Hormonal regulation of activities of 4-ene-5 alpha-reductase and 17 beta-ol-dehydrogenase in adult androgen-sterilized rat ovaries

Steroid biosynthesis in the Sertoli-Leydig cell tumor: effects of insulin and luteinizing hormone

In vitro steroid production by a virilizing Sertoli-Leydig cell tumor of the ovary was studied. For comparison, stromal tissue from the opposite normal ovary was also incubated under similar conditions. The tumor fragments secreted significantly more testosterone (527 +/- 168 versus 48 +/- 29 pg/mg tissue, p less than 0.001), androstenedione (1188 +/- 400 versus 40 +/- 10 pg/mg tissue, p less than 0.001), and dehydroepiandrosterone (419 +/- 132 versus 73 +/- 25 pg/mg tissue, p less than 0.004) than that of normal ovarian stroma. Measurement of steroids in the ovarian venous serum draining the tumor indicated a peripheral ovarian gradient for both delta 4 and delta 5 steroids. Incubation of tumor fragments with luteinizing hormone alone resulted in a significant increase in the secretion of androstenedione and dehydroepiandrosterone (p less than 0.05). Addition of insulin to luteinizing hormone resulted in significantly greater release of androstenedione than that of treatment with luteinizing hormone alone (p less than 0.04). Addition of insulin had no effect on the release of dehydroepiandrosterone. Luteinizing hormone and insulin, either alone or in combination, failed to produce any change in the secretion of testosterone. We conclude that (1) increased testosterone secretion by Sertoli-Leydig cell tumor resulted from increased availability of precursors from both delta 4 and delta 5 pathways; (2) the tumor was responsive to luteinizing hormone with an increase in the secretion of androstenedione and dehydroepiandrosterone; (3) insulin acts synergistically with luteinizing hormone to increase secretion of androstenedione; (4) the tumor has specific binding sites for insulin; and (5) the increased levels of insulin and luteinizing hormone in polycystic ovarian disease may play a role in the pathogenesis of Sertoli-Leydig cell tumor.

Age-dependent changes in the multiple forms of the soluble 17 beta-hydroxysteroid dehydrogenase of female rabbit liver

The soluble NADP-dependent 17 beta-hydroxysteroid dehydrogenase activity of female rabbit liver increases with the age of the animal, the specific activity of the enzyme in the 56-day-old rabbit being 3 times that of the 28-day-old animal. The increase in activity is accompanied by a change in the molecular heterogeneity of the enzyme. Three forms (enzymes I, II and III) were identified in the liver cytosol of the 56-day-old female rabbit, whereas only one major form (enzyme IIIY) was present in the 28-day-old animal. Peptide maps of the four purified enzymes showed that there were minor differences in structure. The enzyme present in the liver of the 28-day-old rabbit was distinct from the three enzymes of the 56-day-old animal. All of the enzymes exhibited bifunctional activity, having 17 beta-hydroxysteroid dehydrogenase activity towards androgen and oestrogen substrates and 3 alpha-hydroxysteroid dehydrogenase activity towards androgens of the 5 beta-androstane series. The differences in substrate specificity of the enzymes paralleled their differences in structure. The data suggest that one enzyme (enzyme III) may have a special role in steroid metabolism during development in the female rabbit.

Differential actions of FSH and androgens on progesterone catabolism by rat granulosa cells

Rat granulosa cells were preincubated with follicle-stimulating hormone (FSH, 1 micrograms/ml) and/or androgens (testosterone and 5 alpha-dihydrotestosterone, 0.5 microM) and subsequent [4-14C]progesterone metabolism by these cells was studied. Granulosa cells metabolized radiolabeled progesterone to three major products 20 alpha-hydroxy-4-pregnen-3-one, 3 alpha-hydroxy-5 alpha-pregnan-20-one, and 5 alpha-pregnane-3 alpha, 20 alpha-diol. Androgens, but not FSH, decreased overall progesterone utilization. Both FSH and androgens decreased conversion of progesterone to 20 alpha-hydroxy-4-pregnen-3-one. The accumulation of 5 alpha-pregnane-3 alpha, 20 alpha-diol was increased by FSH, decreased by testosterone, and not altered by 5 alpha-dihydrotestosterone. The accumulation of 3 alpha-hydroxy-5 alpha-pregnan-20-one was significantly increased by both FSH and androgens. Present results indicate that FSH as well as androgens modulate progesterone metabolism by rat granulosa cells. FSH appears to increase 5 alpha-reductase activity and/or decrease 20 alpha-hydroxysteroid dehydrogenase activity while androgens decrease only 20 alpha-hydroxysteroid dehydrogenase activity.

Regulation of steroid-transforming enzymes by endogenous steroids

The biosynthesis of C21, C19, and C18 steroids in adrenal, ovary, testis and foeto-placental unit is summarized and the properties of the enzymes involved are described, with particular reference to their substrate specificities and to the possible controlling effects of endogenous steroids. It is concluded that these may exert a considerable regulatory role in vivo in steroid hormone biosynthesis.

