[Antagonist protocols: residual LH levels and the value of exogenous LH supplementation]

When administered in the late follicular phase to prevent any LH surge, GnRH antagonists induce a sharp decrease in serum LH levels that may be detrimental for assisted reproductive technology cycle outcome. This decrease in LH levels is dose-dependant. Supplementation with recombinant LH when introducing GnRH antagonist leads to significant changes in E2 secretion. This is consistent with a key role of LH to ensure adequate steroidogenesis. This also indicates that a single dose of GnRH antagonist is able to decrease bioactive LH below a minimal threshold for optimal steroidogenesis. However, supplementation with rLH does not modify the number of retrieved oocytes, obtained embryos and the pregnancy rate. This is in line with the concept that folliculogenesis is mainly dependent on FSH and that the role of LH and E2 is not primordial. Indeed, the findings of our prospective randomized study do not support a systematic supplementation with rLH when introducing antagonist. However, further studies are necessary to determine whether a specific sub group of patients characterized by a low E2/oocyte ratio could benefit from rLH supplementation.

[Biological assessment criteria during antagonist protocols]

Until recently, gonadotropin-releasing hormone (GnRH) agonists were the only choice available to physicians for prevention of premature luteinizing hormone (LH) surges in women undergoing controlled ovarian stimulation. The recent approval of GnRH antagonists for this indication gives clinicians some new options. In several trials performed, the GnRH antagonist regimens have been associated with a slightly lower pregnancy and implantation rates than the established GnRH agonist protocols. This review summarizes the main studies concerning oocyte quality and fertilization in IVF cycles with GnRH antagonists. As a result, there is no difference between GnRH agonist and GnRH antagonists concerning oocyte maturation and fertilization rates. There are very few data about the incidence of oocyte morphology anomalies in IVF cycles with antagonists.

[Introduction of the antagonist: on a determined day or depending on follicular growth?]

Introduction of the antagonist: on a determined day or depending on follicular growth? GnRH antagonists prevent LH surge in IVF cycles. GnRH antagonist can be administrated at a fixed day (day 6) or according to mean follicle size and estradiol levels (flexible regimen). Less monitoring is required for IVF cycles with the fixed regimen. For the flexible regimen, GnRH antagonist should be initiated on the day when the leading follicle reaches 14 mm diameter. Flexible regimen should decrease total antagonist and gonadotropin doses. Similar pregnancy rates are observed between the fixed and the flexible GnRH antagonist regimens.

Serum luteinizing hormone response to administration of gonadotropin-releasing hormone to atrazine-treated gilts

The aim of the study was to evaluate the response of porcine luteinizing hormone (pLH) in serum to a single iv administration of gonadotropin-releasing hormone (GnRH) in atrazine-treated pigs. Experiments were performed in 15 mature female pigs (10 atrazine-treated, 5 control). From the onset of estrous (day 0), the pigs were given 1 mg atrazine/kg body mass in feed for 20 d of the estrous cycle. On the last day, blood samples were collected at min 0 from control and atrazine-exposed, and 5 atrazine-exposed pigs were immediatey given 100 mg GnRH iv. Blood samples were collected from atrazine-exposed and the GnRH-injected atrazine-exposed groups at 20, 30, 40 and 90 min and serum pLH concentrations were determined by radioimmunoassay. The administration of atrazine led to significant (p< 0.001) suppression of serum pLH concentrations (0.57 +/- 0.05 ng/ml) compared to control animals (2.24 +/- 0.20 ng/ml). The single iv GnRH administration to the atrazine-exposed pigs provoked significant pLH release at 20 and 30 min after GnRH administration, indicating attenuation of GnRH release in the atrazine-exposed animals was responsible for the suppression of serum pLH.

Effects of Unkei-to on FSH, LH and estradiol in anovulatory young women with hyper- or hypo-functioning conditions

Eight weeks treatment with Unkei-to induced a significant increase in plasma follicle stimulating hormone (FSH), luteinizing hormone (LH) and estradiol levels in hyper- (robust) and hypo- (asthenia) functioning patients with first- and second-grade amenorrhea. We observed no significant differences in the rate of change of these hormones between hyper- and hypo-functioning patients. Ovulation occurred in 61.3% and 66.7% of patients with first-grade amenorrhea, and in 27.3% and 22.4% of patients with second-grade amenorrhea, respectively. No significant difference was observed in the ovulation rate after an 8-week treatment with Unkei-to between hyper- and hypo-functioning patients. These results indicate that Unkei-to is effective in improving gonadotropin and estradiol secretion in the treatment of either hyper- or hypo-functioning anovulatory women.

