estradiol-3-benzoate and Body-Weight

The objective was to evaluate when the LH reserve was re-established in postpartum Nellore (Bos indicus) cows by evaluating the response of the hypothalamic-pituitary axis responsiveness to exogenous GnRH or estradiol benzoate (EB). Additionally, we tested the influence of dietary supplementation (SUPL) and calf removal (CR) on the duration of postpartum anestrus. Ninety multiparous lactating Nellore cows were randomly assigned to eight groups. The EB and GnRH groups received 1.0 mg EB (N = 7), and 50 μg lecireline (N = 16), respectively. Additional cows were given the same hormones, and subjected to either nutritional supplementation (EB-SUPL, N = 9; GnRH-SUPL, N = 16), or calf removal at 72 hours after calving (EB-CR, N = 4; GnRH-CR, N = 13). The remaining two groups were the LH (12.5 mg, N = 14) and control groups (saline, N = 11). Hormones were administered weekly from 7 (±5) days postpartum to first ovulation (detection of a CL during a weekly ultrasonographic examination). Blood samples were collected just before and 2 hours (GnRH, LH, and control groups) or 18 hours (EB groups) after hormone or saline (control) administration. Ovulation occurred as early as 15 days postpartum in the GnRH group. The mean ± SEM intervals (days) from calving to first ovulation were EB, 87.7 ± 4.2; EB-CR, 20.3 ± 1.2; EB-SUPL, 60.3 ± 3.2; GnRH, 40.4 ± 2.1; GnRH-CR, 21.0 ± 1.1; GnRH-SUPL, 26.4 ± 1.1; LH, 35.6 ± 1.1; and control, 60.9 ± 2.1. We concluded that there was sufficient LH in the pituitary gland (of Nellore cows) from the second week postpartum to induce ovulation in response to exogenous GnRH. Additionally, calf removal and nutritional supplementation reduced, by 2 to 4 weeks, the interval from calving to an LH increase and ovulation induced by GnRH or EB.

Topics: Animal Feed; Animals; Body Weight; Cattle; Estradiol; Female; Gonadotropin-Releasing Hormone; Hypothalamo-Hypophyseal System; Luteinizing Hormone; Ovulation; Postpartum Period

We used temporally-targeted food restriction (TTFR), in which ovariectomized rats had chow only for 2 h/day, to test the hypothesis that estradiol benzoate (EB) suppresses feeding and decreases body weight during brief (4 day) TTFR, as it does during ad libitum feeding. All rats lost weight during TTFR, but the loss was greater with EB treatment. However, OIL and EB-treated rats ate comparable amounts of chow during TTFR. We next investigated central nervous system pathways and peripheral hormonal and metabolic changes that accompany the effects of TTFR to determine the mechanism for this effect. Immunolabeling for fos in the nucleus of the solitary tract, the terminal site of vagal afferents from the gastrointestinal tract, was increased when rats on TTFR had access to chow for 1 h on the test day, indicating neuronal activation associated with consumption of the meal. However, fos immunolabeling was not affected by EB treatment, nor were numbers of the α subtype of estrogen receptors. TTFR had the expected effects on carbohydrate and lipid metabolites and metabolic hormones, with only slight differences in plasma glucose, triglycerides, and free fatty acids attributable to EB treatment. Interestingly, plasma corticosterone levels were greater in EB-treated rats on TTFR, and increased further after eating. Given that corticosterone affects metabolism, these findings suggest that elevated corticosterone may explain the persistence of EB-induced differences in body weight during TTFR despite the lack of effect on food intake.

Topics: Animals; Body Weight; Corticosterone; Eating; Estradiol; Female; Ovariectomy; Rats; Rats, Sprague-Dawley

