing test guidelines and methods and proposes detailed considerations on how to select relevant assays and interpret the findings. If the mammalian dataset used as the starting point indicates no thyroid concern, the Xenopus Eleutheroembryonic Thyroid Assay allows checking out thyroid-mediated activity in non-mammalian vertebrates, whereas the Amphibian Metamorphosis Assay or its extended, fixed termination stage variant inform on both thyroid-mediated activity and potentially population-relevant adversity. In evaluating findings, the response patterns of all assay endpoints are considered, including the direction of changes. Thyroid-mediated effect patterns identified at the individual level in the amphibian tests are followed by mode-of-action and population relevance assessments. Finally, all data are considered in an overarching weight-of-evidence evaluation. The logic has been designed generically and can be adapted, e.g. to accommodate fish tests once available for thyroid disruption assessments. It also ensures that all scientifically relevant information is considered, and that animal testing is minimised. The proposed decision logic can be included in regulatory assessments to facilitate the conclusion on whether substances meet the endocrine disruptor definition for the thyroid modality in non-mammalian vertebrates.
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Affiliation(s)
- Laurent Lagadic
- Bayer AG - R&D, Crop Science Division, Environmental Safety, Monheim, Germany.
| | | | - Oliver Körner
- ADAMA Deutschland GmbH, Environmental Safety, Köln, Germany
| | - Tara J Miller
- Syngenta, Jealott's Hill International Research Centre, Jealott's Hill, United Kingdom
| | | | - Edward R Salinas
- Bayer AG - R&D, Crop Science Division, Environmental Safety, Monheim, Germany
| | - Ursula G Sauer
- Scientific Consultancy - Animal Welfare, Neubiberg, Germany
| | | | - Lennart Weltje
- BASF SE, Agricultural Solutions - Ecotoxicology, Limburgerhof, Germany; Georg-August-University Göttingen, Division of Plant Pathology and Plant Protection, Göttingen, Germany
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Fort DJ, Wolf JC, Langsch A, Fast B, Junker M, Otter R. Inefficacy of dietary test substance administration in Amphibian Metamorphosis Assay (AMA) studies. J Appl Toxicol 2024; 44:733-746. [PMID: 38151988 DOI: 10.1002/jat.4572] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2023] [Revised: 11/30/2023] [Accepted: 12/04/2023] [Indexed: 12/29/2023]
Abstract
Traditionally, the Amphibian Metamorphosis Assay (AMA; OECD TG 231) is performed by exposing Xenopus laevis tadpoles to test substances dissolved in laboratory water. Recently, the use of dietary administration has been proposed to combat poorly soluble test substances in ecotoxicologically-based regulatory endocrine disruption (ED) studies, specifically the AMA warranting an investigation into the efficacy of dietary administration. An efficacy study comprised of two phases: 1) evaluation of the physical influence of the loading process via solvent and 10, 1, and 0.1 mg/l test substance or surrogate (sunflower oil, SFO) on the Sera® Micron Nature (SMN) diet, and 2) performance of a modified AMA in which Nieuwkoop and Faber (NF) stage 51 X. laevis larvae were exposed to dechlorinated tap water using one concentration of the SFO in the diet for 21 days, was performed. In phase 1, the addition of acetone or acetone with bis(2-propylheptyl) phthalate (DPHP) or SFO to SMN with subsequent solvent purge altered the diet reducing the density of the liquified diet and dietary pellet size following centrifugation indicative of alteration of the physical properties of the diet. Treatments used in the modified AMA were acetone alone and 0.1 mg/l SFO dissolved in acetone. These treatments were evaluated against an SMN benchmark using standard AMA endpoints. Both the acetone-treated SMN and 0.1 mg/l SFO-treated diets significantly reduced survival rates, 67 and 70% relative to the SMN benchmark (100%), decreased developmental stage distribution and snout-vent length-normalized hind limb length relative to the SMN benchmark, and slightly increased the prevalence and severity of thyroid follicular cell hypertrophy. Although the acetone-treated diets may have impacted the hypothalamo-pituitary-thyroid axis, clinical signs of gastrointestinal impaction and tail flexure were also observed in the acetone-treated diets, but not the SMN diet alone. Ultimately, test substance exposure via the diet in an AMA study can produce results that may confound data interpretation, which suggests that the traditional aqueous exposure route is generally more appropriate.
