Evidence that androgens are involved in atresia and anovulation induced by antiprogesterone RU486 in rats

Huperzine-A administration recovers rat ovary function after sympathetic stress

Chronic cold stress affects ovarian morphology and impairs fertility in rats. It causes an ovarian polycystic ovary (PCOS)-like phenotype, which resembles PCOS in women. The mechanism of cold stress action involves increased ovarian noradrenaline (NA) levels, which remain elevated after cessation of cold stress. By contrast, ovarian acetylcholine (ACh) levels are only transiently elevated and returned to control levels after a 28-day post stress period. Because ACh can exert trophic actions in the ovary, we hypothesised that a sustained elevation of ovarian ACh levels by intraovarian exposure to the ACh-esterase blocker huperzine-A (Hup-A) may interfere with cold stress-induced ovarian changes. This possibility was examined in female Sprague-Dawley rats exposed to cold stress (4°C for 3 h day^-1 for 28 days), followed by a 28-day period without stress. To elevate ACh, in a second group Hup-A was delivered into the ovary of cold stress-exposed rats. A third group was not exposed to cold stress. As expected, cold stress elevated ovarian NA, reduced the number of corpora lutea and increased the number of follicular cysts. It increased plasma testosterone and oestradiol but decreased plasma levels of progesterone. In the Hup-A group, ovarian levels of both, NA and ACh, were elevated, there were fewer cysts and normal testosterone and oestradiol plasma levels were found. However, progesterone levels remained low. Most likely, low progesterone was associated with impaired mating behaviour and low pregnancy rate. We propose that elevated intraovarian levels of ACh are involved in the rescue of ovarian function, opening a target to control ovarian diseases affecting follicular development.

Rodent models for human polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is the most frequent female endocrine disorder, affecting 5%-10% of women, causing infertility due to dysfunctional follicular maturation and ovulation, distinctive multicystic ovaries and hyperandrogenism, together with metabolic abnormalities including obesity, hyperinsulinism, an increased risk of type 2 diabetes, and cardiovascular disease. The etiology of PCOS is unclear, and decisive clinical studies are limited by ethical and logistic constraints. Consequently treatment is palliative rather than curative and focuses on symptomatic approaches. Hence, a suitable animal model could provide a valuable means with which to study the pathogenesis of the characteristic reproductive and metabolic abnormalities and thereby identify novel and more effective treatments. So far there is no consensus on the best experimental animal model, which should ideally reproduce the key features associated with human PCOS. The prenatally androgenized rhesus monkey displays many characteristics of the human condition, including hyperandrogenism, anovulation, polycystic ovaries, increased adiposity, and insulin insensitivity. However, the high cost of nonhuman primate studies limits the practical utility of these large-animal models. Rodent models, on the other hand, are inexpensive, provide well-characterized and stable genetic backgrounds readily accessible for targeted genetic manipulation, and shorter reproductive life spans and generation times. Recent rodent models display both reproductive and metabolic disturbances associated with human PCOS. This review aimed to evaluate the rodent models reported to identify the advantages and disadvantages of the distinct rodent models used to investigate this complex endocrine disorder.

Radiolabeling, biodistribution and gamma scintigraphy of noscapine hydrochloride in normal and polycystic ovary induced rats

BACKGROUND

Noscapine, an alkaloid from Papaver somniferum, widely used as an antitussive, is being clinically studied in the treatment of polycystic ovary syndrome (PCOS) and a few other cancers primarily because of its anti-angiogenesis properties. With the advent of diverse application of noscapine, we sought to determine whether the radiolabeling method can be useful in studying uptake and kinetics of the molecule in-vivo. Specific objectives of this study were to radiolabel noscapine with Technetium-99m (Tc-99m), to determine its organ biodistribution in rat model and study its uptake kinetics in PCOS model.

METHODS

A method for radiolabeling noscapine with Tc-99m was standardized using stannous reduction method and its in vitro and in vivo stability parameters were studied. The radiopharmaceutical was also evaluated for blood kinetics and biodistribution profile. An animal model of PCOS was created by using antiprogesterone RU486 and uptake of 99mTc-noscapine in normal and PCOS ovaries was compared using gamma scintigraphy.

RESULTS

Noscapine hydrochloride was successfully radiolabeled with Tc-99m with high labeling efficiency and in vitro stability. Most of the blood clearance of the drug (80%) took place in first hour after intravascular injection with maximum accumulation being observed in liver, spleen, kidney followed by the ovary. At 4 hours post injection, radiolabeled complex accumulation doubled in PCOS ovaries in rats (0.9 +/- 0.03% ID/whole organ) compared to normal cyclic rats (0.53 +/- 0.01% ID/whole organ). This observation was further strengthened by scintigraphic images of rats taken at different time intervals (1 h, 2 h, 4 h, and 24 h) where SPECT images suggested discrete accumulation in the PCOS ovaries.

