Acute toxicity and study of "biomarker of effects" in zebrafish embryos and larvae exposed to selected pesticides: A step towards refined risk assessment of chemical agents
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AbstractWe have developed a standard test procedure using zebrafish embryos and larvae to elucidate the water quality guidelines of pesticides in the tropical region. Zebrafish embryos and larvae were tested for specific gene expression in response to different pesticides: heptachlor, methoxychlor, endosulfan, chlorpyrifos, aldicarb, and cypermethrin. The 96 hour(h) median Effective Concentration (EC50) (hatching rate) and 96 h median Lethal Concentration (LC50) values of different pesticides for zebrafish embryos and larvae were first determined. Quantitative Polymerase Chain Reaction (qPCR) was then used to study the gene expression levels of enzyme biomarkers in zebrafish embryos and larvae after 96 h exposure to different pesticides. The biomarker enzymes included cytochrome P450 (CYP) enzymes, CYP1A, and 3A65, glutathione Stransferase (gst), catalase (cat), and resistance gene (mdr1) were studied as responses to chemical exposures. Inhibition of acetylcholinesterase (AChE) activity was also used as a biomarker of toxic effects from organophosphate (chlorpyrifos) and carbamate (aldicarb) pesticides. Inductions of cat and gst mRNA levels demonstrated oxidative-stressinducing potential of chlorpyrifos and cypermethrin. Exposures to chlorpyrifos and to aldicarb significantly inhibited AChE activity in both embryos and larvae, indicating their neurotoxic effects on zebrafish embryo and larvae. The pesticides tested did not affect the mRNA levels of cyp1A, but of cyp3A65 and mdr1 levels in zebrafish embryos and larvae, which were altered by heptachlor, methoxychlor and endosulfan. The use of toxicity tests and a specific gene expression in response to toxic pesticides would help aquatic scientists in determining the permissible concentrations of pesticides in waters.
All Author(s) ListChow W.S., Chan K.M.
All Editor(s) Listed. by Charles A. Lessman and Ethan A. Carver .
Detailed descriptioned. by Charles A. Lessman and Ethan A. Carver .\n\nTo ORKTS:

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Pages265 - 294
LanguagesEnglish-United Kingdom
KeywordsPesticides, Quantitative PCR, Water quality guidelines

Last updated on 2020-13-08 at 03:00