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Affiliation(s)
- Douglas J Fort
- Fort Environmental Laboratories, Stillwater, Oklahoma, USA
| | - Jeffrey C Wolf
- Experimental Pathology Laboratories, Inc., Sterling, Virginia, USA
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Du Pasquier D, Salinier B, Coady KK, Jones A, Körner O, LaRocca J, Lemkine G, Robin-Duchesne B, Weltje L, Wheeler JR, Lagadic L. How the Xenopus eleutheroembryonic thyroid assay compares to the amphibian metamorphosis assay for detecting thyroid active chemicals. Regul Toxicol Pharmacol 2024; 149:105619. [PMID: 38614220 DOI: 10.1016/j.yrtph.2024.105619] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2023] [Revised: 02/05/2024] [Accepted: 04/03/2024] [Indexed: 04/15/2024]
Abstract
The Xenopus Eleutheroembryonic Thyroid Assay (XETA) was recently published as an OECD Test Guideline for detecting chemicals acting on the thyroid axis. However, the OECD validation did not cover all mechanisms that can potentially be detected by the XETA. This study was therefore initiated to investigate and consolidate the applicability domain of the XETA regarding the following mechanisms: thyroid hormone receptor (THR) agonism, sodium-iodide symporter (NIS) inhibition, thyroperoxidase (TPO) inhibition, deiodinase (DIO) inhibition, glucocorticoid receptor (GR) agonism, and uridine 5'-diphospho-glucuronosyltransferase (UDPGT) induction. In total, 22 chemicals identified as thyroid-active or -inactive in Amphibian Metamorphosis Assays (AMAs) were tested using the XETA OECD Test Guideline. The comparison showed that both assays are highly concordant in identifying chemicals with mechanisms of action related to THR agonism, DIO inhibition, and GR agonism. They also consistently identified the UDPGT inducers as thyroid inactive. NIS inhibition, investigated using sodium perchlorate, was not detected in the XETA. TPO inhibition requires further mechanistic investigations as the reference chemicals tested resulted in opposing response directions in the XETA and AMA. This study contributes refining the applicability domain of the XETA, thereby helping to clarify the conditions where it can be used as an ethical alternative to the AMA.
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Affiliation(s)
- David Du Pasquier
- Laboratoire WatchFrog, 1 Rue Pierre Fontaine, 91000, Évry-Courcouronnes, France
| | - Benoît Salinier
- Laboratoire WatchFrog, 1 Rue Pierre Fontaine, 91000, Évry-Courcouronnes, France
| | - Katherine K Coady
- Bayer Crop Science, Environmental Safety, 700 Chesterfield Parkway West, Chesterfield, MO, USA
| | - Alan Jones
- ADAMA US, Environmental Safety, 3120 Highwoods Blvd., Raleigh, NC, 27604, USA
| | - Oliver Körner
- ADAMA, Environmental Safety, Edmund-Rumpler-Strasse 6, 51149, Cologne, Germany
| | - Jessica LaRocca
- Corteva Agriscience, 9330 Zionsville Road, Indianapolis, IN, 46268, USA
| | - Gregory Lemkine
- Laboratoire WatchFrog, 1 Rue Pierre Fontaine, 91000, Évry-Courcouronnes, France
| | | | - Lennart Weltje
- BASF SE, Agricultural Solutions - Ecotoxicology, Speyerer Strasse 2, 67117, Limburgerhof, Germany
| | - James R Wheeler
- Corteva Agriscience, Zuid-Oostsingel 24D, 4611 BB, Bergen op Zoom, the Netherlands
| | - Laurent Lagadic
- Bayer AG R&D Crop Science, Alfred-Nobel-Strasse 50, 40789, Monheim am Rhein, Germany.
