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Detecting Developmental Neurotoxicants Using Zebrafish Embryos
COWDEN, J., D. L. HUNTER, B. K. PADNOS, K. F. JENSEN, R. C. MACPHAIL, AND S. J. PADILLA. Detecting Developmental Neurotoxicants Using Zebrafish Embryos. Presented at TestSmart DNT 2 Developmental Neurotoxicity Meeting, Reston, VA, November 12 - 14, 2008.
As part of EPA’s program on the screening and prioritization of chemicals for developmental neurotoxicity, a rapid, cost-effective in vivo vertebrate screen is being developed using an alternative species approach. Zebrafish (Danio rerio), a small freshwater fish with external fertilization, develop rapidly (3-4 days) in an optically clear chorion allowing visual inspection throughout development. The screen consists of four general endpoints: death, teratology, nervous system structure and locomotor activity. To examine endpoint sensitivity and specificity of the screening approach, zebrafish embryos were exposed to either valproate or saccharin. Valproate is a potent teratogen and developmental neurotoxicant in mammals, whereas current evidence does not demonstrate neurotoxic outcomes following developmental saccharin exposure. Zebrafish embryos were exposed to a wide dose range (0.4 µM to 400 µM) from 6 hours post fertilization to 5 days post-fertilization (dpf). At 2 dpf embryos underwent whole mount anti-acetylated α-tubulin staining; at 6 dpf, animals were assessed for death, teratology, and locomotor activity. Valproate doses under 400 µM did not induce any lethality. Saccharin was not lethal at any dose tested. Valproate produced dose-dependent terata in developing zebrafish embryos, including nervous system terata such as microphthalmia and microencephaly. At a subteratogenic dose of 20 µM, developmental valproate exposure caused transient hyperactivity and reduced retino-tectal projection area. The highest dose of saccharin (400 µM) did not induce terata nor affect retino-tectal projection area. Locomotor activity changes were obtained following developmental saccharin exposure but were neither consistent, nor dose-related. These findings demonstrate that histological and behavioral assessments in zebrafish embryos may be of value in detecting developmental neurotoxicants. This is an abstract of a proposed presentation and does not necessarily reflect Agency policy.
Record Details:Record Type: DOCUMENT (PRESENTATION/ABSTRACT)
Organization:U.S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF RESEARCH AND DEVELOPMENT
NATIONAL HEALTH AND ENVIRONMENTAL EFFECTS RESEARCH LABORATORY
CELLULAR AND MOLECULAR TOXICOLOGY BRANCH