Metoclopramide-induced hyperprolactinaemia caused marked decline in pinopodes and pregnancy rates in mice

Hyperinsulinemia impairs decidualization via AKT-NR4A1 signaling: new insight into polycystic ovary syndrome (PCOS)-related infertility

BACKGROUND

Investigating the underlying molecular mechanisms responsible for endometrial dysfunction in women with PCOS is essential, particularly focusing on the role of hyperinsulinemia.

METHODS

We explored the role of insulin in the decidualization process using a synthetic decidualization assay. To dissect the effects of PI3K/AKT-NR4A signaling, we employed small interfering RNAs (siRNAs) targeting the NR4A genes and inhibitors of the PI3K/AKT pathway. We also investigated the disruption of AKT-NR4A1 signaling in the endometrium of PCOS female rats induced with dehydroepiandrosterone (DHEA). Quantitative real-time PCR (qRT-PCR) and Western blot (WB) analyses were utilized to evaluate gene expression regulation.

RESULTS

Insulin was found to suppress the expression of decidualization markers in human endometrial stromal cells (hESC) in a dose-dependent manner, concurrently triggering an inappropriate activation of the PI3K/AKT pathway. Members of the NR4A family, as downstream effectors in the PI3K/AKT pathway, were implicated in the insulin-induced disruptions during the decidualization process. Moreover, the endometrium of PCOS models showed significantly elevated levels of phosphorylated (Ser473) AKT, with a corresponding reduction in Nr4a1 protein.

CONCLUSIONS

Our research demonstrates that insulin negatively regulates decidualization in hESC via the PI3K/AKT-NR4A pathway. In vivo analysis revealed a significant dysregulation of the AKT-NR4A1 pathway in the endometrium of PCOS rats. These findings offer novel insights into the pathogenesis of infertility and endometrial disorders associated with hyperinsulinemia in PCOS.

Hyperprolactinemia modifies extracellular matrix components associated with collagen fibrillogenesis in harderian glands of non- and pregnant female mice

The harderian gland (HG) is a gland located at the base of the nictating membrane and fills the inferomedial aspect of the orbit in rodents. It is under the influence of the hypothalamic-pituitary-gonadal axis and, because of its hormone receptors, it is a target tissue for prolactin (PRL) and sex steroid hormones (estrogen and progesterone). In humans and murine, the anterior surface of the eyes is protected by a tear film synthesized by glands associated with the eye. In order to understand the endocrine changes caused by hyperprolactinemia in the glands responsible for the formation of the tear film, we used an animal model with metoclopramide-induced hyperprolactinemia (HPRL). Given the evidences that HPRL can lead to a process of cell death and tissue fibrosis, the protein expression of small leucine-rich proteoglycans (SLRPs) was analyzed through immunohistochemistry in the HG of the non- and the pregnant female mice with hyperprolactinemia. The SRLPs are related to collagen fibrillogenesis and they participate in pro-apoptotic signals. Our data revealed that high prolactin levels and changes in steroid hormones (estrogen and progesterone) can lead to an alteration in the amount of collagen, and in the structure of type I and III collagen fibers through changes in the amounts of lumican and decorin, which are responsible for collagen fibrillogenesis. This fact can lead to the impaired functioning of the HG by excessive apoptosis in the HG of the non- and the pregnant female mice with HPRL and especially in the HG of pregnancy-associated hyperprolactinemia.

