Inhibition of metamorphosis in tadpoles of Xenopus laevis exposed to polybrominated diphenyl ethers (PBDEs)
Tadpoles of the African clawed frog, Xenopus laevis were exposed, beginning at stage 50, to a commercial pentabromodiphenyl ether mixture (DE-71) through the diet. Subsequent experiments were conducted using a single intraperitoneal injection at stage 58 with limited quantities of two purified bromi...
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Published in | Chemosphere (Oxford) Vol. 64; no. 2; pp. 328 - 338 |
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Main Authors | , , , , |
Format | Journal Article Conference Proceeding |
Language | English |
Published |
Oxford
Elsevier Ltd
01.06.2006
Elsevier |
Subjects | |
Online Access | Get full text |
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Summary: | Tadpoles of the African clawed frog,
Xenopus laevis were exposed, beginning at stage 50, to a commercial pentabromodiphenyl ether mixture (DE-71) through the diet. Subsequent experiments were conducted using a single intraperitoneal injection at stage 58 with limited quantities of two purified brominated diphenyl ether (BDE) congeners, BDE47 and BDE99 and DE-71 to determine the relative potency of these BDE congeners within the commercial mixture. Significant inhibition of tail resorption, delayed metamorphosis and impacts on skin pigmentation were observed in
Xenopus exposed to DE-71 in the diet at nominal doses of 1000 and 5000
μg
g
−1 of food. The estimated time required for 50% of the tadpoles to complete metamorphosis was significantly lengthened in
Xenopus exposed to a dietary concentration of 1
μg DE-71 per gram of food. Analysis of PBDEs (sum of 32 congeners) in
Xenopus from the treatment with 5000
μg
g
−1 of DE-71 indicated that the frogs accumulated an average of 1030
μg
g
−1 (wet weight) of PBDEs. In the intraperitoneal injection trials, similar inhibitory responses were observed in
Xenopus injected with DE-71 at a nominal dose of 60
μg per tadpole, or injected with BDE47 at a nominal dose of 100
μg per tadpole. No responses were observed in
Xenopus injected with BDE99 at doses up to 100
μg per tadpole. Complete inhibition of metamorphosis was observed only in the highest DE-71 dietary treatment. The results of this study are consistent with a mechanism of action of PBDEs involving competitive inhibition of binding of thyroid hormones to transporter proteins, although the mechanism cannot be definitively determined from this study. The observed effects may have occurred through other mechanisms, including sublethal toxicity. The doses used in this study are greater than the levels of PBDEs to which anurans are exposed in the environment, so further studies are required to determine whether exposure to PBDEs at environmentally relevant concentrations can affect frog metamorphosis. |
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Bibliography: | ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
ISSN: | 0045-6535 1879-1298 |
DOI: | 10.1016/j.chemosphere.2005.12.019 |