FSH-induced aromatase activity in porcine granulosa cells: non-competitive inhibition by non-aromatizable androgens

Ovarian response to follicle-stimulating hormone in women with polycystic ovary syndrome is diminished compared to ovulatory controls

OBJECTIVE

The mechanisms underlying ovarian dysfunction in polycystic ovary syndrome (PCOS) have not been definitively established. Our objective was to perform a detailed examination of ovarian responses to recombinant follicle-stimulating hormone (rFSH) in women with PCOS and controls.

DESIGN

This prospective, crossover, dose-response study included three rFSH stimulation periods. Each stimulation period involved three consecutive, daily, subcutaneous injections of rFSH administered at a single dose. Low, medium and high rFSH doses were weight-adjusted, corresponding to 0.5, 1.1 and 2.2 IU/kg/d, respectively. Stimulation periods occurred in randomized order and were separated by 8-week washouts.

PATIENTS

Thirty participants (8 PCOS and 22 controls) were studied. PCOS was defined by oligomenorrhea and clinical or biochemical androgen excess, excluding other aetiologies of ovulatory dysfunction.

MEASUREMENTS

Blood samples were obtained for hormone measurements before and 24 h after each rFSH injection.

RESULTS

Participants with PCOS had significantly greater body mass index, antral follicle count and circulating testosterone, anti-mullerian hormone (AMH) and luteinizing hormone concentrations compared with controls participants. Baseline estradiol (E2) concentrations were similar in both groups. At the lowest dose of rFSH, PCOS participants did not demonstrate E2 increments, whereas a significant increase occurred in controls. rFSH-induced E2 production per follicle was significantly reduced in PCOS participants compared with controls at all rFSH doses. Increasing T and decreasing AMH concentrations were associated with augmented E2 production per follicle.

COONCLUSIONS

Women with PCOS exhibited diminished initial E2 responses to rFSH compared with controls. These findings suggest that the mechanism of anovulation in PCOS may involve altered ovarian response to gonadotropins.

Seasonal ovarian development in relation to the gonadotropins, steroids, aromatase and steroidogenic factor 1 (SF-1) in the banded gourami, Trichogaster fasciata

The endocrine regulation of gonadal development and annual variation of key sex steroids is the basic knowledge to understand the reproductive cycle of teleost fish. Present study was aimed to investigate the levels of gonadotropins in relation to the follicular development and plasma steroids during the reproductive cycle of female Trichogaster fasciata. Female fish were sampled and ovarian development is described histologically throughout the year in relation to the seasonal variations of gonadosomatic index (GSI); follicle stimulating hormone (FSH) and luteinizing hormone (LH); three key steroids for folliculogenesis and maturation i.e. testosterone (T), 17β-estradiol (E₂) and 17α20βdihydroxy4pregnen3one (17,20β-P). Relatively higher level of FSH was observed till the ovary reaches in late vitellogenic stage confirms that FSH regulates the early folliculogenesis of the ovary, whereas LH peak was observed in the postvitellogenic stage, which indicates that maturation and ovulation were controlled by LH. Seasonal steroid profiles show that both T and E₂ reach its maximum level prior to the 17,20β-P which attain its peak value in the month of August. Thus, single peak values of LH and 17,20β-P coinciding with GSI peak, clearly indicates that T. fasciata breeds only once in a year. Furthermore, to elucidate the molecular basis of the reproductive cycle, this study analyzes the other key factors of ovarian function such as cyp19a1a gene expression, aromatase activity and SF-1 localization throughout the year. cyp19a1a gene expression and the aromatase activity were highest in vitellogenic stages indicate that relatively higher E₂ production in this stage is regulated by FSH. Immunohistochemical localizations of aromatase and SF-1 in the cellular layer of oocytes demonstrated that aromatase is FSH-dependent and SF-1 could be regulated by both FSH and LH as relatively higher amount of aromatase was localized in the vitellogenic stage oocytes than the postvitellogenic and post germinal vesicle breakdown (post-GVBD) stages; whereas, high amount of SF-1 was observed in vitellogenic, postvitellogenic and post-GVBD stages. These data regarding the reproductive endocrinology of T. fasciata may be useful to understand the interaction between gonadotropins, steroids, aromatase and SF-1 in teleost fishes and may contribute to restoration of the ecologically important fish through artificial reproduction.