Prolactin Regulates Ovine Ovarian Granulosa Cell Apoptosis by Affecting the Expression of MAPK12 Gene

Prolactin (PRL) has been reported to influence reproductive performance and cell apoptosis. However, its mechanism remains unclear. Hence, in the present study, ovine ovarian granulosa cells (GCs) were used as a cell model to investigate the relationship between PRL concentration and GC apoptosis, as well as its possible mechanisms. We examined the relationship between serum PRL concentration and follicle counts in sexually mature ewes. GCs were isolated from adult ewes and treated with different concentrations of PRL, while 500 ng/mL PRL was selected as the high concentration of prolactin (HPC). Then, we applied the transcriptome sequencing (RNA-Seq) combined with a gene editing approach to explore the HPC contributing to cell apoptosis and steroid hormones. The apoptosis of GCs gradually increased at PRL concentrations above 20 ng/mL, while 500 ng/mL PRL significantly decreased the secretion of steroid hormones and the expression of L-PRLR and S-PRLR. The results indicated that PRL regulates GC development and steroid hormones mainly through the target gene MAPK12. The expression of MAPK12 was increased after knocked-down L-PRLR and S-PRLR, while it decreased after overexpressed L-PRLR and S-PRLR. Cell apoptosis was inhibited and the secretion of steroid hormones increased after interfering with MAPK12, while the overexpression of MAPK12 showed the opposite trend. Overall, the number of follicles gradually decreased with increasing PRL concentration. HPCs promoted apoptosis and inhibited steroid hormone secretion in GCs by upregulating MAPK12 through reducing L-PRLR and S-PRLR.

Prolactin Relationship with Fertility and In Vitro Fertilization Outcomes-A Review of the Literature

Hyperprolactinemia is a known cause of amenorrhea and infertility. However, there is an increasing body of evidence suggesting that prolactin is involved in multiple physiological aspects of normal reproduction. Thus, the present paper aims to review the current literature regarding the relationship between serum prolactin level and in vitro fertilization (IVF)/intracytoplasmic sperm injection outcome and the role of dopamine agonists treatment in IVF success. Moreover, the mechanisms by which prolactin may exert its role in fertility and infertility were summarized. Although not all studies agree, the available evidence suggests that higher prolactin levels in follicular fluid are associated with increased oocytes competence, but also with positive effects on corpus luteum formation and survival, endometrial receptivity, blastocyst implantation potential and survival of low-motile sperm. Transient hyperprolactinemia found in IVF cycles was reported in most of the studies not to be related to IVF outcome, although a few reports suggested that it may be associated with higher implantation and pregnancy rates, and better-cumulated pregnancy outcomes. Administration of dopamine agonists for hyperprolactinemia preceding IVF treatment does not seem to negatively impact the IVF results, while treatment of transient hyperprolactinemia during IVF might be beneficial in terms of fertilization rates and conception rates. Due to limited available evidence, future studies are necessary to clarify the optimal level of circulating prolactin in patients performing IVF and the role of dopamine agonist treatment.

Effects of clinical and metabolic variables and hormones on the expression of immune protein biomarkers in the endometrium of women with polycystic ovary syndrome and normal-cycling controls

BACKGROUND

Women with polycystic ovary syndrome (PCOS) are at an elevated risk of endometrial cancer, which may be associated with the continuous proliferative state caused by the interaction between hormones and metabolic factors.

OBJECTIVE

To investigate the impact of hormones and metabolic factors in the proliferation and death of endometrium during the proliferative phase.

METHODS

Cross-sectional study with 11 women with PCOS and eight normal-cycling non-PCOS controls at the Federal University of the State of Rio de Janeiro from February 2011 to June 2019. Clinical, biochemical, and hormonal data were collected to analyze their influence on the expression of biomarkers related to the endometrial tissue breakdown. Hysteroscopy and endometrial biopsies were conducted, and the endometrial samples underwent immunohistochemistry for markers of apoptosis B-cell lymphoma 2 (BCL2), cleaved caspase-3 (CASP3), fas cell surface death receptor (FAS), FAS ligand (FASLG), BCL2 associated X (BAX), marker of proliferation Ki-67 (MKI67), and cell death using terminal deoxynucleotidyl transferase dUTP nick and labeling (TUNEL).

