Changes in ovarian steroidogenesis in prepuberal rats induced to ovulate by low doses of human chorionic gonadotrophin.
To determine whether the decrease in ovarian 5 alpha-reduced androgen production before first ovulation might be caused by an increase in serum LH, prepuberal female rats were injected at 28-31 days of age with low doses of human chorionic gonadotrophin (hCG) (0.05-0.075 i.u., four times daily). This treatment resulted in ovulation of six to ten ova per rat on day 32 in all animals. Treatment with hCG resulted in a gradual decrease in ovarian content and production (i.e. content in ovary and medium after 4h of incubation) of 5 alpha-dihydrotestosterone (DHT) and 5 alpha-androstane-3 alpha, 17 beta-diol. The ovarian content of DHT and the production of 5 alpha-androstane-3 alpha, 17 beta-diol decreased within 24 h after the first injection of hCG. Oestradiol content and production increased between 24 and 48 h after the start of treatment and was maximal on day 31 (day of pro-oestrus). Activities of 5 alpha-reductase and aromatase were measured in ovarian homogenates obtained on days 29-31. Activity of 5 alpha-reductase in hCG-treated rats was lower than that in control rats on all days studied. Aromatase activity in hCG-treated rats increased between days 29 and 31. It was concluded that multiple injections of low doses of hCG, which may induce ovulation, cause a decrease in 5 alpha-reduced androgen production, which is probably due to a decrease in 5 alpha-reductase activity. The subsequent increase in oestradiol production corresponds with an increase in aromatase activity.(ABSTRACT TRUNCATED AT 250 WORDS)
D000728:Androgens / Q000096:biosynthesis*; D015113:Androstane-3,17-diol / Q000031:analogs & derivatives / Q000096:biosynthesis; D000818:Animals; D001141:Aromatase / Q000378:metabolism; D042944:Cholestenone 5 alpha-Reductase; D006063:Chorionic Gonadotropin / Q000494:pharmacology; D013196:Dihydrotestosterone / Q000096:biosynthesis*; D004958:Estradiol / Q000096:biosynthesis; D005260:Female; D010053:Ovary / Q000201:enzymology / Q000378:metabolism*; D010062:Ovulation Induction; D010088:Oxidoreductases / Q000378:metabolism; D011359:Proestrus; D051381:Rats; D011919:Rats, Inbred Strains; D012741:Sexual Maturation; D013997:Time Factors
D000728:Androgens; D006063:Chorionic Gonadotropin; D013196:Dihydrotestosterone; C015680:androstane-3,7,17-triol; D015113:Androstane-3,17-diol; D004958:Estradiol; D010088:Oxidoreductases; D001141:Aromatase; D042944:Cholestenone 5 alpha-Reductase