Ovarian Progesterone Secretion Research Articles

Behavioral characterization of co-exposure to cannabinoids and hormonal contraceptives in female rats

Hormonal contraceptives are among the most widely used drugs by young healthy women to block ovulation and avoid pregnancy. They reduce the ovarian secretion of estradiol and progesterone, hormones that also modulate neuronal plasticity, cognitive functions, emotions and mood. Cannabis is the most commonly used illicit drug worldwide and its use is increasing among young women, many of which regularly take the “pill”. Despite evidence of a bidirectional interaction between the endocannabinoid system and gonadal hormones, only very few studies have examined the consequences of cannabis consumption in young females under hormonal contraceptives treatment. To fill this gap, this study evaluated the behavioral effects of co-exposure to chronic 1) hormonal contraceptives, i.e., ethinyl estradiol (EE) plus levonorgestrel (LNG), one of the synthetic estrogen-progestin combinations of hormonal contraceptives, and 2) cannabinoid receptor agonist, i.e., WIN 55,212–2 (WIN), on motor activity, emotional state and cognitive functions in young adult female rats (8–11/experimental group). Hormonal and cannabinoid treatment started at post-natal day (PND) 52 and 56, respectively, while behavioral testing occurred between PND 84–95. The results show that chronic EE-LNG treatment, at doses (0.020 and 0.060 mg/rat, respectively) known to drastically reduce plasma progesterone levels, and the contextual exposure to WIN, at a dose (12.5 μg/kg/infusion) known to be rewarding in the rat, alters the hormonal milieu but does not cause further changes in locomotor activity compared to EE-LNG or WIN alone, and does not modify anxiety-like state (as measured by the elevated plus maze and the marble burying tests) and cognitive abilities (as measured by the novel object recognition and the prepulse inhibition tests) in young adult female rats. Although exposure to EE-LNG and WIN tends to increase the duration of immobility and to reduce the time spent swimming in the forced swimming test, there was not a significant additive effect suggestive of a depressive-like state. These findings allow deepening the current knowledge on the interaction between cannabinoid agonists and hormonal contraceptives and suggest that low, rewarding doses of cannabinoids do not significantly alter the motor and cognitive skills and do not induce anxiety or depressive-like states in females that use hormonal contraceptives.

P-636 Use of Desogestrel as an alternative to GnRH antagonists to inhibit the LH surge: a prospective randomized controlled observational study

Abstract Study question To describe whether desogestrel is as effective as GnRH antagonists in inhibiting the LH surge during controlled ovarian stimulation. Summary answer We conclude that although we can obtain fewer oocytes,desogestrel is effective as GnRH antagonists to inhibit the LH surge during controlled ovarian stimulation. What is known already It is known that ovarian secretion of progesterone has the ability to modulate the secretory pattern of LH of a natural menstrual cycle. Because exposure to high levels of progesterone can generate a phase shift between embryonic development and endometrial receptivity, this was not an option when performing HOC in conventional IVF-ICSI. New technologies and constant advances in vitrification techniques for both gametes and embryos have allowed us to think of different strategies when performing a HOC. This is why a new concept, progestagen priming, was introduced as a safe and comparable alternative to conventional ovarian stimulation with GnRH antagonists. Study design, size, duration We conducted a prospective, observational, randomized, controlled study at our institution IFER affiliated with the University of Buenos Aires, from August 2020 to December 2021. A total of 74 patients were included. Our main objective was to evaluate the efficacy of desogestrel as an LH surge inhibitor in patients undergoing egg donation, medical and social fertility preservation, and controlled ovarian stimulation without fresh embryo transfer. Participants/materials, setting, methods Patients under 39 years of age who underwent controlled ovarian stimulation for egg donation cycles, fertility preservation for medical and social reasons, and IVF-ICSI cycles without fresh transfer (risk of OH,PGS) The patients were separated into two groups. Both groups received conventional HOC.In the DESOGESTREL group received 75mg/day from the start of stimulation to the day of CGH, in the control group, received antagonists 0.25mg/day with follicles 14 mm until the day of CGH.ther parameters Main results and the role of chance We divided the Desogestrel Goup : > 35-35 y (GI) 32 p, 36-39 y (GII) 42p, Control Group : 35-35 y (GIII) 29 p,36-39 y (GIV) 45p. total dose of gonadotrophins used: GI: 1600 UI ± 300 UI, GIII: 1800 UI ± 400 UI ( NS) GII:1900 UI ± 400 UI, G IV : 2200 UI ± 400 UI (NS).Length of HOC: G I: 12 d ± 2 , G III: 13 d ± 2, G II: 14 d ± 2 , G IV: 15 d ± 2 ( NS). MII retrieved: GI: 10 ±3, GIII: 12± 3 (NS), GII : 7± 3, G IV: 7± 2 ( NS).The number of oocytes obtained may be a little lower than those obtained in the control group, but not statistically significant, the same as in the number of doses of gonadotrophins used, nor in the number of days of stimulation. Limitations, reasons for caution Size of study group Wider implications of the findings Although the study group is small, we have shown that the use of desogestrel is similar shown with the use of other gestagens during COH. We believe that desogestrel is a patient-friendly alternative due to its route of administration, price, and longer half-life, compared to antagonist analogs. Trial registration number NA

