Articles Effects of Endocrine-disrupting Contaminants on Amphibian Oogenesis: Methoxychlor Inhibits Progesterone-induced Maturation of Xenopus laevis
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BibTeX
@MISC{Vitro_articleseffects,
author = {Oocytes In Vitro and Daniel B. Pickford and Lan D. Morris},
title = {Articles Effects of Endocrine-disrupting Contaminants on Amphibian Oogenesis: Methoxychlor Inhibits Progesterone-induced Maturation of Xenopus laevis},
year = {}
}
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Abstract
There is currently little evidence of pollution-induced endocrine dysfunction in amphibia, in spite of widespread concem over global declines in this ecologically diverse group. Data regarding the potential effects of endocrine-disrupting coninans (EDCs) on reproductive function in amphibia are pcularly lcking. We hypothesized that estrogenic EDCs may disrupt progesterone-induced oocyte maturtion in the adult amphibian ovary, and tested this with an in vitro germinal vesicle breakdown assay wing defolliculated oocytes fiom the African clawed frog, Xenopus leais While a variety of natural and synthetic estrogens and xenoestrogens were inactive in this sytem, the proestrogenic pesicide methoxychlor was a surprisingly potent inhibitor of progesterone-induced oocyte maturation (median inhibitive concentration, 72 nM). This inhibitory activity was specific to methoxychlor, rather than to its estrogenic contaminants or metabolites, and was not antagonized by the estrogen recptor antagist ICI 182,780, suggesting that this activity is not estrogenic per se. The inhibitory activity of methoxychlor was dose dependent, reversible, and early acting. However, washout was uenabl to revers the efect of short methoxychlor exposure, and methoxychlor did not compet iively displace [3HJprogesterone from a specific binding site in the oocyte phsma membrane. Therefore, methoxychlor may exert its action not directly at the site of progesterone action, but downsteam on early events in maturational signaling, although the precse meanism of action is unclear. The activity of mnethoxychior in this system indicates that xenobiotics may exert endocrine-disrupting effects through interference with progestin-regulated processes and through mechanisms other than receptor antagonism..;iy zwLt amphibi antip rogestn, end e disruptors, eogen, GVBD, methoxychlor, oocyte maturation, progesterone, xenobiotics, Xiwnop. Environ Healo Perte 107:285-292 (1999). [Online 10 March 19991
Keyphrases
progesterone-induced maturation amphibian oogenesis endocrine-disrupting contaminant xenopus laevis article effect inhibitory activity receptor antagonism pollution-induced endocrine dysfunction early event iy zwlt amphibi antip rogestn maturational signaling oocyte phsma membrane progesterone action environ healo perte vitro germinal vesicle progesterone-induced oocyte maturation widespread concem synthetic estrogen proestrogenic pesicide methoxychlor adult amphibian ovary reproductive function potential effect oocyte maturation diverse group endocrine-disrupting coninans assay wing endocrine-disrupting effect precse meanism progestin-regulated process median inhibitive concentration estrogenic contaminant short methoxychlor exposure little evidence global decline potent inhibitor estrogen recptor antagist ici progesterone-induced oocyte maturtion estrogenic edcs