Estrogen-regulated expression of P450arom genes in the brain and ovaries of adult female Indian climbing perch, Anabas testudineus

Cytochrome P450arom (CYP19), a product of cyp19a1 gene, catalyzes the conversion of androgens to estrogens and is essential for regulation of reproductive function in vertebrates. In the present study, we isolated partial cDNA encoding the ovarian (cyp19a1a) and brain (cyp19a1b) P450arom genes from adult female perch, Anabas testudineus and investigated their regulation by estrogen in vivo. Results demonstrated that cyp19a1a and cyp19a1b predominate in ovary and brain respectively, with quantity of both attuned to reproductive cycle. To elucidate estrogen-regulated expression of cyp19a1b in brain and cyp19a1a in ovary, dose- and time-dependent studies were conducted with estrogen in vitellogenic-stage fish in the presence or absence of specific aromatase inhibitor fadrozole. Results demonstrated that treatment of fish with 17β-estradiol (E2; 1.0 μM)) for 6 days caused significant upregulation of cyp19a1b transcripts, aromatase B protein, and aromatase activity in brain in a dose- and time-dependent manner. Ovarian cyp19a1a mRNA, aromatase protein, and aromatase activity, however, was less responsive to E2 than brain. Treatment of fish with an aromatase inhibitor fadrozole for 6 days attenuated both brain and ovarian cyp19a1 mRNAs expression and stimulatory effects of E2 was also significantly reduced. These results indicate that expression of cyp19a1b in brain and cyp19a1a in ovary of adult female A. testudineus was closely associated to plasma E2 levels and seasonal reproductive cycle. Results further show apparent differential regulation of cyp19a1a and cyp19a1b expression by E2/fadrozole manipulation.

Molecular mechanism of mercury-induced reproductive impairments in banded gourami, Trichogaster fasciata

Mercury is one of the key pollutants responsible for the degradation of natural aquatic ecosystems. Among the different forms of mercury that exist in the environment, mercuric chloride (HgCl₂) is the dominant pollutant for freshwater environments as it is used as an ingredient in antiseptics, disinfectants and preservatives, insecticides, batteries and in metallurgical and photographic operations. Pollutant may exert their action on organisms or populations by affecting their normal endocrine function as well as reproduction. Thus, the present study tried to understand the effect of mercuric chloride (HgCl₂) on reproductive function and to decipher the molecular mechanism of Hg-induced reproductive impairments of female Trichogaster fasciata. Both in vivo and in vitro experiments were performed by using ecologically relevant doses of HgCl₂ and the resulting effects on follicular development, steroidogenic potentiality, aromatase activity, aromatase gene expression and steroidogenic factor-1 (SF-1) expression pattern were analysed. In vivo exposure to HgCl₂ caused reproductive impairments as shown by the inhibitory role of HgCl₂ on follicular development, steroid biosynthesis and SF-1 activity. In vitro experiments revealed that aromatase activity, steroidogenesis, aromatase and SF-1 expression were blocked by HgCl₂. The results obtained from this study contribute to understand the molecular mechanism of HgCl₂-induced reproductive impairment of T. fasciata.