RESULTS

CASP3 and TUNEL expressions were lower in both stroma and endometrium gland of PCOS women than in controls. MKI67 and homeostasis indexes (BCL2/BAX; FASLG/FAS) in the endometrium of the PCOS group were significantly higher. Body mass index (BMI) values were positively correlated with the expression of MKI67 and MKI67/TUNEL ratio in the endometrial stroma compartment. Fasting insulin levels were positively correlated with the expression of BCL2, and DHEA-S levels were negatively correlated with the expression of CASP3 of women with PCOS.

CONCLUSION

BMI, insulin, and DHEA-S influence the endometrial homeostasis breakdown in PCOS in the endometrium stroma.

Imbalance between the cellular proliferation and death in harderian gland of female mice with hyperprolactinemia

OBJECTIVE

To assess the impact of the metoclopramide-induced hyperprolactinemia in cellular death and proliferation in the harderian gland of female mice.

METHODS

Twenty female mice were divided into two groups of 10 animals each and treated: 0.2 mL of saline solution (controls, Ctr) and 200 µg of metoclopramide (experimental, hyperprolactinemia), both for 50 consecutive days and at 12:00 a.m. On the 50th day, the female were euthanized, and the harderian glands were removed and processed for immunohistochemistry for detected ki67 and TUNEL method. Data were statistically analyzed by unpaired Student's t test (p<0.05).

RESULTS

The harderian gland of the hyperprolactinemia group showed increase in the immunoexpression of Ki67 and TUNEL compared to the Ctr group (p<0.05), and there was no significant difference in the amount of porphyrin in the HPrl group compared to the Ctr group.

CONCLUSION

The hyperprolactinemia led to increased cell death in the acini the harderian gland and cell proliferation in the stroma glandular, fact that suggesting a reduction process of cellular activity and fibrosis, which suggests impairment in the functioning of the lacrimal harderian.

The Disorders of Endometrial Receptivity in PCOS and Its Mechanisms

Polycystic ovary syndrome (PCOS) is a mysterious and complicated endocrine disease with the combination of metabolic, reproductive, psychological dysfunctions. Impaired endometrial receptivity and ovulation disorders/anovulation are both important causes of PCOS-related infertility. However, change in endometrium has never received the same attention as ovulatory dysfunction. Besides, putting emphasis on endometrial function may be more realistic for PCOS-related infertility, given the wide use of assisted reproductive technology. The present review focuses on the disorders of endometrial receptivity of patients with PCOS, summarizes the changes of the indicators of endometrial receptivity including leukemia inhibitory factor, homeobox genes A, pinopodes, αvβ3-integrin, and intercellular junctions and also analyzes the possible mechanisms of decreased endometrial receptivity and its relationship with the main endocrine and metabolic disorders of PCOS such as hyperandrogenism, inflammation, insulin resistance, and obesity. Despite several biomarkers have been found to be associated with decreased endometrial receptivity in PCOS, the clinical relevance of these findings still awaits future clarification.

No impact of treated hyperprolactinemia on cumulative live birth rate and perinatal outcomes in in vitro fertilization-embryo transfer

AIM

To investigate whether treated hyperprolactinemia has an impact on pregnancy outcomes in in vitro fertilization/intracytoplasmic sperm injection-embryo transfer (IVF/ICSI-ET).

METHODS

A retrospective cohort study was conducted on 535 women who underwent IVF/ICSI-ET between January 2012 and December 2016, of which 123 had treated hyperprolactinemia (case group), 369 were matched controls. Besides, 43 remained hyperprolactinemic after treatment consisted of abnormal group. Cumulative live birth rate (CLBR) after one oocyte retrieval cycle was taken as the primary outcome. A time-to-event analysis using Fine and Gray's test was used to compare CLBR between case and control groups.

