Gonadal differentiation and secretions of estradiol and testosterone of the ovaries of Rana catesbeiana tadpoles treated with 4-hydroxyandrostenedione.

Laparotomized female tadpoles of Rana catesbeiana at TK stages X-XII, about 9 months old, were implanted intraperitoneally with empty capsules or capsules containing 4-hydroxyandrostenedione (4-OHA), known as an aromatase inhibitor in vertebrates. Histology, gonosomatic index, and secretions of estradiol (E2) and testosterone (T) of the ovaries were investigated. Three months after the treatment, histological examination revealed various degrees of sex reversal in the ovaries treated with 4-OHA and 79% (57 in 72) were transformed into testes. The ovaries of control tadpoles, however, displayed normal histological appearance. Radioimmunoassay showed that secretion of E2 was decreased while that of T was increased in 4-OHA treated ovaries. The gonosomatic index displayed a decline tendency from control females through experimental animals to untreated control males. These results indicated that activity of aromatase in the ovaries was inhibited by 4-OHA, resulting in accumulation of T which induced transformation of the ovaries into testes.