Prolactin-stimulated ovarian androgen metabolism.
Activities of 5 alpha, 3 alpha, and 3 beta reductases were studied with the use of microsomal fractions isolated from the ovaries of immature female rats after treatment with pregnant mares' serum (PMS) followed by human chorionic gonadotropin (hCG). The effect of exogenous prolactin treatment was similarly assessed by comparing enzymic activity in prolactin-treated rat ovaries to that in control rat ovaries, after pretreatment with PMS. With the use of 3H-testosterone as substrate, reductase activities were determined by measuring the production of dihydrotestosterone and the 3 alpha- and 3 beta-epimers of androstanediol. The rate of formation of tritiated androstanediol from radiolabeled testosterone was ten times higher than that of tritiated dihydrotestosterone during the follicular phase. After ovulation, the metabolism of testosterone to both androstanediol and dihydrotestosterone decreased markedly. Negligible amounts of estrogen and androsterone were formed, and most of the androstanediol was found to be 5 alpha-androstane-3 beta, 17 beta-diol. The Michaelis-Menten constant (Km) for 5 alpha-reductase was 1.3 x 10(-5)M. During the follicular phase, the sum of 3H-dihydrotestosterone and 3H-androstanediol produced from radiolabeled testosterone was found to be 30% greater in prolactin-treated animals than in control animals. Implication of increased ovarian androgen metabolism as a consequence of hyperprolactinemia are discussed.
D013741:3-Oxo-5-alpha-Steroid 4-Dehydrogenase / Q000096:biosynthesis; D000728:Androgens / Q000096:biosynthesis*; D015113:Androstane-3,17-diol / Q000096:biosynthesis; D000735:Androstenedione / Q000096:biosynthesis; D000818:Animals; D006063:Chorionic Gonadotropin / Q000494:pharmacology; D013196:Dihydrotestosterone / Q000096:biosynthesis; D004958:Estradiol / Q000096:biosynthesis; D005260:Female; D006064:Gonadotropins, Equine / Q000494:pharmacology; D010053:Ovary / Q000187:drug effects / Q000378:metabolism*; D011388:Prolactin / Q000494:pharmacology*; D051381:Rats; D013739:Testosterone / Q000494:pharmacology
D000728:Androgens; D006063:Chorionic Gonadotropin; D006064:Gonadotropins, Equine; D013196:Dihydrotestosterone; D015113:Androstane-3,17-diol; D013739:Testosterone; D000735:Androstenedione; D004958:Estradiol; D011388:Prolactin; D013741:3-Oxo-5-alpha-Steroid 4-Dehydrogenase