Inhibition of 5 alpha-reductase activity in prepubertal female rats: effect on the timing of first ovulation.
The activity of 5 alpha-reductase in the ovary of prepubertal rats decreases prior to first ovulation. To determine whether this decrease causes the onset of first ovulation, prepubertal female were treated with a specific inhibitor of 5 alpha-reductase activity and the effect on the time of first ovulation was studied. The steroid (6-methylene-progesterone, MEP) gives irreversible inhibition of ovarian 5 alpha-reductase activity in vitro with testosterone as well as progesterone as substrate. A MEP-containing silicone tube, releasing 245 nmol per 24 h in vitro, was implanted sc in the back of 25-day-old female rats. This resulted a day 30 in a significantly lower 5 alpha-reductase activity in the ovary than in control rats (42.0 +/- 3.8 pmol/min per mg ovary in MEP-treated rats vs 98.8 +/- 2.4 pmol/min per mg ovary in control rats). Nearly the same extent of inhibition was found at day 35 27.4 +/- 2.1 in MEP-treated rats vs 56.2 +/- 5.9 in control rats). However, implantation of a MEP-containing silicone tube under the skin or inserting a pellet containing MEP under the ovarian capsule did not result in advancement of the first ovulation. These data indicate that in the female rat a decrease of 5 alpha-reductase activity alone is not sufficient to induce the first ovulation.
Uilenbroek
J T
JT
Department of Endocrinology, Growth and Reproduction, Faculty of Medicine, Erasmus University, Rotterdam, The Netherlands.
Woutersen
P J
PJ
D013741:3-Oxo-5-alpha-Steroid 4-Dehydrogenase / Q000378:metabolism*; D015113:Androstane-3,17-diol / Q000378:metabolism; D000736:Androstenes / Q000494:pharmacology; D000818:Animals; D005260:Female; D010053:Ovary / Q000201:enzymology*; D010060:Ovulation / Q000187:drug effects*; D011374:Progesterone / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D013739:Testosterone / Q000378:metabolism / Q000494:pharmacology
D000736:Androstenes; C036790:6-methylene-4-pregnene-3,20-dione; D015113:Androstane-3,17-diol; C004251:etienic acid; D013739:Testosterone; D011374:Progesterone; D013741:3-Oxo-5-alpha-Steroid 4-Dehydrogenase