The influence of progesterone on the conversion of 17-hydroxyprogesterone to testosterone in the mouse testis.

PIP: Tritiated-progesterone and 17-hydroxyprogesterone-carbon 14 were incubated with mouse testis homogenates obtained from adult Swiss mice. The distribution of each isotope in 17-hydroxyprogesterone, androstenodione and testosterone when the 2 precursors were present in various ratios were compared with the amounts when each precursor was present alone. Formation of the major compound in these experiments occurs by a series of sequential reactions: progesterone to 17-hydroxyprogesterone to androstenodione to testosterone, and the assumption is made that the sum of the products beyond a given enzymatic step equals the amount of a particular precursor undergoing that reaction. The presence of equal amounts of progesterone and 17-hydroxyprogesterone caused a small but significant reduction in 17-hydroxyprogesterone activity. The presence of added 17-hydroxyproesterone essentially did not affect the rate at which 17-hydroxyprogesterone or 17-oxy radical formed from progesterone, but the amount of C-19 steroids progressively decreased as progesterone concentration was raised above 2.5 nmales per ml. This was probably because of the close association of active sites of the 17-hydroxylase and lyase. The presence of progesterone markedly inhibited the rate of splitting of the added 17-hydroxyprogesterone. The inhibition was probably competitive as previously reported for rat testis. The results indicate that the active site of the 17-beta-dehydrogenase was not closely associated with the lyase. At higher levels of either precursor alone the 17-beta-dehydrogenase approached saturation, but the inhibition of lyase activity by progesterone left the 1-beta-dehydrogenase unsaturated and a higher proportion of the smaller amounts of androstenodione formed was converted to testesterone.^ieng

Changes in the concentration of 17 alpha,20 alpha-dihydroxypregn-4-en-3-one during pregnancy, labor, and delivery and the effect of dexamethasone treatment during the third trimester of pregnancy.

To study whether an alteration of placental steroid metabolism occurs during human pregnancy similar to that in the ewe, we measured the concentration of 17 alpha,20 alpha-dihydroxypregn-4-en-3-one (17,20 alpha-OHP) in peripheral plasma. As the pregnant ewe nears term, the utero-ovarian venous concentrations of 17,20 alpha-OHP increase, suggesting induction of placental 17 alpha-hydroxylase. The mean plasma concentration of 17,20 alpha-OHP measured by RIA in normal menstruating women was 1.1 +/- 0.12 (+/- SE) ng/ml. Similar values were found in plasma from ovariectomized women. In the first and second trimesters of pregnancy, the plasma values of 17,20 alpha-OHP were not significantly different from those in the nonpregnant women, while in the third trimester, the mean plasma concentration was significantly increased (mean +/- SE, 2.6 +/- 0.3 ng/ml). The plasma concentration of 17,20 alpha-OHP was studied in 15 women in late pregnancy, during labor, at delivery, and postpartum. The concentration increased during labor as delivery approached and reached a maximum at the time of delivery, ranging from 4.1-11.2 ng/ml, followed by a significant decrease within 1-4 h postpartum. The mean (+/- SE) 17,20 alpha-OHP concentrations in the venous and arterial cord blood were 8.7 +/- 1.6 and 5.8 +/- 2.0 ng/ml, respectively. To study the effect of increased circulating level of corticosteroids on the serum concentration of progestins, 74 women with premature labor with or without premature rupture of membranes were treated with either placebo or 4 im injections of dexamethasone phosphate (5 mg each) at 12-h intervals. Blood samples were drawn at 0, 14, 26, and 46 h, approximately 2 h after each dexamethasone dose. Plasma progesterone, 17 alpha-hydroxyprogesterone (17-OHP), and 17,20 alpha-OHP values at zero time were 140 +/- 15.8 (+/- SE; n = 21), 7.8 +/- 1.5 ng/ml (n = 16), and 2.3 +/- 0.3 ng/ml (n = 20), respectively. In patients treated with dexamethasone, the plasma progesterone values tended to increase at 14, 20, and 46 h, but 17-OHP and 17,20 alpha-OHP values decreased significantly compared to levels in placebo-treated patients. In conclusion, the concentration of plasma 17,20 alpha-OHP increased during the third trimester of pregnancy, and the increment continued through labor and delivery. During antenatal dexamethasone administration, progesterone in the maternal circulation tended to increase, while 17-OHP and 17,20 alpha-OHP decreased significantly. In the human, in contrast to the ewe, dexamethasone treatment in the third trimester does not appear to stimulate placental 17 alpha-hydroxylase activity.

Polycystic ovarian disease: animal models.