Endocrine regulation of puberty in cows and ewes

Sexual maturation in cows and ewes is modulated through changes in hypothalamic inhibition. This inhibition results in little or no stimulation of the release of gonadotrophins from the anterior pituitary. The ovary has a primary role in inhibiting gonadotrophin secretion during the prepubertal period and the responsiveness to the negative feedback effects of oestrogen decreases during the peripubertal period. There is also an increased secretion of ovarian progesterone during the peripubertal period but its role in the process of sexual maturation is not clear. Photoperiodic cues and dietary intake act upon the hypothalamus to modulate gonadotrophin secretion during sexual maturation and, in turn, influence the time when puberty occurs.

Role of RFRP-3 in the development of cold stress-induced polycystic ovary phenotype in rats

RFamide-related peptide (RFRP-3) is a regulator of GnRH secretion from the brain, but it can also act in human ovary to influence steroidogenesis. We aimed to study the putative local role of RFRP-3 in the ovary and its potential participation in the development of a polycystic ovary phenotype induced by chronic sympathetic stress (cold stress). We used adult Sprague–Dawley rats divided into control and stressed groups. In both groups, we studied the effect of intraovarian exposure to RFRP-3 on follicular development and plasma ovarian steroid concentrations. We also tested the effect of RFRP-3 on ovarian steroid production in vitro. Chronic in vivo intraovarian exposure to RFRP-3 decreased basal testosterone concentrations and cold stress-induced progesterone production by the ovary. In vitro, RFRP-3 decreased hCG-induced ovarian progesterone and testosterone secretion. Immunohistochemistry and mRNA expression analysis showed a decrease in Rfrp and expression of its receptor in the ovary of stressed rats, a result which is in line with the increased testosterone levels found in stressed rats. In vivo application of RFRP-3 recovered the low levels of secondary and healthy antral follicles found in stressed rats. Taken together, our data indicate a previously unknown response of hypothalamic and ovarian RFRP-3 to chronic cold stress, influencing ovarian steroidogenesis and follicular dynamics. Thus, it is likely that RFRP-3 modulation in the ovary is a key component of development of the polycystic ovary phenotype.

Temporary undernutrition during early gestation, corpora lutea morphometrics, ovarian progesterone secretion and embryo survival in gilts.

The present study reports effects of severe undernutrition on luteal function and pregnancy in pigs. Gilts were inseminated and either fasted on Day 10 and 11 after conception (n=11) or fully fed throughout (n=10). Fasting did not affect LH or progesterone pulsatile secretion pattern on Day 11 in samples taken from blood vessels draining an ovary. Ultrasonographic measurements of the size of the corpora lutea did not show any effect of fasting either. However, fasted gilts had 10 to 30% lower systemic progesterone from Day 12 through Day 15 after conception (P<0.05). All gilts farrowed, but fasted gilts had fewer born piglets than fully fed gilts (8.8±0.8 vs 10.9±0.5 respectively; P<0.05). In conclusion, fasting during embryo elongation can compromise embryonic survival by affecting ovarian function in the days after fasting, without having an immediate effect on LH secretion and progesterone output by the ovaries.

