The effect of methylmercury exposure on early central nervous system development in the zebrafish (Danio rerio) embryo

• Published in: Journal of applied toxicology Vol. 32; no. 9; pp. 707 - 713
• Main Authors: Hassan, S. A., Moussa, E. A., Abbott, L. C.
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 01.09.2012; Wiley; Wiley Subscription Services, Inc
• Subjects: Animals; Biological and medical sciences; Biomarkers - metabolism; Cell Proliferation - drug effects; Central nervous system; Chemical and industrial products toxicology. Toxic occupational diseases; CNS development; Dose-Response Relationship, Drug; Embryo Loss - chemically induced; Embryo, Nonmammalian - drug effects; Embryo, Nonmammalian - embryology; Embryo, Nonmammalian - metabolism; Embryos; Ethanol - toxicity; Ethyl alcohol; Exposure; Female; Freshwater; immunohistochemistry; Male; Medical sciences; Mercury; Metals and various inorganic compounds; methylmercury; Methylmercury Compounds - toxicity; Mortality; Nervous system; Neural Tube - drug effects; Neural Tube - embryology; Neural Tube - metabolism; PCNA; Proliferating Cell Nuclear Antigen - metabolism; Toxicology; Tubes; Water Pollutants, Chemical - toxicity; Zebrafish; Zebrafish - embryology; Zebrafish - physiology; zebrafish embryos; Immunohistochemistry; Embryo; PCNA; Central nervous system; Exposure; CNS development; Heavy metal; methylmercury; Vertebrata; Brachydanio rerio; Pisces; Development; Early; Mercury Organic compounds; zebrafish embryos; PCNA antigen
• ISSN: 0260-437X; 1099-1263
• DOI: 10.1002/jat.1675

ABSTRACT Much attention is focused on environmental contamination by heavy metals. The heavy metal mercury is found worldwide and is ranked number 3 on the Comprehensive Environmental Response, Compensation and Liability Act substance list. We examined the effect of low‐level methylmercury exposure on central nervous system development of wild‐type zebrafish embryos (ZFEs) of the AB strain because methylmercury is the most common form of mercury to which humans are exposed in the environment. ZFEs were exposed to nine different concentrations of methylmercury [0 (negative control), 5, 10, 50, 80, 100, 200, 500 and 1000 parts per billion (μg l−1)] starting at 6 h post‐fertilization, which is the time the neural tube is first beginning to form. ZFEs were exposed to 2% ethanol as positive controls (100% embryonic death). ZFEs were assessed at 30, 54, 72 and 96 h post‐fertilization for changes in embryonic development, mortality, time of hatching and morphological deformities. No abnormalities were observed in ZFEs exposed to 5 μg l−1 methylmercury. The time of hatching from the chorion was delayed in ZFEs exposed to methylmercury concentrations of 50 μg l−1 or higher. Significantly more ZFEs exposed to 0, 5 or 10 μg l−1 methylmercury successfully completed hatching compared with ZFEs exposed to 50 μg l−1 or higher methylmercury. ZFEs exposed to more than 200 μg l−1 methylmercury exhibited 100% embryonic mortality. The rate of cell proliferation within the neural tube was significantly decreased in embryos exposed to 10, 50 and 80 μg l−1 methylmercury and there were no differences between these doses. Copyright © 2011 John Wiley & Sons, Ltd. Zebrafish embryos (ZFEs) were exposed 24 hours to one of nine concentrations of methylmercury (0 to 1000 parts per billion (μg/L)) starting at 6 hours post‐fertilization. No abnormalities were observed in ZFEs exposed to 5 μg/L methylmercury. Hatching was delayed in ZFEs exposed to methylmercury concentrations of 50 μg/L or higher. ZFEs exposed to more than 200 μg/L methylmercury exhibited 100% mortality. Neural tube cell proliferation was significantly decreased in embryos exposed to 10, 50, and 80 μg/L methylmercury.