Masculinization diminished by disruption of prenatal estrogen biosynthesis in male rats

Male rats were exposed to the aromatization inhibitor 1,4,6-androstatriene-3, 17-dione (ATD) in utero via prenatal injections to the mother on days 10 through 22 of gestation. At birth anogenital distance (AGD) and body weight (BW) were measured to assess effects of ATD on the development of genital morphology and body weight. Animals were castrated in adulthood and tested for the display of masculine sexual behavior in response to daily injections of 100 μg testosterone propionate replacement therapy. Prenatal exposure to ATD resulted in males with significantly decreased copulatory rates (MIPM) and slightly diminished probabilities of ejaculating when compared to control animals. Overall mounting, and intromission frequencies as well as percentages of animals displaying mounts and intromissions did not differ significantly across groups. These data lend support to the idea of a prenatal androgen-sensitive phase of neural sexual differentiation in which masculinization occurs, and further suggests that androgen aromatized to estrogen may be important for masculinization prenatally.