Estrogenic effects of toremifene and tamoxifen in postmenopausal breast cancer patients

Intrinsic estrogenicities of the selective estrogen receptor modulators (SERMs) toremifene 60 mg daily or 200 mg daily and tamoxifen 20 mg daily (TOR60, TOR200 and TAM20) were compared in a randomized clinical study in postmenopausal women with advanced breast cancer. The study was open label in three parallel groups. Variables for analysis were serum follicle stimulating hormone (FSH), luteinizing hormone (LH), sex hormone binding globulin (SHBG), estradiol (E2), antithrombin III (AT III), aspartate aminotransferase (ASAT) and vaginal cytology. Clinical efficacy and safety have been reported earlier. A total of 648 patients were randomized (221 to TOR60, 212 to TOR200 and 215 to TAM20). Sera were available for the analysis from 148, 165 and 156 and for vaginal cytology from 98, 93 and 86 patients, respectively. All treatment regimens showed tissue-specific and dose-dependent estrogen agonist effect. In the primary measure of in vivo estrogenicity, effect on hypothalamus-pituitary-axis, all three treatment regimens decreased serum FSH (p < 0.001). TOR200 was more potent than the two other treatments (p < 0.05), but surprisingly, TAM20 was more estrogenic than TOR60 (p < 0.001). As could be expected in postmenopausal women, the treatments had no effect on mean serum E2 concentrations and decrease of serum LH was similar to that of FSH. Estrogenic effect on the liver was seen as dose-dependent increase of SHBG with statistically significant differences between the treatment groups (p < 0.001). Trends of transient ASAT elevations in TOR200 group (p = 0.07) and in all treatment groups AT III decrease (p = 0.1) were seen in the beginning of the treatment. TOR60 or TAM20 did not have an effect on mean ASAT values, and AT III decreased in TAM20 group more than in the two other groups (p = 0.1 compared to TOR60 and p < 0.05 compared to TOR200). Estrogenic effects on vaginal superficial cells were higher in TOR60 and TOR200 groups when compared to TAM20 (p < 0.05). Toremifene and tamoxifen had tissue-specific and partially dose-dependent estrogenic effects in hypothalamus-pituitary-axis, in the liver and in the vaginal epithelium of postmenopausal women. In some tissues tamoxifen 20 may be more estrogenic than toremifene 60 mg/day.

Genistein, a phytoestrogen, effectively modulates luteinizing hormone and prolactin secretion in ovariectomized ewes during seasonal anestrus

Through binding with estrogen receptors, phytoestrogens, plant-derived estrogen-like compounds, affect numerous reproductive functions. It is not known whether these compounds are capable of evoking effective changes in luteinizing hormone (LH) and prolactin (PRL) secretion in ewes by acting directly within the central nervous system (CNS). The hypothesis studied was that genistein, infused for several hours into the third ventricle, could immediately affect LH and PRL secretion in ovariectomized (OVX) ewes during seasonal anestrus. Two doses of genistein, 1 microg/100 microl/h (total 4 microg, n = 7) and 10 microg/100 microl/h (total 40 microg, n = 7), were infused intracerebroventricularly from 12.00 to 16.00 h and blood samples were collected from 8.00 to 20.00 h at 10-min intervals. Randomly selected ewes were infused with a vehicle (control, n = 5). The mean plasma LH concentration in control ewes was significantly (p < 0.01) higher during infusion of the vehicle than before the infusion. It remained on an insignificantly changed level after the infusion. The frequency of LH pulses in control ewes did not differ significantly before, during, or after vehicle infusion. In ewes infused with a lower dose of genistein, plasma LH concentrations decreased significantly (p < 0.001) after the infusion, as compared with the values noted before and during genistein infusion. Only a tendency towards a decrease in LH pulse frequency occurred after infusion of a lower dose of genistein. In ewes infused with a higher dose of genistein, the plasma LH concentration decreased significantly (p < 0.01) after phytoestrogen administration as compared with the values noted before and during infusion. The frequency of LH pulses was also significantly (p < 0.01) lower after genistein administration. Because the changes in PRL secretion were more dynamic in response to genistein infusion, the statistical analysis included 2-hour periods. The mean plasma PRL concentration in control animals was significantly enhanced (p < 0.01) only during the first 2-hour period of sampling. After that it decreased and remained on an unchanged level up to the end of sampling. Similar changes in PRL secretion were observed in both experimental groups before genistein infusion. In contrast, significant (p < 0.01 to p < 0.001) increases in PRL concentration were noted regularly during and shortly after the genistein infusion in either low-dose or high-dose genistein-infused ewes, compared with the concentrations noted before genistein treatment. Plasma PRL concentrations during and after genistein infusion in both experimental groups were also significantly higher than the control (p < 0.01 to p < 0.001). The presented data demonstrate that genistein, a phytoestrogen, may effectively modulate LH and PRL secretion in OVX ewes by acting within the CNS.