Biphasic action of iodine in excess at different doses on ovary in adult rats

Iodine consumption in excess of its recommended levels over a prolonged period of time is well known to cause thyroid disorders. The thyroid hormones on the other hand are responsible in maintenance of the physiology of the reproductive system. Excess iodine intake affects male reproductive physiology. However, the effects of excess iodine on the ovarian structure and function is yet to be established. The present study has thus been undertaken to investigate the effect of excess iodine on the ovarian physiology. Excess iodine was administered through oral gavage in the form of potassium iodide (KI) for duration of 60days, at two different doses. The doses used were 100 EI, i.e., 100 times more than the recommended level but tolerable to the thyroid gland and 500 EI, i.e., 500 times more than the recommended level that altered thyroid physiology. The animals were divided into three groups, one control group, and the other two receiving two separate doses (100 EI and 500 EI) of excess KI. Estrous cyclical changes, ovarian morphological changes, ovarian iodine accumulation and ovarian steroidogenic enzyme activities were analysed. The thyroid functional status was studied from the serum thyroid hormones levels. The overall results revealed a biphasic action of excess iodine that depends on its dose. At 100 EI, excess iodine did not alter thyroid physiology but lead to the development of a hypoestrogenic state. There was an increased accumulation of iodine in the ovary with decreased activity of ovarian steroidogenic enzymes and lowered serum estradiol levels. However, at 500 EI, excess iodine developed a hyperthyroid condition, which further leads to a hyperestrogenic state. There was an increased activity of serum steroidogenic enzymes as well as elevated serum estradiol levels. Fertility index was zero in both the 100 EI and 500 EI treated groups of experimental animals. Thus excess iodine (100 EI) ingestion within tolerable range though maintained a euthyroid condition yet developed a state of hypofunctioning ovary. Conversely, excessive iodine (500 EI) is intolerable to thyroid, develops a hyperthyroid condition that leads to a hyperfunctioning ovary. Therefore prolonged exposure of iodine in excess exerts biphasic mode of action depending on the dose in female reproductive physiology and both the doses used in this study affected fertility equally.

Gonadotropin and sf-1 regulation of cyp19a1a gene and aromatase activity during oocyte development in the rohu, L. rohita

Cytochrome P450 aromatase (P450arom), a product of cyp19a1 gene, plays pivotal roles in vertebrate steroidogenesis and reproduction. In this study, we isolated partial cDNA encoding the ovarian (cyp19a1a) and brain (cyp19a1b) P450arom genes from adult female rohu, Labeo rohita and investigated the regulation of cyp19a1a by gonadotropin and SF-1. The cyp19a1a and cyp19a1b were expressed predominantly in the ovary and brain respectively, with quantity of the former attuned to reproductive cycle. To elucidate gonadotropin regulation of cyp19a1a mRNA expression and P450 aromatase activity for 17β-estradiol (E2) biosynthesis in vitro by the vitellogenic ovarian follicles, time- and dose-dependent studies were conducted with HCG and porcine FSH. Results demonstrated that HCG stimulated significantly higher expression of cyp19a1a mRNA and aromatase activity leading to increased biosynthesis of E2 than FSH. To understand the involvement of SF-1 to in the regulation of cyp19a1a and aromatase activity, ovarian follicles were incubated with increasing concentrations of HCG and expression of sf1gene and activation of SF-1 protein were measured. Results demonstrated that HCG significantly induced expression of sf-1 gene and activation of SF-1 protein suggesting a link between SF-1 and P450 aromatase activation in this fish ovary during gonadotropin-induced steroidogenesis.

Effects of phenol on ovarian P450arom gene expression and aromatase activity in vivo and antioxidant metabolism in common carp Cyprinus carpio

Ovarian cyp19a mRNA expression and P450 aromatase activity were measured in vivo in common carp Cyprinus carpio exposed to phenol for 96 h. Production of reactive oxygen species (ROS) and parameters of antioxidant defense system in serum ovary and liver of this fish after long-term phenol exposure were also studied. In vivo exposure of fish to sublethal dose of phenol for 96 h caused marked attenuation of ovarian cyp19a1a gene expression and P450 aromatase activity. Production of ROS like hydrogen peroxide and hydroxyl radicals in serum, liver and ovary in fish exposed to phenol for 15 days elevated significantly from day 1 to day 7 with no further significant increase thereafter compared to their respective control values. Total superoxide dismutase (SOD) and catalase activities in serum and ovary decreased gradually and significantly from day 1 to day 4, which then increased significantly for the rest of the exposure days. Liver SOD activity seemed to be distinctly responsive to phenol. SOD activity in liver of phenol-exposed fish started to increase gradually from day 1 to 4 with no further increase thereafter. Catalase activities in all the tissues showed significant inhibition up to day 4 which then increased gradually and significantly up to day 15 of phenol exposure compared to their respective control values. From our results, it appears that sublethal dose of phenol has the endocrine disruptive potential and effect is mediated via inhibition of ovarian P450arom gene expression and aromatase activity in vivo. Sublethal dose of phenol also caused oxidative stress, and antioxidant systems are very much effective to prevent the damages caused by the generation of ROS.