Overnutrition due to a high-fat diet (HFD) can increase the vulnerability of the metabolic system to maladjustments. Estradiol has an inhibitory role on food intake and this hormone has demonstrated to be a crucial organizer during brain development.. Our aim was to determine whether increased levels of estradiol in the early postnatal period modulate the alterations in metabolism and brain metabolic circuits produced by overnutrition.. Twenty-four male and 24 female Wistar rats were submitted to a HFD (34.9% fat) or a control diet (5% fat) from gestational day 6. From postnatal (P) 6 to P13, both control and HFD groups were administered a s.c. injection of vehicle or estradiol benzoate (0.4 mg/kg), resulting in eight experimental groups (n = 6 in each group). Body weight, food intake and subcutaneous, visceral, and brown fat pads were measured. Agouti-related peptide, neuropeptide Y, orexin, and proopiomelanocortin (POMC) were analyzed by quantitative real-time polymerase chain reaction assay and plasma estradiol levels were measured by ELISA.. Males fed a HFD showed an increase in body weight and the amount of visceral and subcutaneous fat, which was coincident with an increase in the number of kilocalories ingested. Neonatal estradiol treatment restored the body weight and subcutaneous fat of HFD males to control levels. Hypothalamic POMC mRNA levels in HFD females were increased with respect to control females. This increase was reverted with estradiol treatment during development.. HFD and estradiol treatment have different effects on males and females. Overnutrition affects physiological parameters, such as body weight, visceral, and subcutaneous fat content, in males, while females present alterations in hypothalamic POMC mRNA levels. Hence, the increase in estradiol levels during a period that is critical for the programing of the feeding system can modulate some of the alterations produced by the continuous intake of high-fat content food.

Topics: Adiposity; Animals; Body Weight; Diet; Diet, High-Fat; Disease Models, Animal; Estradiol; Female; Hypothalamus; Male; Neuropeptide Y; Orexins; Overnutrition; Pro-Opiomelanocortin; Rats; Rats, Wistar; Sex Factors

Multiple stimulatory and inhibitory neural circuits control eating, and these circuits are influenced by an array of hormonal, neuropeptide, and neurotransmitter signals. For example, estrogen and oxytocin (OT) both are known to decrease food intake, but the mechanisms by which these signal molecules influence eating are not fully understood. These studies investigated the interaction between estrogen and OT in the control of food intake. RT-qPCR studies revealed that 17β-estradiol benzoate (EB)-treated rats showed a two-fold increase in OT mRNA in the paraventricular nucleus of the hypothalamus (PVN) compared to Oil-treated controls. Increased OT mRNA expression may increase OT protein levels, and immunohistochemistry studies showed that EB-treated rats had more intense OT labeling in the nucleus of the solitary tract (NTS), a region known to integrate signals for food intake. Food intake measurements showed that EB treatment reduced food intake, as expected. EB-treated rats lost weight over the course of the experiment, as expected, and EB-treated rats that received the highest dose of OT lost more weight than EB-treated rats that did not receive OT. Finally, OT antagonist administered to EB-treated rats reversed the effect of EB on food intake, suggesting that estrogen effects to decrease food intake may involve the oxytocinergic pathway.

Topics: Animals; Appetite Regulation; Body Weight; Eating; Estradiol; Estrogens; Female; Hypothalamus; Ovariectomy; Oxytocin; Paraventricular Hypothalamic Nucleus; Rats; Rats, Sprague-Dawley; Receptors, Oxytocin; Signal Transduction; Solitary Nucleus

Polycystic ovary syndrome (PCOS) is frequently associated with non-alcoholic fatty liver disease (NAFLD), but the mechanisms involved in the development of NAFLD in PCOS are not well known. We investigated histological changes and metabolomic profile in the liver of rat models of PCOS phenotype induced by testosterone or estradiol. Two-day old female rats received sc injections of 1.25 mg testosterone propionate (Testos; n = 10), 0.5 mg estradiol benzoate (E2; n = 10), or vehicle (control group, CNT; n = 10). Animals were euthanized at 90-94 d of age and the liver was harvested for histological and metabolomic analyses. Findings showed only Testos group exhibited fatty liver morphology and higher levels of ketogenic and branched-chain amino acids (BCAA). Enrichment analysis showed effects of testosterone on BCAA degradation pathway and mitochondrial enzymes related to BCAA metabolism. Testos group also had a decreased liver fatty acid elongase 2 (ELOVL2) activity. E2 group had reduced lipid and acylcarnitine metabolites in the liver. Both groups had increased organic cation transporters (SLC22A4 and SLC16A9) activity. These findings indicate that neonatal testosterone treatment, but not estradiol, produces histological changes in female rat liver that mimic NAFLD with testosterone-treated rats showing impaired BCAA metabolism and dysfunctions in ELOVL2, SLC22A4 and SLC16A9 activity.

