Administration Of Cetrorelix Research Articles

The Effects of Human Chorionic Gonadotropin and Gonadotropin-Releasing Hormone Receptor Antagonist on Testicular Steroidogenesis in Normal and Obese Rats.

We studied the effect of a high-fat, high-carbohydrate diet (HFHCD) on basal testosterone levels in the blood and testosterone, its precursors, and expression of steroidogenic genes in the testes of rats treated with human chorionic gonadotropin (hCG, 10 IU/rat, subcutaneously, once), gonadotropin-releasing hormone receptor antagonist cetrorelix (75 μg/kg, subcutaneously, 3 days), and their combination. In HFHCD rats, no obvious signs of androgen deficiency were observed and the response of the testes to hCG stimulation was preserved. Unlike control rats (normal diet), the expression of the luteinizing hormone receptor gene in these rats did not change in response to hCG stimulation and cetrorelix administration; they also showed a paradoxical, more pronounced response to hCG administration under conditions of suppression of the gonadotropin secretion by cetrorelix. This suggests that the etiology and pathogenesis of obesity may have different effects on the hormonal status of the male reproductive system.

Modulating Effect of the Leptin Fragment 116–122 on Testicular Steroidogenesis in Male Rats

Adipokine leptin plays an important role in the regulation of the reproductive system. It stimulates the activity of the hypothalamic-pituitary-gonadal axis by indirectly acting on GnRH-secreting neurons and modulates testicular steroidogenic function by binding to leptin receptors in Leydig cells. A leptin fragment 116–122 (LF) including the main receptor-binding determinants of this adipokine, normalizes metabolic parameters in animals with diet-induced obesity. However, its ability to influence the steroidogenic function of the testes, including through interaction with GnRH neurons of the hypothalamus, has not been studied. The aim of this work was to study the effects of a single and three-day intranasal administration of LF (200 μg/rat) on the blood testosterone level and the expression of steroidogenic genes in the testes in mature male Wistar rats. To evaluate the effect of LF on testicular steroidogenesis upon stimulation with human chorionic gonadotropin (hCG, 15 IU/rat, s/c), a stimulator of testosterone synthesis and an antagonist of the GnRH receptor cetrorelix (75 μg/kg, s.c.) an inhibitor of testicular steroidogenesis. It has been shown that LF increases the level of testosterone in the blood after a single injection, and after a three-day administration it enhances the steroidogenic effect of hCG. LF and hCG increased the expression of the Star gene encoding the key regulatory protein of steroidogenesis StAR. Administration of cetrorelix reduced testosterone levels and Star expression, and compensatory increased expression of the luteinizing hormone receptor gene. The potentiating effect of LF on hCG-induced stimulation of testosterone levels and Star expression was not detected under conditions of GnRH antagonist treatment. Thus, LF is capable of stimulating steroidogenesis in rat testis by itself and potentiating the steroidogenic effects of hCG. Since its effects are suppressed in the presence of a GnRH antagonist, there is reason to assume that the effect of LF is realized through stimulation of hypothalamic GnRH neurons.

Effect of Cetrorelix administration on ovarian stimulation in aged mice.

In mice, ovarian stimulation via hormone administration is an effective method for obtaining many ova simultaneously, but its effect is reduced by the influence of aging. In this study, we demonstrate that this problem can be improved by administering the gonadotropin-releasing hormone antagonist Cetrorelix prior to ovarian stimulation. Before 12-month-old female mice were injected with 5 IU pregnant mare serum gonadotropin and 5 IU human chorionic gonadotropin, we administered 5 µg/kg Cetrorelix for 7 consecutive days (7 times) or 3 times once every 3 days. As a result, 8.7 ± 1.9 (mean ± SEM, n=10) and 9.8 ± 1.3 (n=10) oocytes were obtained, respectively, as opposed to 4.7 ± 1.2 oocytes (n=9) in the case of no administration. Collagen staining of ovarian tissue showed that Cetrorelix administration reduced the degree of fibrosis, which improved ovarian function. In addition, equivalent fertilization and fetal development rates between control and Cetrorelix-treated aged mouse-derived oocytes were confirmed by in vitro fertilization and embryo transfer (Fertilization rate; control: 92.2% vs. 3 times: 96.9%/7 times: 88.5%, Birth rate; control: 56.4% vs. 3 times: 58.3%/7 times: 51.8%), indicating the normality of the obtained oocytes. It is concluded that Cetrorelix improved the effect of superovulation in aged mice without reducing oocyte quality. This procedure will contribute to animal welfare by extending the effective utilization of aged female breeding mice.

