Steroidogenesis in porcine atretic follicles: loss of aromatase activity in isolated granulosa and theca

Incessant ovulation: a review of its importance in predicting cancer risk

Estrous cycles are recurring changes in therian mammals induced by estrogen, progesterone, and other hormones culminating in endometrial proliferation, ovulation, and implantation if fertilization occurred. In women, the estrous cycle is the menstrual cycle; but, unlike most mammals, the end of an infertile cycle is marked by endometrial sloughing and the start of another without an anestrous phase. Women stop cycling at menopause, while in most mammals, cycles continue until death. Epidemiologic studies identified menarche, menopause, births, lactation, and oral contraceptive (OC) use as key risk factors for ovarian, breast, and endometrial cancers. A composite variable was created to estimate the number of cycles not interrupted by events that stop ovulation. Captured by the phrase "incessant ovulation", repetitive cycles were first postulated to affect ovarian cancer risk and later extended to breast and endometrial cancers. These associations could be explained by cumulative effects of repetitive tissue changes within reproductive organs, immune consequences of repetitive ovulation through the glycoprotein mucin 1, and residual effects of past ovulations that enhance ovarian production of testosterone. The latter two pathways could affect the risk for cancers in other organs not considered "reproductive".

Estimated Ovulatory Years Prior to Menopause and Postmenopausal Endogenous Hormone Levels

BACKGROUND

Lifetime ovulatory years (LOY) is estimated by the difference between ages at menopause and menarche subtracting time for events interrupting ovulation. We tested whether LOY influences sex hormone levels in postmenopausal women with at least one intact ovary not using hormones.

METHODS

Estradiol, estrone, estrone sulfate, total testosterone, dehydroepiandrostendione sulfate, prolactin, and sex hormone binding globulin were measured in 1,976 postmenopausal women from the Nurses' Health Study. Associations of age, body mass index (BMI), smoking, alcohol use, and other factors on hormones were assessed by t tests and ANOVA. Linear regression was used to assess multivariable adjusted associations between LOY and hormones and trends in hormone levels per 5-year increases in LOY were estimated.

RESULTS

Women averaged 61.4 years old, 11.0 years since menopause, with BMI of 25.8 kg/m2. A total of 13.6% had irregular cycles, 17.5% hysterectomy, 6.4% unilateral oophorectomy, and 13.8% were current smokers. Variables associated with one or more hormone levels were included as covariates. Each 5-year increase in LOY was significantly associated with a 5.2% increase in testosterone in women with BMI < 25 kg/m2 and a 7.4% increase in testosterone and 7.3% increase in estradiol in women with above-average BMI.

CONCLUSIONS

This is the first study to show that greater LOY is associated with higher testosterone in postmenopausal women and higher estradiol in those with elevated BMI, suggesting accumulation of functioning stromal and thecal cells from repeated ovulations and peripheral conversion of testosterone.

IMPACT

A possible explanation for why greater LOY increases risk for breast, endometrial, and ovarian cancer is offered.

Localization of phosphatidylinositol 4-phosphate 5-kinase (PIP5K) α confined to the surface of lipid droplets and adjacent narrow cytoplasm in progesterone-producing cells of in situ ovaries of adult mice

Phosphatidylinositol(4,5)bisphosphate (PI(4,5)P2) produced by phosphatidylinositol phosphate 5 kinase (PIP5K) plays not only as a precursor of second messengers in the phosphoinositide signal transduction, but also multiple roles influencing a variety of cellular activities. From this viewpoint, the present study attempted to localize PIP5Kα in the ovaries in situ of adult mice. PIP5Kα-immunoreactivity was confined to the surfaces of lipid droplets (LDs) and their adjacent cytoplasm in progesterone-producing cells of the interstitial glands, corpora lutea and theca interna. The LDs often contained membranous tubules/lamellae along their surfaces and within their interior whose membranes were continuous with those delineating LDs composed of a monolayer of phospholipids and were partially PIP5Kα-immunoreactive. Although granulosa cells of healthy-looking follicles were immunonegative, as the atresia progressed, PIP5Kα-immunoreactivity first appeared in sparsely dispersed dot forms in mural cells of the follicular epithelia, and then were dominant in almost all mural cells that remained after desquamation of the antral cells. The present study provides evidence suggesting that PI(4,5)P2 locally synthesized by PIP5K in LDs is involved in the lipid transfer between lipid droplets (LDs) and the endoplasmic reticulum, which eventually regulates ovarian progesterone production through control of multiple dynamic activities of LDs. It is also suggested that PIP5Kα and PI(4,5)P2 are implicated in the modulation of programmed cell death and/or acquiring the ability of progesterone production in some follicular cells surviving atresia.

Altrenogest affects the development and endocrine milieu of ovarian follicles in prepubertal and mature gilts†

Altrenogest with gonadotropins is commonly used to synchronize the estrous cycle, but it can also lead to follicular cyst formation, especially in prepubertal gilts. Here, we aimed to investigate how maturity and altrenogest treatment affect the development, endocrine milieu, and molecular control of ovarian follicles. Crossbred prepubertal and mature gilts were challenged or not (control) with altrenogest, and ovaries were collected in the morning on the first day of behavioral estrus. In prepubertal gilts, altrenogest decreased the percentage of primordial and atretic small follicles, but increased large antral follicles when compared with controls. In mature gilts, altrenogest reduced the percentage of primary follicles and elevated the total number of antral follicles. Maturity affected the estradiol level in the follicular fluid of preovulatory follicles, luteinizing hormone (LH)-stimulated cyclic adenosine monophosphate (cAMP) generation, and LH receptor messenger RNA (mRNA) expression in granulosa. Moreover, cytochrome P45017A1 (CYP17A1) mRNA levels in the theca layer were affected and correlated with follicular androstendione and estradiol concentration. Altrenogest negatively affected follicular fluid progesterone concentration and decreased levels of prostaglandin (PG) E2 in prepubertal gilts and PGF2alpha metabolite in mature gilts. LH-stimulated cAMP release in granulosa cells of mature gilts as well as human chorionic gonadotropin- and forskolin-induced cAMP were also affected. In addition, altrenogest downregulated CYP17A1 mRNA in the prepubertal theca layer and PGF2alpha synthase expression in the granulosa and theca layer of mature gilts. To the best of our knowledge, this is the first study to report multiple effects of maturity and altrenogest on the endocrine milieu and molecular regulations governing ovarian follicle development in gilts.