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Wolf JC, Green JW, Mingo V, Marini JP, Schneider SZ, Fort DJ, Wheeler JR. Historical control histopathology data from amphibian metamorphosis assays and fathead minnow fish short term reproductive assays: A tool for data interpretation. AQUATIC TOXICOLOGY (AMSTERDAM, NETHERLANDS) 2024; 267:106811. [PMID: 38159458 DOI: 10.1016/j.aquatox.2023.106811] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/20/2023] [Revised: 12/17/2023] [Accepted: 12/19/2023] [Indexed: 01/03/2024]
Abstract
The Amphibian Metamorphosis Assay (AMA) is used to determine if a tested chemical has potential to impact the hypothalamic-pituitary-thyroid (HPT) axis of Xenopus laevis tadpoles, while the Fish Short Term Reproduction Assay (FSTRA) assesses potential effects on the hypothalamic-pituitary-gonadal (HPG) axis of fish such as the fathead minnow (Pimephales promelas). Several global regulatory programs routinely require these internationally validated tests be performed to determine the potential endocrine activity of chemicals. As such, they are conducted in accordance with standardized protocols and test criteria, which were originally developed more than a decade ago. Sizeable numbers of AMA and FSTRA studies have since been carried out, which allows for the mining of extensive historical control data (HCD). Such data are useful for investigating the existence of outlier results and aberrant control groups, identifying potential confounding variables, providing context for rare diagnoses, discriminating target from non-target effects, and for refining current testing paradigms. The present paper provides histopathology HCD from 55 AMA studies and 45 fathead minnow FSTRA studies, so that these data may become publicly available and thus aid in the interpretation of future study outcomes. Histopathology is a key endpoint in these assays, in which it is considered to be one of the most sensitive indicators of endocrine perturbation. In the current review, granular explorations of HCD data were used to identify background lesions, to assess the utility of particular diagnostic findings for distinguishing endocrine from non-endocrine effects, and to help determine if specific improvements to established regulatory guidance may be warranted. Knowledge gleaned from this investigation, supplemented by information from other recent studies, provided further context for the interpretation of AMA and FSTRA histopathology results. We recommend HCDs for the AMA and FSTRA be maintained to support the interpretation of study results.
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Affiliation(s)
- Jeffrey C Wolf
- Experimental Pathology Laboratories, Inc., 45600 Terminal Drive, Sterling, VA 20166, USA.
| | - John W Green
- John W Green Ecostatistical Consulting, LLC 372 Chickory Way, Newark, DE 19711, USA
| | - Valentin Mingo
- Corteva Agriscience, Riedenburger Str. 7, München 81677, Germany
| | | | | | - Douglas J Fort
- Fort Environmental Laboratories, Stillwater, OK 74074, USA
| | - James R Wheeler
- Corteva Agriscience, Zuid-Oostsingel 24D, Bergen op Zoom 4611 BB, the Netherlands
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Otero MA, Grenat PR, Pollo FE, Baraquet M, Martino AL. Effect on growth and development of common toad (Rhinella arenarum) tadpoles in environment related to fluorite mine. THE SCIENCE OF THE TOTAL ENVIRONMENT 2023; 904:166936. [PMID: 37690762 DOI: 10.1016/j.scitotenv.2023.166936] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/05/2023] [Revised: 08/23/2023] [Accepted: 09/07/2023] [Indexed: 09/12/2023]
Abstract
Fluorite mining activities have been scarcely evaluated so far and the potential effect of this activity on larval stages is poorly known. Thus, studies addressing the effect of contaminants present in water bodies on the health of amphibian larvae are crucial information for their conservation and constitute a warning sign of environmental modification. This study aims to evaluate the effects of natural and artificial surface waters associated with a fluorite mine on the early life stages of Rhinella arenarum. Using microcosms, we assessed four sites with different degrees of disturbance by the fluorine mine: Vallecitos stream (undisturbed); Cerros Negros upstream of mining camp (low disturbance); Cerros Negro downstream of mining camp (medium disturbance); Decantation Ponds (high disturbance). For 65 days we measured different endpoints at different periods of tadpole development. The highest mortality of tadpoles was observed in the Decantation Ponds. In the same way, larval body condition was lower at Decantation Ponds throughout the study, due mainly to the lower weight. A significant decrease in growth and development was observed in Cerros Negro downstream of the mining camp and Decantation Ponds. No significant differences in growth, development and mortality were observed for the other two sites. At the metamorphic climax we observe a lower body condition and a reduced recruitment of individuals in Decantation Ponds. This study allowed us to assess the effect on larvae of R. arenarum of fluorite mining wastewater compared with other near-natural sites. Given the potentially negative synergic effects of mixed water pollutants on tadpoles, this study suggests that chronic exposure to fluorite mining water may significantly impact the adult amphibian population structure, thus altering population viability. Therefore, we propose to monitor the correct functioning of the mine and especially of Decantation Ponds to avoid discharges into the natural streams.
