Relative embryotoxicity of two classes of chemicals in a modified zebrafish embryotoxicity test and comparison with their in vivo potencies

Abstract

The zebrafish embryotoxicity test (ZET) is a fast and simple method to study chemical toxicity after exposure of the complete vertebrate embryo during embryogenesis in ovo. We developed a novel quantitative evaluation method to assess the development of the zebrafish embryo based on specific endpoints in time, the general morphology score (GMS) system. For teratogenic effects a separate scoring list was developed. The relative effects of eight glycol ethers and six 1,2,4-triazole anti-fungals were evaluated in this system and results were compared with in vivo developmental toxicity potencies. Methoxyacetic acid and ethoxyacetic acid appeared as the most potent glycol ether metabolites, inducing growth retardation and malformations. Other glycol ethers showed no developmental toxicity. Flusilazole appeared the most potent triazole, followed by hexaconazole, cyproconazole, triadimefon, myclobutanil and triticonazole, respectively. In general, the potency ranking of the compounds within their class in the ZET was comparable to their in vivo ranking. In conclusion, the ZET with the GMS system appears an efficient and useful test system for screening embryotoxic properties of chemicals within the classes of compounds tested. This alternative test method may also be useful for the detection of embryotoxic properties of other classes of chemicals.

Developmental toxicity of thyroid-active compounds in a zebrafish embryotoxicity test

“…Given that alterations in the thyroid system can have severe effects on development (Boyages and Halpern, 1993;Haddow et al, 1999;Utiger, 1999), the aim of the present study was to investigate whether a zebrafish-based developmental toxicity assay would be able to detect thyroid hormone-active compounds. Hermsen et al (2011) developed a zebrafish-based quantitative scoring system for developmental and teratogenic endpoints, with the former called the general morphology score (GMS). the developmental endpoints include abnormalities related to the completion of gastrulation, formation of somites, development of the eyes, spontaneous movement, blood circulation, pigmentation, edemata, malformations of the chorda structure, spinal cord (scoliosis, rachitis), head, sacculi/otoliths, tail, heart, yolk sac, growth retardation, and tail length (Nagel, 2002).…”

“…the developmental endpoints include abnormalities related to the completion of gastrulation, formation of somites, development of the eyes, spontaneous movement, blood circulation, pigmentation, edemata, malformations of the chorda structure, spinal cord (scoliosis, rachitis), head, sacculi/otoliths, tail, heart, yolk sac, growth retardation, and tail length (Nagel, 2002). the GMS is meant to be semi-quantitative and hence more efficient than more complex scoring systems while maintaining the same relevance in terms of output (Hermsen et al, 2011). the GMS scoring system uses the 0-72 hpf time window and was validated using eight glycol ethers and six 1,2,4-triazole antifungals (Hermsen et al, 2011).…”

“…the GMS is meant to be semi-quantitative and hence more efficient than more complex scoring systems while maintaining the same relevance in terms of output (Hermsen et al, 2011). the GMS scoring system uses the 0-72 hpf time window and was validated using eight glycol ethers and six 1,2,4-triazole antifungals (Hermsen et al, 2011). While alternative methods for developmental toxicity testing are unlikely to replace testing on rodents, they can potentially be used in pre-screening in order to reduce the need for consecutive in vivo testing (Piersma, 2006).…”

Alternative models in developmental toxicology

“…Another assay was described by Hermsen et al [2011]. The authors treated embryos beginning at the 4-to 32-cell stage to 72 hpf without removing the chorion.…”

“…The authors used the validated rat WEC and mEST protocols along with the zebrafish assay as conducted by Hermsen et al [2011]. The chemicals tested included six triazoles for which the in vivo developmental toxicity activity was available through the ToxRefDB database from the EPA [http://www.epa.gov/ncct/toxrefdb].…”