RESULTS

The median prolactin level was 80.00 ng/mL before dopamine agonist treatment in case group, and it reduced to 14.80 ng/mL after the treatment, similar to the level of control group (15.17 ng/mL, P = 0.316). No significant differences in baseline characteristics were found between case and control groups. The CLBR after one oocyte retrieval cycle were 69.1% (85/123) and 66.4% (245/369) in the case group and control group, respectively (P = 0.580). No significant differences were found between case and control groups in perinatal outcomes. Pregnancy and perinatal outcomes of abnormal group were similar to those of case and control groups.

CONCLUSION

Impact of treated hyperprolactinemia on CLBR and perinatal outcomes in IVF-ET was not evident.

Effects of hyperprolactinemia on the tibial epiphyseal plate of mice treated with sex hormones

The aim of this study was to evaluate the effects of metoclopramide-induced hyperprolactinemia on the tibial epiphyseal plate of hormone-treated oophorectomized mice. For this purpose, 18 animals with intact ovaries were allocated to two groups, M (metoclopramide) and V (vehicle). One hundred and eight oophorectomized animals were allocated to 12 subgroups: Oophx/V (vehicle); Ooph/M (metoclopramide); Oophx/V + E (vehicle + estradiol); Oophx/M + E (metoclopramide + estradiol); Oophx/V + P (vehicle + progesterone); Oophx/M + P (metoclopramide + progesterone); Oophx/V + T (vehicle + testosterone); Oophx/M + T (metoclopramide + testosterone); Oophx/V + E + P (Vehicle + estradiol + progesterone); Oophx/M + E + P (metoclopramide + estradiol + progesterone); Oophx/V + E + P + T (vehicle + estradiol + progesterone + testosterone); Oophx/M + E + P + T (metoclopramide + estradiol + progesterone + testosterone). After a 50-day treatment was performed histomorphometric and immunohistochemical cell death analysis. In the epiphyseal plate of the hyperprolactinemic and/or oophorectomized animals, cell proliferation and bone formation decreased, inducing intensified cell death. In the sex steroid-treated animals, estrogen boosted cell proliferation; progesterone, bone formation and testosterone, both cell proliferation and bone formation. These findings suggest that oophorectomy and hyperprolactinemia changed epiphyseal plate morphology causing cartilage degeneration. Treatment with combined sex steroids may diminish such deleterious effects.

Influence of hyperprolactinemia on collagen fibers in the lacrimal gland of female mice

OBJECTIVE

To quantify the collagen fibers in the lacrimal gland of female mice with hyperprolactinemia.

METHODS

Forty adult female mice were randomly divided into two groups with 20 animals each: nonpregnant control (CTR1, control group, 0.2 mL of saline solution) and nonpregnant experimental (HPRL1, experimental group, 200 µg/day metoclopramide). Treatments lasted for 50 consecutive days. On day 50, 10 females from each group (control and experimental) were euthanized in the proestrus phase; then, the blood was collected and the lacrimal glands were removed. Thereafter, the remaining females were placed with the mates and continued to receive treatment with saline solution or metoclopramide. On the 6th post-coital day, 10 pregnant females from the control group (CTR2) and 10 pregnant females from the experimental group (HPRL2) were euthanized, after which blood was collected and the lacrimal glands removed. The lacrimal glands were processed for morphological analyses and collagen quantification, and prolactin and sex steroid levels were measured in the blood samples. Data were statistically analyzed using an unpaired Student t test (p<0.05).

RESULTS

Morphological analysis revealed greater structural tissue disorganization of the lacrimal glands in the metoclopramide-treated groups. The total collagen content was significantly higher in the HPRL1 group than in the CTR1 group (p<0.05), whereas the difference between the CTR2 and HPRL2 groups was not significant.

CONCLUSION

Our data suggest an impairment in the functioning of the lacrimal gland as a consequence of increased prolactin levels and decreased serum levels of estrogen and progesterone.

