title: The biosynthesis of some androst-16-enes from C21 and C19 steroids in boar testicular and adrenal tissue.
abstract: 1. The formation of androst-16-enes from [4-(14)C]progesterone has been investigated with long-term incubations and short-term kinetic studies. After 4hr., 1.7 and 10.3% respectively of 3alpha- and 3beta-hydroxy-5alpha-androst-16-enes were formed in boar testis minces, but much smaller yields were obtained in boar adrenal. Both tissues formed small quantities of androsta-4,16-dien-3-one. 2. The amounts of androst-4-ene-3,17-dione and testosterone isolated were small, suggesting that androst-16-ene formation may occur preferentially in the boar testis. 3. In the absence of tissue no radioactive androst-16-enes were formed. 4. Incubation of both [4-(14)C]pregnenolone and [7alpha-(3)H]progesterone resulted in 3alpha- and 3beta-hydroxy-5alpha-androst-16-enes containing (3)H/(14)C ratios of near unity and confirmed that both C(21) steroids were precursors. A similar incubation with 17alpha-hydroxy[4-(14)C]-progesterone and [7alpha-(3)H]progesterone gave the same Delta(16)-alcohols, but they contained only (3)H, indicating that side-chain cleavage of pregnenolone and progesterone occurred before 17alpha-hydroxylation. 5. Dehydroepiandrosterone, testosterone, testosterone acetate and 16-dehydroprogesterone were not found to be precursors of Delta(16)-steroids. 6. A pathway is proposed for the biosynthesis of 3alpha- and 3beta-hydroxy-5alpha-androst-16-enes from pregnenolone and progesterone; this may involve androsta-4,16-dien-3-one as an intermediate, but excludes 17alpha-hydroxyprogesterone, testosterone and dehydroepiandrosterone.
mesh_terms: D000311:Adrenal Glands / Q000378:metabolism*; D000731:Androstanes / Q000096:biosynthesis*; D000818:Animals; D001345:Autoradiography; D002247:Carbon Isotopes; D002855:Chromatography, Thin Layer; D003687:Dehydroepiandrosterone / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D011284:Pregnenolone / Q000378:metabolism*; D011374:Progesterone / Q000378:metabolism*; D013552:Swine; D013737:Testis / Q000378:metabolism*; D013739:Testosterone / Q000378:metabolism*; D014316:Tritium
chemical_list: D000731:Androstanes; D002247:Carbon Isotopes; D014316:Tritium; D013739:Testosterone; D003687:Dehydroepiandrosterone; D011374:Progesterone; D011284:Pregnenolone