Document Detail

Inhibition of metamorphosis in tadpoles of Xenopus laevis exposed to polybrominated diphenyl ethers (PBDEs).
MedLine Citation:
PMID:  16455129     Owner:  NLM     Status:  MEDLINE    
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 microgg(-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 microg DE-71 per gram of food. Analysis of PBDEs (sum of 32 congeners) in Xenopus from the treatment with 5000 microgg(-1) of DE-71 indicated that the frogs accumulated an average of 1030 microgg(-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 microg per tadpole, or injected with BDE47 at a nominal dose of 100 microg per tadpole. No responses were observed in Xenopus injected with BDE99 at doses up to 100 microg 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.
Gordon C Balch; Luis A Vélez-Espino; Colleen Sweet; Mehran Alaee; Chris D Metcalfe
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2006-02-07
Journal Detail:
Title:  Chemosphere     Volume:  64     ISSN:  0045-6535     ISO Abbreviation:  Chemosphere     Publication Date:  2006 Jun 
Date Detail:
Created Date:  2006-06-12     Completed Date:  2006-08-14     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0320657     Medline TA:  Chemosphere     Country:  England    
Other Details:
Languages:  eng     Pagination:  328-38     Citation Subset:  IM    
Environmental and Resource Studies Program, Trent University, 1600 West Bank Drive, Peterborough, Ont., Canada.
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MeSH Terms
Administration, Oral
Body Burden
Flame Retardants / toxicity*
Injections, Intraperitoneal
Larva / drug effects,  metabolism
Metamorphosis, Biological / drug effects*
Phenyl Ethers / toxicity*
Polybrominated Biphenyls / toxicity*
Water Pollutants, Chemical / toxicity*
Xenopus laevis
Reg. No./Substance:
0/Flame Retardants; 0/Phenyl Ethers; 0/Polybrominated Biphenyls; 0/Water Pollutants, Chemical

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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