Effects of melatonin and prolactin in reproduction: review of literature

Summary The pineal gland is responsible for producing a hormone called melatonin (MEL), and is accepted as the gland that regulates reproduction in mammals. Prolactin (PRL) also exhibits reproductive activity in animals in response to photoperiod. It is known that the concentrations of PRL are high in the summer and reduced during winter, the opposite of what is seen with melatonin in these seasons. In placental mammals, both prolactin and melatonin affect implantation, which is considered a critical point of pregnancy, since a successful pregnancy requires the development of a synchronous interaction between the endometrium and blastocyst for placental development. It is also known that PRL levels during pregnancy are essential for the maintenance of pregnancy, because this hormone induces the corpus luteum to produce progesterone, in addition to stimulating blastocyst implantation to maintain pregnancy and form the placenta. However, melatonin levels in plasma have also been shown to increase during pregnancy, peaking at the end of this period, which suggests that this hormone plays an important role in the maintenance of pregnancy. Thus, it is clear that treatment with prolactin or melatonin interferes with the processes responsible for the development and maintenance of pregnancy.

The progesterone and estrogen modify the uterine prolactin and prolactin receptor expression of hyperprolactinemic mice

The aim of this study was to evaluate the effects of metoclopramide-induced hyperprolactinemia on the prolactin (PRL) and PRL receptor's expression in the uterus of mice. For this purpose, 49 Swiss mice were divided into the following groups: GrSS (non-ovariectomized mice given vehicle); GrMET (non-ovariectomized mice treated with metoclopramide); OvSS (ovariectomized mice given vehicle); OvMET (ovariectomized mice treated with metoclopramide); OvMET+17βE (ovariectomized mice treated with metoclopramide and 17β estradiol); OvMET+MP (ovariectomized mice treated with metoclopramide and micronized progesterone); OvMET+17βE+MP (ovariectomized mice treated with metoclopramide and a solution of 17β estradiol and micronized progesterone). Immunohistochemical analyzes were evaluated semi-quantitatively. Our results showed that GrMET, OvMET+MP, and OvMET+17βE+MP presented strong PRL expression. OvMET and OvMET+17βE presented mild reaction, while GrSS and OvSS presented weak reaction. Concerning PRL receptor, OvMET+MP and OvMET+17βE+MP showed strong reaction; GrMET, OvSS, and OvMET+17βE showed mild reaction; and GrSS and OvMET showed weak reaction. These findings suggest that progesterone alone or in combination with estrogen may increase the expression of uterine PRL and PRL receptor.

Effects of metoclopramide-induced hyperprolactinemia on the prolactin and prolactin receptor expression of murine adrenal

The aim of this study was to evaluate the effects of metoclopramide-induced hyperprolactinemia on the prolactin (PRL) and prolactin receptor's (PRLR) expression in the adrenal. For this purpose, a total of 12 animals with intact ovaries were allocated to two groups: G1 (saline solution) and G2 (metoclopramide). A total of 30 oophorectomized animals was randomized to five subgroups: G3 (saline solution), G4 (metoclopramide), G5 (metoclopramide + 17β-estradiol), G6 (metoclopramide + progesterone), and G7 (metoclopramide + 17β-estradiol + progesterone). Immunohistochemical analyses were evaluated semi-quantitatively. For PRLR, the area fraction of labeled cells (ALC) varied from 1 (0-10%) to 3 (> 50%). Based on the mean of the immunostaining intensity, G2 and G4 showed strong expression; G6 and G7 presented a mild reaction; and G1, G3, and G5 exhibited a weak reaction. Concerning PRL, the ALC varied from 1 (0-10%) to 3 (> 50%), and groups G6 and G7 showed a strong reaction; G2, G4, and G5 showed a mild reaction; and G1 and G3 exhibited a weak reaction. These findings suggest that metoclopramide-induced hyperprolactinemia increases PRL expression in the adrenal glands of mice. Furthermore, progesterone alone or in association with estrogen also increases PRL expression, but to a lesser extent.