Systemic morphine treatment derails normal uterine receptivity, leading to embryo implantation failure in mice.

Morphine is the oldest worldwide well-known opioid agonist used for pain treatment in clinic, and its illicit use is often associated with adverse pregnancy outcomes in humans. Because of recent dramatic increases in nonmedicinal morphine abuse, one emerging issue is the further revelation of the dark side of illicit opioid uses, particularly in early pregnancy events. In this respect, we have demonstrated that opioid signaling is functionally operative during preimplantation embryo development in mice. However, the pathophysiological significance of the opioid system on uterine functions at peri-implantation remained elusive. In the present study, we demonstrated that opioid receptors were spatiotemporally expressed in the uterus during the peri-implantation period. Employing a pharmacological approach combined with embryo transfer experiments, we further observed that although systemic morphine treatment exerts no apparent adverse influence on preimplantation ovarian secretion of progesterone and estrogen, this aberrant activation of opioid signaling by morphine induces impaired luminal epithelial differentiation, decreased stromal cell proliferation, and poor angiogenesis, and thus hampers uterine receptivity and embryo implantation. These novel findings add a new line of evidence to better understand the causes for obvious adverse effects of opioid abuse on pregnancy success in women.

Ovarian LGR5 is critical for successful pregnancy

Leucine-rich repeat-containing G-protein-coupled receptor 5 (Lgr5) is expressed in many organs, including female reproductive organs, and is a stem cell marker in the stomach and intestinal epithelium, hair follicles, and ovarian surface epithelium. Despite ongoing studies, the definitive physiological functions of Lgr5 remain unclear. We utilized mice with conditional deletion of Lgr5 (Lgr5(d/d)) in the female reproductive organs by progesterone receptor-Cre (Pgr(Cre)) to determine Lgr5's functions during pregnancy. Only 30% of plugged Lgr5(d/d) females delivered live pups, and their litter sizes were lower. We found that pregnancy failure in Lgr5(d/d) females was due to insufficient ovarian progesterone (P4) secretion that compromised decidualization, terminating pregnancy. The drop in P4 levels was reflected in elevated levels of P4-metabolizing enzyme 20α-hydroxysteroid dehydrogenase in corpora lutea (CL) inactivated of Lgr5. Of interest, P4 supplementation rescued decidualization failure and supported pregnancy to full term in Lgr5(d/d) females. These results provide strong evidence that Lgr5 is critical to normal CL function, unveiling a new role of LGR5 in the ovary.

SSRIs and the female brain – potential for utilizing steroid-stimulating properties to treat menstrual cycle-linked dysphorias

One unexpected property of selective serotonin reuptake inhibitors is their ability, at doses well below those that effect 5-HT systems, to raise brain concentrations of neuroactive steroids such as the progesterone metabolite allopregnanolone. In women, rapid withdrawal from allopregnanolone when progesterone secretion drops sharply in the late luteal phase precipitates menstrual cycle-linked disorders such as premenstrual syndrome and catamenial epilepsy. Short-term, low-dose fluoxetine during the late luteal phase has the potential to prevent the development of such disorders, by raising brain allopregnanolone concentration. In female rats, withdrawal from allopregnanolone, as ovarian progesterone secretion falls rapidly in the late diestrus phase (similar to late luteal phase in women), induces upregulation of extrasynaptic GABAA receptors on GABAergic neurons in brain regions involved in mediating anxiety-like behaviors. The functional consequence of this receptor plasticity is disinhibition of principal neurons, hyperexcitable neuronal circuitry and increased behavioral responsiveness to anxiogenic stress. These withdrawal responses were prevented by short-term treatment with fluoxetine during the late diestrus phase, which raised brain allopregnanolone concentration, so blunting the rapid physiological fall. The steroid-stimulating properties of fluoxetine offer untapped opportunities for developing new treatments for menstrual cycle-linked disorders in women, which are precipitated by abrupt falls in brain concentration of allopregnanolone.

