Sites of action of local estradiol feedback mechanism in the frog (Rana esculenta) testis.
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.
Fasano
S
S
Dipartimento di Fisiologia Umana e Funzioni Biologiche Integrate F. Bottazzi, I Facoltà di Medicina e Chirurgia, Università di Napoli, Italy.
D'Antonio
M
M
Pierantoni
R
R
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
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