CONCLUSION

Through our study we report direct radiolabeling of noscapine and its biodistribution in various organs and specific uptake in PCOS that may show its utility for imaging ovarian pathology. The increased ovarian uptake in PCOS may be related to its receptor binding suggesting possible role of 99mTc-noscapine in PCOS diagnostics and therapeutics.

Permselectivity of blood follicle barriers in mouse ovaries of the mifepristone-induced polycystic ovary model revealed by in vivo cryotechnique

Despite the potential association of polycystic ovary (PCO) syndrome with hemodynamic changes, follicular microenvironment and the involvement of blood follicle barriers (BFB), a histopathological examination has been hampered by artifacts caused by conventional preparation methods. In this study, mouse ovaries of a mifepristone-induced PCO model were morphologically and immunohistochemically examined byin vivocryotechnique (IVCT), which prevents those technical artifacts. Ovarian specimens of PCO model mice were prepared by IVCT or the conventional perfusion fixation after s.c. injection of mifepristone. Their histology and immunolocalization of plasma proteins, including albumin (molecular mass, 69 kDa), immunoglobulin G (IgG, 150 kDa), inter-α-trypsin inhibitor (ITI, 220 kDa), fibrinogen (340 kDa), and IgM (900 kDa), were examined. In the PCO model, enlarged blood vessels with abundant blood flow were observed in addition to cystic follicles with degenerative membrana granulosa. The immunolocalization of albumin and IgM in the PCO model were similar to those in normal mice. Albumin immunolocalized in the blood vessels, interstitium or follicles, and IgM was mostly restricted within the blood vessels. In contrast, immunolocalization of IgG, ITI, and fibrinogen changed in the PCO model. Both IgG and ITI were clearly blocked by follicular basement membranes, and hardly observed in the membrana granulosa, though fibrinogen was mostly observed within blood vessels. These findings suggest that increased blood flow and enhanced selectivity of molecular permeation through the BFB are prominent features in the PCO ovaries, and changes in hemodynamic conditions and permselectivity of BFB are involved in the pathogenesis and pathophysiology of PCO syndrome.

Aortic function is compromised in a rat model of polycystic ovary syndrome

BACKGROUND

Arterial mechanical parameters are modified in women with polycystic ovary syndrome (PCOS), before and during pregnancy. This study tested the hypothesis that aortic mechanics and endothelial function are modified in the mifepristone-treated rat model of PCOS.

METHODS

Female rats injected daily with mifepristone or vehicle for 7-9 days were assessed by ultrasound to allow estimation of aortic stiffness index and compliance. The influence of acetylcholine (ACh) and sodium nitroprusside (SNP) on dissected phenylephrine-contracted aortic rings was assessed.

RESULTS

Aortic compliance was reduced by 67% in mifepristone-treated rats versus controls (P<0.05), while stiffness index was increased 2.3-fold (P<0.02). ACh-induced dilation was less in aortic rings from mifepristone-treated rats (P=0.022) and was less sensitive to the nitric oxide (NO) synthase inhibitor NG-nitro-L-arginine methyl ester (L-NAME) (P<0.001), while SNP-induced dilation was greater (P=0.001).

CONCLUSIONS

Aortic mechanics in vivo and endothelial function in vitro were consistently perturbed in mifepristone-treated rats. Aortic ring behaviour suggested that NO release was depressed or degradation elevated, with a compensatory increase in NO sensitivity and/or activation of a non-NO-mediated relaxation mechanism. The mifepristone-treated rat is a valid model for investigation of the vascular deficits seen in PCOS.

Progesterone receptor antagonists Org 31710 and RU 486 increase apoptosis in human periovulatory granulosa cells

OBJECTIVE

To investigate if progesterone receptor (PR)-mediated effects are involved in regulating the susceptibility to apoptosis in LH receptor-stimulated human luteinizing granulosa cells.

DESIGN

Laboratory study.

SETTING

Göteborg University and an in vitro fertilization laboratory of a university hospital.

PATIENT(S)

Women undergoing oocyte retrieval for in vitro fertilization after ovulation induction with gonadotropins.