Introduction to special topic—estrogenic control of hypothalamic GnRH neurons

In female mammals, sexual maturation is initiated by a change in the release pattern of pituitary gonadotropins, luteinizing hormone (LH) and follicle-stimulating hormone (FSH), and a consequential increase in the secretion of ovarian sex-steroids, estradiol and progesterone. Orchestrating these endocrine changes is a diffuse population of hypothalamic neurons that produce the neuropeptide, gonadotropin-releasing hormone (GnRH). Although the development and functional integration of GnRH neurons with the rest of the central nervous system is still poorly understood, recent progress has been made on several fronts. For example, there is now evidence that some mammalian species express more than one molecular form of GnRH (GnRH-I and GnRH-II), and that the two corresponding GnRH neuronal sub-populations may play different roles in the regulation of reproductive function and behavior. Moreover, through the use of transgenic animal models, neuronal fiber tracing, gene expression profiling, and electrophysiologcal recordings, new insights have been gained into the mechanisms that regulate GnRH release. This volume brings together 10 articles that reflect current thinking about the role of GnRH in mediating estrogenic feedback to the neuroendocrine reproductive axis. The main focus is on the negative and positive actions that estrogens exert within the hypothalamus of mammals, especially around the time of the preovulatory LH surge. However, the articles also present findings from other vertebrate classes, and so provide an intersting comparative perspective. Taken together, the knowledge presented in this volume represents a foundation upon which to develop more effective therapies for pubertal disorders, infertility, and menopause. The first article (Sower and Baron, 2011) demonstrates the expression of estrogen receptors within the lamprey hypothalamus, suggesting potential feedback interactions between esatradiol and GnRH neurons. Phylogenetically, lampreys are positioned as basal vertebrates, and like many other non-mammalian vertebrates they express multiple forms of GnRH. Consequently, studies in lampreys provide us with important insights into the molecular evolution of estrogenic-GnRH interactions. A cluster of three articles then focus on hypothalamic neuropeptides that exert a major influences on the secretion of GnRH, and which are thought to mediate the feedback effects of sex-steroids on the reproductive axis. For example, studies in rodents have clearly shown the importance of kisspeptin to both pulsatile and surge modes of GnRH release (Navarro, 2012), while human studies have observed sexual dimorphism in kisspeptin neurons during aging (Hrabovszky et al., 2011). Again, an interesting evolutionary perspective is provided by comparing the steroid sensitivity of kisspeptin neurons in various non-mammalian vertebrates (Kanda and Oka, 2012). Although the exact mechanism by which estrogens interact with the reproductive neuroendocrine axis is unclear, our general understanding of this issue is neatly summarized by a series of three reviews (Micevych and Sinchak, 2011; Kenealy and Terasawa, 2012; Radovick et al., 2012). Of particular interest is the finding that sex-steroids exert their feedback not only through classic estrogen receptors located in the nucleus, but also more rapidly through receptors located in the cell membrane. Various physiological functions show adaptations for life in an environment that undergoes marked changes across the 24-h day. For example, in many mammals the timing of the preovulatory LH surge occurs at a very specific time of day. Two articles discuss the interactions between the circadian timing system and estrogen-sensitive neural circuits that regulate GnRH secretion and the preovulatory surge (Sun et al., 2012; Williams and Kriegsfeld, 2012). Finally, a novel hypothesis is proposed to explain the conundrum of how estrogens appear to exert both negative and positive feedback actions on the reproductive axis (Urbanski, 2012). Data is presented from non-human primate studies to suggest that negative and positive estrogen feedback are two completely separate mechanisms, which are mediated, respectively, by two distinct GnRH neuronal populations. This hypothesis challenges the common assumption that has dominated the field for the past four decades, namely that individual GnRH neurons are relatively homogenous and can mediate both negative and positive estrogen feedback.

Interrelationship between prolactin and progesterone in normal mammary gland growth in SHN virgin mice.