The reproductive systems of human beings and other vertebrates are grossly similar. In the ovary particularly, the biochemical and physiologic processes are identical not only in the formation of germ cells, the development of primordial follicles and their subsequent growth to Graafian follicles, and eventual ovulation but also in anatomic structure. In a noncarcinogenic human ovary, hypersecretion of androgen causes PCOD. Such hypersecretion may result from a nonpulsatile, constant elevated level of circulating LH or a disturbance in the action of neurotransmitters in the hypothalamus. In studying the pathophysiology of PCOD in humans, one must be aware of the limitations for manipulating the hypothalamic-pituitary axis. Although the rat is a polytocous rodent, the female has a regular ovarian cyclicity of 4 or 5 days, with distinct proestrus, estrus, and diestrus phases. Inasmuch as PCOD can be experimentally produced in the rat, that species is a good model for studying the pathophysiology of human PCOD. These PCOD models and their validity have been described: (1) estradiol-valerate, (2) DHA, (3) constant-light (LL), and (4) neonatally androgenized. Among these, the LL model is noninvasive and seems superior to the others for study of the pathophysiology of PCOD. The production of the polycystic ovarian condition in the rat by the injection of estrogens or androgens in neonate animals, or estradiol or DHA in adult rats, or the administration of antigonadotropins to these animals all cause a sudden appearance of the persistent estrus state by disturbing the metabolic and physiologic processes, whereas exposure of the adult rat to LL causes polycystic ovaries gradually, similar to what is seen in human idiopathic PCOD. After about 50 days of LL, the rat becomes anovulatory and the ovaries contain thickened tunica albuginea and many atretic follicles, and the tertiary follicles are considerably distended and cystic. The granulosa and theca cells appear normal histologically, although some of the stromal cells appear hypertrophic. The anatomic features consequent to polycystic ovaries resulting from LL are similar to those in human PCOD, and both rat and human PCOD ovarian cells still retain the ability to respond to FSH/LH, LHRH, and unilateral ovariectomy. In the estradiol valerate rat model, although the anatomy and physiology of the ovary resemble those of PCOD patients, the progressive degeneration of the hypothalamus and the altered response of the pituitary to LHRH make this model inappropriate for studying the hypothalamic-pituitary-ovarian axis in the polycystic ovary condition.(ABSTRACT TRUNCATED AT 400 WORDS)

Steroidogenesis in human polycystic ovary.

Polycystic ovarian disease (PCOD) is a heterogenous condition with a broad clinical and pathologic spectrum that may reflect the effects of diverse etiologic factors. Depending on the diagnostic data available from patients, various steroidogenic enzyme blocks have been postulated, mostly implicating higher-than-normal production of circulating delta 4-androstenedione, testosterone, and, in some cases, dehydroisoandrosterone. These high levels of androgens, because of their peripheral conversion to estrogens, lead to inappropriate secretion of gonadotropins in PCOD. Whatever may be the etiologic factors, the common entity is a polycystic ovary. Such an ovary contains preantral follicles, few antral follicles, many atretic follicles, and follicular and degenerative cysts. The follicles lack a sufficient number of mature granulosa cells to produce enough estrogens. On the other hand, there is a hypertrophy of stromal and thecal tissue continuously producing androgens. The steroid analysis of the follicular fluid obtained from the cystic follicles of the polycystic ovary revealed high concentration of delta 4-androstenedione and absence of, or only minute amounts of, estrogens. Early studies of biosynthesis of steroids in the polycystic ovary demonstrated conversion of progesterone mainly to androgens. Arising from these observations was the suggestion that an aromatase enzyme block existed. That suggestion was corroborated in the findings of higher-than-normal circulating androgens in PCOD. Later, other partial enzymatic blocks of beta-hydroxydehydrogenase and 17-hydroxylase were also suggested. However, it is known that the therapies such as wedge resection, administration of FSH, or FSH/LH (Pergonal) and LHRH leads to ovulation and, in most cases, normal cyclicity in the polycystic ovary. The knowledge gained from these therapies clearly indicates that the enzymatic blocks or abnormal steroidogenesis in the polycystic ovary may be due to the absence of proper gonadotropin response, and the main defect may be at the hypothalamic-pituitary axis. In PCOD with hyperinsulinemia, insulin and IGF-I have been implicated in the production of androgens by the polycystic ovary. The mechanism of the action of insulin or IGF-I is not yet known, however.

Dietary fat up-regulates the apolipoprotein E mRNA level in the Zucker lean rat brain.