The GnRH analogues affect novel neuropeptide SMIM20/phoenixin and GPR173 receptor expressions in the female rat hypothalamic-pituitary-gonadal (HPG) axis.

The recently discovered peptide phoenixin (PNX) and its receptor GPR173 are novel factors that exhibit a large spectrum of regulatory activity, especially when considered as a central modulator of GnRH-related hormonal control of reproductive processes. It has been already proven that GnRH agonists and antagonists can modulate peptidergic signalling in the HPG axis. Despite these findings, there is so far no information regarding the influence of treatment with GnRH analogues on SMIM20/phoenixin signalling in the hypothalamic-pituitary-gonadal axis. In the current study, SMIM20/phoenixin and GPR173 mRNA levels were measured in the hypothalamus, pituitary and ovaries of female rats in the dioestrus phase following treatment with GnRH-R agonist (buserelin) and antagonist (cetrorelix) using quantitative real-time PCR. The serum PNX concentrations were also estimated with ELISA technique. The hypothalamic, hypophyseal and especially ovarian levels of SMIM20 mRNA were increased after both buserelin and cetrorelix administration. The GPR173 expressions were in turn decreased in the hypothalamus and pituitary. Treatment with the GnRH analogues led to the modulation of SMIM20/phoenixin and GPR173 mRNA expression in the female rat hypothalamic-pituitary-gonadal axis. By identifying buserelin and cetrorelix as novel modulators of phoenixin signalling in the animal HPG axis, these results cast new light on the GnRH analogues mode of action and contribute to a better understanding of the mechanisms responsible for the hormonal control of reproduction.

PP-008 - GnRH antagonist cetrorelix administration before hCG for protection against ovarian hyperstimulation syndrome

PP-008 - GnRH antagonist cetrorelix administration before hCG for protection against ovarian hyperstimulation syndrome

Cetrorelix preserves follicular viability in Cyclophosphamid-induced ovarian toxicity

Background & Aims: Anticancer drugs are known to have great impact on spermatogenesis process and germinal epithelium. The present study is to investigate the preventive effect of Cetrorelix (GnRH antagonist) on Cyclophosphamide- induced spermatogenic defect. Methods and Materials: Fifty adult female mice aging 6-8 weeks (30±4 gr) were divided into 3 groups as: Control, Experimental 1 and Experimental 2. The animals in Experimental 1 group received Cyclophosphamide (2.5 mg/kg, ip) for 5 days and in Experimental 2 group received Cetrorelix (0.25 mg/kg, ip) one week before Cyclophosphamide treatment and continued for 3 weeks. The mice in all groups were sacrificed 35 days after the last injection. Ovarian follicles were isolated mechanically and the viability was studied by trypan blue staining. Results: Ovarian follicles of animals in Experimental 2group, retained higher percentage of normal morphology (P<0.001) than which in Experimental 1 group and their condition were similar to control group. Conclusion: These results indicate that the Cetrorelix administration before cancer treatment may protect ovarian tissue against side effects of cisplatin.

Cetrorelix in COH cycles: time of change for the daily administered dose? A response to Kerimoğlu et al. (10.1007/s00404-013-2806-z)