INTERVENTION(S)

Luteinizing granulosa cells were isolated from follicular aspirates after oocyte removal. The cells were treated with or without RU 486 (1 microM-100 microM), Org 31710 (1 microM-100 microM), progesterone (1 nM-10 microM), dexamethasone (0.5 microM-100 microM), dihydrotestosterone (1 nM-25 microM), RU 486 (10 microM-100 microM) + dexamethasone (50 microM), and picrotoxin (1 microM-100 microM) and were cultured under serum-free conditions.

MAIN OUTCOME MEASURE(S)

Measurement of caspase-3 activity; detection of internucleosomal DNA fragmentation using gel electrophoresis and fluorospectrophotometry; progesterone analysis of spent medium.

RESULT(S)

Addition of the PR antagonists RU 486 or Org 31710 in vitro to human luteinizing granulosa cells caused an increase in caspase-3 activity and a dose-dependent increase in internucleosomal DNA fragmentation. No effect on DNA fragmentation was seen after addition of dexamethasone, dihydrotestosterone, or picrotoxin.

CONCLUSION(S)

Nuclear PR-mediated effects are involved in regulating the susceptibility to apoptosis in LH receptor-stimulated human luteinizing granulosa cells.

Time-dependent ovulation inhibition of a selective progesterone-receptor antagonist (Org 31710) and effects on ovulatory mediators in the in vitro perfused rat ovary

Progesterone (P) is one of several local mediators in the ovulatory cascade in the rat. The precise mechanisms of action for P in ovulation and in what phase of the ovulatory process P is critical, however, need to be clarified. The present study used a selective P-receptor antagonist, Org 31710, in the in vitro perfused rat ovary model to examine the local role of P and possible effects on prostaglandin (PG) and plasminogen-activator (PA) release in ovulation. Ovaries from eCG (15 IU)-primed rats were perfused for 20 h with LH (0.2 microg/ml) and 3-isobutyl-1-methylxanthine (IBMX, 200 microM) to induce ovulation (median = 10.0, 25%-75% range = 8.5-13). Org 31710 was added at either 0, 3.5, 7, or 9 h after LH+IBMX, resulting in significant suppression of ovulation after addition at 0 and 3.5 h (1.0, 1-5.5; and 5.0, 2.5-7.75 ovulations, respectively) but no suppressive effect when added at later time points. Progesterone and estradiol levels in the perfusion media were increased after LH+IBMX but were not affected by the presence of Org 31710. Ovarian tissue levels of PGE(2), PGF(2 alpha), and PA activity were measured in ovaries that had been perfused for 10 h, a time that was 2 to 5 h before anticipated ovulation. The presence of Org 31710 significantly decreased the levels of PGE(2), PGF(2 alpha), and PA activity. These results suggest that P is essential in ovulation during the initial stages of the ovulatory process. The effect of P to facilitate ovulation seems to relate to stimulation of the PG- and PA-mediator systems.

Progesterone maintains large rat granulosa cell viability indirectly by stimulating small granulosa cells to synthesize basic fibroblast growth factor

Ovarian follicles are composed of small and large granulosa cells (GCs). Since progesterone (P4) inhibits large GCs from undergoing apoptosis, studies were designed to determine whether both sizes of GCs bind P4. These studies revealed that fluorescein isothiocyanate-BSA-P4 bound only to the surface membranes of small GCs. This binding was steroid-specific and inhibited by an antibody directed against the ligand-binding domain of the nuclear P4 receptor (PR). In addition, a cell-impermeable derivative of P4, BSA-conjugated P4, was as effective as P4 in preventing apoptosis. Quantitative in situ hybridization studies showed that P4 increased the relative amount of basic fibroblast growth factor (bFGF) mRNA expressed per cell as well as the percentage of small GCs that expressed bFGF. To determine whether the anti-apoptotic action of P4 was mediated by bFGF, GCs were cultured in control medium supplemented with either P4, a neutralizing antibody to bFGF, or both P4 and the bFGF antibody. The results from this study demonstrated that P4 suppressed apoptosis and that this effect was attenuated in presence of the bFGF antibody. Basic FGF also prevented GC apoptosis, and its action was not influenced by either the PR antagonist (RU-486), an inhibitor of P4 synthesis (aminoglutethimide), or a PR antibody. Finally, FGF receptors were detected on both small and large GCs. Collectively, these data support the hypothesis that P4 acts through a putative membrane receptor on small GCs to stimulate the synthesis of bFGF. Basic FGF then activates its receptors within large GCs, and this initiates a signal transduction pathway that maintains large GC viability.