Raf-ERK1/2 signalling pathways mediate steroid hormone synthesis in bovine ovarian granulosa cells

Steroid hormones are required for normal reproductive function of female. The aim of this study was to investigate the role of Raf-ERK1/2 on steroid hormone synthesis in bovine ovarian granulosa cells. Immunohistochemistry assay showed that both B-Raf and C-Raf were expressed in granulosa cells, theca cells and Sertoli cells. The protein expression of Raf or ERK1/2 was clearly decreased by Raf inhibitor GSK2118436 or ERK1/2 inhibitor SCH772984, respectively (p < 0.05). In addition, western blotting was performed for investigating the crosstalk between Raf and ERK1/2, the data showed that Raf positively regulated ERK1/2, whereas ERK1/2 had a negative feedback effect on Raf. The biosynthesis of oestradiol or testosterone was significantly decreased by treatment with GSK2118436 or SCH772984 (p < 0.05). Conversely, the progesterone biosynthesis was clearly increased by treatment with those inhibitors (p < 0.05). Furthermore, the mRNA expression of STAR, aromatase and CYP17 was blocked by Raf-ERK1/2 signalling inhibition, which oppositely induced the mRNA expression of CYP11. Together, these findings suggested that Raf-ERK1/2 signalling pathways mediate steroid hormone synthesis via affecting the expression of steroidogenic enzymes.

Molecular regulation of miR-378 on the development of mouse follicle and the maturation of oocyte in vivo

MicroRNAs (miRNAs) are small, endogenous, non-coding RNAs which can bind to completely or partially complementary sequences in the 3'UTR of target mRNAs, therefore degrading the mRNA or repressing translation. We previously reported that miR-378 played a role in estradiol production via suppression of aromatase translation in porcine granulosa cells and could affect oocyte maturation in vitro by inhibiting cumulus cell expansion. However, the role of miR-378 on ovary development in vivo is unknown. The current study aimed to uncover the molecular mechanism of miR-378 in regulating mouse follicular development via micro-injection of CMV-miR-378 lentivirus into the bursa of mouse ovary. The results showed that CMV-miR-378 lentivirus transduction in the mouse ovaries resulted in reduced ovary size, extended oestrous cycle (6-7 d in miR-378 overexpression group and 4-5 dyas in GFP control group) due to continuous oestrum, decreased percentage of oocytes in vitro maturation rate (IVM 60.8% vs. 89.4% in GFP control), increased apoptosis rate (Bax/Bcl2 in mRNA and protein level), decreased expression of genes associated with gap junction, such as connexin 43 (Cx-43) and connexin (Cx-37) and decreased expression of genes associated with follicular development, such as BMP15 and GDF9. Moreover, the number of pups/litter was consistently lower in the miR-378 group in each batch of the paired breeding. Our data suggest that miR-378 alters gene expression in cumulus cells and indirectly influences oocyte maturation competency, possibly via inhibition of oocyte-cumulus interaction or induction of apoptosis.

Immunolocalization of Orexin A and its receptors in the different structures of the porcine ovary

Orexins are neuropeptides with pleiotropic functions, involved in the coordination of multiple versatile physiological processes, in particular related to food intake and several aspects of the reproductive process. Their actions are carried out through the bond with the related Orexin 1 (OXR1) and Orexin 2 (OXR2) G-protein-coupled receptors. Studies on the expression of the orexinergic system in the female genital organs are scarce and limited to preovulatory gametogenic follicles and corpora lutea isolated from the rest of the ovary. As the description of only these structures is insufficient to provide a complete picture of the organ, the present study is aimed to give a panoramic view of all the ovarian structures and cells expressing Orexin A (OXA) and its receptors in their original localization. Double labeling immunofluorescent methods, applied on frozen sections of the whole organ in both follicular and luteal phase, were used to highlight the particular distribution and colocalization of the proteins. For a better recognition of cellular morphology and a better distinction between gametogenic (healthy) and atretic follicles, also a single labeling immunolocalization of OXA on formalin fixed paraffin embedded tissues and a TUNEL staining were performed. The results indicate that OXA and its two receptors subtypes are expressed in all the different structures composing the swine ovary, albeit in different ways, in both phases of the ovarian cycle. In general, OXA and OXR2 appear diffusely distributed within "health", proliferating and steroid producing cells, while has granular appearance, being presumably associated to cytoplasmic vesicles, in degenerating cells, independently if apoptotic or not. The immunoreactivity for OXR1, instead, is often associated with the nuclear envelope but it is also detectable, to a lesser extent, diffusely distributed in the cytoplasm of growing or steroid producing cells. When cells undertake the path leading to degeneration, also OXR1 immunoreactivity assumes a granular appearance in the cytoplasm and is colocalized with OXA and OXR2. Different roles for the two receptors in the same cell and a different regulation of their expression remain to be investigated. Their comprehension could help studies of follicle development in pig, as part of in vitro oocyte maturation and fertilization programs in livestock.

Trajectories and phenotypes with estrogen exposures across the lifespan: What does Goldilocks have to do with it?

This article is part of a Special Issue "Estradiol and cognition". Estrogens impact the organization and activation of the mammalian brain in both sexes, with sex-specific critical windows. Throughout the female lifespan estrogens activate brain substrates previously organized by estrogens, and estrogens can induce non-transient brain and behavior changes into adulthood. Therefore, from early life through the transition to reproductive senescence and beyond, estrogens are potent modulators of the brain and behavior. Organizational, reorganizational, and activational hormone events likely impact the trajectory of brain profiles during aging. A "brain profile," or quantitative brain measurement for research purposes, is typically a snapshot in time, but in life a brain profile is anything but static--it is in flux, variable, and dynamic. Akin to this, the only thing continuous and consistent about hormone exposures across a female's lifespan is that they are noncontinuous and inconsistent, building and rebuilding on past exposures to create a present brain and behavioral landscape. Thus, hormone variation is especially rich in females, and is likely the destiny for maximal responsiveness in the female brain. The magnitude and direction of estrogenic effects on the brain and its functions depend on a myriad of factors; a "Goldilocks" phenomenon exists for estrogens, whereby if the timing, dose, and regimen for an individual are just right, markedly efficacious effects present. Data indicate that exogenously-administered estrogens can bestow beneficial cognitive effects in some circumstances, especially when initiated in a window of opportunity such as the menopause transition. Could it be that the age-related reduction in efficacy of estrogens reflects the closure of a late-in-life critical window occurring around the menopause transition? Information from classic and contemporary works studying organizational/activational estrogen actions, in combination with acknowledging the tendency for maximal responsiveness to cyclicity, will elucidate ways to extend sensitivity and efficacy into post-menopause.