It is with great interest that we have read the paper published in your journal by Kerimoglu et al. [1] which addresses an important clinical question: the decrease of daily administered Cetrorelix dose in controlled ovarian hyperstimulation (COH) cycles to avoid premature LH surge while improving pregnancy rates mainly by the subsequent modifications at a cellular level. However, the article reports somewhat precipitate ‘conclusions’, which have the potential for misinterpretation and are in contrast, in several ways, with some important studies published in the past (see Table 1). Firstly, a ‘dose-finding’ study cannot be, by definition, ‘‘retrospective’’. Therefore, it is premature to state that ‘there is no difference...’ between the two regimens, as there have been studies in the past (even referred in Kerimoglu’s et al. [1]), with a prospective and, sometimes, even with a randomized design that clearly state that the lowest daily effective dosage for pituitary down-regulation with Cetrorelix is 0.25 mg/day. Furthermore, in an important—because of its design— randomized controlled trial (RCT) (not mentioned in Kerimoglu’s et al. [1]), Chang and colleagues [2] compared efficacy and efficiency of Cetrorelix and found to be 0.2 and 0.15 mg, respectively; they concluded that even for Asian women (for whom BMI is known to be lower than the Caucasian population), the lowest daily dose of Cetrorelix (in achieving satisfactory pituitary down-regulation) was 0.2 mg, and thus stated that daily administration of 0.15 mg ‘is not suitable’ for pituitary down-regulation. In addition to this, Chen et al. [3] also suggest that for Asian population ‘the lowest effective daily dosage is that of 0.2 mg’ and not 0.25 mg; even if one disregards the design of the study (non-randomized observational), that dose is closer to the ‘established’ one (0.25 mg) than the dosage of 0.125 mg suggested by Kerimoglu et al. [1]. Closely related to this are the findings of a more recent and larger retrospective study by Hsieh et al. [4]. That study concludes that ‘even for individuals with lower body weight (\50 kg), participants required 0.25 mg Cetrorelix daily. Furthermore, Tzeng’s study protocol [5], mentioned in Kerimoglu’s et al. [1], is quite different from daily Cetrorelix administration of 0.125 mg as it depends on leading follicular size; however, even with that protocol, the mechanism for LH-surge avoidance (which is used in 3 patients to end with the one LH surge that is mentioned in the paper) was the increase of the Cetrorelix dose to 0.25 mg/day. Finally, we should acknowledge the (potential) first ‘dose-finding’ study by Albano et al. [6], which concluded that ‘the minimal effective dose of Cetrorelix’ to prevent premature LH surge is 0.25 mg/daily. If a decrease in dosage is to be considered, further larger RCTs need to be conducted before we can move with confidence, to change in current clinical practice. T. Kalampokas Division of Applied Health Sciences, Assisted Reproduction Unit, University of Aberdeen, Aberdeen, UK

Protective Role of GnRH Antagonist on Chemotherapy-induced Spermatogenesis Disorder: A Morphological Study.

Anti cancer drugs is one of the most important chemotherapeutic factors which can influence spermatogenesis process and germinal epithelium. Since dividing cells are mainly affected by anticancer drugs, the aim of the present study is to investigate the preventive effect of GnRH antagonist on spermatogenic defect produced by anticancer drugs. In the present study thirty adult male mice aging 6-8 weeks were divided into 3 groups as: Control, Experimental 1 and Experimental 2. Experimental 1 group received Cisplatin for 5 days as 2.5 mg/kg intraperitoneally and Experimental 2 group received 0.25 mg/kg cetrorelix (GnRH antagonist) one week before cisplatin treatment and continued for 3 weeks. The mice in all groups were sacrificed 35 days after the last injection and testis specimens were fixed in boueins, formaldehyde fixative and 2.5% Glutaraldehide then prepared for light and electron microscopic examination. Light microscopy (LM) study showed that the number of spermatogonial cells, thickness of germinal epithelium, was decreased in Experimental 1group. Electron microscopy revealed that in this group several intercellular spaces appeared between spermatogenic cells and secretory granules in interstitial cells was increased. There were several vacuolated mitochondria and destroyed organelles in spermatogonial cells but in Experimental 2 group condition was similar to control group. These results indicate that the cetrorelix administration before cancer treatment may protect germinal epithelium against side effects of cisplatin.

A mathematical model of the human menstrual cycle for the administration of GnRH analogues

The paper presents a differential equation model for the feedback mechanisms between gonadotropin-releasing hormone (GnRH), follicle-stimulating hormone (FSH), luteinizing hormone (LH), development of follicles and corpus luteum, and the production of estradiol (E2), progesterone (P4), inhibin A (IhA), and inhibin B (IhB) during the female menstrual cycle. Compared to earlier human cycle models, there are three important differences: The model presented here (a) does not involve any delay equations, (b) is based on a deterministic modeling of the GnRH pulse pattern, and (c) contains less differential equations and less parameters. These differences allow for a faster simulation and parameter identification. The focus is on modeling GnRH-receptor binding, in particular, by inclusion of a pharmacokinetic/pharmacodynamic (PK/PD) model for a GnRH agonist, Nafarelin, and a GnRH antagonist, Cetrorelix, into the menstrual cycle model. The final mathematical model describes the hormone profiles (LH, FSH, P4, E2) throughout the menstrual cycle of 12 healthy women. It correctly predicts hormonal changes following single and multiple dose administration of Nafarelin or Cetrorelix at different stages in the cycle.