Alpha-melanocyte-stimulating hormone through melanocortin-4 receptor inhibits nitric oxide synthase and cyclooxygenase expression in the hypothalamus of male rats

There is evidence that alpha-melanocyte-stimulating hormone (alpha-MSH) has immunomodulatory and anti-inflammatory actions within the brain. In this study, we tested whether these actions are due to inhibition of the synthesis of nitric oxide (NO) and prostaglandins induced by lipopolysaccharide (LPS). Since melanocortin subtype MC4 receptor has been detected in the hypothalamus, we investigated the effect of central administration of alpha-MSH and HS024 (a selective MC4 receptor antagonist) on the gene expression of inducible, neuronal and endothelial NO synthase (iNOS, nNOS and eNOS) and on cyclooxygenase (COX-1 and COX-2) expression in the mediobasal hypothalamus (MBH) of LPS-treated male Wistar rats. Peripheral administration of LPS (250 microg/rat, 3 h) induced iNOS and COX-2 gene expression in the MBH. This stimulatory effect was reduced by alpha-MSH (3 nmol/rat) injected 30 min before LPS. alpha-MSH and HS024 (1 nmol/rat) alone had no effect on iNOS and COX-2 expression. The action of alpha-MSH on LPS-induced iNOS and COX-2 mRNA levels was not observed in the presence of HS024, suggesting that MC4-R may be involved in the modulatory effect of alpha-MSH. None of these treatments produced any modifications in nNOS, eNOS and COX-1 expression in MBH. The increase in serum corticosterone levels induced by LPS was attenuated by alpha-MSH. Both LPS and alpha-MSH decreased serum LH and prolactin levels. HS024 failed to modify the inhibitory effects of LPS and alpha-MSH on prolactin release but reverted the effect of LPS on LH secretion, indicating that MC4-R activation may be involved in the effects of alpha-MSH on LH secretion in male rats. When we examined the in vitro effect of LPS (10 microg/ml) and LPS plus interferon-gamma (IFN-gamma, 100 ng/ml) on iNOS expression in MBH, an increase in iNOS mRNA levels was observed only in the presence of LPS + IFN-gamma. This stimulatory effect was attenuated in the presence of alpha-MSH (5 microM), which by itself had no effect. No changes were found in nNOS, eNOS, COX-1 or COX-2 expression. These results indicate that alpha-MSH reduces the induction of iNOS and COX-2 gene expression at the hypothalamic level during endotoxemia and suggest that endogenous alpha-MSH may exert an inhibitory tone on iNOS and COX-2 transcription via MC4 receptors acting as a local anti-inflammatory agent within the hypothalamus.

Biological role of pituitary estrogen receptors ERalpha and ERbeta on progesterone receptor expression and action and on gonadotropin and prolactin secretion in the rat