Effects of follicular size and FSH on granulosa cell apoptosis and atresia in porcine antral follicles

The purpose of this study was to establish a culture model for isolated intact porcine antral follicles and investigate the relationship between granulosa cell apoptosis and follicular atresia. Small (<3 mm), medium (3-5 mm) and large (>5 mm) healthy porcine follicles were isolated and cultured in serum-free TCM199 with or without follicular stimulating hormone (FSH). Microscopic identification of healthy follicles was confirmed by histology. A spontaneous onset of apoptotic cell death in granulosa cells was observed from cultured antral follicles. The apoptotic rate of granulosa cells from small follicles cultured for 24 hr was higher than those of large and medium follicles, accompanied with high FasL mRNA abundance in granulosa cells. Supplementation with 3 or 5 IU/ml FSH significantly inhibited the percentage of granulosa cells that became apoptotic. FSH did not significantly alter estradiol secretion from cultured follicles. Progesterone secretion significantly decreased after culture for 48 hr, coinciding with the morphological changes observed. FasL and Fas mRNA were expressed in the healthy, early atretic, and progressed atretic porcine follicles regardless of follicular size. However, FasL but not Fas mRNA levels increased during follicular atresia. Addition of FSH significantly decreased FasL rather than Fas mRNA levels in granulosa cells and could attenuate apoptosis. Small follicles seemed to be more susceptible to atresia as compared to medium and large follicles.

Dihydrotestosterone influenced numbers of healthy follicles and follicular amounts of LH receptor mRNA during the follicular phase of the estrous cycle in gilts

The present experiments were conducted to determine androgenic effects on numbers, health, and amounts of gonadotropin receptor mRNA in late developing follicles of gilts. Gilts (n=5 per group) received daily injections of one of the following treatments on days 13–16 or days 13–18 of the estrous cycle: corn oil, 5α-dihydrotestosterone (DHT, 10 mg), flutamide (1.5 g, an androgen receptor inhibitor), DHT (10 mg) plus flutamide (1.5 g), testosterone (10 mg), and testosterone (10 mg) plus flutamide (1.5 g). Ovarian follicles ≥5 mm in diameter were evaluated on day 17 or 19, 24 h after receiving the last treatment dose. Follicles were classified as healthy (H), moderately atretic (MA), or very atretic (VA). Treatment with DHT increased (P<0.05) the numbers of H follicles relative to control gilts on days 17 and 19. DHT administration from days 13 to 16 diminished (P<0.05) the amounts of LH receptor (LHR) mRNA in H follicles from day 17 (relative amounts: 1.45±0.33 and 2.72±0.33 for DHT- and vehicle-treated gilts respectively). The effects of DHT on numbers of H follicles and LHR mRNA were not observed in gilts receiving DHT plus flutamide. Androgens did not influence numbers of MA, VA, and total follicles, or follicular estradiol-17β concentrations and amounts of FSHR mRNA. Treating gilts with DHT during follicular recruitment and selection did not induce changes in the numbers of total follicles ≥5 mm, but rather increased the numbers of healthy follicles in this follicular population in association with decreased amounts of LHR mRNA.

Implication of cortisol and 11β-hydroxysteroid dehydrogenase enzymes in the development of porcine (Sus scrofa domestica) ovarian follicles and cysts

This study investigated cortisol inactivation by 11β-hydroxysteroid dehydrogenase (11β HSD) enzymes in porcine granulosa cells from antral follicles at different developmental stages and in ovarian cysts. In granulosa cells, cortisol oxidation increased threefold with antral follicle diameter (P< 0.001). This trend was paralleled by a threefold increase in NADP+-dependent 11β-dehydrogenase activity in granulosa cell homogenates with follicle diameter. Intact granulosa cells from ovarian cysts exhibited significantly lower enzyme activities than cells from large antral follicles. Neither intact cells norcell homogenates displayed net 11-ketosteroid reductase activities. Since porcine follicular fluid (FF) from large antral follicles and ovarian cysts contains hydrophobic inhibitors of glucocorticoid metabolism by type 1 11β HSD, this studyalso investigated whether levels of 11β HSD inhibitors changed during follicle growth and could affect cortisol metabolism in granulosa cells. The extent of inhibition of 11β HSD1 activity in rat kidney homogenates decreased progressively from 50 ± 8% inhibition by FF from small antral follicles (P< 0.001) to 23 ± 6% by large antral FF (P< 0.05). Cyst fluid inhibited 11β HSD1 activity by 59 ± 4% (P< 0.001). Likewise, net cortisol oxidation in granulosa cells was significantly decreased by large antral FF (35–48% inhibition,P< 0.05) and cyst fluid (45–75% inhibition,P< 0.01). We conclude that inactivation of cortisol by 11β HSD enzymes in porcine granulosa cells increases with follicle development but is significantly decreased in ovarian cysts. Moreover, changes in ovarian cortisol metabolism are accompanied by corresponding changes in the levels of paracrine inhibitors of 11β HSD1 within growing ovarian follicles and cysts, implicating cortisol in follicle growth and cyst development.

Exogenous estradiol enhances apoptosis in regressing post-partum rat corpora lutea possibly mediated by prolactin

BACKGROUND

In pregnant rats, structural luteal regression takes place after parturition and is associated with cell death by apoptosis. We have recently shown that the hormonal environment is responsible for the fate of the corpora lutea (CL). Changing the levels of circulating hormones in post-partum rats, either by injecting androgen, progesterone, or by allowing dams to suckle, was coupled with a delay in the onset of apoptosis in the CL. The objectives of the present investigation were: i) to examine the effect of exogenous estradiol on apoptosis of the rat CL during post-partum luteal regression; and ii) to evaluate the post-partum luteal expression of the estrogen receptor (ER) genes.

METHODS

In a first experiment, rats after parturition were separated from their pups and injected daily with vehicle or estradiol benzoate for 4 days. On day 4 post-partum, animals were sacrificed, blood samples were taken to determine serum concentrations of hormones, and the ovaries were isolated to study apoptosis in situ. In a second experiment, non-lactating rats after parturition received vehicle, estradiol benzoate or estradiol benzoate plus bromoergocryptine for 4 days, and their CL were isolated and used to study apoptosis ex vivo. In a third experiment, we obtained CL from rats on day 15 of pregnancy and from non-lactating rats on day 4 post-partum, and studied the expression of the messenger RNAs (mRNAs) encoding the ERalpha and ERbeta genes.

RESULTS

Exogenous administration of estradiol benzoate induced an increase in the number of apoptotic cells within the CL on day 4 post-partum when compared with animals receiving vehicle alone. Animals treated with the estrogen had higher serum prolactin and progesterone concentrations, with no changes in serum androstenedione. Administration of bromoergocryptine blocked the increase in serum prolactin and progesterone concentrations, and DNA fragmentation induced by the estrogen treatment. ERalpha and ERbeta mRNAs were expressed in CL of day 4 post-partum animals at levels similar to those found in CL of day 15 pregnant animals.

CONCLUSION

We have established that estradiol accelerates apoptosis in the CL during post-partum luteal regression through a mechanism that possibly involves the secretion of pituitary prolactin. We have also shown that the post-partum rat CL express ERalpha and ERbeta mRNAs suggesting that they can be targeted by estrogen.