Clearance of high-risk HPV infection in Chinese women with normal cervical cytology

protection resumed cyclic ovarian function, despite the increased follicle-stimulating hormone levels for the first year after chemotherapy [2]. Similarly, cetrorelix might protect the surviving undifferentiated germline stem cells from gonadotoxicity, allowing them to regenerate ovarian follicles and restore regular menses and fertility. Longer follow up is required to estimate the incidence of permanent ovarian failure. Future studies are needed with more patients and adjustment of cetrorelix administration because the dose used in the present study might not achieve full suppression of gonadotropins. A recent pilot study has been conducted involving patients treated with cyclophosphamide for malignancies and autoimmune diseases [4]. Although the study reported similar results, it is not directly comparable with the present study because the patients received significantly lower doses of cetrorelix, for a shorter period and without a control group. In conclusion, administration of 3 mg of cetrorelix every second day in women treated with chemotherapy for hematological malignancies significantly decreased the incidence of secondary amenorrhea, although full protection of ovarian function was not achieved. Conflict of interest

Effect of the gonadotropin-releasing hormone antagonist cetrorelix on the prevention of chemotherapy-induced ovarian damage in women with hematological malignancy

Gonadotropin-releasing hormone (GnRH) agonists are the most commonly used pharmaceutical treatment for ovarian protection during chemotherapy [1,2]. A recent study showed that a combination of GnRH agonists and antagonists induced a long-lasting suppression of gonadotropins but did not completely prevent flare-up of follicle stimulating hormone [3]. The aim of the present study was to evaluate the use of cetrorelix, a GnRH antagonist, for prevention of ovarian damage during chemotherapy in patients with a hematologic malignancy, such as Hodgkin lymphoma (HL), non-Hodgkin lymphoma (NHL), and acute leukemia (AL). The study included 24 women (mean age at diagnosis, 23.3± 6.4 years) who had been diagnosed with a hematologic malignancy (15 HL, 4 NHL, and 5 AL). All patients received chemotherapy with various cytotoxic agents, including cyclophosphamide, and 3 mg of cetrorelix subcutaneously every second day. Data were compared retrospectively with 31 women (mean age, 26.4±6.2 years) who had been diagnosed with a hematologic cancer (18 HL, 12 NHL, and 3 AL) and received the same chemotherapy, but without cetrorelix. The study was approved by the Institutional Review Board. Pb0.05 was considered significant at statistical analysis. Among the 23 evaluable women (1 died) who received cetrorelix, the incidence of secondary amenorrhea 6 months after cessation of treatment was significantly lower compared with the women who did not receive cetrorelix (4.3% vs 27.3%, P=0.036; Table 1). No significant differences were observed between the 2 groups in the mean serum levels of follicle-stimulating hormone, estradiol, and anti-Mullerian hormone after completion of chemotherapy (P>0.05; Table 1), suggesting a degree of ovarian damage despite cetrorelix administration.

Administration of a gonadotropin-releasing hormone antagonist to mares at different times during the luteal phase of the estrous cycle