In order to clarify the interrelationship between prolactin and progesterone on normal mammary gland growth, SHN strain of virgin mice were given the pituitary grafting under the kidney capsule, the subcutaneous implantation of progesterone pellet or the bilateral ovariectomy singly or in combination at 40 days of age. All mice were killed 60 days after treatments and mammary end-bud formation, mammary DNA content and plasma prolactin level were examined. The single pituitary grafting elevated plasma prolactin levels in both the intact and the ovariectomized animals, however, mammary gland growth was enhanced only in the former. Progesterone pellet implantation also stimulated mammary gland growth in the intact mice, while prolactin changed little. Progesterone effect was nullified by ovariectomy associated with the decline in plasma prolactin level. The simultaneous single pituitary grafting and progesterone pellet implantation in combination or the grafting with three pituitaries restored mammary gland regression by ovariectomy. All findings have demonstrated that the manifestation of progesterone effect on mammary glands is dependent upon prolactin and that the role of prolactin is both direct on the glands and indirect through its luteotropic effect - through its stimulation of ovarian progesterone secretion.

Comparison of ovarian oestradiol and progesterone secretion, in vitro, between ewe lambs and ewes

Reproductive performance of ewe lambs is lower than that of adult ewes (Quirke 1979). This is mainly the result of preimplantation losses, which can exceed 50% of fertilised eggs. Previous evidence from this laboratory suggests that these losses may be associated with abnormal ovarian hormone production (Davies and Beck 1993). Khan (1999) demonstrated that blood progesterone levels during the oestrous cycle and pregnancy were lower in ewe lambs than in ewes. Furthermore, both progesterone and oestradiol concentrations were lower in ewe lambs, than in ewes, following gonadotrophin stimulation (Khan, Beck and Khalid 1999). These results suggest that ewe lamb corpora lutea and follicles secrete less progesterone and oestradiol, respectively, than those of ewes. The aim of this study was to determine whether there is a difference in vitro steroid hormone production by corpora lutea and follicles, from ewe lambs and ewes.

The preovulatory rise of ovarian ornithine decarboxylase is required for progesterone secretion by the corpus luteum

Ovarian progesterone secretion during the diestrus stage of the estrous cycle is produced by luteal cells derived from granulosa and thecal cells after the differentiation process that follows ovulation. Our results show that blockade of the preovulatory rise of ovarian ornithine decarboxylase (ODC), a key enzyme in polyamine biosynthesis, by treatment with the specific inhibitor α-difluoromethylornithine (DFMO) leads to a significant decrease in the ovarian progesterone content and a dramatic fall in the plasma levels of this hormone during the following diestrus. The same inhibition was produced in spite of the fact that both luteinizing and follicle stimulating hormones were given concomitantly with DFMO. On the other hand, the acute rise in the plasma progesterone levels observed after administration of human chorionic gonadotropin to mice at different periods of the estrous cycle was not affected by DFMO administration. Our results indicate that although elevated levels of ODC are not required for acute ovarian steroidogenesis, the preovulatory peak of ovarian ODC activity observed in the evening of proestrus may be critical for the establishment of a constitutive steroidogenic pathway and progesterone secretion by the corpus luteum during the diestrus stage of the murine estrous cycle.

Coeliac ganglion adrenergic activity modifies ovarian progesterone during pregnancy: its inter-relationship with LH.