Regulation mechanism of selective atresia in porcine follicles: regulation of granulosa cell apoptosis during atresia

More than 99% of follicles undergo a degenerative process known as "atresia", in mammalian ovaries, and only a few follicles ovulate during ovarian follicular development. We have investigated the molecular mechanism of selective follicular atresia in mammalian ovaries, and have reported that follicular selection dominantly depends on granulosa cell apoptosis. However, we have little knowledge of the molecular mechanisms that control apoptotic cell death in granulosa cells during follicle selection. To date, at least five cell death ligand-receptor systems [tumor necrosis factor (TNF)alpha and receptors, Fas (also called APO-1/CD95) ligand and receptors, TNF-related apoptosis-inducing ligand (TRAIL; also called APO-2) and receptors, APO-3 ligand and receptors, and PFG-5 ligand and receptors] have been reported in granulosa cells of porcine ovaries. Some cell death ligand-receptor systems have "decoy" receptors, which act as inhibitors of cell death ligand-induced apoptosis in granulosa cells. Moreover, we showed that the porcine granulosa cell is a type II apoptotic cell, which has the mitochondrion-dependent apoptosis-signaling pathway. Briefly, the cell death receptor-mediated apoptosis signaling pathway in granulosa cells has been suggested to be as follows. (1) A cell death ligand binds to the extracellular domain of a cell death receptor, which contains an intracellular death domain (DD). (2) The intracellular DD of the cell death receptor interacts with the DD of the adaptor protein (Fas-associated death domain: FADD) through a homophilic DD interaction. (3) FADD activates an initiator caspase (procaspase-8; also called FLICE), which is a bipartite molecule, containing an N-terminal death effector domain (DED) and a C-terminal DD. (4) Procaspase-8 begins auto-proteolytic cleavage and activation. (5) The auto-activated caspase-8 cleaves Bid protein. (6) The truncated Bid releases cytochrome c from mitochondrion. (7) Cytochrome c and ATP-dependent oligimerization of apoptotic protease-activating factor-1 (Apaf-1) allows recruitment of procaspase-9 into the apoptosome complex. Activation of procaspase-9 is mediated by means of a conformational change. (8) The activated caspase-9 cleaves downstream effector caspases (caspase-3). (9) Finally, apoptosis is induced. Recently, we found two intracellular inhibitor proteins [cellular FLICE-like inhibitory protein short form (cFLIPS) and long form (cFLIPL)], which were strongly expressed in granulosa cells, and they may act as anti-apoptotic/survival factors. Further in vivo and in vitro studies will elucidate the largely unknown molecular mechanisms, e. g. which cell death ligand-receptor system is the dominant factor controlling the granulosa cell apoptosis of selective follicular atresia in mammalian ovaries. If we could elucidate the molecular mechanism of granulosa cell apoptosis (follicular selection), we could accurately diagnose the healthy ovulating follicles and precisely evaluate the oocyte quality. We hope that the mechanism will be clarified and lead to an integrated understanding of the regulation mechanism.

Expression of Cytoskeletal Proteins in the Follicular Wall of Induced Ovarian Cysts

Several experimental models have been developed for the study of the polycystic ovarian syndrome in the rat. In the present study, the syndrome was induced by exposure to constant light, and the expression of cytoskeletal proteins in the follicular wall was evaluated by immunohistochemistry. We analyzed the immunohistochemically stained area (IHCSA) by image analysis to evaluate the expression of intermediate filaments (vimentin, desmin, cytokeratins, gliofibrillary acidic protein and neurofilaments) and alpha-smooth muscle actin (alpha-SMA) in cystic ovaries in relation to normal ovaries. The granulosa cell layer of cystic follicles had a significantly greater IHCSA for vimentin than the normal antral follicles. This difference was also significant between atretic and antral follicles. Cytokeratins showed a very low expression in the granulosa cells of antral follicles of control ovaries while in granulosa cells of atretic and cystic follicles they showed a significantly higher IHCSA. Immunohistochemical localization of desmin and alpha-SMA was restricted to the theca externa. Immunoreactivity for gliofibrillary acidic protein and neurofilament was negative. The highest intensity in the staining with vimentin and cytokeratins observed in the granulosa cells of the cystic follicles is probably due to structural and functional changes that occur during the process of cystogenesis and they could be associated with intense changes in the expression of cytoskeletal proteins that may be essential to the proper cellular functioning.

Prostaglandin F2α-induced estrus in ewes exhibiting estrous cycles of different duration

Effects of prostaglandin F(2alpha) (PGF(2alpha)), administered during the mid-luteal phase of the estrous cycle, were examined in ewes exhibiting estrous cycles classified as short (< or =16.5 days, short-cycle ewes, n = 10) or long (> or =18 days, long-cycle ewes, n = 9) based on the durations of two estrous cycles (cycles -2 and -1) before treatment. The ewes received (i.m.) 20mg of PGF(2alpha) on day 10 of the third estrous cycle (cycle 0) followed, 36 h later, by 25 microg of gonadotropin releasing hormone (GnRH) to time the events of ovulation. Duration of subsequent estrous cycles +1 and +2 were recorded, and then the ewes were treated with the same combination of PGF(2alpha) and GnRH beginning on day 10 of estrous cycle +3. Ovaries were recovered 6h after GnRH administration to assess development of pre-ovulatory follicles. The proportion of ewes that exhibited estrus after PGF(2alpha) and GnRH treatment on cycle 0 was not different (P > 0.05) between short- and long-cycle ewes. Onset of estrus occurred sooner (P < 0.05) after PGF(2alpha) injection in short-cycle ewes than in long-cycle ewes (1.9 +/- 0.1 days and 2.3 +/- 0.1 days, duration of cycle 0 was 11.9 and 12.3 days, respectively). Duration of estrous cycle +1 was 1.2 days longer (P < 0.01) than cycle -1 in short-cycle ewes. However, duration of estrous cycle +1 did not change (P > 0.05) after PGF(2alpha) and GnRH administration in ewes having long cycles. Pre-ovulatory follicles did not differ (P > 0.05) in numbers, diameter, layers of granulosa cells nor concentrations of progesterone and estradiol-17beta in follicular fluid between short- and long-cycle ewes after PGF(2alpha) and GnRH treatment. In conclusion, ewes having short or long estrous cycles responded differently to PGF(2alpha) and GnRH treatment with respect to the interval to onset of estrus and duration of the subsequent estrous cycle.