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Affiliation(s)
- Manuel A Otero
- Instituto de Ciencias de La Tierra, Biodiversidad y Ambiente (ICBIA), UNRC-CONICET, Argentina; Ecología, Departamento de Ciencias Naturales, Facultad de Ciencias Exactas, Físico-Químicas y Naturales, Universidad Nacional de Río Cuarto, Ruta Nacional N 36 e Km 601, CP 5800 Río Cuarto, Argentina.
| | - Pablo R Grenat
- Instituto de Ciencias de La Tierra, Biodiversidad y Ambiente (ICBIA), UNRC-CONICET, Argentina; Ecología, Departamento de Ciencias Naturales, Facultad de Ciencias Exactas, Físico-Químicas y Naturales, Universidad Nacional de Río Cuarto, Ruta Nacional N 36 e Km 601, CP 5800 Río Cuarto, Argentina
| | - Favio E Pollo
- Instituto de Ciencias de La Tierra, Biodiversidad y Ambiente (ICBIA), UNRC-CONICET, Argentina; Ecología, Departamento de Ciencias Naturales, Facultad de Ciencias Exactas, Físico-Químicas y Naturales, Universidad Nacional de Río Cuarto, Ruta Nacional N 36 e Km 601, CP 5800 Río Cuarto, Argentina
| | - Mariana Baraquet
- Instituto de Ciencias de La Tierra, Biodiversidad y Ambiente (ICBIA), UNRC-CONICET, Argentina; Ecología, Departamento de Ciencias Naturales, Facultad de Ciencias Exactas, Físico-Químicas y Naturales, Universidad Nacional de Río Cuarto, Ruta Nacional N 36 e Km 601, CP 5800 Río Cuarto, Argentina
| | - Adolfo L Martino
- Instituto de Ciencias de La Tierra, Biodiversidad y Ambiente (ICBIA), UNRC-CONICET, Argentina; Ecología, Departamento de Ciencias Naturales, Facultad de Ciencias Exactas, Físico-Químicas y Naturales, Universidad Nacional de Río Cuarto, Ruta Nacional N 36 e Km 601, CP 5800 Río Cuarto, Argentina
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Brix KV, Baken S, Poland CA, Blust R, Pope LJ, Tyler CR. Challenges and Recommendations in Assessing Potential Endocrine-Disrupting Properties of Metals in Aquatic Organisms. ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY 2023; 42:2564-2579. [PMID: 37671843 DOI: 10.1002/etc.5741] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/24/2023] [Revised: 07/25/2023] [Accepted: 08/29/2023] [Indexed: 09/07/2023]
Abstract
New tools and refined frameworks for identifying and regulating endocrine-disrupting chemicals (EDCs) are being developed as our scientific understanding of how they work advances. Although focus has largely been on organic chemicals, the potential for metals to act as EDCs in aquatic systems is receiving increasing attention. Metal interactions with the endocrine system are complicated because some metals are essential to physiological systems, including the endocrine system, and nonessential metals can have similar physiochemical attributes that allow substitution into or interference with these systems. Consequently, elevated metal exposure could potentially cause endocrine disruption (ED) but can also cause indirect effects on the endocrine system via multiple pathways or elicit physiologically appropriate compensatory endocrine-mediated responses (endocrine modulation). These latter two effects can be confused with, but are clearly not, ED. In the present study, we provide several case studies that exemplify the challenges encountered in evaluating the endocrine-disrupting (ED) potential of metals, followed by recommendations on how to meet them. Given that metals have multiple modes of action (MOAs), we recommend that assessments use metal-specific adverse outcome pathway networks to ensure that accurate causal links are made between MOAs and effects on the endocrine system. We recommend more focus on establishing molecular initiating events for chronic metal toxicity because these are poorly understood and would reduce uncertainty regarding the potential for metals to be EDCs. Finally, more generalized MOAs such as oxidative stress could be involved in metal interactions with the endocrine system, and we suggest it may be experimentally efficient to evaluate these MOAs when ED is inferred. These experiments, however, must provide explicit linkage to the ED endpoints of interest. Environ Toxicol Chem 2023;42:2564-2579. © 2023 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.