Most of the fibres that constitute the superior ovarian nerve (SON) originate at the neuronal bodies of the coeliac ganglion and innervate rat ovarian stroma cells. The purpose of this work was to study the part played by innervation on ovarian release of progesterone on day 15 and at the end of pregnancy in an integrated in vitro system known as the coeliac ganglion-SON-ovary system. We also investigated, in the same system, whether there is some kind of inter-relationship between the effect of adrenergic agents and LH on progesterone release on day 15 of pregnancy. The coeliac ganglion and the ovary were incubated in separate compartments, linked by the SON. The ovary was immersed in 2 ml buffer solution (ovarian compartment) and the coeliac ganglion was immersed in 2 ml of a different buffer solution (ganglion compartment). Under these conditions, the accumulation of progesterone in the ovarian compartment medium was used as an endpoint. Conditions were standardised on day 15 of pregnancy, when the decrease in the release of ovarian progesterone caused by non-specific stimulation on the ganglion with KCl (56 mM) demonstrated the functional integrity of the system. Neural influence was evaluated by the addition of adrenergic agents at a concentration of 10(-6)M to the coeliac ganglion. On day 15 of pregnancy, noradrenaline and propranolol increased progesterone release while phentolamine diminished it. The existence of ganglionic tone was assessed by analysing progesterone basal levels at different stages of pregnancy. The highest secretion of progesterone was found to take place on day 15, diminishing as pregnancy advanced. In addition, adrenergic neural participation was studied during the physiological luteolysis occurring at the end of pregnancy. Major findings were that noradrenaline increased ovarian accumulation of progesterone on day 19 and decreased it on day 20, while propranolol and phentolamine diminished progesterone release on both days. In additional studies, some neuroendocrine aspects were investigated at a peripheral level. The addition of LH only to the ovarian compartment did not affect progesterone secretion. However, when LH in the ovarian compartment was accompanied by noradrenaline, propranolol or phentolamine in the ganglion compartment, the release of progesterone decreased. It can be concluded that modifications of the neural state of the coeliac ganglion affect ovarian progesterone secretion and the physiology of pregnancy via the SON. The results may confirm that the coeliac ganglion-SON-ovary system provides a direct link between the autonomic nervous system and physiological events during pregnancy.

Substance P downregulates basal and gonadotropin-releasing hormone-induced gonadotropin in vitro secretion by pituitary gland of crested newt, Triturus carnifex.

The possible role of Substance P (SP) was studied in the modulation of basal and gonadotopin-releasing hormone (GnRH)-induced gonadotropin secretion in the urodele crested newt, Triturus carnifex. During prereproduction, reproduction (noncourtship and courtship), refractory, recovery and aestivation, male and female pituitaries were incubated with medium-alone, GnRH, SP, GnRH receptor antagonist (antide), and SP receptor antagonist (L-703606). Since antisera raised against gonadotropins are not available for this species, we measured these hormones indirectly through their effects on the secretion of testicular androgens and ovarian progesterone from gonads superfused with the preincubated pituitaries. Pituitaries of both sexes preincubated with medium-alone, GnRH, GnRH plus L-703606, and GnRH plus SP plus L-703606 increased steroid secretion during prereproduction, noncourtship, courtship, and recovery; the increase induced by the pituitaries incubated with medium-alone was lower during prereproduction, noncourtship, and recovery. Pituitaries preincubated with SP, GnRH plus SP, GnRH plus SP plus antide, and SP plus antide did not change basal steroid secretion in any of the reproductive phases considered. Antide, L-703606, GnRH plus antide, GnRH plus SP plus antide plus L-703606, SP plus L-703606, and antide plus L-703606 experimental groups showed the same results as those with medium-alone. These results suggest that SP downregulates gonadotropin release in both Triturus carnifex sexes. In addition, an antagonist role, through receptor-independent mechanisms, exists between GnRH (upregulation) and SP (downregulation) in the modulation of pituitary.

Characterization of serum hormone profiles in growing heifers implanted with anabolic growth promotants (2000)

A 147-day study was conducted to determine the sequential growth responses and serum hormone profiles of growing heifer calves implanted with anabolic growth promotants. Forty eight previously nonimplanted crossbred beef heifers averaging 396 lb were assigned to one of three treatments: 1) nonimplanted controls (NC), 2) Revalor-G (REV-G), and 3) Synovex-H (SYN-H). Accumulative gain response from day 84 through the end of the trial was significantly faster for both implant treatments than controls. Implant response was not consistent across time; heifers in both implant treatments gained faster than controls (P<.05) during the early (days 22-42) and later (days 64-84 and 85-105) weigh periods. By day 2, serum estradiol concentrations were increased in REV-G (P<.05) and SYN-H (P<.01) heifers relative to NC. Only REV-G contains trenbolone acetate, and none was detected in NC and SYN-H heifers, but serum levels in REV-G heifers were increased on days 2 (P<.001), 4 (P<.05), and 63 (P<.001). Only SYN-H contained testosterone; its level peaked by day 63 in SYN-H heifers. Throughout the study, progesterone was higher in NC heifers than in SYN-H or REV-G heifers, which suggests that the exogenous steroids reduced pituitary gonadotropin secretion and, thus, ovarian progesterone secretion. Our results suggest that the release of trenbolone and estradiol from REV-G implants is complete by 84 days after implanting. (

Nitric oxide reverses prostaglandin-induced inhibition in ovarian progesterone secretion in rats.