High-fat diet alters apo E-dependent processing of beta-amyloid precursor protein. Here we have evaluated the effects of dietary fat on brain apo E mRNA in Zucker lean and obese rats. After approximately 2 months on a high-fat diet, there was significant up-regulation of brain apo E mRNA in the Zucker lean rat in parallel with weight gain. Densitometric quantification revealed a 17% increase in apo E mRNA in the brains of lean rats fed high-fat diet compared with those of lean rats fed rat chow. No significant difference in brain apo E mRNA of Zucker obese rats fed different diets was found. These results suggest that dietary fat alters brain apo E levels, which may be regulated, in part, through the leptin receptor.

Mifepristone (RU486): a review.

OBJECTIVE: To review the literature concerning the mechanism of action and pharmacodynamics of mifepristone (RU486), potential new uses of RU486, and its current use not only as an abortifacient but also as therapy for endometriosis, leiomyoma, breast cancer, and meningioma. DATA IDENTIFICATION AND SELECTION: Studies that relate to RU486 were identified through a MEDLINE search. CONCLUSION(S): RU486 is an 11 beta-dimethyl-amino-phenyl derivative of norethindrone with a high affinity for P and glucocorticoid receptors. The receptor binding is not followed by transcription of P-dependent genes. Mifepristone effectively blocks P receptors in the placenta, resulting in the termination of pregnancy. In addition, it has been used in the treatment of leiomyomata, endometriosis, advanced breast cancer, and meningioma. It is a powerful tool to study the molecular action of P and in the future may be used as an estrogen-free contraceptive.

PIP: Through an online search of MEDLINE, the authors reviewed the literature on the development of mifepristone (RU-486); RU-486's mechanism of action, pharmacodynamics, and distribution; the physiologic action of RU-486; potential new uses for RU-486; and its current use as both an abortifacient and therapy for endometriosis, leiomyoma, breast cancer, and meningioma. RU-486 is an 11beta-dimethyl-amino-phenyl derivative of norethindrone with a high affinity for P and glucocorticoid receptors. Receptor binding is not followed by the transcription of P-dependent genes. RU-486 effectively blocks P receptors in the placenta, resulting in the termination of pregnancy. It has also been used to treat leiomyomata, endometriosis, advanced breast cancer, and meningioma. The following therapeutic uses of RU-486 are discussed: the termination of early pregnancy, treatment with RU-486 in combination with prostaglandins, the termination of second-trimester pregnancy, cervical ripening, labor induction, postcoital contraception, uterine leiomyomata, endometriosis, breast cancer, and meningioma.

Inhibition of 17,20(17-hydroxyprogesterone)-lyase by progesterone.

14C-17-hydroxyprogesterone was incubated with 7000 times g times 20 min supernatants of rat testis homogenates in the presence of various concentrations of 3H-progesterone, both under conditions where metabolism would take place and where it would be prevented. When metabolism was prevented, the ratio of progesterone to 17-hydroxyprogesterone in the microsomal fraction was 3 times that which was added to the incubation medium. Progesterone competitively inhibited 17,20-lyase action on added 17-hydroxyprogesterone but not on 17-hydroxyprogesterone formed from the added progesterone. The rate of formation of 17-hydroxyprogesterone from progesterone, however, was inhibited by added 17-hydroxyprogesterone. The results indicate that there is no free exchange of an intermediate between progesterone and androstenedione with the soluble fraction, either inside or outside the microsomal vesicle. The limited exchange with 17-hydroxyprogesterone in solution probably represents exchange with an enzyme-bound intermediate.

Ultrastructural basis for continued steroidogenesis in the rat polycystic ovary.

Because constant light causes persistent estrus in the rat, that animal provides a suitable experimental model for studying the pathogenesis of polycystic ovary disease. We studied the scanning and transmission electron microscopic features of the rat polycystic ovary along with changes in serum estradiol and progesterone concentrations to further elucidate the mechanism of chronic anovulation during persistent estrus. The surface epithelium of the polycystic ovary showed no ovulatory stigmas and contained focal areas of degenerating and proliferating cells. The tunica albuginea was conspicuous, with many fibrils, collagenous materials and fibroblastlike cells adjoining the theca externa layer. The cytoplasm of theca interna cells contained numerous lipid vacuoles and images of extracted cholesterol crystals. The granulosa cells were atrophic and lacked the prominent Golgi apparatus typically found in granulosa cells of proestrous ovaries in cycling rats. With an increasing duration of constant light and chronic anovulation, the mean serum estradiol concentration in persistent-estrus rats was significantly higher and the mean serum progesterone concentration significantly lower than in age-matched controls. Alterations in estradiol-progesterone metabolism in the ovaries may be important etiologic factors in the pathogenesis of chronic anovulation found in polycystic ovary disease in rats.