Metoclopramide-induced hyperprolactinemia effects on the pituitary and uterine prolactin receptor expression

In this work we have evaluated the gene expression profile of prolactin and prolactin receptor in the pituitary and the uterus of female mice with metoclopramide-induced hyperprolactinemia treated with estrogen and/or progesterone. For this purpose, 49 Swiss female mice were allocated to seven groups.

INTERVENTIONS

50-day treatment with metoclopramide, progesterone and estrogen. Our results showed that in the pituitary, metoclopramide-induced hyperprolactinemia increased prolactin expression. In the castrated animals, progesterone, with or without estrogen, produced an increase in prolactin. Pituitary prolactin receptor and the estrogen and progesterone treatment were responsible for the rise in PRLR-S2. In the uterus, no differences in prolactin expression were found between the different study groups. PRLR-S1 had its expression reduced in all castrated animals as against the castrated group treated with vehicle. In the noncastrated animals, PRLR-S2 rose in the metoclopramide-treated group, and, in the castrated animals, its expression diminished in all groups in relation to the vehicle-treated castrated controls. An increase in PRLR-S3 was found in the oophorectomized animals treated with a combination of estrogen and progesterone. PRLR-L rose in the oophorectomized animals treated with progesterone in isolation or in association with estrogen. These findings suggest that metoclopramide associated to progesterone or estrogen may determine an increase in pituitary prolactin and PRLR-S2 expression. The estrogen-progesterone may enhance the expression of PRLR-S3 and PRLR-L isoform of prolactin receptor.

A study of prevention and regression of cardiac hypertrophy with a prolactin inhibitor in a biological model of ventricular hypertrophy caused by aorto caval fistulae in rat

BACKGROUND

The possibility of decreasing or reverting left ventricular hypertrophy and, therefore, cardiac hypertrophy (CH) is an important medical issue. The aim of the present study was to evaluate these two possibilities with a 3-week daily dose of captopril, losartan, or bromocriptine in a preventive or corrective model.

METHODS

After aorto caval fistulae (ACF) surgery on adult male Wistar rats to induce CH, animals were assigned to the preventive protocol (drug treatment began immediately after surgery) or corrective protocol (hypertrophy was allowed to develop before drug treatment). After treatments, isoproterenol was administered to half of the animals to further induce CH. The groups included the passive control, the sham-operated animals, those with ACF surgery but without drug treatment, and the 3-week treatments with captopril, losartan, or the low or high dose of bromocriptine.

RESULTS

Three treatments, with captopril, losartan, or the high dose of bromocriptine, significantly impeded/reverted an increase in CH-related parameters in the preventive/corrective model compared to the surgically treated group without drug treatment. The same effect was found after isoproterenol administration. The present results show an avoidance/reversion of CH with these three treatments. Better results were found with the angiotensin converting enzyme inhibitor (captopril) than with the prolactin inhibitor (bromocriptine).

CONCLUSIONS

Treatments with captopril, losartan, and the high dose of bromocriptine were effective in preventing/reversing the manifestation of CH in the preventive/corrective rat models. Further studies are needed to identify the initial mediator, the key component, and the molecular events involved in the pathogenesis of CH.

Effects of metformin on the reproductive system of androgenized female rats

Metformin improved the glucose rate and the homeostasis model assessment-insulin resistance (HOMA-IR) index and caused partial reversion of ovaries and uterine morphology in female rats androgenized with testosterone.

