title: Sites of action of local estradiol feedback mechanism in the frog (Rana esculenta) testis.
abstract: The direct effect of estradiol on testicular androgen biosynthesis was studied in the frog, Rana esculenta, measuring progesterone, 17 alpha-OH-progesterone, androstenedione, and androgens (T + DHT) in supernatants and testes incubated (6 hr, 15 degrees) with estradiol alone (10(-6) M) or in combination with crude pituitary homogenate (1 pituitary equivalent/tube). Estradiol, either alone or in combination with pituitary homogenate, induced decreases of 17 alpha-OH-progesterone, androstenedione, and androgens but was ineffective in modulating progesterone levels. Pituitary homogenate was effective in inducing a significant increase of androstenedione and androgens but was ineffective in modulating both progesterone and 17 alpha-OH-progesterone production. It is concluded that estradiol acts by decreasing the activity of steroidogenic enzymes starting from 17 alpha-hydroxylase, while pituitary homogenate does not affect the 17 alpha-hydroxylase activity, but it acts starting from 17,20-lyase.
authors.affiliation: Dipartimento di Fisiologia Umana e Funzioni Biologiche Integrate F. Bottazzi, I Facoltà di Medicina e Chirurgia, Università di Napoli, Italy.
authors.forename: S
authors.initials: S
authors.lastname: Fasano
authors.forename: M
authors.initials: M
authors.lastname: D'Antonio
authors.forename: R
authors.initials: R
authors.lastname: Pierantoni
mesh_terms: D019326:17-alpha-Hydroxyprogesterone; D000728:Androgens / Q000096:biosynthesis*; D000735:Androstenedione / Q000096:biosynthesis; D000818:Animals; D013196:Dihydrotestosterone / Q000378:metabolism; D004958:Estradiol / Q000494:pharmacology*; D005246:Feedback; D006908:Hydroxyprogesterones / Q000378:metabolism; D007986:Luteinizing Hormone / Q000494:pharmacology; D008297:Male; D010902:Pituitary Gland / Q000502:physiology; D011374:Progesterone / Q000096:biosynthesis; D011893:Rana esculenta / Q000378:metabolism*; D013254:Steroid 17-alpha-Hydroxylase / Q000378:metabolism; D013737:Testis / Q000187:drug effects / Q000378:metabolism*; D013739:Testosterone / Q000096:biosynthesis; D014020:Tissue Extracts / Q000494:pharmacology
chemical_list: D000728:Androgens; D006908:Hydroxyprogesterones; D014020:Tissue Extracts; D013196:Dihydrotestosterone; D013739:Testosterone; D000735:Androstenedione; D011374:Progesterone; D004958:Estradiol; D019326:17-alpha-Hydroxyprogesterone; D007986:Luteinizing Hormone; D013254:Steroid 17-alpha-Hydroxylase