Estradiol Secretion by Tadpole Ovaries Masculinized by Implanted Capsules of Cyanoketone

Female tadpoles of Rana catesbeiana were laparotomized at metamorphic stages XI-XIII and an empty capsule or one containing cyanoketone (CK), which is an inhibitor of Δ⁵-3β-hydroxysteroid dehydrogenase (Δ⁵-3β-HSD), was implanted intraperitoneally. Ovarian activity of Δ⁵-3β-HSD was examined histochemically 2 months later, estradiol-17β (E₂) secretion by the ovaries was measured by RIA 4 months later and histological changes of the ovaries were examined 6 months later. The Δ⁵-3β-HSD activity of the CK-treated ovaries was much lower than that of controls. E₂ secretion per froglet by CK-treated ovaries was about one third that of controls (p<0.001). Histological examination showed various degrees of masculinization of the ovaries, about 28% of which were totally transformed into testis-like structures.
As a result of suppressed Δ⁵-3β-HSD activity, dehydroepiandrosterone would have accumulated, resulting in deficient E₂ secretion and, therefore, ovarian masculinization. In tadpoles, this effect does not depend on the pituitary, whereas interrenal hyperplasia and hyperactivity do, indicating that interrenal function is not essential for ovarian masculinization. From these findings and our previous results, we suggest that disturbance of steroidogenesis by CK in the ovaries results in their masculinization.