The present studies were undertaken to determine whether nitric oxide (NO) is involved in the regulation of ovarian progesterone and oestradiol secretion in rats. Immature female Sprague-Dawley rats at 27 days of age were injected s.c. with 4 IU pregnant mare's serum gonadotrophin (PMSG) and were killed 72 h after the injection. The ovaries were collected, weighed and cultured in Dulbecco's modified Eagle's medium containing saline, NO donor, NO synthesis inhibitor or prostaglandin F2 alpha (PGF2 alpha). After 24 h culture, the medium concentrations of progesterone and oestradiol were measured by radioimmunoassay. Results showed that: (i) diethylenetriamine (DETA)/NO (1 x 10(-6), 1 x 10(-5), 1 x 10(-4) M), an NO donor, caused a dose-dependent increase in progesterone synthesis (355 +/- 43, 443 +/- 46, 647 +/- 55 ng/g ovary respectively, P < 0.01) with a concomitant decrease in ovarian oestradiol secretion (408.1 +/- 50.7, 272.9 +/- 28.2, 132.6 +/- 34.6 pg/g ovary respectively, P < 0.01); (ii) neither progesterone nor oestradiol concentrations in the culture medium were altered by DETA without NO; (iii) NG-nitro-l-arginine methyl ester (1 x 10(-4) M), an inhibitor of NO synthesis, did not significantly affect progesterone and oestradiol secretion by rat ovaries; (iv) PGF2 alpha(1 x 10(-6) M) caused a fall in progesterone and oestradiol synthesis; (v) co-incubation with DETA/NO, significantly reversed the PGF2 alpha-induced decrease in progesterone concentrations from 184 +/- 29 to 388 +/- 60 ng/g (P < 0.01), but not that of oestradiol. It can be concluded that NO up-regulates progesterone secretion and down-regulates oestradiol secretion in rat ovaries, and NO can reverse PGF2 alpha-induced inhibition in ovarian progesterone secretion.

Effects of arterial infusions of adrenalin and acetylcholine on luteal secretion of progesterone and oxytocin in goats

The effects of close intra-arterial infusion of acetylcholine and adrenalin on ovarian secretion of progesterone and oxytocin were examined on Day 10 of the estrous cycle in goats (estrus = Day 0). Acetylcholine (15 μg/min) was without effect, but adrenalin (10 μg/min) significantly (P < 0.001) raised both progesterone and oxytocin concentrations in ovarian vein plasma. These results show that luteal hormone secretion is enhanced in the goat by β-adrenergic stimulation and suggest that, as in the sheep and cow, there may be neuroendocrine involvement in the regulation of caprine luteal function.

Nitric oxide mediates gonadotropin-releasing hormone effects on frog pituitary.

We studied the possible role of nitric oxide (NO) in GnRH-induced gonadotropin secretion in the female water frog, Rana esculenta. During pre-reproduction, pre-ovulation, ovulation, post-ovulation, refractory, recovery and hibernation, pituitaries were incubated with medium-alone, GnRH, NO donor (NOd), NO synthase inhibitor (NOSi), cyclic GMP analogue (cGMPa), soluble guanylate cyclase inhibitor (sGCi), GnRH plus NOSi, GnRH plus sGCi, and NOd plus sGCi. Because antisera raised against gonadotropins are not available for this species, we measured these hormones indirectly through their effects on ovarian progesterone secretion. The ovaries were superfused with the pituitaries pre-incubated as reported above. In addition, NOS activity and cGMP levels were determined in the pre-incubated pituitaries. Those pre-incubated with medium-alone and with GnRH increased progesterone secretion during pre-reproduction, pre-ovulation, ovulation and recovery; the increase induced by GnRH was higher than that induced by medium-alone during pre-reproduction, pre-ovulation and recovery. NOd and cGMPa increased progesterone in all considered reproductive phases except ovulation; the increase induced by NOd and cGMP was higher than that induced by medium-alone during pre-reproduction, pre-ovulation and recovery. NOS activity was highest during ovulation and lowest during post-ovulation, refractory and hibernation. GnRH increased NOS activity during pre-reproduction, pre-ovulation and recovery. Cyclic GMP levels were highest during ovulation and lowest during post-ovulation, refractory and hibernation. GnRH increased cGMP levels during pre-reproduction, pre-ovulation and recovery, NOd during all considered reproductive phases. These results suggest that NO mediates basal and GnRH-induced gonadotropin secretion in female Rana esculenta.