The GnRH antagonist cetrorelix was given during the early (Days 1–5), mid (Days 6–10 or 5–12) or for the entire (Days 1–16) luteal phase of mares to inhibit the secretion of FSH and LH (Day 0 = ovulation). Frequent blood sampling from Day 6 to Day 14 was used to determine the precise time-course of the suppression (cetrorelix given Days 6–10). Cetrorelix treatment caused a decrease in FSH and LH concentrations by 8 and 16 h, respectively, and an obliteration of the response to exogenous GnRH given 24 h after treatment onset. Treatment never suppressed gonadotropin concentrations to undetectable levels; e.g. frequent sampling showed that the nadirs reached in FSH and LH were 46.2 ± 6% and 33.1 ± 11%, respectively, of pre-treatment concentrations. Daily FSH concentrations were decreased in all treatment groups but daily LH concentrations were lower only when treatment commenced at the beginning of the luteal phase; progesterone concentrations depended on the time of cetrorelix administration, but the changes suggested a role for LH in corpus luteum function. The inter-ovulatory interval was longer than controls when cetrorelix was given in the mid- or for the entire luteal phase, but was unaffected by treatment in the early phase. Nevertheless, in all groups, FSH concentrations were higher ( P < 0.05 when compared to Day 0, subsequent ovulation) approximately 6–10 days before this next ovulation. This consistent relationship suggests a stringent requirement for a GnRH-induced elevation of FSH above a threshold at, but only at, this time; i.e. approximately 6–10 days before ovulation.

Dynamics of circulating concentrations of gonadotropins and ovarian hormones throughout the menstrual cycle in the bonnet monkey: role of inhibin A in the regulation of follicle‐stimulating hormone secretion

In higher primates, increased circulating follicle-stimulating hormone (FSH) levels seen during late menstrual cycle and during menstruation has been suggested to be necessary for initiation of follicular growth, recruitment of follicles and eventually culminating in ovulation of a single follicle. With a view to establish the dynamics of circulating FSH secretion with that of inhibin A (INH A) and progesterone (P(4)) secretions during the menstrual cycle, blood was collected daily from bonnet monkeys beginning day 1 of the menstrual cycle up to 35 days. Serum INH A levels were low during early follicular phase, increased significantly coinciding with the mid cycle luteinizing hormone (LH) surge to reach maximal levels during the mid luteal phase before declining at the late luteal phase, essentially paralleling the pattern of P(4) secretion seen throughout the luteal phase. Circulating FSH levels were low during early and mid luteal phases, but progressively increased during the late luteal phase and remained high for few days after the onset of menses. In another experiment, lutectomy performed during the mid luteal phase resulted in significant decrease in INH A concentration within 2 hr (58.3+/-2 vs. 27.3+/-3 pg/mL), and a 2- to 3-fold rise in circulating FSH levels by 24 hr (0.20+/-0.02 vs. 0.53+/-0.14 ng/mL) that remained high until 48 hr postlutectomy. Systemic administration of Cetrorelix (150 microg/kg body weight), a gonadotropin releasing hormone receptor antagonist, at mid luteal phase in monkeys led to suppression of serum INH A and P(4) concentrations 24 hr post treatment, but circulating FSH levels did not change. Administration of exogenous LH, but not FSH, significantly increased INH A concentration. The results taken together suggest a tight coupling between LH and INH A secretion and that INH A is largely responsible for maintenance of low FSH concentration seen during the luteal phase.

Impact of estradiol patterns in clomiphene citrate/human menopausal gonadotropin/cetrorelix protocol

The importance of serum estradiol changes associated with gonadotropin-releasing hormone antagonists is not clear. The purpose of the present study was to analyze the impact of estradiol changes after cetrorelix injection on the outcome of intracytoplasmic sperm injection (ICSI) cycles. This was a prospective observational study. One hundred and thirteen women with male-factor infertility who were undergoing first ICSI cycles were reviewed for this study. Excluding seven cycles with incomplete data, 106 cycles were included in the analysis. The women were stimulated with clomiphene citrate and human menopausal gonadotropin (hMG). Cetrorelix acetate (2.5 mg) was given when the leading follicles reached 14 mm. After cetrorelix administration, serum estradiol rose in 48 cycles (45.3%), plateaued in 26 cycles (24.5%) and dropped in 32 cycles (30.2%). Mean age and day-3 follicle-stimulating hormone, luteinizing hormone and estradiol levels were similar among the three groups. The mean ampoules of hMG used, estradiol levels on the day of human chorionic gonadotropin injection and the clinical outcomes, including numbers of oocytes retrieved and fertilization, implantation and pregnancy rates, were similar in all three groups regardless of the trend of estradiol. In conclusion, estradiol patterns after cetrorelix injection show no correlation with clinical outcome and ovarian reserve, and falling estradiol is not associated with adverse outcome.

