Ontogeny and pathway of formation of 5α-androstane-3α,17β-diol in the testes of the immature brushtail possum Trichosurus vulpecula

The testicular androgen 5α-androstane-3α,17β-diol (androstanediol) mediates virilisation in pouch young of a marsupial, the tammar wallaby, and is the principal androgen formed in immature rodent testes. To chart the pattern of androstanediol formation in another marsupial species, the testes or fragments of testes from brushtail possums (Trichosurus vulpecula) that spanned the age range from early pouch young to mature adults were incubated with ³H-progesterone and the products were identified by high-performance liquid chromatography. The only 19-carbon steroids identified in pouch young and adult testes were the Δ ⁴-3-keto-steroids testosterone and androstenedione. However, androstanediol and another 5α-reduced androgen (androsterone) were synthesised by testes from Day 87-200 males and these appeared to be formed from the 5α-reduction and 3-keto reduction of testosterone and androstenedione. In the prostate and glans penis of the immature male, ³H-androstanediol was converted to dihydrotestosterone. We conclude that the timing of androstanediol formation in the possum testis resembles the process in rodents rather than in the tammar wallaby and that any androstanediol in the circulation probably acts in target tissues via conversion to dihydrotestosterone.