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(246) Ammonium perchlorate induced thyroid disruption in developing fathead minnows.
Crane, HM1, Pickford, DB2, Hutchinson, TH2, Brown, JA1, 1 University of Exeter, Exeter, Devon, UK2 AstraZeneca Brixham Environmental Laboratory, Brixham, Devon, UK
ABSTRACT- Against a background of concern over potential thyroid toxicants in surface waters, there are few studies available that explore the use of OECD fish species for evaluating environmental thyroid disruption. In the present study, fathead minnows, Pimephales promelas, were exposed as embryos to environmentally relevant (nominal) levels of the ammonium perchlorate (zero, 1, 10, 100 ppm), for 28 days. Growth, measured as weight and length, was significantly retarded in fish exposed to 10 or 100 ppm ammonium perchlorate, versus control fish (P < 0.05). Fish exposed to 100 ppm ammonium perchlorate had significantly higher whole body T4 than controls (P < 0.05), but there were no significant alterations in plasma T3 in fish exposed to ammonium perchlorate. Histological examination of thyroid tissue revealed visible changes in thyroid follicles at all concentrations of ammonium perchlorate. All follicles exhibited significantly increased epithelial cell height (P < 0.05) and reduced luminal thyroglobulin, indicative of over stimulation of the thyroid tissue, in response to the inhibitory actions of ammonium perchlorate. This work strongly suggests that environmental levels of ammonium perchlorate can disrupt thyroid function in freshwater fish and the overall 28d NOEC is <1 ppm (based on histology). Further studies are warranted to examine the potential impacts of these histological changes over the full lifecycle of the fathead minnow and the impacts on other fish populations.
Key words: perchlorate, Pimephales promelas, thyroid, development
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