Both prolactin and progesterone in proestrus are necessary for the induction of apoptosis in the regressing corpus luteum of the rat

This study was conducted to analyze the roles of prolactin (PRL) and progesterone in the induction of luteal cell apoptosis and accumulation of macrophages in the regressing corpus luteum. We studied the number of apoptotic cells and macrophages in regressing corpora lutea in estrus 1) in cycling rats or after blocking PRL secretion with the dopaminergic agonist CB154, and 2) after blocking progesterone actions with the progesterone receptor antagonists RU-486 or ZK98299. Cells showing the morphological features characteristic of apoptosis contained fragmented DNA as indicated by in situ 3' end labeling. In cycling rats, a 100-fold increase in the number of apoptotic cells and a 4-fold increase in the number of macrophages was found from the evening (1600 h) of proestrus to the morning (1100 h) of estrus. Both increases were blocked by PRL suppression with CB154. Furthermore, blocking progesterone actions with progesterone receptor antagonists RU-486 or ZK98299 without affecting PRL secretion inhibited apoptosis but did not affect the accumulation of macrophages, whether treatment was started on the morning of metestrus (blocking diestrous and proestrous progesterone) or on proestrus (blocking only proestrous progesterone). Otherwise, exogenous progesterone was not effective in inducing apoptosis in the absence of PRL. These results indicate that both PRL and progesterone in proestrus are necessary for the induction of apoptosis in the regressing corpora lutea, whereas the accumulation of macrophages seemed to be dependent exclusively on the PRL surge.

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.

Serum levels of GH, IGF-I, LH and ovarian steroids in cyclic and RU486-treated rats

Rats lacking progesterone action due to RU486 treatment have been reported to show numerous endocrine and morphological similarities with respect to human polycystic ovary syndrome (PCO). Nevertheless, abnormalities on insulin or insulin-like growth factor I (IGF-I) production, a frequent finding in the polycystic disease, have not been studied in such rats yet. The aim of these experiments was to evaluate the serum concentrations of IGF-I in rats treated with 4 mg of the antiprogestagen RU486 over 4 or 8 consecutive days starting on estrus (day 1) and decapitated on the morning of day 5 and 9. Serum levels of growth hormone (GH), luteinizing hormone (LH), testosterone (T) and 17 beta estradiol (E2) were determined and correlated with those of IGF-I. Controls were rats injected with oil and killed in the morning of metestrus, diestrus, proestrus and estrus. Rats treated with RU486 had increased serum concentrations of IGF-I, LH, T and E2 with respect to control rats on estrus, while no differences were found in the serum concentrations of GH. Parallel estrous cycle related changes were observed in the serum concentrations of IGF-I, T and E2 with the highest values at proestrus. However, changes on serum concentrations of GH were not associated with those of IGF-I in control rats through the estrous cycle. The present results are consistent with the idea that beside on GH, serum concentrations of IGF-I in the rat depend also on LH or LH-dependent ovarian steroid production. Moreover, the results indicate that IGF-I production increased in RU486-treated rats, which may have a role in the ovarian abnormalities induced by RU486 treatment in the rat.

The antiovulatory activity of progesterone antagonists is not correlated to their antiprogestational potency in the rat

Progesterone antagonists often differ in regard to their potency to block ovulation in rats although they may possess similar 'antiprogestational' (abortive) activity. Therefore, the questions arose as to: (a) whether antiovulatory and antiprogestational effects (on endometrial and mammary gland parameters) of antiprogestins correlate at all; and (b) which mechanism(s) may be responsible for their ability to abolish ovulation. To answer these questions we set out to compare the influences of two progesterone antagonists, Onapristone (ON) a very potent and ZK 136798 only a weak inhibitor of ovulation, to assess changes on the one hand on typical progestational actions and on the other hand on factors known to regulate ovulation. For this purpose immature PMSG/hCG primed and adult female rats and infantile female rabbits were treated either with ON, ZK 136798 or vehicle in different treatment schedules. In these investigations ON and ZK 136798 showed similar antiprogestational activities on the progesterone-induced development of mammary glands (rats) and the secretory transformation of endometrium (rabbits). ON blocked an induced or a spontaneous ovulation, whereas ZK 136798 only revealed a very weak antiovulatory effect. Both ON and ZK 136798 stimulated basal levels of LH, estradiol, and testosterone, whereas the preovulatory LH surge was decreased to the same extent. Interestingly, in contrast to ZK 136798, ON reduced the preovulatory increase in progesterone secretion. These results clearly indicate: (a) that antiovulatory potency and antiprogestational activity may not be correlated in the rat; and (b) that decreased preovulatory levels of progesterone following treatment with ON may play an important role in intraovarian mechanism(s) contributing to a blocking of ovulation.