Topics: Amino Acids, Branched-Chain; Animals; Animals, Newborn; Body Weight; Estradiol; Estrous Cycle; Female; Humans; Liver; MCF-7 Cells; Non-alcoholic Fatty Liver Disease; Polycystic Ovary Syndrome; Rats; Rats, Wistar; Testosterone

Body fluid homeostasis requires a complex suite of physiological and behavioral processes. Understanding of the role of the central nervous system (CNS) in integrating these processes has been advanced by research employing immunohistochemical techniques to assess responses to a variety of body fluid challenges. Such techniques have revealed sex/estrogen differences in CNS activation in response to hypotension and hypernatremia. In contrast, it has been difficult to conclusively identify specific CNS areas and neurotransmitter systems that are activated by hyponatremia using these techniques. In part, this difficulty is due to the temporal disconnect between the physiological effects of treatments commonly used to deplete body sodium and the behavioral response to such depletion. In some methods, sodium ingestion is delayed in association with increased oxytocin (OT), suggesting an inhibitory role for OT in sodium intake. Urinary sodium loss increases within an hour after treatment with furosemide, a natriuretic-diuretic, but sodium intake is delayed for 18-24h. Accordingly, we hypothesized that acute furosemide-induced sodium loss activates centrally-projecting OT neurons which provide an initial inhibition of sodium intake, and tested this hypothesis in ovariectomized Sprague-Dawley rats with or without estrogen using immunohistochemical methods. Neuronal activation in the hypothalamic paraventricular nuclei (PVN) after administration of furosemide corresponded to the timing of the physiological effects. The activation was not different in estrogen-treated rats, nor did estrogen alter the initial suppression of sodium intake. However, virtually no fos immunoreactive (fos-IR) neurons in the parvocellular PVN were also immunolabeled for OT. Thus, acute sodium loss after furosemide produces neural activation and an early inhibition of sodium intake that does not appear to involve activation of centrally-projecting OT neurons and is not influenced by estrogen.

Topics: Analysis of Variance; Animals; Body Weight; Contraceptive Agents; Drinking; Estradiol; Female; Furosemide; Oncogene Proteins v-fos; Ovariectomy; Oxytocin; Paraventricular Hypothalamic Nucleus; Rats; Rats, Sprague-Dawley; Sodium Potassium Chloride Symporter Inhibitors; Sodium, Dietary; Supraoptic Nucleus; Urination; Uterus

Estradiol (E2) is a potent regulator of feeding behavior, body weight and adiposity in females. The hypothalamic neuropeptide, QRFP, is an orexigenic peptide that increases the consumption of high fat diet (HFD) in intact female rats. Therefore, the goal of the current series of studies was to elucidate the effects of E2 on the expression of hypothalamic QRFP and its receptors, QRFP-r1 and QRFP-r2, in female rats fed a HFD. Alterations in prepro-QRFP, QRFP-r1, and QRFP-r2 expression across the estrous cycle, following ovariectomy (OVX) and following estradiol benzoate (EB) treatment were assessed in the ventral medial nucleus of the hypothalamus/arcuate nucleus (VMH/ARC) and the lateral hypothalamus. In intact females, consumption of HFD increased prepro-QRFP and QRFP-r1 mRNA levels in the VMH/ARC during diestrus, a phase associated with increased food intake and low levels of E2. To assess the effects of diminished endogenous E2, rats were ovariectomized. HFD consumption and OVX increased prepro-QRFP mRNA in the VMH/ARC. Ovariectomized rats consuming HFD expressed the highest levels of QRFP. In the third experiment, all rats received EB replacement every 4days following OVX to examine the effects of E2 on QRFP expression. Prepro-QRFP, QRFP-r1 and QRFP-r2 mRNA were assessed prior to and following EB administration. EB replacement significantly reduced prepro-QRFP mRNA expression in the VMH/ARC. Overall these studies support a role for E2 in the regulation of prepro-QRFP mRNA in the VMH/ARC and suggest that E2's effects on food intake may be via a direct effect on the orexigenic peptide, QRFP.