Assessment of luteinizing hormone level in the gonadotropin-releasing hormone antagonist protocol

In the GnRH-antagonist multiple-dose protocol, the LH level retrieved from a single measurement during ovarian stimulation and concomitant GnRH-antagonist administration can vary according to [1] the time point of sampling with respect to the GnRH-antagonist injection and [2] episodic changes in circulating LH concentration due to the pulsatile release of LH from the pituitary gland. To exemplify the size of pharmacodynamic effect of a single 0.25-mg cetrorelix administration on LH concentration profile and pulsatility, we measured endogenous LH levels every 15 minutes from 8 hours before the first cetrorelix administration until 24 hours thereafter on ovarian stimulation day 6 and 7 in a single patient.

Recombinant gonadotrophins associated with GnRH antagonist (cetrorelix) in ovarian stimulation for ICSI: Comparison of r-FSH alone and in combination with r-LH

Objective The objective was to verify the outcome of intracytoplasmic sperm injection (ICSI) with ovulation induction performed with GnRH antagonists, comparing the use of recombinant follicle-stimulating hormone (r-FSH) alone and in combination with recombinant luteinizing hormone (r-LH) in a prospective and randomized trial. Study design Forty male-factor infertile normo-ovulatory patients undergoing ovarian stimulation for ICSI took part in the study. After initiating ovarian stimulation with only r-FSH, all patients were treated with GnRH antagonist (cetrorelix). When beginning cetrorelix administration, the patients were randomized into two groups: in group I, 20 patients continued to receive r-FSH alone and in group II, 20 patients received combined r-FSH and r-LH. The number of metaphase II oocytes, estradiol concentration at the time of hCG administration, fertilization rate, grade 1 embryo rate, pregnancy rate per cycle, and implantation rate were measured. Results are expressed as mean ± S.D. Results In group I, the women's age was 32.3 ± 2.30 years, and FSH concentration was 7.8 ± 1.7 IU/ml. In group II, the women's age was 32.2 ± 2.46 years and FSH concentration was 7.5 ± 1.7 IU/ml. The number of oocytes retrieved was 9.6 ± 2.9 and the number of metaphase II oocytes was 6.7 ± 2.2 in group I. In group II the number of retrieved oocytes were 9.9 ± 2.6 and the number of metaphase II oocytes 6.9 ± 2.1 ( p > 0.05). Estradiol concentration at the time of hCG was 4.6 ± 1.8 nm/l in group I and 6.7 ± 2.0 nm/l in group II ( p < 0.01). Fertilization rate was 73.0% in group I versus 78.2% in group II. In group I, we obtained 53.9% of grade 1 embryos versus 54.4% in group II ( p > 0.05). Pregnancy and implantation rates in group I were 30.0 and 16.7%, respectively and in group II 35.0 and 20.4%, respectively ( p > 0.05). Conclusions The use of recombinant LH in addition to recombinant FSH may prevent a decrease in estradiol after GnRH antagonist administration, but does not influence positively the outcome of oocyte number, maturation, embryo quality, fertilization rate, pregnancy rate per cycle, and implantation rate.

Short Communication: FSH Time-Concentration Profiles Before and After Administration of 0.25 mg Cetrorelix in the GnRH-Antagonist Multiple-Dose Protocol for Ovarian Hyperstimulation

To determine FSH concentration behavior before and after cetrorelix 0.25 mg administration in the GnRH-antagonist multiple-dose protocol on day 6 of ovarian stimulation with 150-300 IU daily recombinant FSH. Blood samples for FSH measurements were drawn from seven women every 15 min from 8 h prior to the first cetrorelix administration in the GnRH-antagonist multiple-dose protocol until 15-32 h thereafter. No significant change of FSH concentration was observed. This observation indicates that no rationale exists of increasing the daily FSH dosage concomitantly to the GnRH-antagonist administration to compensate for a drop of endogenous FSH.

The administration of the GnRH antagonist, cetrorelix, to ooctye donors simplifies oocyte donation.

