Steroid biosynthesis by the testes of the dogfish Scyliorhinus caniculus

Dogfish testes were incubated with radioactive progesterone, pregnenolone, and testosterone, and both free and conjugated metabolites were examined. In the free fraction, which contained 42–70% of the incubated radioactivity, progesterone, androstenedione, and testosterone were identified as incubation products of both progesterone and pregnenolone. In addition, a small amount of 17α-hydroxyprogesterone was identified as a metabolite of progesterone in one fish. Testosterone and androstenedione were the only free steroids isolated from incubations of testosterone. Although steroid glucuronide formation was insignificant, very large amounts of solvolysable steroids were isolated from all incubations. With pregnenolone and progesterone, 10–30% of the incubated radioactivity was recovered in this solvolysable fraction, in which the major products were identified as testosterone and 17α,20β-dihydroxy-4-pregnen-3-one. With two fish incubated with ¹⁴C]testosterone, 5α-androstane-3β, 17β-diol was isolated in low yield from the solvolysable fraction in addition to testosterone, but in one incubation with ³H]testosterone, the sole component of this fraction was testosterone which accounted for 21% of the initial radioactivity.