Topics: Animals; Body Weight; Diet, High-Fat; Eating; Estradiol; Estrous Cycle; Female; Gene Expression; Hypothalamic Area, Lateral; Hypothalamus; Intercellular Signaling Peptides and Proteins; Ovariectomy; Peptides; Rats; Rats, Long-Evans; Receptors, G-Protein-Coupled; RNA, Messenger

The beneficial effects of physical exercise to reduce anxiety and depression and to alleviate stress are increasingly supported in research studies. The role of ovarian hormones in interactions between exercise and anxiety/stress has important implications for women's health, given that women are at increased risk of developing anxiety-related disorders, particularly during and after the menopausal transition. In these experiments, we tested the hypothesis that estrogen enhances the positive impact of exercise on stress responses by investigating the combined effects of exercise and estrogen on anxiety-like behaviors and stress hormone levels in female rats after an acute stressor. Ovariectomized female rats with or without estrogen were given access to running wheels for one or three days of voluntary running immediately after or two days prior to being subjected to restraint stress. We found that voluntary running was not effective at reducing anxiety-like behaviors, whether or not rats were subjected to restraint stress. In contrast, stress-induced elevations of stress hormone levels were attenuated by exercise experience in estrogen-treated rats, but were increased in rats without estrogen. These results suggest that voluntary exercise may be more effective at reducing stress hormone levels if estrogen is present. Additionally, exercise experience, or the distance run, may be important in reducing stress.

Topics: Analysis of Variance; Animals; Anxiety; Body Weight; Corticosterone; Estradiol; Estrogens; Female; Ovariectomy; Rats, Sprague-Dawley; Restraint, Physical; Running; Stress, Psychological; Time Factors; Volition

Selective estrogen receptor modulators (SERMs) are a class of therapeutic chemicals which present tissue-specific estrogen receptor modulating activity. Neonatal exposure to SERMs has been reported to adversely affect central nervous system development, however, mechanism and involvement of hypothalamic kisspeptin neurone in this impairment remains undetermined. To clarify this uncertainty, neonates from female Donryu rats were subcutaneously injected with raloxifene (RLX) at 0.1, 1, and 10mg/kg or tamoxifen (TMX) at 10mg/kg on postnatal day 0, and then hypothalamic KiSS1 mRNA expression and gonadotropin levels were investigated during young adulthood and estrous cycling was monitored until middle age. Treatment with RLX or TMX at 10mg/kg significantly depressed luteinizing hormone surge levels and KiSS1 mRNA expression in the anteroventral periventricular nucleus (AVPV), the control center of estrous cyclicity. The 10mg/kg TMX group also showed decreased levels of follicle-stimulating hormone and KiSS1 mRNA expression in the arcuate nucleus (ARC). Early cessation of normal estrous cycling was observed in the 10mg/kg RLX group, while the estrous cycle in the 10mg/kg TMX group had ceased by the start of the analysis. The same dose of tamoxifen or raloxifene had either weak-estrogenic or anti-estrogenic activity on the uterus, respectively; however, treatment in adulthood with both SERMs did not affect KiSS1 mRNA expression in either the AVPV or ARC in the present study. These results indicate that neonatal exposure to SERMs could disrupt neuroendocrine development and postnatal reproductive function through the alteration of kisspeptin neurons.

Topics: Age Factors; Animals; Animals, Newborn; Body Weight; Developmental Disabilities; Disease Models, Animal; Endocrine System Diseases; Estradiol; Estrous Cycle; Female; Hormones; Hypothalamus; Kisspeptins; Neurons; Ovariectomy; Pregnancy; Progesterone; Raloxifene Hydrochloride; Rats; Selective Estrogen Receptor Modulators; Tamoxifen

Short-term abstinence from food intake, planned or unplanned, is unavoidable in modern life, but negatively correlated with appetite control and obesity. This study investigated the role of estradiol in feeding and body weight (BW) reactions to short-span cessation of feeding. During acute 1-6-h re-feeding, 12-h food-deprived (FD), estradiol benzoate (EB)-implanted ovariectomized rats ate less food and gained less weight than FD animals implanted with oil (O). Full fed (FF)- and FD-EB consumed equal amounts of food over 24 h, but weight gain was greater in the latter; 24-h food intake and BW gain in FD-O exceeded FD-EB. Caudal fourth ventricular administration of the AMPK activator AICAR increased dorsal vagal complex AMPK activity in FD-EB and FD-O, but elicited dissimilar adjustments in hypothalamic metabolic neuropeptide transmitter expression, while respectively enhancing or reducing acute re-feeding in these animals and reversing FD-O weight gain. Drug-treated FD-EB and FD-O exhibited respective feeding and weight gain increases between 6-24 h. AICAR enhanced 24-h consumption in FD-EB vs. FF-EB, but cumulative intake and BW gain were greater in AICAR-treated FD-O vs. FD-EB. Results show that estradiol limits acute re-feeding after short-term feeding suspension, but augments acute re-feeding when energy depletion coincides with suspended feeding. This compound metabolic stress exerts steroid-dependent effects during later resumption of circadian-induced feeding, for example, increased consumption vs. weight gain in the presence vs. absence of estradiol. These studies provide novel evidence that estrogen mitigates acute and post-acute adverse effects of disrupted fuel acquisition on energy balance.

