Androgen receptor antagonist flutamide modulates estrogen receptor alpha expression in distinct regions of the hypospadiac rat penis

Emilie Elmelund¹Monica Kam Draskau¹Marie Berg¹Ida W Strand¹Jay R Black²Marta Axelstad¹Andrew Pask³Terje Svingen^1*

• ¹Danmarks Tekniske Universitet Fodevareinstituttet, Lyngby, Denmark
• ²The University of Melbourne School of Geography Earth and Atmospheric Sciences, Parkville, Australia
• ³The University of Melbourne School of BioSciences, Parkville, Australia

Intrauterine exposure to endocrine disrupting chemicals (EDCs), particularly anti-androgens, has been implicated in hypospadias by disrupting fetal masculinization of the genital tubercle (GT). Other pathways, including estrogen signaling, may also contribute but remain poorly characterized, especially in rats – a key model in chemical toxicity testing. Estrogen signaling has also been linked to hypospadias in mice, raising questions about androgen-estrogen interactions in guiding GT differentiation. Here, we induced hypospadias in male rat offspring via intrauterine exposure to the anti-androgenic drug flutamide and characterized androgen and estrogen receptor expression. We observed key structural and transcriptional changes in the developing penis, including altered estrogen receptor α (ERα, Esr1) expression. Notably, beyond this established androgen-estrogen relationship in hormone-sensitive tissues, anti-androgenic exposure also induced spatial changes in Esr1 expression in specific regions of the GT. Future toxicological testing using new approach methodologies (NAMs) should consider androgen-estrogen balance and crosstalk in reproductive tissues as a mechanism of action.