Relationship between follicular fluid hormone levels, embryo quality, and maternal age during in vitro fertilization after the short or long protocol with a gonadotropin releasing hormone agonist

Purpose:  To examine the relationship between embryo quality and follicular fluid hormonal level in short and long protocol gonadotrophin releasing hormone agonist treatment cycles. Methods:  A total of 90 patients had non-polycystic ovary syndrome (non-PCOS) and 10 had PCOS. A total of 100 subjects underwent in vitro fertilization (IVF). Thirty-six subjects underwent conventional IVF and 64 subjects underwent intracytoplasmic sperm injection (ICSI). The dominant follicles were initially retrieved and a hormonal assay was done. A total of 32 patients underwent a short protocol and 66 patients were treated with the long protocol. Estradiol (E₂), progesterone (P₄), total testosterone (TTE) and androstenedione (ASG) levels in follicular fluid (FF) were compared in the two treatment groups (short and long protocol), in regard to maternal age and oocyte/embryo quality. Results:  The retrieval FF volume was not significantly different between the PCOS and non-PCOS patients; however, P₄ was significantly lower with PCOS (P < 0.01). Analysis of four different hormone levels was not significantly different between the short and long protocol groups. No significant relationship was found between four hormone levels in regard to oocyte morphology and embryo quality. The levels of P₄ of younger women was significantly lower than that of older women; furthermore, a significantly higher TTE and ASG were found in the younger women. Progesterone was found to statistically significantly increase with FF volume. Conclusion:  Follicular fluid P₄ from the younger group was significantly lower, and TTE and ASG was significantly higher when compared to the older group. Analysis of four different hormone levels revealed no significant difference between the short and long protocol groups. No significant relationship was found between four hormone levels, oocyte morphology, and embryo quality. (Reprod Med Biol 2003; 2: 165-169).

Apoptosis in human granulosa cells after induction of ovulation in women participating in an intracytoplasmic sperm injection program

OBJECTIVES

To investigate whether analysis of granulosa cell apoptosis can be useful in assessing follicular and oocyte maturation and the regulation of granulosa cell apoptosis by follicular fluid steroids in preovulatory follicles of stimulated women.

STUDY DESIGN

Apoptosis in aspirated granulosa cells (n=64) was measured using the Annexin V-affinity assay by flow cytometry. Follicular fluid steroids were determined by ELISA and RIA. Statistics were evaluated using the Levenne test, Student t-test and simple linear regression analysis.

RESULTS

No significant differences in the number and percentage of apoptotic granulosa cells per follicle were observed according to the maturity and fertilizability of the oocytes by intracytoplasmic sperm injection within these follicles. No correlations were found between levels of steroid hormones in follicular fluid and the number and proportion of granulosa cells undergoing apoptosis.

CONCLUSIONS

The percentage of apoptosis in granulosa cells is not related to oocyte maturity and fertilizability by ICSI or to follicular quality in stimulated cycles of normal women. However, the possibility cannot be discarded that this parameter may be of importance at other phases of follicular development or in natural cycles when no treatment that influences follicular physiology is being applied.

Serum and follicular fluid hormone levels during in vitro fertilization after short- or long-course treatment with a gonadotropin-releasing hormone agonist

OBJECTIVE

To examine the impact of flare (short) vs. down-regulation (long) GnRH agonist (GnRH-a) on serum and follicular fluid (FF) LH and androgen concentrations in women undergoing IVF treatment cycles.

DESIGN

Prospective observational study.

SETTING

IVF clinic.

PATIENT(S)

One hundred sixteen ovulatory subjects undergoing IVF.

INTERVENTION(S)

Fifty-eight ovulatory patients undergoing a down-regulation regimen matched with 58 undergoing the flare regimen as part of an IVF cycle.

MAIN OUTCOME MEASURE(S)

Serum concentrations of LH, FSH, Progesterone (P4), Androstenedione (A), T, and E(2) on the day of hCG administration were compared between the two groups. In addition, the FF P4, 17OHP4, A, T, and E(2) levels were compared in the two groups.

RESULT(S)

Serum LH was significantly higher with the flare regimen (15.2 +/- 1.14 IU/L, P<.05) when compared with results with the down-regulation protocol (9.5 +/- 0.77 IU/L). In addition, FF A was significantly higher in the flare protocol (57.3 +/- 13.3 ng/mL, P<.05) compared with in the down-regulation protocol (27 +/- 2.44 ng/mL). Serum and FF P4, 17OH P4, T, and E(2) were not statistically significantly different between the two groups.

CONCLUSION(S)

Serum LH and FF A are significantly higher in the flare regimen in comparison with the down-regulation regimen. Circulating LH appears to play a role in determining FF A concentration.

Characterization of the antiapoptotic Bcl-2 family member myeloid cell leukemia-1 (Mcl-1) and the stimulation of its message by gonadotropins in the rat ovary

The majority of ovarian follicles undergo atresia mediated by apoptosis. Bcl-2-related proteins act as regulators of apoptosis via the formation of dimers with proteins inside and outside the Bcl-2 family. Previous studies have identified BAD as a proapoptotic Bcl-2 family member expressed in the ovary. It is known that BAD phosphorylation induced by survival factors leads to its preferential binding to 14-3-3 and suppression of the death-inducing function of BAD. To identify ovarian binding partners for hypophosphorylated BAD, we performed a yeast two-hybrid screening of a rat ovary complementary DNA library using as bait a mutant BAD incapable of binding to 14-3-3. Screening of yeast transformants yielded positive clones encoding the rat ortholog of Mcl-1 (myeloid cell leukemia-1), an antiapoptotic Bcl-2 protein. Amino acid sequence analysis revealed that rat and human Mcl-1 showed a complete conservation of the Bcl-2 homology domains BH1, BH2, and BH3. In the yeast two-hybrid system, Mcl-1 binds to the hypophosphorylated mutant of BAD and interacts preferentially with different proapoptotic (Bax, Bak, Bok, Bik, and BOD) compared with antiapoptotic Bcl-2 family members (Bcl-2, Bcl-xL, Bcl-w, Bfl-1, CED-9, and BHRF-1). Northern blot hybridization demonstrated expression of Mcl-1 transcripts of 2.3 and 3.7 kb in the ovary and diverse other rat tissues. In immature rats, PMSG treatment led to a transient increase in the 2.3-kb Mcl-1 transcript, peaking at 6 h after injection and returning to baseline levels after 24 h. Moreover, the same transcript was induced in the PMSG-primed preovulatory rat ovary 6 h after the administration of ovulatory doses of either hCG or FSH. In situ hybridization studies revealed that the gonadotropin stimulation of ovarian Mcl-1 message occurs in both granulosa and thecal cells. In conclusion, rat Mcl-1 was identified as an ovarian BAD-interacting protein and the message for the antiapoptotic Mcl-1 protein was induced after treatment with gonadotropins in granulosa and thecal cells of growing follicles.