Topics: Aminoimidazole Carboxamide; Animals; Behavior, Animal; Body Weight; Estradiol; Estrogens; Feeding Behavior; Female; Food Deprivation; Hypoglycemic Agents; Ovariectomy; Rats; Rats, Sprague-Dawley; Ribonucleotides; Weight Gain

Progesterone receptor (PR) activation in the ventrolateral division of the hypothalamic ventromedial nucleus (VMNvl) is essential for promoting female sexual behavior. Estrogen receptor (ER) α, in contrast to ERβ, has been implicated in the induction of PRs. The simultaneous activation of ERα and ERβ, although not increasing the number of PR-immunoreactive neurons in the VMNvl, facilitates lordosis, which suggests that ERβ and/or the ERα-ERβ interaction might play a role in PR dynamics and/or PR expression by individual neurons. To address this question, we used western blot and immunohistochemical studies to determine the amounts and subcellular distributions of both PR isoforms in VMNvl neurons of ovariectomized rats injected with estradiol benzoate or with specific agonists of ERα and ERβ, alone or in association. The present data show that ERα activation does not change PR expression in individual neurons, but increases the number of PRs in the VMNvl, because it increases the number of neurons expressing PRs. Conversely, ERβ activation does not change the total number of PRs in the VMNvl, but increases the labeling intensity of the perikaryal cytoplasm, which suggests that it promotes the transport of PRs from neurites into cell bodies. In addition, the simultaneous activation of ERα and ERβ increases the expression of PRs by individual neurons and, consequently, increases the total number of PRs in the VMNvl. Our findings reveal that individual and simultaneous activation of ERα and ERβ have different effects on the levels and subcellular location of PRs in VMNvl neurons.

Topics: Animals; Body Weight; Cell Nucleus; Cytoplasm; Estradiol; Estrogen Receptor alpha; Estrogen Receptor beta; Female; Gene Expression Regulation; Hypothalamus; Immunohistochemistry; Lordosis; Microscopy, Confocal; Neurons; Rats; Rats, Wistar; Receptors, Progesterone; Uterus

Ghrelin is a peptidergic hormone known to be one of the main hormones involved in the regulation of energy balance. Here we evaluated ghrelin response to stress in rats after ovariectomy and during estradiol benzoate (EB) therapy and compared results of males and females, to know whether ghrelin is involved in disordered eating behaviors in response to stress, and for understanding differences between males and females in food intake and weight gain especially during stress. 96 adult rats were classified into; male, female, ovariectomized (Ovx), Ovx with EB. Half animals of each group were exposed to immobilization stress 20 min/day for 21 days. We found that chronic stress significantly augments serum ghrelin levels in both males and females, which is correlated with an increase in food intake and body weight. Females displayed significant higher ghrelin than males especially in response to stress, ovariectomy suppresses serum ghrelin in both unstressed and stressed females which is rescued by replacement with EB. EB replacement augments ghrelin response to stress in Ovx female, and reduces food intake and body weight. In conclusion, there is a clear sex difference in ghrelin secretion in response to stress caused by EB, since it amplifies ghrelin response to stress in females.

Topics: Animals; Body Weight; Eating; Estradiol; Estrogens; Feeding Behavior; Female; Ghrelin; Immobilization; Male; Ovariectomy; Rats; Sex Factors; Stress, Psychological