Effect of phenol on ovarian secretion of 17β-estradiol in common carp Cyprinus carpio

Phenol is a common substance present in many industrial wastewaters and in nonspecific pesticides. Due to its solubility and volatility phenol is often found in marine and freshwater environment. It is lipophilic compound and has a high potential for accumulating along the trophic chain. Phenol thus is not only a threat to natural environment but also to human health. The effects of phenol on the secretion of 17β-estradiol were examined in female common carp Cyprinus carpio. Vitellogenic stage fish were exposed to physiological safe dose of phenol for 0, 24, 48 and 96 h. In the in vitro experiments, vitellogenic follicles were incubated with phenol and dose- and time-course effects on leuteinising hormone (LH) induced steroid production were examined. Exposure of fish with phenol gradually attenuated serum and ovarian 17β-estradiol levels with increasing time and maximum inhibition was noticed after 96 h. Administration of phenol significantly inhibited LH-induced secretion of 17β-estradiol by the ovarian follicles in vitro. To clarify the mechanism of attenuated production of 17β-estradiol in phenol-treated follicles, stimulated by LH, in vitro effect phenol and LH on aromatase activity (conversion of testosterone to 17β-estradiol) and cytochrome P450arom gene expression in carp ovarian follicles were investigated. Physiological safe dose of phenol significantly inhibited LH-stimulated aromatase activity and P450arom gene expression in ovarian follicles. The present study further demonstrated that LH-induced activation of ovarian steroidogenic factor-1 (SF-1) is strongly inhibited by phenol treatment. These results suggest that physiological safe dose of phenol as endocrine disruption (ED) potential and the effect can be mediated via several cellular pathways including the inhibition of SF-1 activity, aromatase activity and P450arom gene expression.

Effect of cadmium chloride on secretion of 17β-estradiol by the ovarian follicles of common carp, Cyprinus carpio

Cadmium (Cd(2+)) is a common environmental pollutant present in wastes associated with mining, smelting and electroplating. It is a major constituent of the tobacco smoke. Exposure of this heavy metal has been linked to wide range of detrimental effects on mammalian reproduction particularly on ovarian steroidogenesis. Low doses of Cd(2+) are reported to stimulate ovarian luteal progesterone synthesis whereas high doses inhibited it. Cd(2+) exposure is also reported to inhibit gonadal function in fish. In the present study the effects of cadmium chloride (CdCl(2)) on the secretion of gonadotropin-induced 17β-estradiol was examined in female common carp Cyprinus carpio. Vitellogenic stage fish were exposed to physiological safe dose of CdCl(2) for 0, 24, 48 and 96 h and serum and ovarian 17β-estradiol levels were estimated. In the in vitro experiments, vitellogenic follicles were incubated with CdCl(2) and a dose- and time-dependent effects on steroid production were estimated induced by LH. Exposure of fish with CdCl(2) gradually attenuated serum and ovarian 17β-estradiol levels with increasing time and maximum inhibition was noticed after 96 h. Administration of CdCl(2) to the incubations significantly inhibited LH-induced release of 17β-estradiol in vitro. To clarify the mechanism of attenuated production of 17β-estradiol, in vitro effects of CdCl(2) on LH induced P450 aromatase activity (conversion of testosterone to 17β-estradiol) and cytochrome P450arom gene expression in carp ovarian follicles were evaluated. Results show that LH-stimulated P450 aromatase activity and P450arom gene expression in ovarian follicles were significantly inhibited by CdCl(2). The present study further demonstrated that LH-induced stimulation of ovarian steroidogenic factor-1 (SF-1) which activates aromatase enzyme, is strongly inhibited by cadmium chloride treatment.

Dedifferentiated follicular granulosa cells derived from pig ovary can transdifferentiate into osteoblasts

Transdifferentiation is the conversion of cells from one differentiated cell type into another. How functionally differentiated cells already committed to a specific cell lineage can transdifferentiate into other cell types is a key question in cell biology and regenerative medicine. In the present study we show that porcine ovarian follicular GCs (granulosa cells) can transdifferentiate into osteoblasts in vitro and in vivo. Pure GCs isolated and cultured in Dulbecco's modified Eagle's medium supplemented with 20% FBS (fetal bovine serum) proliferated and dedifferentiated into fibroblast-like cells. We referred to these cells as DFOG (dedifferentiated follicular granulosa) cells. Microarray analysis showed that DFOG cells lost expression of GC-specific marker genes, but gained the expression of osteogenic marker genes during dedifferentiation. After osteogenic induction, DFOG cells underwent terminal osteoblast differentiation and matrix mineralization in vitro. Furthermore, when DFOG cells were transplanted subcutaneously into SCID mice, these cells formed ectopic osteoid tissue. These results indicate that DFOG cells derived from GCs can differentiate into osteoblasts in vitro and in vivo. We suggest that GCs provide a useful model for studying the mechanisms of transdifferentiation into other cell lineages in functionally differentiated cells.