Restricted expression of WT1 messenger ribonucleic acid in immature ovarian follicles: uniformity in mammalian and avian species and maintenance during reproductive senescence

WT1 is a zinc finger protein with transcriptional repressor activity on several growth factor and growth factor receptor genes. In the ovary, a potential role for WT1 in the suppression of the development of immature follicles has been demonstrated. Here, gel retardation assays further showed that recombinant WT1 protein interacted with consensus DNA sequences in the inhibin-alpha gene promoter. We investigated the pattern of WT1 expression in a wide variety of species and also over the reproductive life span in rats. In chicken ovaries, Northern blot analysis revealed the presence of WT1 transcript in small healthy white follicles (1-5 mm in diameter) and its absence in small yellow (6-12 mm in diameter) or larger follicles (F1-F5). In pig and monkey ovaries, WT1 expression was limited to granulosa cells of preantral follicles, as shown by in situ hybridization analysis. In rats, Northern blot analyses demonstrated the presence of WT1 transcript in the ovaries of young (3-mo-old) and middle-aged (9-mo-old) rats on the proestrous day, with a decrease in old (12-mo-old) rats in persistent estrus. In situ hybridization analysis further suggested that the decrease in WT1 expression in aging ovaries was associated with fewer immature follicles. Thus, WT1 expression is restricted to immature follicles in diverse avian and mammalian species and over the reproductive life span in rats. These data demonstrated that WT1 is a marker for immature follicles and suggested a potential role of this transcriptional repressor in the slow growth of early follicles.

Paracrine mechanisms of ovarian follicle apoptosis

It has become evident that the physiological removal of cells through apoptosis during embryonic and postnatal development of multicellular organisms is a mandatory process to maintain a homeostatic state of the individual. In the ovary, massive cell death occurs during neonatal and postnatal life as an integral part of the normal ovarian development. At birth, mammalian ovaries are endowed with a fixed number of non-growing follicles that will be gradually recruited into a growing pool during reproductive life. Once follicles start growth they are either selected for ovulation or, for the majority of them, removed by apoptosis. Thus, removal of excess ovarian cells by apoptosis is necessary for normal development of the ovary. Despite the important role of follicle atresia in the maintenance of normal follicle development, studies on the hormonal control of follicle cell demise during follicle growth have not been possible until the recent development of apoptosis detection methods. Recent biochemical analysis has revealed the occurrence of internucleosomal DNA fragmentation, a hallmark of apoptosis, in atretic follicles and has facilitated the investigation into the intra-ovarian hormonal regulation of follicle atresia. This review summarizes the recent advances in the intra-ovarian hormonal mechanisms that control follicle apoptosis.

Prolactin in follicular fluid and intracellular store calcium in follicular cells are related to morphological signs of ovarian follicle atresia in cows: work in progress

It is known that prolactin (PRL) is the third pituitary hormone serving gonadotropic function in mammals. However, its role in the regulation of ovarian folliculogenesis and, in particular, its relationship to follicular atresia as well as the mechanism of its influence on follicular cells are poorly understood. We investigated PRL levels in follicular fluids (FFs) and intracellular store calcium ([Ca2+]is) in cell walls of bovine ovarian follicles with diameters of 10 to 20 mm and their relationship to follicular atresia. Ovarian follicles were categorized on the basis of macroscopic criteria and of microscopic examination of granulosa cell (GC) smears. Prolactin concentrations in FFs were measured by RIA and levels of [Ca2+]is in follicular cells were determined by using the fluorophore chlortetracycline. Compared to atretic follicles, morphologically normal follicles were characterized by higher concentrations of PRL in FFs (P < 0.001) and lower contents of [Ca2+]is in follicular cells (P < 0.01). Furthermore, follicles containing no more than 20% of pycnotic GCs had higher levels of PRL in their fluids than those containing over 40% of pycnotic GCs (P < 0.05). Finally, the direct effect of PRL on [Ca2+]is content in follicular cells was studied in vitro. Compared to control, PRL decreased (P < 0.001) the levels of [Ca2+]is in the cells after 24 h culture of follicular walls from morphologically normal follicles in TCM 199 supplemented by 10% fetal calf serum. Our findings suggest that the decline of PRL concentrations in FFs and the rise of [Ca2+]is contents in follicular cells are related to atresia of large bovine follicles and that there appears to be a relationship between the two biochemical parameters.

Exogenous gonadotropin stimulation is associated with increases in serum androgen levels in in-vitro fertilization-embryo transfer cycles

OBJECTIVE

To examine serum androgen profiles in women undergoing ovarian stimulation with exogenous gonadotropins in the setting of IVF-ET.

DESIGN

Prospective study.

SETTING

University hospital IVF-ET program.

PATIENT(S)

Seventeen ovulatory women undergoing IVF-ET for endometriosis, male factor infertility, or tubal disease.

INTERVENTION(S)

A standard long protocol of GnRH agonist (GnRH-a) pretreatment (1 mg of leuprolide acetate SC for 10 days) was administered before ovulation induction with a urinary gonadotropin preparation.

MAIN OUTCOME MEASURE(S)

After 10 days of GnRH-a treatment and on the day of hCG administration, serum concentrations of LH, T, androstenedione (A), sex hormone-binding globulin (SHBG), and DHEAS; the free androgen index (T/SHBG); and the number of follicles, oocytes, and embryos were assessed.

RESULT(S)

Serum samples after 10 days of GnRH-a treatment showed incomplete LH suppression. While continuing the agonist during ovarian stimulation, LH values were suppressed further. However, serum T and A concentrations and the free androgen index showed a significant increase (samples drawn just before hCG administration). Serum T levels after 10 days of GnRH-a (before the administration of exogenous gonadotropins) were correlated negatively with the subsequent number of embryos.

CONCLUSION(S)

Serum LH suppression with a conventional regimen of GnRH-a is incomplete in this heterogeneous group of ovulatory women. Exogenous gonadotropin stimulation results in a marked increase in ovarian androgen secretion.

Expression of Fas-Fas ligand system associated with atresia in murine ovary

We detected that Fas receptor (Fas) was expressed at transcriptional levels in oocytes/eggs and some granulosa cells of murine ovary, whereas, Fas ligand (FasL) was found to be strongly expressed in granulosa cells by means of in situ hybridisation. These results were supported by an indirect immunofluorescence (IIF) test with anti-Fas monoclonal antibody (mAb)/FasL Ab. The lysates from granulosa cells were precipitated by anti-FasL Ab, exhibiting a specific band at 40 kDa. When zona pellucida (ZP)-free eggs were incubated with granulosa cells in vitro, apoptosis (DNA fragmentation) was induced in the eggs, as detected by the terminal deoxynucleotide transferase mediated dUTP-nick end labelling (TUNEL) method. To examine whether FasL-bearing cells can induce apoptosis in eggs expressing Fas through molecular interaction between FasL and Fas, we employed a baculovirus expression system to generate FasL on the surface of Spodoptera frugiperda (Sf9) cells. The co-incubation of eggs with Autographa californica nuclear polyhedrosis virus (AcNPV) and FasL transfected Sf9 (Sf9-FasL) cells in vitro was performed and resulted in the induction of apoptosis in eggs as detected by the TUNEL method. Apoptosis was absent in eggs co-incubated with AcNPV-1393 transfected Sf9 (Sf9-1393) cells. Thus, ovarian atresia was suggested to be induced by molecular interaction between FasL on granulosa cells and Fas on oocytes/eggs during oogenesis.