Estrogen (E) is a key regulator of the synthesis and secretion of pituitary reproductive hormones [luteinizing hormone (LH), follicle-stimulating hormone (FSH) and prolactin (PRL)]. Until recently, it was thought that all biological actions of E at the pituitary were manifested through a single E receptor (R). The pituitary, like many other reproductive tissues, expresses two isoforms of ER, alpha and beta, both activated by E. The relative contribution of alpha and beta forms in E regulatory actions is largely unknown. To this end, 2-week-old ovariectomized (OVX) rats were injected over 3 days with 25 microg estradiol benzoate (EB), 1.5 mg of propylpyrazole triol (PPT), a selective ERalpha agonist, 1.5 mg of the selective ERbeta agonist diarylpropionitrile (DPN) or a combination of PPT and DPN. Controls were injected with 0.2 ml oil. At 10:00 h on the day after treatment, trunk blood was collected to determine serum concentration of LH, FSH and PRL, and pituitaries were processed for RT-PCR analysis of total (A+B) progesterone receptor (PR) mRNA, immunocytochemistry of PR and incubation. Pituitaries from each of the five groups were incubated in DMEM, with or without 20 nM of the antiprogestin at the receptor ZK299, for 3 h with: 10(-8)M 17beta-estradiol, 10(-6)M PPT, 10(-6)M DPN, PPT+DPN or medium alone, respectively, to determine LH, FSH and PRL secretion, and, when challenged with two pulses of 15 min 1 h apart of 10(-8)M gonadotropin-releasing hormone (GnRH) (GnRH self-priming). EB, PPT and PPT+DPN treatments increased PR mRNA and the number and intensity of nuclei immunoreactive (IR) for PR in gonadotropes, and reduced the number of gonadectomy cells. Like E, PPT alone or in combination with DPN stimulated PRL secretion, increased basal and GnRH-stimulated LH and FSH secretion and induced GnRH self-priming in the absence of ZK299 in the incubation medium. DPN alone had only a significant E-like effect on gonadectomy cells and IR-PR, but not on GnRH self-priming. In addition, while DPN lacked an agonistic action on peripheral tissue and serum pituitary reproductive hormones concentration, EB, PPT and PPT+DPN induced similar uterine ballooning and vaginal cornification, and increased and decreased, respectively, serum concentrations of PRL and gonadotropins. Overall, these results indicate that most of these E actions on the pituitary are exerted through the ERalpha isoform. The finding that activation of ERbeta with its selective DPN agonist had an estrogenic effect on IR-PR nuclei, but not on GnRH self-priming, a characteristic ERalpha-mediated effect of E, suggests that the biological action of E at the pituitary may involve both isoforms of ER.

[Endocrine and metabolic effects of metformin in combination with compound cyproterone acetate in women with polycystic ovarian syndrome]

OBJECTIVE

To study the endocrinologic and metabolic effects of metformin in combination with compound cyproterone acetate (CPA) on patients with polycystic ovarian syndrome (PCOS).

METHODS

A prospective study involved total 45 PCOS patients as group A and 20 non-PCOS infertility patients as control (group B). Complete baseline work-up including body mass index (BMI), waist/hip ratio (WHR), ferriman-Gallwey score (FGS), gonadotrophin, testosterone (T), sex hormone-binding globulin (SHBG), dehydroepiandrosterone sulfate (Ds), insulin (FI) and glucose tolerance test, were performed in all patients. Patients in group A were treated with CPA alone (group A1), metformin alone (group A2) or combination of CPA with metformin (group A3), respectively by randomization. At the end of 12-week therapy, subjects were re-evaluated and above parameters were measured.

RESULTS

Women in group A had significant increases in BMI, WHR, FGS, luteinizing hormone (LH), T, FI, insulin resistance, and significantly decrease in high-density lipoprotein (HDL)-C comparing with the control group (P < 0.01). No significant difference among A1, A2 and A3 was found at baseline. LH, T, free testosterone (FT) were significant decreased from (13.9 +/- 5.9) IU/L, (2.1 +/- 0.8) nmol/L and (2.8 +/- 2.3) nmol/L respectively to (5.8 +/- 2.2) IU/L, (1.2 +/- 0.4) nmol/L and (0.8 +/- 0.5) nmol/L respectively and SHBG was significant increased from (99 +/- 42) nmol/L to (187 +/- 64) nmol/L in group A3, when compared with LH, T and FT from (13.8 +/- 7.6) IU/L, (2.2 +/- 1.1) nmol/L and (2.5 +/- 1.9) nmol/L respectively to (11.8 +/- 6.5) IU/L, (1.8 +/- 0.8) nmol/L and (1.7 +/- 1.0) nmol/L respectively and SHBG from (99 +/- 40) nmol/L to (120 +/- 51) nmol/L in group A2 (P < 0.05 approximately 0.001). HDL-C were significantly increased from (1.5 +/- 0.3) mmol/L to (1.8 +/- 0.3) mmol/L in group A3 comparing with HDL-C from (1.5 +/- 0.4) mmol/L to (1.6 +/- 0.4) mmol/L in group A1 (P < 0.001).

CONCLUSIONS

The PCOS patients treated with metformin in combination with compound cyproterone acetate may be more effective in inhibiting hyperandrogen and hypersecretion of LH than metformin alone and more obvious in improving lipid profiles than CPA alone.