Regulation of ovarian steroidogenesis in vitro by IGF-I and insulin in common carp, Cyprinus carpio: stimulation of aromatase activity and P450arom gene expression

Regulation of ovarian steroidogenesis in vitro by recombinant human insulin-like growth factor-I (IGF-I) and bovine insulin (b-insulin) was investigated in intact follicles and isolated follicular cells of carp, Cyprinus carpio at vitellogenic stage of oocyte maturation. In intact follicles, IGF-I and b-insulin stimulated testosterone and 17beta-estradiol production in vitro. In isolated theca cells, IGF-I and b-insulin stimulated testosterone production, whereas in granulosa cells, they stimulated 17beta-estradiol production when testosterone was added in the incubation medium as precursor substrate. In intact follicles and in theca cells, IGF-I and b-insulin had no effect on HCG-stimulated testosterone production. HCG-stimulated 17beta-estradiol production, however, was significantly increased by IGF-I and b-insulin. To clarify the mechanism of 17beta-estradiol production by the ovarian follicles during vitellogenic stage of carp, effects of IGF-I and b-insulin either alone or in combination with HCG on aromatase activity (conversion of testosterone to 17beta-estradiol) and cytochrome P450 aromatase (P450arom) gene expression were investigated in vitro. IGF-I and b-insulin alone stimulated aromatase activity and P450arom gene expression and significantly enhanced HCG-induced enzyme activity and P450arom gene expression. Our results thus indicate that IGF-I and b-insulin alone can stimulate testosterone and 17beta-estradiol production in vitellogenic follicles of C. carpio by stimulating aromatase activity and P450arom gene expression. Evidence also provided for the modulation of HCG-induced aromatase activity and P450arom gene expression by IGF-I and b-insulin in such follicles.

Mechanism for normal splenic T lymphocyte functions in proestrus females after trauma: enhanced local synthesis of 17beta-estradiol

Trauma-hemorrhage and resuscitation (TH) produces profound immunodepression and enhances susceptibility to sepsis in males but not in proestrus females, suggesting gender dimorphism in the immune responses. However, the mechanism responsible for the maintenance of immune functions in proestrus females after TH is unclear. Splenic T lymphocytes express receptors for estrogen (ER), contain enzymes involved in estrogen metabolism, and are the major source of cytokine production; the metabolism of 17beta-estradiol was assessed in the splenic T lymphocytes of proestrus and ovariectomized mice by using appropriate substrates after TH. Analysis for aromatase and 17beta-hydroxysteroid dehydrogenases indicated increased 17beta-estradiol synthesis and low conversion into estrone in T lymphocytes of proestrus but not of ovariectomized mice. The effect of 17beta-estradiol on T lymphocyte cytokine release was reliant on ER expressions. This was apparent in the differences of ER expression, especially that of ER-beta, and an association between increased 17beta-estradiol synthesis and sustained release of IL-2 and IL-6 in T lymphocytes of proestrus females after TH. Because 17beta-estradiol is able to regulate cytokine genes, and the splenic T lymphocyte cytokine releases is altered after TH, continued synthesis of 17beta-estradiol in proestrus females appears to be responsible for the maintenance of T lymphocyte cytokine release associated with the protection of immune functions after TH.

