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Teratological and Behavioral Screening of the National Toxicology Program 91-Compound Library in Zebrafish (Danio
Katharina Dach1, Bianca Yaghoobi1, Martin R Schmuck1
1Department of Molecular Biosciences, School of Veterinary Medicine, University of California-Davis, Davis, CA California 95616.
Abstract:
To screen the tens of thousands of chemicals for which no toxicity data currently exists, it is necessary to move from in vivo rodent models to alternative models, such as zebrafish. Here, we used dechorionated Tropical 5D wild-type zebrafish embryos to screen a 91-compound library provided by the National Toxicology Program (NTP) for developmental toxicity. This library contained 86 unique chemicals that included negative controls, flame retardants, polycyclic aromatic hydrocarbons (PAHs), drugs, industrial chemicals, and pesticides. Fish were exposed to 5 concentrations of each chemical or an equal amount of vehicle (0.5% DMSO) in embryo medium from 6 h post-fertilization (hpf) to 5 days post-fertilization (dpf). Fish were examined daily for mortality and teratogenic effects and photomotor behavior was assessed at 4 and 5 dpf. Of the 5 negative control compounds in the library, none caused mortality/teratogenesis, but two altered behavior. Chemicals provided in duplicate produced similar outcomes. Overall, 13 compounds caused mortality/teratology but not behavioral abnormalities, 24 only affected behavior, and 18 altered both endpoints, with behavior affected at concentrations that did not cause mortality/teratology (55/86 hits). Of the compounds that affected behavior, 52% caused behavioral abnormalities at either 4 or 5 dpf. Compounds within the same functional group caused different behavioral abnormalities, while similar behavioral patterns were caused by compounds from different groups. Our data suggest that behavior is a sensitive endpoint for developmental toxicity screening that integrates multiple modes of toxic action and is influenced by the age of the larval fish at the time of testing.
Insights
Zebrafish embryos screened 86 chemicals for developmental toxicity. Behavioral changes were observed at lower concentrations than physical abnormalities, indicating behavior is a sensitive toxicity screening endpoint.
Area of Science:
- Environmental Toxicology
- Developmental Biology
- Chemical Screening
Background:
- Thousands of chemicals lack toxicity data, necessitating alternative screening models.
- Zebrafish embryos offer a viable alternative to traditional in vivo rodent models for toxicity testing.
Purpose of the Study:
- To screen a National Toxicology Program (NTP) library of 86 unique chemicals for developmental toxicity using zebrafish embryos.
- To evaluate mortality, teratogenesis, and photomotor behavior as toxicity endpoints.
Main Methods:
- Dechorionated Tropical 5D wild-type zebrafish embryos were exposed to 5 concentrations of 86 chemicals from 6 hours post-fertilization (hpf) to 5 days post-fertilization (dpf).
- Daily assessments for mortality and teratogenic effects were conducted.
- Photomotor behavior was assessed at 4 and 5 dpf.
Main Results:
- 55 out of 86 tested compounds showed toxicity.
- 13 compounds caused mortality/teratology, 24 affected only behavior, and 18 affected both.
- Behavioral abnormalities were detected at concentrations lower than those causing mortality/teratology.
- 52% of behavior-altering compounds showed abnormalities at 4 or 5 dpf.
Conclusions:
- Behavioral assessment in zebrafish is a sensitive endpoint for developmental toxicity screening.
- Behavioral changes can indicate toxicity even at concentrations below lethal or teratogenic thresholds.
- Zebrafish behavior screening integrates multiple toxic action modes and is age-dependent.
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