Neuropeptide Y (NPY) delays the oestrogen-induced luteinizing hormone (LH) surge in the ovariectomized ewe: further evidence that NPY has a predominant negative effect on LH secretion in the ewe

Studies in rats suggest that neuropeptide Y (NPY) plays a stimulatory role in the generation of the preovulatory luteinizing hormone (LH) surge, via the Y1 receptor. We have investigated this issue using the oestradiol benzoate (EB)-treated ovariectomized (OVX) ewe which is a model for the preovulatory LH surge. A Y1 receptor antagonist (BIBO3304) was infused (25 microg/h) into the third cerebral ventricle (III-V) from 2 h before EB injection for 24 h, and had no effect on the ensuing LH surge. Using in situ hybridization, we then examined expression of NPY mRNA in the arcuate nucleus during the luteal, follicular and oestrous phases of the oestrous cycle, and found that levels were greatest during the luteal phase. Thus, reduced NPY synthesis might be an integral factor in the events leading to the cyclic preovulatory LH surge. This was tested by infusion of NPY (25 microg/h) into the III-V (as above). The NPY infusion delayed the LH surge until the infusion was ceased. High levels of NPY expression during the luteal phase of the oestrous cycle may be caused by progesterone. Thus, we determined whether NPY cells possess progesterone receptors (PR) and whether progesterone treatment up-regulates NPY mRNA expression in the arcuate nucleus. Immunohistochemistry for NPY and PR was performed in OVX, oestrogen-treated ewes, but no NPY cells of the arcuate nucleus were seen to colocalize PR. In situ hybridization for NPY was performed in OVX and OVX ewes treated with progesterone. There was no significant effect of progesterone treatment on NPY mRNA expression in the arcuate nucleus. We conclude that chronically elevated levels of NPY block the preovulatory surge of gonadotropin-releasing hormone/LH secretion in sheep, but high levels of NPY mRNA expression in the luteal phase of the oestrous cycle cannot be explained by an action of progesterone.

Food restriction during lactation results in prolonged hyposensitivity to the positive-feedback effects of oestradiol

Food restriction prolongs lactational infertility in rats. Here, we investigated whether an attenuated response to the positive-feedback effects of oestrogen on luteinizing hormone release contributed to this effect. The ability of oestrogen to induce surges in luteinizing hormone in ad libitum fed and food-restricted dams at different times of lactation was compared. The results showed that, on day 20 postpartum, ad libitum fed dams showed luteinizing hormone surges after oestrogen treatment, but food-restricted dams did not. Ovariectomy or RU486 treatment restored the ability of oestrogen to induce luteinizing hormone surges in food-restricted dams, and chronic progesterone exposure reduced oestrogen-induced surges of luteinizing hormone in ad libitum fed ovariectomized dams. Food restriction also resulted in a reduced ability of oestrogen to induce progesterone receptor immunoreactivity, but did not reduce the number of oestrogen receptors (ERalpha) in the anteroventralperiventricular area. As with the surge in luteinizing hormone, the effects of food restriction on oestrogen induction of progesterone receptors were mediated by progesterone. Together, these results suggest that the ability of food restriction to extend the length of lactational diestrus is mediated, in part, by a decrease in sensitivity to the positive-feedback effects of oestrogen. This results from high circulating concentrations of progesterone which apparently reduce the ability of oestrogen to induce progesterone receptor expression.

Receptor-mediated targeting of a photosensitizer by its conjugation to gonadotropin-releasing hormone analogues

Photodynamic therapy uses a combination of light, oxygen, and a photosensitizer to induce the death of malignant cells. To improve the selectivity of a photosensitizer toward cancerous cells that express gonadotropin-releasing hormone (GnRH) receptors, protoporphyrin IX (PpIX) was conjugated to a GnRH agonist, [d-Lys6]GnRH, or to a GnRH antagonist, [d-pGlu1, d-Phe2, d-Trp3, d-Lys6]GnRH. The condensation of the peptide with PpIX was carried out in a homogeneous solution using benzotriazole-1-yloxytris(pyrrolidinophosphonium) hexafluorophosphate as a coupling reagent. Although these conjugates had lower binding affinity to rat pituitary GnRH receptors than their parent analogues, they fully preserved their agonistic or antagonistic activity in vitro and in vivo. The GnRH agonist conjugate proved to be long-acting in vivo. Thus, 24 h after its administration to rats (2 nmol/rat), serum LH concentrations were significantly higher than in rats treated with the same amount of the parent peptide. The conjugates, notably the agonist, were more phototoxic toward pituitary gonadotrope alphaT3-1 cell line than was unconjugated PpIX. In contrast to PpIX, the phototoxicity of the conjugates toward alphaT3-1 cells or to human breast cancer cells (MCF-7 cells that were transfected with human GnRH receptors) was alleviated by co-incubation with the parent peptide, indicating that phototoxicity is receptor-mediated. The selectivity of the GnRH antagonist conjugate to gonadotrope cells in a primary pituitary culture was approximately 10 times higher than that of the unconjugated PpIX. Thus, GnRH-based conjugates may affect cancer cells not only by acting as classic GnRH analogues to reduce the plasma levels of steroids by desensitization of the pituitary gland but also by selective photodamage of cells that express GnRH receptors.