Monoclonal antibodies against pig ovarian follicular granulosa cells induce apoptotic cell death in cultured granulosa cells

Two monoclonal antibodies capable of inducing granulosa cell apoptosis were produced against granulosa cells prepared from antral follicles of pig ovaries. The healthy follicles, 4-5 mm in diameter, were dissected from the ovaries of gilts, and then granulosa cells were isolated. BALB/c female mice were immunized with the isolated granulosa cells. Antibodies against the granulosa cells were detected by immunofluorescent staining using frozen ovarian sections. The isolated spleen cells prepared from immunized mice producing antibodies against the granulosa cells were fused with Sp2/O-Ag 14 mouse myeloma cells by standard hybridization techniques. Two hybridoma clones, PFG-1 and PFG-2, which produced specific IgM antibodies against granulosa cells were selected. Western blotting analysis revealed that PFG-1 and PFG-2 antibodies specifically recognized cell-membrane proteins with molecular weights of 55 and 70 kD and isoelectric points of 5.9 and 5.4, respectively. The monoclonal antibodies immunohistochemically reacted with granulosa cells of healthy follicles. When the isolated granulosa cells prepared from healthy follicles were cultured in medium containing 0.1 or 10 micrograms/m/PFG-1 or PFG-2 antibodies, respectively, the cells underwent apoptosis as determined by nuclear morphology, DNA electrophoresis and flow cytometric analysis. In conclusion, these two monoclonal antibodies against granulosa cells have cell-killing activity in cultured granulosa cells.

Expression of Fas ligand in murine ovary

Corresponding to the expression of Fas in the ovarian oocytes as previously reported (Guo et al., Biochem Biophys Res Commun 1994; 203:1438-1446; Mori et al., JSIR 1995; 9:49-50), the expression of Fas ligand (FasL) in the ovarian follicle was found to be restricted in the area of granulosa cells by the indirect immunofluorescence (IIF) test. Reverse transcriptase/polymerase chain reaction (RT/PCR) technique coupled with Southern blot hybridization analysis showed that the highest level of FasL mRNA was demonstrated in murine ovaries and granulosa cells 1 day after the administration of pregnant mare's serum gonadotropin (PMSG), while the level of FasL mRNA became very weak on the day 5, respectively. The observed gradual decrease in FasL mRNA could not be attributed to a generalized degradation of cellular RNA during atresia, as evidenced by the presence of constitutive expression of elongation factor 1 alpha (EF-1 alpha) mRNA in murine ovaries and granulosa cells treated with PMSG. Furthermore, in situ hybridization analysis with a FasL-specific probe confirmed that FasL was specifically localized in the granulosa cells of most follicles and its expression was regulated by PMSG administration. FasL localized in granulosa cells might possibly play an important role in the formation of the ovarian atretic follicles, most likely depending on PMSG administration.

Effect of the rate of progesterone decline at luteolysis on the ovulatory follicles and subsequent estrous cycle length in ewes

Follicular and interestrous characteristics were examined in 34 ewes after experiencing either a rapid decline in plasma concentrations of progesterone at luteolysis [prostaglandin F2 alpha (PGF2 alpha)-induced] or a slow rate of decline, lasting over 72 h. All ewes were given PGF2 alpha on day 10 (day 0 = estrus). A slow rate of decline was established in 17 ewes by the intravenous infusion of progesterone initially at 72 ml h-1, delivering 4.5 mg progesterone h-1, then decreasing the infusion rate by 1 ml h-1 for the next three days. Seventeen additional ewes, predestined to experience a rapid decline in progesterone, were infused with vehicle. In Experiment 1, after infusion, ewes (6 ewes/group) were necropsied at the onset of estrus and follicle diameter was determined, follicular fluid was aspirated and the remaining follicular wall was microscopically examined to determine the number of granulosa cell layers. In Experiment 2, the interestrous interval, after infusion, was observed in both groups of ewes (11 ewes/group). Ewes experiencing a rapid rate of progesterone decline at luteolysis had no differences in follicle diameter nor follicular concentration of progesterone or estradiol but their ovulatory follicles contained fewer (P < 0.01) granulosa cell layers and the resulting estrous cycle was longer (P < 0.05) than ewes experiencing a slow rate of progesterone decline.

Apoptosis occurs in granulosa cells but not cumulus cells in the atretic antral follicles in pig ovaries

The porcine antral follicles, 3-6 mm in diameter, were dissected from the ovaries of mature pigs, and then granulosa and cumulus cells were isolated from each follicle. In atretic follicles, high activity of neutral Ca2+/Mg2+-dependent endonuclease and DNA ladder formation, estimated by electrophoresis, were noted in granulosa cells but not in cumulus cells. Extremely low activity of the endonuclease and no DNA ladder formation were observed in both types of cells obtained from healthy follicles. Moreover, apoptotic cells were observed histochemically among granulosa cells only. A good correlation (r = 0.987) between the endonuclease activity of granulosa cells and the progesterone/estradiol ratio of follicular fluid in each follicle was found. These results suggest that apoptosis occurs in granulosa cells but not cumulus cells in the atretic antral follicles in pigs.

Steroidogenic activity of atretic follicles in the cycling hamster ovary and relation to ultrastructural observations

To evaluate the relation between the steroidogenic activity and cell proliferation of individual follicles in mature hamster ovaries during the estrous cycle, the localization of enzymes involved in estrogen biosynthesis and bromodeoxyuridine (BrdU) incorporation were examined immunohistochemically. Moreover, granulosa cells from the early atretic follicle were examined by scanning and transmission electron microscopy. Immunoreactivity for aromatase was localized in the granulosa cells of healthy developing follicles and Graafian follicles, as well as in newly formed granulosa lutein cells. In the healthy follicles of an ovulation cycle, intensity of aromatase immunoreactivity was suddenly decreased on day 3. The theca interna cells of healthy developing follicles were immunopositive for 17 alpha-hydroxylase/C17-C20 lyase (17 alpha-lyase) from day 2 to the morning of day 4, but on the evening of day 4 most theca interna cells were immunonegative except for only a few cells of the large Graafian follicles. BrdU incorporation was observed in the granulosa cells of healthy developing follicles, in the endothelial cells of capillaries around the developing follicles, and of newly formed corpora lutea. Very early morphological signs of atresia was the pyknotic change of a few granulosa cells lining the antral cavity. In that follicle, the number of BrdU-incorporating granulosa cells was suddenly decreased whilst immunoreactivity of aromatase and 17 alpha-lyase were gradually decreased. These data suggest that the mechanism of the loss of aromatase activity from the granulosa cells of atretic follicles appears to differ from that in cycling follicles.(ABSTRACT TRUNCATED AT 250 WORDS)

Can macroscopic identification of large ovarian follicles be useful in eliminating follicles with impaired steroid function?