We report our experience on the efficacy of a new regimen of the GnRH antagonist, cetrorelix, and recombinant FSH, Gonal-F, for controlled ovarian stimulation in a donor oocyte programme. Six oocyte donors were commenced on Gonal-F (150 IU) and two on Gonal-F 225 IU daily on day 4 together with cetrorelix 0.25 mg daily on day 8 until the day of administration of hCG. Six premenopausal recipients were down-regulated with intranasal Nafarelin 400 micro g twice daily; two women with premature menopause did not require down-regulation for synchronization between donor and recipient cycles. The median (range) of oocytes retrieved and the median (range) fertilization rates were 7 (3-13) and 50% (0-71%) respectively. With the exception of a recipient who had failed fertilization, seven recipients had two embryos transferred. The median (range) number of days of ovarian stimulation, cetrorelix administration and number of Gonal-F ampoules administered for ovarian stimulation were 9 (7-12) days, 5 (3-8) and 18 (14-24) respectively. The clinical pregnancy rate per cycle was 50% (4/8) and one of the latter women miscarried at eight weeks gestation. Three women (37.3%) had full term deliveries. This preliminary study has shown that using a combination of cetrorelix and Gonal-F resulted in a high pregnancy rate, reduced the duration of treatment for the donor and simplified oocyte donation.

Administration of the GnRH antagonist cetrorelix during the luteal phase of the mare

The GnRH antagonist cetrorelix was given during the early (Days 1–5), mid (Days 6–10 or 5–12) or for the entire (Days 1–16) luteal phase of mares to inhibit the secretion of FSH and LH (Day 0 = ovulation). Frequent blood sampling from Day 6 to Day 14 was used to determine the precise time-course of the suppression (cetrorelix given Days 6–10). Cetrorelix treatment caused a decrease in FSH and LH concentrations by 8 and 16 h, respectively, and an obliteration of the response to exogenous GnRH given 24 h after treatment onset. Treatment never suppressed gonadotropin concentrations to undetectable levels; e.g. frequent sampling showed that the nadirs reached in FSH and LH were 46.2 ± 6% and 33.1 ± 11%, respectively, of pre-treatment concentrations. Daily FSH concentrations were decreased in all treatment groups but daily LH concentrations were lower only when treatment commenced at the beginning of the luteal phase; progesterone concentrations depended on the time of cetrorelix administration, but the changes suggested a role for LH in corpus luteum function. The inter-ovulatory interval was longer than controls when cetrorelix was given in the mid- or for the entire luteal phase, but was unaffected by treatment in the early phase. Nevertheless, in all groups, FSH concentrations were higher (P < 0.05 when compared to Day 0, subsequent ovulation) approximately 6–10 days before this next ovulation. This consistent relationship suggests a stringent requirement for a GnRH-induced elevation of FSH above a threshold at, but only at, this time; i.e. approximately 6–10 days before ovulation.

Changes in subcellular distribution of pituitary receptors for luteinizing hormone-releasing hormone (LH-RH) after treatment with the LH-RH antagonist cetrorelix.

Treatment with antagonists of luteinizing hormone-releasing hormone (LH-RH) leads to down-regulation of pituitary LH-RH receptors. Thus, the effect of LH-RH antagonists is similar to that of the LH-RH agonists, but the mode of action of antagonists is not completely understood. The aim of this study was to investigate the effects of LH-RH antagonist cetrorelix on the binding characteristics and subcellular localization of receptors for LH-RH in rat pituitaries. Radioligand binding studies, performed after in vitro desaturation, revealed that a single s.c. injection of cetrorelix at a dose of 100 microg per rat significantly decreased the number of pituitary membrane receptors for LH-RH in a time-dependent manner with the nadir occurring at 6 h. In contrast, 2-6 h after cetrorelix treatment, the concentration of binding sites for LH-RH in the nuclei of rat pituitaries was significantly higher (P < 0.01) than in controls. Chronic administration of cetrorelix also decreased the level of membrane receptors for LH-RH by 83% (P < 0.01) after 7 days, and 86% (P < 0.01) after 14 days. The number of LH-RH binding sites in the nuclear pellet was increased 3-fold (P < 0.01) by days 7 and 14 after the initiation of treatment with cetrorelix. A single injection or prolonged treatment with LH-RH antagonist also decreased the mRNA expression of pituitary receptors for LH-RH. Our results demonstrate that the down-regulation of LH-RH receptors on the cell membranes of rat pituitaries after therapy with antagonist cetrorelix is associated with an increase in receptor concentration in the nuclei. These phenomena could be related to the internalization and subcellular translocation of LH-RH receptors.