The improvement of luteal insufficiency in fecund women by tokishakuyakusan treatment

The effect of tokishakuyakusan, a Chinese herbal medicine, was examined, in vivo, in women with luteal insufficiency and in women with normal menstrual cycles. Luteal insufficiency was determined by daily measurement of basal body temperature and plasma progesterone levels. Tokishakuyakusan improved luteal insufficiency. Furthermore, the effects of tokishakuyakusan on prolactin, gonadotropins, steroids, angiotensin II, ANP and renin levels in the blood of women with normal menstrual cycles were studied, as were the medicine's effects on estrogens, pregnenediol and LH in the urine of the same women. Tokishakuyakusan had no adverse effect on hormonal levels in either blood or urine. Furthermore, no clinical side effects were detected. These results suggest that tokishakuyakusan improves luteal insufficiency in women but does not affect the hormonal levels of women with normal menstrual cycles.

Oral and transdermal estrogens both lower plasma total homocysteine in male-to-female transsexuals

Plasma total homocysteine (tHcy) levels are on average lower in women versus men, indicating an estrogenic effect. Oral estrogens (absorbed via the liver) may be hypothesized to have stronger effects on hepatic homocysteine metabolism than transdermal estrogens. We randomly assigned 30 male-to-female transsexuals (20-44 years old) to 4 months' administration of oral ethinyl estradiol (n=15) or transdermal 17beta-estradiol (n=15), both with the antiandrogen cyproterone acetate (CA). Ten other male controls were treated with CA only. At baseline and after 2 and 4 months, plasma tHcy was analyzed in conjunction with plasma folate. Oral ethinyl estradiol and transdermal 17beta-estradiol similarly reduced plasma tHcy (geometric mean 10.6 micromol/l [95% CI 8.2-13.9] to 7.5 [6.5; 8.8], and 11.3 [8.1; 16.4] to 8.4 [6.5; 11.1]; P<0.001 for both), whereas CA had no effects. No effects were found on folate levels. Thus, oral and transdermal estrogens decrease plasma tHcy to a similar degree (by geometric mean -26%), which suggests that a hepatic mechanism is unlikely to play an important role in the decline of tHcy levels.

Effect of oral tamoxifen on semen characteristics and serum hormone profile in male bonnet monkeys

The effects of oral tamoxifen were studied at a dose of 0.4 mg/kg per day, on the serum hormones and semen parameters in adult male bonnet monkeys, for a period of 90 days. Honey was used as vehicle. Monkeys were treated with honey for 30 days, followed by tamoxifen from Day 30-120 (90 days). Thereafter the treatment was withdrawn until Day 150 of schedule. Blood samples were drawn at 12 and 24 clock hours at monthly intervals for the analysis of luteinizing hormone, follicle-stimulating hormone and testosterone. Semen samples were also collected for analysis once a month, from Day 0-150 of exposure. Tamoxifen treatment produced a transient but significant increase in circulating gonadotropins, at Day 90 of treatment schedule, corresponding to 60 days of treatment. Whilst serum testosterone levels were normal throughout treatment period, an increase was observed after 30 days of drug withdrawal. No effect of oral tamoxifen was evident on semen parameters, viz., volume, counts, morphology and motility. However, throughout the exposure period to honey, a significant increase was observed in sperm counts without any effect on testosterone levels. The present study suggests that oral tamoxifen has a transient antiestrogenic effect on the serum hormones and no effect on semen parameters of adult nonhuman primate males. It is concluded that bioefficacy of oral tamoxifen may have been reduced due to hepatic metabolism.