We aimed to investigate the effect of ghrelin antagonist (D-Lys3) GHRP-6 on the treatment of ovariectomy-induced obesity as compared to hormone replacement therapy with estradiol.. Twenty eight rats were divided into four groups: control sham operated (C), ovariectomized non-treated (OVX), ovariectomized+estradiol-treated (OVX+E) groups, and ovariectomized+ghrelin antagonist-treated group (OVX+GA). Rats were allowed free water and commercial standard diet ad libitum for 5 weeks after surgery. Body mass index (BMI) was determined at the beginning and the end of the experiment. Rats were sacrificed by decapitation and blood samples were collected for measurements of serum lipid profile, insulin, and glucose levels. Gastrocolic omental fat (GCOF) was removed and weighed.. Ovariectomy was accompanied with a significantly higher body weight, food intake, BMI, GCOF, serum total cholesterol (TC), low density lipoprotein-cholesterol (LDL-C), glucose, insulin, and homeostatic model assessment - insulin resistance (HOMA-IR), with a significant decrease in high density lipoprotein-cholesterol (HDL-C) and triglycerides (TGs) in comparison with C group. Estradiol reversed the ovariectomy-induced changes except that of TGs. Administration of ghrelin antagonist was effective in treating the ovariectomy-induced obesity as evidenced by normalization of body weight, food intake, BMI, and GCOF weight, serum levels of insulin, glucose, HOMA-IR, and HDL-C. The serum levels of TC, LDL-C and TGs were improved but did not reach the control values.. Although estradiol succeeded in the prevention of almost all ovariectomy-induced disturbances, it had a potential cardiovascular risk due to a marked increase in serum TGs. Ghrelin antagonist was effective in ameliorating ovariectomy-induced obesity, so it may be used as a promising treatment for postmenopausal obesity, irrespective of hormonal replacement.

Topics: Animals; Anti-Obesity Agents; Blood Glucose; Body Weight; Eating; Estradiol; Female; Ghrelin; Hormone Replacement Therapy; Insulin; Insulin Resistance; Lipids; Obesity; Oligopeptides; Ovariectomy; Rats

Polychlorinated biphenyls (PCBs) are industrial contaminants and known endocrine-disrupting chemicals. Previous work has shown that gestational exposure to PCBs cause changes in reproductive neuroendocrine processes. Here we extended work farther down the life spectrum and tested the hypothesis that early life exposure to Aroclor 1221 (A1221), a mixture of primarily estrogenic PCBs, results in sexually dimorphic aging-associated alterations to reproductive parameters in rats, and gene expression changes in hypothalamic nuclei that regulate reproductive function. Pregnant Sprague Dawley rats were injected on gestational days 16 and 18 with vehicle (dimethylsulfoxide), A1221 (1 mg/kg), or estradiol benzoate (50 μg/kg). Developmental parameters, estrous cyclicity (females), and timing of reproductive senescence were monitored in the offspring through 9 months of age. Expression of 48 genes was measured in 3 hypothalamic nuclei: the anteroventral periventricular nucleus (AVPV), arcuate nucleus (ARC), and median eminence (females only) by real-time RT-PCR. Serum LH, testosterone, and estradiol were assayed in the same animals. In males, A1221 had no effects; however, prenatal estradiol benzoate increased serum estradiol, gene expression in the AVPV (1 gene), and ARC (2 genes) compared with controls. In females, estrous cycles were longer in the A1221-exposed females throughout the life cycle. Gene expression was not affected in the AVPV, but significant changes were caused by A1221 in the ARC and median eminence as a function of cycling status. Bionetwork analysis demonstrated fundamental differences in physiology and gene expression between cycling and acyclic females independent of treatment. Thus, gestational exposure to biologically relevant levels of estrogenic endocrine-disrupting chemicals has sexually dimorphic effects, with an altered transition to reproductive aging in female rats but relatively little effect in males.

Topics: Aging; Animals; Arcuate Nucleus of Hypothalamus; Aroclors; Body Weight; Endocrine Disruptors; Environmental Pollutants; Estradiol; Estrous Cycle; Female; Gene Expression; Gestational Age; Hypothalamus; Luteinizing Hormone; Male; Median Eminence; Midline Thalamic Nuclei; Pregnancy; Prenatal Exposure Delayed Effects; Rats; Rats, Sprague-Dawley; Reproduction; Reverse Transcriptase Polymerase Chain Reaction; Sex Factors

The purpose of this study was to compare the effects of conjugated equine estrogens (CEE) and estradiol benzoate on the blood pressure and body weight of spontaneously hypertensive rats (SHRs) and the associated changes in several components of the natriuretic peptide system.. The blood pressure of randomly distributed female SHRs and Wistar rats was determined by tail plethysmography. The rats were ovariectomized and, after 3 weeks, injected daily for 4 days with estradiol benzoate (5 μg/100 g/d), CEE (50 μg/100 g/d), or vehicle (corn oil 0.1 mL/100 g/d). One day after the last injection, the rats were decapitated, and their blood was collected to measure atrial natriuretic peptide (ANP) and estradiol. The atria were removed to measure ANP levels using radioimmunoassay and to quantify ANP messenger RNA expression using real-time polymerase chain reaction. The kidneys and adipose tissue were removed to analyze the expression of natriuretic peptide clearance receptor messenger RNA.. A reduction in blood pressure was observed in estradiol-treated SHRs, but CEE treatment had no effect. Estradiol decreased the body weight and parametrial adipose tissue mass of SHRs. Estradiol-induced alterations in SHRs were accompanied by increased synthesis and release of ANP. CEE had no effect on body weight but increased the mesenteric adipose tissue mass of SHRs.. These results indicate that estradiol and CEE have different effects on the reduction in body weight and blood pressure. These results are correlated with changes in plasma ANP levels.

