| 16337670 |
Hoekstra PF, Burnison BK, Garrison AW, Neheli T, Muir DC: Estrogenic activity of dicofol with the human estrogen receptor: Isomer- and enantiomer-specific implications. Chemosphere. 2006 Jun;64(1):174-7. Epub 2005 Dec 7.
Dicofol is a non-systemic acaricide/miticide currently registered in the US and Canada for use on a wide variety of crops. This agrochemical has been identified as a potential candidate substance for the United Nations Economic Commission for Europe (UN-ECE) Persistent Organic Pollutant (POP) Protocol and implicated as a potential "endocrine disrupting compound". The technical product is usually synthesized from technical DDT and consists of approximately 80% and 20% of p,p'- and o,p'-dicofol isomers. The o,p'-substituted isomer of dicofol is chiral and may have enantiomer-specific activity; however, the stereospecific activity of o,p'-dicofol has not been reported. In this study, we examined the isomer- and enantiomer-specific endocrine disruption potential of dicofol using yeast-based steroid hormone receptor gene transcription assay designed with the human estrogen receptor (hER). Estrogenic activity of (+)-17-beta estradiol (positive control), p,p'-dicofol, racemic o,p'-dicofol [(+/-)-o,p'-dicofol] and the individual o,p'-dicofol enantiomers was measured via quantification of beta-galactosidase. The (+/-)-o,p'- and p,p'-dicofol were weak estrogen mimics (EC (50): 4.2 x 10 (-6) and 1.6 x 10 (-6) M, respectively) relative to estradiol (3.7 x 10 (-10) M). For o,p'-dicofol, the beta-galactosidase induction by (-)-o,p'-dicofol (EC (50): 5.1 x 10 (-7) M) was greater than the racemic mixture. However, the (+)-o,p'-dicofol enantiomer was found to have negligible estrogenic activity. These data indicate that dicofol is a weak hER agonist due to activity of the achiral p,p'-isomer and (-)-o,p'-substituted enantiomer and emphasizes the influence of chemical structure and configuration on biological responses to exposure from chiral compounds. |
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