Zebrafish Embryos: Tiny Models, Big Impact in Toxicology

 Zebrafish embryotoxicity test (ZET) is a method used as an easy method to study the effect of toxicity after exposure to chemicals in ovo during embryogenisis. ZET is a unique alternative that helps study the developmental period. Some of the main advantages of the ZET is that the zebrafish embryos develop seperately from the maternal fishes in water, The embryos are transparent enabling direct observation of internal structures and development without invasive techniques and the development period of zebrafishes is short. Apart from this the zebrafish embryos are not considered as experimental animals under European Legislation. Fertilised eggs are collected 30 minutes after spawingand rinsed, the embryos are kept in an incubator at 26.5 C±1 C with a photoperiod of 14 h light: 10 h dark.  During the exposure period, various concentrations of test substances are introduced into the water containing the embryos.

GMS system is a novel quantitative evaluation tool used to assess embryo growth and development at specific time points throughout the exposure period. This scoring system evaluates several parameters, including:

• Body Shape: Assessing overall morphology and any deformities.
• Hatching Rate: Monitoring the percentage of embryos that successfully hatch.
• Organ Development: Evaluating the formation and functionality of important organs such as the heart and eyes.
• Pigmentation Changes: Monitoring changes in pigmentation, which may suggest developmental problems.

Using the GMS system, researchers can develop quantitative data that will allow comparison of studies across different chemical exposures.

Some of the well known applications ZET in various fields,

• Toxicity Testing: It tests pharmaceuticals, industrial chemicals, and environmental pollutants on embryonic development.
• Nanotoxicology: It tests for the potential toxic effects of nanomaterials on developing organisms.
• Regulatory Compliance: Provides data required for regulatory submissions related to chemical safety and environmental impact assessments.

The Zebrafish Embryotoxicity Test represents a significant advancement in developmental toxicity testing methodologies. Its advantages—such as rapid development, transparency, ethical considerations, and predictive value—make it an attractive alternative to traditional mammalian testing methods. As research continues to evolve and regulatory frameworks adapt to include such innovative approaches, it is an attractive alternative to traditional mammalian testing methods.

Reference:

• Hermsen SA, van den Brandhof EJ, van der Ven LT, Piersma AH. Relative embryotoxicity of two classes of chemicals in a modified zebrafish embryotoxicity test and comparison with their in vivo potencies. Toxicology in Vitro. 2011 Apr 1;25(3):745-53.

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