"In vitro" studies, commonly using porcine ovarian follicles, may generate inconsistent results when atretic follicles are not eliminated from the pool of experimental follicles. The present experiment was conducted to test the practical value of the macroscopie identification of large porcine follicles, which were assumed to be atretic. Histological observations of hematoxylin-eosin stained follicular sections confirmed the results of the macroscopic classification. The follicles classified as presumably abnormal revealed signs of atresia at the light microscopic level. Such follicles (type 2) showed decreased levels of estradiol and androgens in comparison with the healthy-looking follicles (type 1).Steroid analysis also revaled that practically all estradiol from an ovarian follicle could be detected in the follicular fluid, whereas androgens extracted from follicular fluid represented approximately half of the total amount of follicular androgens.The experimental results indicate that the introduced macroscopic classification could be helpful in eliminating follicles with an impaired steroid function.

Changes in follicular estradiol-17 beta, progesterone and inhibin immunoactivity in healthy and atretic follicles during preovulatory maturation in the pig

Follicular hormones, growth and granulosa cell gonadotropin sensitive adenylate cyclase activity were determined in healthy and atretic follicles during preovulatory maturation in pigs. Ovaries were recovered at slaughter which was 1, 3, 5 or 7 d after the last administration of a progesterone agonist (altrenogest). Plasma FSH decreased (P < .05) by 64% between days 1 and 3 and remained low through day 5. The number of large (> 5 mm) follicles increased from 2.7 on day 1 to 14.8 on day 3 and did not differ significantly among days 3, 5 and 7. The number of small (1-2 mm) and medium (3-5 mm) follicles decreased (P < or = .05) by 82% between days 3 and 5. Follicles first became estrogen-active (EA) (> or = 100 ng of estradiol-17 beta/ml of follicular fluid) on day 3, with 14.3% of medium and 73.8% of large follicles being EA. About 30% of small and 13% of medium follicles were morphologically atretic on days 1 and 3. However, by day 5, the proportion of atretic small and medium follicles had increased (P < or = .05) to 100 and 59%, respectively. Follicular fluid inhibin immunoactivity and estradiol-17 beta were lower (P < or = .05) and progesterone was greater (P < or = .05) in atretic than healthy follicles. Granulosa cells from large follicles produced (P < or = .05) more cAMP than cells from healthy or atretic small/medium follicles. Compared to control or pFSH treatment, pLH increased cAMP production by granulosa cells from large follicles on all days and from small/medium follicles on days 1 and 5; pLH had no effect on granulosa cells from atretic follicles. Compared to control, pFSH increased cAMP production in granulosa cells from healthy small/medium follicles only on day 1; no effect was detected in granulosa cells from large or atretic follicles on any day. We conclude that decreased secretion of FSH increased loss and atresia among non-ovulatory follicles. Atretic follicles were marked by loss of granulosa cell gonadotropin-sensitive adenylate cyclase activity and by low concentrations of estradiol-17 beta.

Changes in follicular endocrinology during final maturation of porcine oocytes

Thirty-one gilts were ovariectomized between 21 and 34 hr after the onset of estrus to compare changes in follicular endocrinology with stages of oocyte maturation. Oocytes were recovered from 6 to 8 mm follicles and classified by stage of meiosis. Remaining follicular fluid was assayed for steroids and dermatan sulfate. Amounts of prostaglandin F2 alpha (PGF2 alpha) and E2 (PGE2) were measured in intramural tissues. Coincident with germinal vesicle breakdown, the follicular content of all steroids except testosterone decreased (P less than .05). As oocytes approached metaphase II, the amount of progesterone within follicles increased (P less than .05), and estradiol continued to decrease (P less than .05). The pattern of dermatan sulfate content was biphasic and peaked at germinal vesicle breakdown and anaphase stages. Amounts of PGF2 alpha and PGE2 within intramural tissues increased (P less than .05) throughout oocyte maturation. Follicular atresia was evident during estrus; however, more (P less than .05) atretic follicles were recovered at germinal vesicle than metaphase II stages (20 vs 3%, respectively). Follicular development, within a gilt, was skewed (P less than .05) and classification of follicles by hormone content demonstrated that a majority were more mature than a minority of less mature follicles. These data suggest that follicular maturation and oocyte development are highly correlated in swine. Furthermore, partitioning the follicular variability by hour and stage of oocyte maturation allowed for more precise assessment of follicular endocrinology than previously reported.

Hydrolase cytochemistry during follicular atresia in mammals

Activity changes of thiamine pyrophosphatase (TPPase), acid phosphatase (aP), non-specific esterase (nE), acid beta-galactosidase (a beta Gal), beta-glucuronidase (beta-Gluc), and beta-D-N-acetylglucosaminidase (NAG) in follicles during atresia were investigated in the ovaries of mice, rats, Mongolian gerbils, hamsters, guines pigs, rabbits, cats, and pigs. Changes of hydrolase activity were highly enzyme dependent, species-specific and mostly confined to the granulosa. Decrease of TPPase activity and increase of lysosomal enzyme activities during atresia appeared to be true for all mammals. The start of activity changes in the time course of atresia depended on the occurrence of the enzyme in the growing granulosa. Continuous increase of lysosomal enzyme activity appeared in follicles where these enzymes could also be found in the growing granulosa. In contrast, when lysosomal enzyme activity was low or could not be detected in the growing granulosa, increased enzyme activity could only be observed at a time when degenerative processes have already progressed considerably. This distribution pattern suggests that hydrolytic enzymes in the granulosa cells as well as hydrolases of invading macrophages participate in this degenerative process. In some mammals, enzyme activity changes appeared in the cumulus oophorus for the first time in advanced stages of degeneration. In some mammals enzyme activity changes were dependent on the developmental stage of the follicle. This stage dependency argues for an interrelationship between activation of lysosomal enzymes and androgen metabolism.

Oestrogens inhibit steroid production by dispersed porcine thecal cells

An intra-ovarian role for oestrogens in the control of steroid production was investigated using dispersed thecal cells obtained from porcine follicles. Thecal cells were incubated for 14 h at 37 degrees C and the media subsequently assayed for androstenedione, progesterone and cyclic AMP. LH caused a dose-dependent stimulation of both steroids and the addition of oestradiol at doses of 10 ng-10 micrograms/ml significantly (P less than 0.01) inhibited both basal and LH-stimulated steroid production from doses of 500 ng/ml and upwards. Of other oestrogens investigated, oestrone and oestriol were somewhat less potent than oestradiol in inhibiting steroid synthesis, whereas the synthetic oestrogen diethylstilbestrol (DES) was more potent. The presence of oestradiol at doses of 10 ng-10 micrograms/ml had no significant effect (P less than 0.05) on either basal or LH-stimulated cAMP suggesting that the oestradiol inhibition does not involve inhibition of LH receptor-linked adenylate cyclase. These results demonstrate that physiological doses of oestrogen can act by local negative feedback to control the synthesis of its own precursor and thus regulate intrafollicular steroidogenesis.