Rat pinealectomy: a modified direct visual approach

PURPOSE: To report a new, direct visual approach for rat pinealectomy. METHODS: Eighty adult female rats (Rattus norvegicus albinus EPM-1 strain) were weighted and anesthetized intraperitoneally with 15 mg/kg xylazine and 30 mg/kg ketamine. The animal was fastened to a dissection table, an incision was made in the skin and the subcutaneous tissue, bringing the lambda into view. The skullcap was opened with a dental drill, bringing the cerebral hemispheres and the superior sagittal sinus into view. The pineal gland, located under the venous sinus, was removed in a single piece using tweezers. Next, the bone fragment was returned to its place and the surgical layers were sutured. RESULTS: This new technique is easy to be done, avoids bleedings and removes only the pineal gland without damage to the remaining encephalon. In addition it makes possible the achievement of a sham surgery, allowing the pineal gland to remain intact. CONCLUSION: The proposed technique intends to facilitate studies aiming to better understanding the complexity and importance of the pineal gland on reproductive and other body systems.

Effects of metoclopramide-induced hyperprolactinemia on the prolactin receptor of murine endometrium

OBJECTIVE

To evaluate the effects of metoclopramide-induced hyperprolactinemia on the prolactin receptor of murine endometrium.

DESIGN

Experimental study using the RNA extraction to detect tissue prolactin receptor isoforms by reverse-transcriptase polymerase chain reaction (RT-PCR).

SETTING

University-based laboratory.

ANIMAL(S)

Seventy-two female swiss albino mice (Mus musculus), approximately 100 days old, were divided into six 12-animal groups: (GI) nonoophorectomized mice given vehicle; (GII) nonoophorectomized mice treated with metoclopramide; (GIII) oophorectomized mice treated with metoclopramide; (GIV) oophorectomized mice treated with metoclopramide and 17beta-estradiol; (GV) oophorectomized mice treated with metoclopramide and micronized progesterone; (GVI) oophorectomized mice treated with metoclopramide and a solution of 17beta-estradiol and micronized progesterone.

INTERVENTION(S)

Drugs were administered for 50 days. Following euthanasia, the middle portions of the uterine horns were removed, sectioned, and immediately frozen for RT-PCR procedures. Blood was collected for the dosage of prolactin and serum estrogen and progesterone using radioimmune assay.

MAIN OUTCOME MEASURE(S)

Identification of uterine prolactin receptor isoforms.

RESULT(S)

The PRL receptor and its isoform L were identified only in GI (control group) and GII (metoclopramide), the two groups with nonoophorectomized animals. The amount of PRL receptor mRNA and that of its isoform L from GII were the largest. No other isoforms of the prolactin receptor were identified in any of the groups.

CONCLUSION(S)

Our results suggest that replacement of estrogen and progestin may not increase the mRNA of endometrial PRL receptor in metoclopromide-induced hyperprolactinemia in rats after castration.

Effects of melatonin on the endometrial morphology and embryo implantation in rats

OBJECTIVE

To determine the effects of melatonin on rat endometrium morphology and embryo implantation.

DESIGN

Experimental study.

SETTING

Federal University of São Paulo, Brazil.

ANIMAL(S)

Forty female rats.

INTERVENTION(S)

GI: control, GII: sham-operated, GIII: pinealectomized, and GIV: pinealectomized rats that received melatonin during 3 months. The GI, GII, and GIII groups received the vehicle of melatonin (NaCl + ethanol). At the end of the treatment, the animals were killed during the estrous phase; the uterus was removed for morphometric analysis. Urine was collected for 6-sulfatoxymelatonin. Blood was collected for estrogen (E) and progesterone (P) level determinations. In a second experiment, female rats were used to evaluate the endometrial embryo implantation.

MAIN OUTCOME MEASURE(S)

Endometrial morphology and embryo implantation.

RESULT(S)

GIII presented the highest values for endometrial area and thickness index, number of endometrial glands, and eosinophils. The number of vessels of groups I, II, and IV was fewer than that of GIII. The highest number of eosinophils was detected in GIII in comparison to other groups. The implantation rate in GIII was the lowest of all groups. This implantation rate was significantly increased and restored toward normal in GIV.

CONCLUSION(S)

Our data suggested that, in nonphotoperiodic animals such as rats, melatonin may positively affect the endometrial morphology and improve embryo implantation.