Biphasic role of dopamine on female sexual behaviour via D2 receptors in the mediobasal hypothalamus

Dopamine has been implicated in the control of sexual behaviour, but its role seems quite complex and controversial. The aim of the present experiments was to investigate the effects of dopamine (DA) acting on D2 receptors in the mediobasal hypothalamus (MBH) on sexual behaviour in female sheep. To achieve this, the D2 agonist, quinpirole, was administered bilaterally via microdialysis probes into the MBH of ovariectomized ewes either before or after oestradiol (E2) administration. Quinpirole (100 ng/ml) infused for 6 h just before E2 hastened the onset of oestrus behaviour and the luteinizing hormone surge, whereas the same treatment given 6-12 h or 18-21 h after E2 decreased the intensity of sexual receptivity without affecting LH or prolactin secretion. We then tested the hypothesis that E2 stimulates the onset of oestrus partly by decreasing DA activation of D2 receptors. In this case the D2 antagonists pimozide or spiperone (100 ng/ml) were infused into the MBH via microdialysis probes for 11 h in the absence of E2 administration. A significant number of ewes showed induction of receptivity with both antagonists, although its intensity was significantly lower than that induced by E2. These treatments generally did not significantly alter extracellular concentrations of monoamines or aminoacids although quinpirole modulated the ability of sexual interactions to increase noradrenaline release. These experiments show that DA acts via D2 receptors in the MBH to control female sexual behaviour in a biphasic manner: the onset of sexual motivation and receptivity requiring an initial increase in activation followed by a decrease. This dual action could explain some of the controversies concerning DA action on sexual behaviour.

The effect of melatonin administration on circulating plasma luteinizing hormone concentration in castrated White Leghorn roosters

Melatonin (MLT) has a significant role in mammalian reproduction, with little or no effect in birds. In the present study we studied the role of MLT in regulation of luteinizing hormone (LH) secretion in castrated White Leghorn (WL) roosters. In Experiment 1, castrated WL roosters (n = 30) were divided into three groups, and each group (n = 10) was subdivided into two subgroups (n = 5). Birds in one subgroup received an injection of MLT at 5 mg (MLT-5), 20 mg (MLT-20), or 80 mg (MLT-80)/kg BW. Birds in the second subgroup were vehicle-injected and served as controls. Each dose of MLT was administered on a separate day at 1100 h. Blood was sampled 30 min before and 10, 30, 60, and 120 min after MLT or vehicle administration. Ten minutes after MLT administration, a significant reduction in plasma LH was observed in the MLT-20 and -80 groups, i.e., 70.3 +/- 8.3% and 62.2 +/- 4.1% of control values, respectively. In the MLT-80 group, plasma LH further declined to 42.1 +/- 9.7% of control values 60 min after injection. In Experiment 2, 18 castrated WL roosters were divided into three groups of six birds each. Two groups were injected with 80 mg MLT/kg BW at the beginning of the experiment; the second group received an additional dose of 80 mg MLT/ kg BW 140 min after the first injection. The third group was injected twice (as in second group) with vehicle and served as control. Blood was sampled 30 min before and 30, 60, 120, 170, 200, and 240 min after injection. Repeated MLT injection maintained low levels of plasma LH level until the end of the experiment. In Experiment 3, 10 castrated WL roosters were divided into two groups (n = 5). The first group was injected daily, for 10 d, with 80 mg MLT/kg BW, the second group was vehicle-treated and served as a control. At Day 3, there was a significant reduction in plasma LH level in the MLT-treated group, which continued for 7 d. This study demonstrates that, in birds, MLT suppresses LH secretion in a dose- and a time-related manner.

Characterization of mono- and diaminopyrimidine derivatives as novel, nonpeptide gonadotropin releasing hormone (GnRH) receptor antagonists

A novel series of derivatives of mono- and diaminopyrimidines 1 potently displaced binding of a radiolabeled GnRH analogue to human and rat GnRH receptors. Analogues from these series competitively antagonized GnRH-stimulated increases in extracellular acidification in vitro and suppressed GnRH-mediated increases in circulating luteinizing hormone (LH) in castrated rats and testosterone in intact rats. These compounds or their analogues may be useful in treating sex hormone-dependent disease.