Decreased 5alpha-dihydrotestosterone catabolism suppresses T lymphocyte functions in males after trauma-hemorrhage

Trauma-hemorrhage produces profound immunosuppression in males but not in proestrus females. Prior castration or flutamide treatment of males following trauma-hemorrhage prevents immunosuppression, implicating 5alpha-dihydrotestosterone for the immunosuppressive effects. 5alpha-dihydrotestosterone, a high-affinity androgen receptor-binding steroid, is synthesized in tissues as needed and seldom accumulates. The presence of steroidogenic enzymes in T lymphocytes suggests both synthesis and catabolism of 5alpha-dihydrotestosterone. We hypothesized, therefore, that the basis for high 5alpha-dihydrotestosterone activity in T lymphocytes of males following trauma-hemorrhage is due to decreased catabolism. Accordingly, catabolism of 5alpha-dihydrotestosterone was assessed in splenic T lymphocytes by examining the activity and expression of enzymes involved. Analysis showed increased synthesis and decreased catabolism of 5alpha-dihydrotestosterone in intact male T lymphocytes following trauma-hemorrhage. In contrast, reduced 5alpha-reductase activity and increased expression of 17beta-hydroxysteroid dehydrogenase oxidative isomers suggest inactivation of 5alpha-dihydrotestosterone in precastrated males. Thus our study suggests increased synthesis and decreased catabolism of 5alpha-dihydrotestosterone as a reason for loss of T lymphocyte functions in intact males following trauma-hemorrhage, as evidenced by decreased release of interleukin-2 and -6.

Steroid metabolism by ovarian follicles and extrafollicular tissue of the guppy (Poecilia reticulata) during oocyte growth and gestation

In the viviparous guppy, fertilization and gestation are intrafollicular. Fully developed embryos are ovulated at the end of gestation just prior to parturition. The metabolism in vitro of various radiolabeled steroid precursors by isolated ovarian follicles at various stages of the reproductive cycle and extrafollicular (EF) tissue of the guppy was investigated. While estradiol-17 beta was one of the end products of metabolism in vitellogenic follicles, 17 alpha, 20 beta-P and several 5-reduced metabolites were synthesized by postvitellogenic follicles. The yield of 17 alpha, 20 beta-P, however, was much lower than some 5 beta-reduced metabolites synthesized by postvitellogenic follicles. Gestation stage follicles rapidly converted the precursors into 5-reduced and polar 7-hydroxylated steroids, and their glucuronides. Although postpartum follicles showed very poor potential for steroid metabolism, they synthesized estradiol-17 beta from testosterone. These results demonstrate distinct changes occurring in the steroidogenic potential of the follicles during the reproductive cycle. Unlike in other viviparous vertebrates, no particular steroid seems to be involved in maintaining gestation in the guppy; all the steroid precursors are converted into highly polar metabolites and their conjugates during gestation, thereby facilitating their excretion. The EF ovarian tissue also synthesized 7-hydroxylated steroids and their glucuronides, providing evidence for the first time that the teleost ovarian EF tissue plays a role in steroidogenesis. The possible physiological significance of the synthesis of the novel polar steroids by the follicles and the EF tissue is discussed.

In vitro effects of dihydrotestosterone on granulosa cell production of estrogen and progesterone

To investigate the direct effects of androgens on follicle development, intact, immature female rats were given 8 IU PMSG (0 hour) and four injections of either vehicle or dihydrotestosterone (DHT), 1 mg/kg body weight, at 0, 12, 24, and 36 hours after PMSG. Granulosa cells from small (less than 200 microns), medium (200 to 400 microns), and large (greater than 400 microns) follicles were isolated and cultured in the presence or absence of 0.5 microM DHT in vitro for 48 hours, and the medium was assayed for progesterone and estrogen. Results show that DHT caused an increase in progesterone accumulation in all granulosa cells, regardless of follicle size. However, DHT inhibited estrogen accumulation in granulosa cells from different-size follicles and the inhibition varied depending on the duration of androgen exposure in vivo. The inhibition of estrogen accumulation was seen in granulosa cells from small follicles without prior exposure to DHT in vivo, while an inhibition of estrogen accumulation was seen in granulosa cells from medium and large follicles exposed to DHT treatment in vivo. Taken together, the results of experiments with in vivo and/or in vitro DHT treatment show that the androgen increases granulosa cell progesterone synthesis regardless of follicle size. However, the estrogen accumulation by granulosa cell is dependent on follicle size and duration of DHT exposure.