Nitric oxide reverses prostaglandin-induced inhibition in ovarian progesterone secretion in rats

The present studies were undertaken to determine whether nitric oxide (NO) is involved in the regulation of ovarian progesterone and oestradiol secretion in rats. Immature female Sprague-Dawley rats at 27 days of age were injected s.c. with 4 IU pregnant mare's serum gonadotrophin (PMSG) and were killed 72 h after the injection. The ovaries were collected, weighed and cultured in Dulbecco's modified Eagle's medium containing saline, NO donor, NO synthesis inhibitor or prostaglandin F2 alpha (PGF2 alpha). After 24 h culture, the medium concentrations of progesterone and oestradiol were measured by radioimmunoassay. Results showed that: (i) diethylenetriamine (DETA)/NO (1 x 10(-6), 1 x 10(-5), 1 x 10(-4) M), an NO donor, caused a dose-dependent increase in progesterone synthesis (355 +/- 43, 443 +/- 46, 647 +/- 55 ng/g ovary respectively, P < 0.01) with a concomitant decrease in ovarian oestradiol secretion (408.1 +/- 50.7, 272.9 +/- 28.2, 132.6 +/- 34.6 pg/g ovary respectively, P < 0.01); (ii) neither progesterone nor oestradiol concentrations in the culture medium were altered by DETA without NO; (iii) NG-nitro-l-arginine methyl ester (1 x 10(-4) M), an inhibitor of NO synthesis, did not significantly affect progesterone and oestradiol secretion by rat ovaries; (iv) PGF2 alpha(1 x 10(-6) M) caused a fall in progesterone and oestradiol synthesis; (v) co-incubation with DETA/NO, significantly reversed the PGF2 alpha-induced decrease in progesterone concentrations from 184 +/- 29 to 388 +/- 60 ng/g (P < 0.01), but not that of oestradiol. It can be concluded that NO up-regulates progesterone secretion and down-regulates oestradiol secretion in rat ovaries, and NO can reverse PGF2 alpha-induced inhibition in ovarian progesterone secretion.

Dietary carrot results in diminished ovarian progesterone secretion, whereas a metabolite, retinoic acid, stimulates progesterone secretion in the in vitro perfused rabbit ovary

Objective: To determine the effects of dietary carrots and retinoic, acid on P secretion in the in vitro perfused rabbit ovary. Design: Controlled experiment. Setting: Laboratory. Subjects: Sexually mature New Zealand white rabbits. Intervention(s): Experiments were done in vitro using an isolated rabbit ovarian perfusion system after acute feeding of carrots or with in vitro exposure to retinoic acid. Main Outcome Measure(s): Progesterone and E 2 were measured in aliquots taken from arterial and venous cannulas. Result(s): Progesterone secretion during the in vitro perfusion of six ovaries is significantly diminished after the acute feeding of carrots. Human chorionic gonadotropin-induced P secretion also is significantly reduced. Progesterone secretion during in vitro perfusion on day 1 of pseudopregnancy was significantly increased in the perfusate samples from ovaries taken from rabbits not acutely fed carrots but that were exposed to retinoic acid. Progesterone secretion was increased but only marginally significant on day 11 of pseudopregnancy in perfusate samples from ovaries exposed to retinoic acid. Conclusion(s): Rabbit ovarian P secretion may be modified by carrots and carotene metabolites. This effect on steroid secretion may contribute to the relationship between hypercarotenemia and alterations in menstrual function.