Effect of centrally administered insulin on gonadotropin-releasing hormone neuron activity and luteinizing hormone surge in the diabetic female rat

Diabetic female rats have decreased ovulation, sexual behavior, and luteinizing hormone (LH) surges. Peripheral insulin treatment restores the phenotype to normal. We administered central insulin and analyzed serum LH during the time of the LH surge in diabetic and non-diabetic animals to determine if central insulin was sufficient to normalize the phenotype. We assessed the activity and number of hypothalamic gonadotropin-releasing hormone (GnRH) neurons by double label immunocytochemistry for C-FOS and GnRH to determine if decreased GnRH neuron activity or number could account for the diabetes-induced deficits in neuroendocrine function. All animals were ovariectomized and given estradiol and progesterone. Diabetic and control animals were given either intracerebroventricular (ICV) insulin or saline. In experiment I, serial blood collection was performed. In experiment II, animals were sacrificed and their brains were processed for immunocytochemistry during the presumed LH surge. Experiment I showed that diabetic, saline-treated animals were unable to trigger an LH surge. Central insulin restored LH production to control levels. Experiment II revealed similar numbers and activation of GnRH neurons in all four groups. Therefore, the diabetes-induced loss of the LH surge cannot be explained simply by a reduction of GnRH-expressing neurons or by a decrease in GnRH neuronal activity.

Effects of ospemifene (FC-1271a) on uterine endometrium, vaginal maturation index, and hormonal status in healthy postmenopausal women

OBJECTIVE

Selective estrogen receptor modulators (SERMs) are drugs that exhibit both estrogen agonistic and antagonistic effects that are tissue-specific. Ospemifene (FC-1271a) is a novel SERM compound, which has been shown in animal models to have estrogen-like effects on bone and the cardiovascular system, while having antiestrogen-like effects in uterus and breast. In this study, we investigated the effects of ospemifene on the uterine endometrium, vaginal maturation index and hormonal status in healthy postmenopausal women.

METHODS

The study was conducted as a double-blind, placebo-controlled phase I study, where 40 healthy postmenopausal women volunteers were randomized to receive daily oral doses of ospemifene either 25, 50, 100 or 200 mg or placebo for 12 weeks. Vaginal ultrasonography and endometrial biopsy were performed and vaginal maturation index determined at baseline and at 12 weeks' visit. Serum concentrations of estradiol, luteinizing hormone, follicle stimulating hormone (FSH), sex-hormone binding globulin (SHBG), parathyroid hormone and prolactin were determined from samples taken at baseline, at 4 days and at 4, 12, and 16 weeks' visits. Climacteric symptoms were assessed using 12 visual analogue scales (VAS) at baseline and at the end of the study.

RESULTS

No clinically significant changes were seen in endometrial thickness at any dose level. Ospemifene exerted a very weak estrogenic effect on endometrial histology. On the other hand, it induced a clear estrogenic effect on vaginal epithelium. Among the endocrine parameters only FSH and SHBG showed significant dose dependent changes; FSH decreased and SHBG increased during the treatment. In general, ospemifene was well tolerated. The 25 and 50 mg doses tended to reduce climacteric symptoms, but no statistically significant differences were observed between different doses of ospemifene and placebo. The highest dose level (200 mg) induced more subjective adverse reactions, especially hot flushes, than lower doses.

CONCLUSION

Our study suggests that a safe and well tolerated dose of ospemifene for potential clinical use may be between 25 and 100 mg. Further studies are needed to substantiate the results of this Phase I pilot study.

Profiles of in vivo gamma-aminobutyric acid release in the medial preoptic area of intact and castrated male rats

We have suggested that gamma-aminobutyric acid (GABA) in the hypothalamus plays a tonic inhibitory role in the control of the luteinizing hormone (LH) release in intact male rats. To assess whether feedback from the testis alters the inhibitory GABAergic tone in the medial preoptic area (MPO) of male rats, an in vivo microdialysis study was performed in gonadally intact (n = 10), castrated (n = 12) and castrated testosterone-primed (n = 10) male rats. The microdialysis samples were collected and sequential blood samples were also obtained at 1-hour intervals. GABA in the dialysate was determined by high-performance liquid chromatography system and serum LH concentration was determined by radioimmunoassay. Episodic GABA release in the MPO was observed in all three groups of male rats, although castrated male rats showed lower GABA release (2.3 +/- 0.3 ng/h) than intact and castrated testosterone-primed male rats (4.0 +/- 0.5 and 4.6 +/- 1.0 ng/h, respectively). Conversely, castrated male rats showed higher serum LH concentration (7.31 +/- 0.46 ng/ml) than intact and castrated testosterone-primed male rats (0.71 +/- 0.04 and 0.53 +/- 0.07 ng/ml, respectively). In addition, intravenous infusion of bicuculline significantly increased serum LH in intact male rats, whereas bicuculline did not alter serum LH concentrations in castrated male rats. These results are consistent with the hypothesis that the feedback of testosterone stimulates GABA release in the region of the GnRH cell bodies and dendrites in male rats.