Changes in plasma follicle-stimulating hormone, luteinizing hormone, estrogen and progesterone during growth of ovulatory follicles in the pig

This experiment was conducted to determine the changes in secretion of LH, FSH, estrogen and progesterone during follicle maturation. Ovaries were recovered from 11 non-treated (control) gilts, three on day 13, four on day 16, and four on day 19 of the estrous cycle, and from four altrenogest-treated gilts on day 19. Altrenogest, a progesterone agonist, was fed at a dose of 20 mg once daily from days 13 to 18 to block spontaneous follicle maturation. Gilts were bled daily from day 12 until slaughter. For control gilts, the number of follicles/gilt 1-6 mm in diameter decreased (P less than .05) from 93.5 on day 13 to 21.5 on day 19, and the number of large (greater than 6 mm) follicles increased (P less than .05) from 5.3 to 13.2. Altrenogest treatment blocked loss of small follicles and growth of large follicles between days 13 and 19. Plasma progesterone decreased (P less than .001) between days 12 and 16 in both control and altrenogest-treated gilts. Plasma FSH decreased (P less than .05) between days 12 and 16 only in control gilts. Plasma LH was not significantly affected by day or altrenogest treatment. Plasma estrogen increased (P less than .05) between days 15 and 19 only in control gilts. These results indicate that 1) no increased LH secretion was detected in conjunction with emergence of ovulatory follicles, and 2) atresia of nonovulatory follicles was associated with decreased secretion of FSH. Both atresia and decreasing FSH secretion began before estrogen concentration increased in the systemic circulation.

Regulation of steroid hormone synthesis by human corpora lutea: failure of follicle-stimulating hormone to support steroidogenesis in vivo and in vitro

The authors studied the role of follicle-stimulating hormone (FSH) in luteal steroidogenesis by replacing gonadotropin-releasing hormone (GnRH) infusion with pure FSH 48 hours after ovulation in two hypogonadotropic patients. Plasma progesterone (P) and estradiol (E2) decreased after FSH administration. Human luteal cells were cultured for 48 hours in the presence and absence of FSH, human chorionic gonadotropin (hCG), testosterone (T), or dibutyryl cyclic adenosine monophosphate (Bu2cAMP). In the presence of T, E2 synthesis increased significantly, indicating an active aromatase system in these cells. Human chorionic gonadotropin as well as Bu2cAMP significantly increased E2, T, and P synthesis. Follicle-stimulating hormone did not stimulate luteal E2, T, or P synthesis. The authors conclude that FSH does not sustain luteal steroidogenesis. Moreover, the in vitro findings reveal that hCG modulation of luteal E2 synthesis is mediated principally by an increase in androgen precursors. These in vivo and in vitro results confirm a crucial role for luteinizing hormone (LH) in the maintenance of luteal steroidogenesis.

The inhibition of 3 beta HSD activity in porcine granulosa cells by 4-MA, a potent 5 alpha-reductase inhibitor

Addition of 17 beta-N,N,-diethylcarbamoyl-4-methyl-4-aza-5 alpha-androstane-3-one, a potent 5 alpha-reductase inhibitor, to granulosa cell cultures inhibited the FSH-stimulated progesterone synthesis during both the initial 48 h induction period and the subsequent 6h test period in a dose-dependent fashion. Besides being a more potent inhibitor of FSH-stimulated progesterone synthesis than testosterone, 4-MA also synergized with the androgen to inhibit progesterone synthesis. These results indicate that 4-MA has a direct inhibitory action on 3 beta-HSD.

Induction of aromatase activity in porcine granulosa cells by FSH and cyclic AMP

This paper examines the involvement of mRNA and protein synthesis in the induction of aromatase activity by FSH and also the site of action of androgens on FSH induction of aromatase activity in porcine granulosa cells. Treatment of cells with FSH or dbcAMP for an initial 48 h (induction period) resulted in an induction of aromatase activity, as measured by the production of estradiol during a subsequent 6h test period. Addition of testosterone to cells cultured with dbcAMP during the induction period enhanced the aromatase activity during both the induction and test periods. However, while DHT has no effect during the induction period, it significantly inhibited the aromatase activity during the test period. Culturing the granulosa cells with actinomycin D or cycloheximide during the induction period resulted in a dose-dependent inhibition of FSH induction of aromatase activity, suggestive of the synthesis of new protein(s). These results indicate clearly that FSH induction of aromatase activity involves the synthesis of mRNA and proteins.