Androgenic alteration in pathways of C19-steroid metabolism by cultured rat granulosa cells

Pretreatment of rat granulosa cells with androgens altered the subsequent metabolism of [4-14C]testosterone in vitro. In cells pretreated with testosterone or 5 alpha-dihydrotestosterone, the accumulation of radiolabeled 5 alpha-androstane-3 alpha, 17 beta-diol decreased by 40% and 36%, respectively, when compared with control, while the levels of androstenedione increased by 64% and 54%, respectively. For comparison, pretreatment with 0.5 microM 17 beta-estradiol failed to affect the level of radioactivity incorporated into all three major metabolites. In other experiments, granulosa cells were incubated in the presence of 0.5 microM [4-14C]dihydrotestosterone. While 5 alpha-androstane-3 alpha, 17 beta-diol was decreased slightly by pretreatment with testosterone or 5 alpha-dihydrotestosterone, radiolabeled androsterone was increased significantly. These data suggest a possible modulatory action of androgens on ovarian 17 beta-hydroxysteroid dehydrogenase and/or 5 alpha-reductase activity.

Comparative studies of androgen metabolism in theca and granulosa cells of human follicles in vitro

In eight separate experiments, theca and granulosa were isolated from human follicles (5-25 mm in diameter), and their capacities to metabolize radiolabelled testosterone in 24 hour cultures were assessed. Theca metabolized testosterone primarily to androstenedione, however significant aromatization to estradiol-17 beta and to estrone was also observed. Granulosa metabolized testosterone primarily to estra-diol-17 beta and estrone, while smaller quantities were converted to androstenedione. In seven of these experiments, the intermediate of aromatization, 19-hydroxytestosterone, was identified. In six of these experiments, theca, when compared to granulosa, produced more androstenedione but less estradiol-17 beta and estrone. 5 alpha-Reduced androgens were non-detectable or produced in small quantities. In a single experiment, metabolism of androstenedione was compared to metabolism of testosterone by both theca and granulosa. Theca metabolized androstenedione to testosterone in smaller quantities than testosterone to androstenedione. Granulosa metabolized androstenedione to testosterone in higher quantities than testosterone to androstenedione. Both theca and granulosa aromatized androstenedione more readily than testosterone.

Metabolism of testosterone by human granulosa cells in culture: influence of follicle-stimulating hormone and luteinizing hormone

Human granulosa cells were isolated from follicles (8 to 15 mm) and cultivated for 24 hours in the presence or absence of follicle-stimulating hormone (NIH-FSH-HS-1, 1 microgram/ml) and luteinizing hormone (NIAMDD-hLH-1, 1 microgram/ml). Testosterone -4-14C was added subsequently to all cultures for 4-, 6-, and 24-hour periods. Of the seven metabolites of testosterone studied, 17 beta-estradiol (E2) and estrone (E1) were the major products. In all patients, levels of E2 were three to ten times higher than those of E1. Production of E2, but not E1, was stimulated by either follicle-stimulating hormone (FSH) or luteinizing hormone (LH). The cells of the largest follicle (15 mm) showed greater response to LH than to FSH. Production of the other C19 and C18 metabolites was very low or negligible. These results further suggest that FSH regulates the aromatization of testosterone in human granulosa cells, and that LH may have the same effect on the matured follicle during the preovulatory period.

5 beta- and 5 alpha-reductases for 4-ene-3-ketosteroids in golden hamster ovaries at different stages of development

Ovarian homogenates from 10-, 23- 128- and 60-day-old golden hamsters were incubated with [14C]-4-androstene-3,17-dione or [7-3H]-progesterone in the presence of NADPH and enzyme activities and metabolism of progesterone were estimated. A rapid increase in uterine weight was found around 28 days of age. The activity of 5 alpha-reductase was very high in the ovaries of 23-day-old hamsters (647 +/- 117 (SD) nmol/g tissue/h), high in those of 28-day-old hamsters (135 +/- 4) and low in those of 10- and 60-day-old animals (20 +/- 16, 39 +/- 11). However, the activity of 5 beta-reductase was high in all ovaries of golden hamsters at different stages of development (84-132 nmol/g tissue/h). The major C-21-17-hydroxysteroids and C19-steroids formed from progesterone by the ovaries of 23-day-old hamsters were 5 alpha-steroids such as 3 alpha, 17-dihydroxy-5 alpha-pregnan-20-one and androsterone, whereas those by the ovaries of 28- and 60-day-old hamsters were 4-ene-3-ketosteroids and 5 beta- and 5 alpha-steroids such as 17-hydroxy-4-pregnene-3,20-dione. 3 alpha, 17-dihydroxy-5 alpha- and 5 beta-pregnan-20-one, 4-androstene-3,17-dione, testosterone and androsterone. The formation of oestradiol-17 beta and oestrone from progesterone was found only in the ovaries of 38- and 60-day-old hamsters. These results show that similarly high levels of 5 beta-reductase are present in all ovaries from suckling, immature and adult golden hamsters and that high levels of 5 alpha-reductase are formed only in ovaries from immature hamsters, especially those with small uterus. The active 5 alpha-reduction of 4-ene-3-ketosteroids may be responsible for the decrease in the formation of oestrogens in immature hamster ovaries.