Significant role of 5 alpha-reductase on feedback effects of androgen in rat anterior pituitary cells demonstrated with a nonsteroidal 5 alpha-reductase inhibitor ONO-3805.
A 5 alpha-reductase inhibitor with nonsteroidal structure, ONO-3805, has been used to study the role of 5 alpha-reductase on positive and negative feedback effects of androgen on gonadotropin secretion in the rat anterior pituitary gland. Initially, the potential of ONO-3805 to inhibit the formation of 5 alpha-dihydrotestosterone (DHT) was evaluated. The activity of 5 alpha-reductase in rat anterior pituitary gland was approximately one-fourth of that in rat prostate gland or epididymis, with a Michaelis' constant (Km) value for testosterone of 5-6 x 10(-7) M. When homogenates of rat anterior pituitary glands were incubated with 14C-testosterone (14C-T) in the presence of > or = 10(-7) M ONO-3805, the formation of labeled DHT and its metabolite 5 alpha-androstane-3 alpha,17 beta-diol was inhibited by > 90%. The inhibition pattern was non-competitive, and the inhibition constant (Ki value) derived from Lineweaver-Burk plots was 3.9 x 10(-11) M. Dispersed pituitary cells (1-2 x 10(5)/ml) were cultured for 48 hours and then further incubated with or without androgen and/or the inhibitor for 72 hours (basal secretion). After this incubation, the media were saved, and 10 nM of luteinizing hormone-releasing hormone (LH-RH) with the same concentration of androgen and/or the inhibitor as used in the 72-hour incubation was added to the cultures for 6 hours (LH-RH-induced secretion). Secreted follicle-stimulating hormone (FSH) and luteinizing hormone (LH) were assayed by radioimmunoassay (RIA). Both testosterone (T) and DHT stimulated 72-hour basal FSH secretion from cultured pituitary cells in a dose-dependent fashion.(ABSTRACT TRUNCATED AT 250 WORDS)
Nagamoto
A
A
Department of Urology, Yokohama City University, School of Medicine, Japan.
Noguchi
K
K
Murai
T
T
Kinoshita
Y
Y
D013741:3-Oxo-5-alpha-Steroid 4-Dehydrogenase / Q000502:physiology*; D058891:5-alpha Reductase Inhibitors; D000726:Androgen Antagonists / Q000494:pharmacology*; D000728:Androgens / Q000494:pharmacology*; D000818:Animals; D001549:Benzamides / Q000494:pharmacology*; D002087:Butyrates / Q000494:pharmacology*; D002478:Cells, Cultured; D013196:Dihydrotestosterone / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005246:Feedback / Q000502:physiology; D005640:Follicle Stimulating Hormone / Q000378:metabolism; D007987:Gonadotropin-Releasing Hormone / Q000494:pharmacology; D006062:Gonadotropins / Q000378:metabolism; D007986:Luteinizing Hormone / Q000378:metabolism; D008297:Male; D010903:Pituitary Gland, Anterior / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D013739:Testosterone / Q000494:pharmacology; D013997:Time Factors
D058891:5-alpha Reductase Inhibitors; D000726:Androgen Antagonists; D000728:Androgens; D001549:Benzamides; D002087:Butyrates; D006062:Gonadotropins; C076552:ONO 3805; D013196:Dihydrotestosterone; D007987:Gonadotropin-Releasing Hormone; D013739:Testosterone; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone; D013741:3-Oxo-5-alpha-Steroid 4-Dehydrogenase