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Affiliation(s)
- Kevin V Brix
- EcoTox, Miami, Florida, USA
- Rosenstiel School of Marine, Atmospheric & Earth Science, University of Miami, Miami, Florida, USA
| | - Stijn Baken
- International Copper Association, Brussels, Belgium
| | - Craig A Poland
- Regulatory Compliance Limited, Loanhead, United Kingdom
- Centre for Inflammation Research, Queen's Medical Research Institute, University of Edinburgh, Edinburgh, United Kingdom
| | - Ronny Blust
- Department of Biology, University of Antwerp, Antwerp, Belgium
| | | | - Charles R Tyler
- Biosciences, Faculty of Health and Life Sciences, University of Exeter, Exeter, United Kingdom
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Wolf JC, Segner HE. Hazards of current concentration-setting practices in environmental toxicology studies. Crit Rev Toxicol 2023; 53:297-310. [PMID: 37439631 DOI: 10.1080/10408444.2023.2229372] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2023] [Revised: 06/16/2023] [Accepted: 06/16/2023] [Indexed: 07/14/2023]
Abstract
The setting of concentrations for testing substances in ecotoxicological studies is often based on fractions of the concentrations that cause 50% mortality (LC50 or LD50) rather than environmentally relevant levels. This practice can result in exposures to animals at test concentrations that are magnitudes of order greater than those experienced in the environment. Often, such unrealistically high concentrations may cause non-specific biochemical or morphologic changes that primarily reflect the near-lethal health condition of the animal subjects, as opposed to effects characteristic of the particular test compound. Meanwhile, it is recognized that for many chemicals, the toxicologic mode of action (MOA) responsible for lethality may differ entirely from the MOAs that cause various sublethal effects. One argument for employing excessively high exposure concentrations in sublethal studies is to ensure the generation of positive toxicological effects, which can then be used to establish safety thresholds; however, it is possible that the pressure to produce exposure-related effects may also contribute to false positive outcomes. The purpose of this paper is to explore issues involving some current usages of acute LC50 data in ecotoxicology testing, and to propose an alternative strategy for performing this type of research moving forward. Toward those ends, a brief literature survey was conducted to gain an appreciation of methods that are currently being used to set test concentrations for sublethal definitive studies.
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Affiliation(s)
- Jeffrey C Wolf
- Experimental Pathology Laboratories, Inc., Sterling, VA, USA
| | - Helmut E Segner
- Vetsuisse Faculty, Centre for Fish and Wildlife Health, University of Bern, Bern, Switzerland
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Marini JP, Wolf JC, Mingo V, Sayers LE, Jamieson SY, Wheeler JR. An Amphibian Metamorphosis Assay Dietary Restriction Study: Lessons for Data Interpretation. ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY 2023; 42:1061-1074. [PMID: 36848316 DOI: 10.1002/etc.5596] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2022] [Revised: 01/03/2023] [Accepted: 02/22/2023] [Indexed: 06/18/2023]
Abstract
The amphibian metamorphosis assay (AMA) is a key in vivo endocrine screen to investigate chemicals with potential thyroid activity. The test guidelines and associated guidance consider that treatment-related effects on thyroid gland histomorphology 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. An AMA study was conducted with five different feeding rations equivalent to 50%, 30%, 20%, 10%, and 5% of the recommended feeding rate. 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. There was no effect on survival or clinical signs of toxicity. Effects related to feed reduction generally occurred in a feeding ration-response manner and included reduced development stage; reduced body weight and body length metrics; decreased prevalence of thyroid follicular cell hyperplasia and hypertrophy, and the occurrence of thyroid atrophy; reduced liver vacuolation; and the occurrence of liver atrophy. The results indicate that treatment-related histopathological changes in the AMA can be induced by Non-chemical factors; therefore histopathological results are not necessarily diagnostically specific for chemically induced thyroid endocrine activity. Consequently, the interpretation of data from AMA studies should be adjusted accordingly. We recommend that the decision logic presented in the test guidelines and associated guidance be changed to reflect a requirement for directional agreement between the thyroid histopathology findings and the growth and developmental endpoints before it is concluded that a test substance has thyroid endocrine activity. Environ Toxicol Chem 2023;42:1061-1074. © 2023 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.
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Affiliation(s)
| | - Jeffrey C Wolf
- Experimental Pathology Laboratories, Sterling, Virginia, USA
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