Inhibition of induction of 20 alpha-hydroxysteroid dehydrogenase activity in rat corpora lutea in vitro by the progesterone antagonist RU486.

To determine if the antiprogestagen RU486 has a direct effect on luteal progesterone secretion, whole corpora lutea or dispersed luteal cells were incubated in the presence of RU486. Whole corpora lutea, isolated from rats at day 5 of pseudopregnancy, were incubated individually in hormone-free medium. The concentrations of progesterone and 20 alpha-dihydroprogesterone in the medium plus corpus luteum was measured before and after 24 h of incubation.

Sex difference in whole-body androgen content in rats on fetal days 18 and 19 without evidence that androgen passes from males to females.

The whole-body content of androgen (testosterone + 5 alpha-dihydrotestosterone) was significantly higher on Fetal Days 18 and 19 in male than in female rats; androgen content was equivalent in the two sexes at other fetal ages, including Days 16, 17, 20, and 21, and prior to parturition on Fetal Day 22. These results partially corroborate previous data of Weisz and Ward (Endocrinology 1980; 106:306-316), who measured testosterone in pooled plasma from rat fetuses and suggest that androgens contribute to masculine brain sexual differentiation only briefly during fetal life. No significant differences in whole-body androgen content were observed among groups of females situated in utero between 0, 1, or 2 males on each side (contiguous male model) or among groups of females with 0, 1, or 2 or more males located caudally (on the cervical side) in the same uterine horn, regardless of whether combined data from Fetal Days 17-22 or only Fetal Days 18 and 19 were considered.

Steroid concentrations in rat corpora lutea isolated during the oestrous cycle and pseudopregnancy: effect of induction of ovulation at dioestrus.

Corpora lutea could be identified under the dissection microscope up to 7 days after formation. They were isolated during the oestrous cycle and pseudopregnancy and the progesterone and 20 alpha-OH-progesterone contents were compared with serum values of these steroids. The pattern of progesterone in serum resembled that found in the corpora lutea.

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.

Periovulatory changes in serum concentration and ovarian content of 5 alpha-androstane-3 alpha, 17 beta-diol in the adult rat.

The high amounts of 5 alpha-androstane-3 alpha, 17 beta-diol (3 alpha-diol) present in immature female rats decline towards first ovulation, but on the day of first proestrus a peak is seen. This raises the possibility that during adulthood similar proestrous peaks may occur. Therefore, serum concentrations and ovarian content of 3 alpha-diol were estimated every two hours between 0900 and 2100 h in adult cyclic rats on the day of proestrus.