ToxSci Advance Access originally published online on January 11, 2007
Toxicological Sciences 2007 96(2):335-345; doi:10.1093/toxsci/kfm002
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Published by Oxford University Press 2007.
Prenatal Testosterone Exposure Permanently Masculinizes Anogenital Distance, Nipple Development, and Reproductive Tract Morphology in Female Sprague-Dawley Rats
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* Department of Zoology, North Carolina State University, Raleigh, North Carolina 27695
Reproductive Toxicology Division, Endocrinology Branch, National Health and Environmental Effects Research Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711
USEPA/NCSU Cooperative Training agreement, Raleigh, North Carolina 27695
Merck Research Laboratories, West Point, Pennsylvania 19486
1 To whom correspondence should be addressed at Reproductive Toxicology Division, Endocrinology Branch, MD 72, National Health and Environmental Effects Research Laboratory, US Environmental Protection Agency, Research Triangle Park, NC 27711. Fax: (919) 541-4017. E-mail: gray.earl{at}epa.gov.
Received October 25, 2006; accepted January 2, 2007
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Abstract |
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In mammals, abnormal increases in fetal androgens disrupt normal development of the female phenotype. Due to the recent concern regarding environmental androgen-active chemicals, there is a need to identify sources of fetal androgen variation and sensitive developmental markers for androgenic activity in female rats. Anogenital distances (AGD), nipple retention, reproductive tract, and external genitalia are morphological parameters organized by prenatal androgens and are predictive of altered masculinized/defeminized phenotype in adult female mice and rats. The objectives of this study were to (1) characterize the natural prenatal androgen environment of rats including the magnitude of the intrauterine position (IUP) effect, (2) characterize the permanent effects of prenatal androgen exposure on female rats, and (3) determine the ability of AGD and areolas to predict these permanent androgenic alterations in female rats. Untreated male fetal rats had higher tissue testosterone (T) concentrations than females in the amniotic fluid, reproductive tract, gonad, and fetal body. The intrauterine position (IUP) of male and female fetuses did not affect T concentrations or AGD in male or female rats at gestational day (GD) 22. Female offspring exposed to 0, 1.5, and 2.5 mg/kg/day testosterone propionate (TP) on GDs 14–18 displayed increased AGD at postnatal day (PND) 2 and decreased nipples at PND 13 and as adults. TP-induced changes in neonatal AGD and infant areola number were reliable indicators of permanently altered adult phenotype in female rats. Further, females in the two high-dose groups displayed increased incidences of external genital malformations and the presence of prostatic tissue, not normally found in female rats.
Key Words: AGD; areola; masculinization; reproductive development; fetal androgen; intrauterine position.
Disclaimer: The research described in the article has been reviewed by the National Health and Environmental Effects Laboratory, US Environmental Protection Agency and approved for publication. Approval does not signify that the contents necessarily reflect the views and policies of the agency nor does mention of trade names or commercial products constitute endorsement or recommendation for use.
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