Effect of obesity on the clinical and hormonal characteristics of the polycystic ovary syndrome.

The polycystic ovary (PCO) syndrome is frequently associated with obesity. That subset of women reportedly shows a much higher incidence of hirsutism and menstrual irregularities than do nonobese women with PCO syndrome. We evaluated the clinical features and hormonal profiles of 56 women with PCO syndrome and correlated them with the presence or absence of obesity. Thirty-eight (67.8%) of these women were obese (body mass index > or = 25 kg/m2). While presenting with the classic manifestations of PCO, they did not differ significantly from the manifestations of nonobese women with PCO syndrome. Although obese women with PCO had a lower incidence of oligomenorrhea as compared to nonobese women with PCO (57.9% vs. 83.3%, respectively) and amenorrhea was more frequent in the former group (42.1% vs. 16.6%, respectively), these findings are not statistically significant. The incidences of hirsutism and anovulatory infertility in the obese group as compared to the nonobese group were 81.6% vs. 77.8% and 28.9% vs. 27.8%, respectively (not statistically significantly different). The mean (+/- SE) serum levels of luteinizing hormone (LH), follicle stimulating hormone (FSH), LH/FSH ratios, prolactin and testosterone were not statistically significantly different among the two groups. The present study found that obesity is common in PCO syndrome but that there are no significant differences in the clinical and hormonal characteristics of obese and nonobese women with it. Further studies are warranted to clarify the impact of obesity on clinical, metabolic and hormonal changes in PCO syndrome.

Clomiphene-dexamethasone treatment of clomiphene-resistant women with and without the polycystic ovary syndrome.

We used clomiphene and dexamethasone in 40 infertile women to treat chronic anovulation resistant to the use of clomiphene alone. Eighteen (45%) of the women had the polycystic ovary (PCO) syndrome; the remaining 22 (55%) had clomiphene-resistant anovulation from idiopathic causes. Both groups of women were similar in regard to age, parity, duration of infertility and absence of other causes of infertility besides chronic anovulation. Ovulation could be induced in approximately 90% of the women in each group. Altogether, 19 of 36 women (52.8%) conceived without any side effects or complications. The cumulative probability of conception at nine months of treatment was 87.5% in PCO patients and 46% in the non-PCO group. Clomiphene plus dexamethasone was highly effective in the treatment of clomiphene-resistant anovulation associated with infertility in women with and without the PCO syndrome.

Hormonal modulation of the vaginal bacterial flora in experimental polycystic ovarian disease.

Rats exposed to constant light develop polycystic ovarian (PCO) disease with persistent estrus, representing an estrogen-dominant condition. Herein, we report that fluctuations seen in the vaginal microflora in cyclic rats were not observed in PCO rats with persistent estrus. The vaginal-cervical mucosa of PCO rats showed numerous adherent bacteria by scanning electron microscopy, similar to that seen in proestrus and estrus rats, but unlike the diestrus rats in which fewer organisms adhered to the mucosa. Administration of human chorionic gonadotropin induced ovulation in PCO rats, which was associated with a significant decrease in serum estradiol, an increase in progesterone, and a significant decrease in the estradiol/progesterone ratio compared with baseline values (P < 0.01). This also resulted in an influx of leukocytes in the vagina with a significant decrease in vaginal anaerobic as well as aerobic bacterial flora. These data demonstrate that loss of cyclic ovarian activity in PCO rats with persistent estrus causes increased bacterial colonization of the vaginal-cervical mucosa, and the ovarian hormones appear to modulate the colonization of bacteria in the lower genital tract.

Ethinyl estradiol administration and plasma steroid concentrations in ovariectomized women.

The effect of ethinyl estradiol treatment on the plasma levels of cortisol, corticosterone, deoxycorticosterone, progesterone, testosterone, dehydroepiandrosterone sulfate, delta4-androstenedione, and estrone was studied in eight women. All the subjects had undergone ovariectomy and hysterectomy at least one year prior to this study. The systemic concentration of cortisol and the binding of cortisol were significantly increased, paralleling the increased transcortin concentration due to ethinyl estradiol treatment. Corticosterone concentration was also significantly increased after three days of estrogen administration and this level continued to be higher than normal as long as patients were treated with estrogens, but there was no change in the plasma concentration of deoxycorticosterone. The plasma levels of progesterone testosterone, dehydroepiandrosterone sulfate, delat4-androstenedione and estrone or the ratio of estrone to delta4-androstenedione did not change with ethinyl estradiol treatment. These observations suggest that the administered estrogen increased the transcortin concentration and had only a limited effect on adrenocortical steroidogenesis.