title: The in vitro biosynthesis of epitestosterone and testosterone from C19 steroid precursors in the testis of the lizard Tiliqua rugosa.
abstract: The metabolism of androgens in the testis of the lizard Tiliqua rugosa has been studied in vitro by incubating cellular homogenates with radiolabeled C19-steroid substrates. The identification 17 beta-oxidoreductase and 3 beta-hydroxysteroid dehydrogenase/isomerase activities. Aromatase, 5 alpha-reductase, and 17 alpha/beta-epimerase activities were not detected. The 17 alpha-oxidoreductase activity was temperature dependent (maximal at 32 degrees), while the 17 beta-oxidoreductase activity was temperature independent. Time yield and dual-label studies indicated that testosterone biosynthesis mainly involves the 4-ene pathway (via androstenedione), whereas the formation of epitestosterone uses both the 4-ene and 5-ene (via 5-androstene-3 beta, 17 alpha-diol) pathways. The function of alternative pathways in androgen biosynthesis is discussed, as is the role of temperature in the intratesticular regulation of androgen production.
authors: Biological Sciences, Deakin University, Geelong, Victoria, Australia.
authors: P A
authors: PA
authors: Huf
authors: A R
authors: AR
authors: Bourne
authors: T G
authors: TG
authors: Watson
mesh_terms: D015114:Androstenediol / Q000302:isolation & purification / Q000378:metabolism*; D000734:Androstenediols / Q000378:metabolism*; D000818:Animals; D002250:Carbon Radioisotopes; D004845:Epitestosterone / Q000096:biosynthesis*; D008116:Lizards; D008297:Male; D013696:Temperature; D013737:Testis / Q000378:metabolism*; D013739:Testosterone / Q000096:biosynthesis*; D014316:Tritium
chemical_list: D000734:Androstenediols; D002250:Carbon Radioisotopes; D014316:Tritium; D013739:Testosterone; D004845:Epitestosterone; D015114:Androstenediol