Prenatal Testosterone Exposure Permanently Masculinizes Anogenital Distance, Nipple Development, and Reproductive Tract Morphology in Female Sprague-Dawley Rats

Abstract

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.

Environmental levels of oestrogenic and antiandrogenic compounds feminize digit ratios in male rats and their unexposed male progeny

“…We jointly assessed the AGD-a confirmed sexually dimorphic marker in rodents that is disrupted during the perinatal period by sex steroids as well as endocrine disruptor exposure (at non-environmental levels) [18]-because it represents the reference endpoint routinely measured in reproductive toxicology as well as in tests for regulatory purposes. Therefore, we considered comparatively assessing both methods, because this may have implications in various domains such as clinical studies (it is obviously easier to measure digit length ratios than AGD in humans) or reproductive toxicology, with the particular question of the effect of low doses and mixtures of EASs.…”

“…Intriguingly, significant feminization of 2D : 4D was also found in the unexposed progeny. We also comparatively assessed the AGD-a confirmed sexually dimorphic marker in rodents that is disrupted during the perinatal period by sex steroids as well as endocrine disruptor exposure (at nonenvironmental levels) [18]-because it represents the reference endpoint routinely measured in reproductive toxicology as well as in tests for regulatory purposes, and we found neither differences in AGD when comparing exposed and control rats or an association between AGD and digit ratios.…”

Homosexuality as a Consequence of Epigenetically Canalized Sexual Development

“…The same relationship is found in the rat, in which T concentrations strongly overlap between the sexes during the time (and all points previous) when the phallus and vulva are differentiating (Weisz and Ward 1980). Yet discordance between the gonad and the genitalia (including ambiguous genitalia) is rare in both humans (Sax 2002) and rats (Ostby et al 1999;Hotchkiss et al 2007). Therefore, the available data do not fully support the prenatal androgen paradigm because there is too much overlap in circulating androgens to be consistent with the observed low discordance between the gonad and the genitalia observed in both humans and the rat model system.…”

Factors controlling testis descent

“…Studies in rodents can replicate the effects of androgen insufficiency by administering such compounds to pregnant dams anddemonstrating undescended testes, hypospadias and reduced anogenital distance in male offspring (48). The latter morphological marker is a sensitive bioassay of androgen action in animal reproductive toxicology studies (49). Data are available on anogenital distance in newborns measured according to the anatomical landmarks illustrated in Fig.…”