Presence of 11-ketotestosterone in pre-differentiated male gonads of Odontesthes bonariensis

The involvement of androgens during sex differentiation period was investigated in the pejerrey Odontesthes bonariensis, by classic biochemical studies and gonadal histology. We studied in particular whether the enzyme activities involved in 11-oxygen- ated androgen production were active in a gonadal/ peritoneum complex (GPC) of very small larvae exposed to masculinizing temperatures previous to morphological sex differentiation (5 weeks post- hatching). The GPC was incubated with 17-hydroxy- progesterone ( 3 H-17P), and the presence of 11-KT as major metabolite in early gonads undergoing mascu- line pathway after temperature treatment exposure is reported. 11-KT was identified by thin-layer chroma- tography and high-pressure liquid chromatography. The present results show that 11-KT is produced at very early stages of testis development in pejerrey, being this androgen one of the main mediators of the masculinization induced by temperature treatment at the gonad level.