Topics: Adipose Tissue; Animals; Atrial Natriuretic Factor; Blood Pressure; Body Weight; Estradiol; Estrogens; Estrogens, Conjugated (USP); Female; Gene Expression; Heart Atria; Kidney; Mesentery; Ovariectomy; Rats; Rats, Inbred SHR; Rats, Wistar; Receptors, Atrial Natriuretic Factor; RNA, Messenger

The purpose of this study was to demonstrate that a barren parous Thoroughbred mare with lactation induced by hormonal treatment can be introduced to an orphan foal at the same farm and that the mare can become pregnant after the end of the hormonal treatment. An additional purpose was to investigate the changes in the plasma concentrations of prolactin, estradiol-17β, progesterone, follicle-stimulating hormone, and luteinizing hormone before, during, and after hormonal treatment. The difference in body weight between the adopted foal and the control foals, which were at the same farm and raised by their natural mothers, was 17 kg at 24 weeks old, when the foals were weaned. However, the adopted foal and the control foals had almost the same weight at 35 weeks old and later. The first ovulation after hormonal treatment was confirmed 10 days after the end of hormonal treatment and then the normal estrous cycle resumed. Furthermore, the changes in plasma progesterone, estradiol-17β, follicle-stimulating hormone, and luteinizing hormone showed regular patterns after the first ovulation. Conception was confirmed in the fifth ovulation. Meanwhile, another study demonstrated that conception was confirmed in the first ovulation after hormonal treatment. The present study is the first to demonstrate the hormonal profiles during and after induction of lactation in a Thoroughbred mare. This approach is useful for solving the economic and epidemic problems of introducing a nurse mare to an orphan foal.

Topics: Aging; Animals; Body Weight; Estradiol; Female; Horses; Insemination, Artificial; Lactation; Pregnancy; Prostaglandins; Sulpiride; Trenbolone Acetate

The reproductive performance of postpartum cows is affected by factors such as suckling and nutrition. We investigated the effect of a restricted suckling period on the superovulatory response and the fertility after flushing in postpartum Japanese Black cows. Forty-seven postpartum cows were used in this study. At 7 days postpartum, the cows were divided into 2 groups: (1) continuous access to calves from birth to weaning at 3 months postpartum (ad libitum suckling group; n=20); and (2) twice daily suckling to the calves penned adjacent to them (restricted suckling group; n=27). All cows were initiated a superstimulatory treatment with a controlled internal drug releasing device and follicle stimulating hormone at 40 days postpartum. Embryos were nonsurgically collected at 7 or 8 days after estrus. After uterine flushing, the cows were again used for reproduction. There were no significant differences between the ad libitum and restricted suckling groups in terms of the numbers of transferable (6.7 ± 5.4 versus 7.9 ± 7.0) and freezable embryos (5.5 ± 4.9 versus 6.2 ± 7.0). In contrast, the interval to the first estrus after flushing in the restricted suckling group was lower (P<0.05) than that in the ad libitum suckling group (8.9 ± 5.7 days versus 27.9 ± 24.2 days). These results suggest that restricted suckling in postpartum Japanese Black cows does not affect the superovulatory response and embryo quality; however, it improves their fertility after flushing.

Topics: Analysis of Variance; Animal Husbandry; Animals; Body Weight; Cattle; Delayed-Action Preparations; Estradiol; Female; Fertility; Follicle Stimulating Hormone; Japan; Lactation; Reproduction; Reproductive Techniques, Assisted; Superovulation; Time Factors

Gestational exposure to the estrogenic endocrine disruptor methoxychlor (MXC) disrupts the female reproductive system at the molecular, physiological, and behavioral levels in adulthood. The current study addressed whether perinatal exposure to endocrine disruptors re-programs expression of a suite of genes expressed in the hypothalamus that control reproductive function and related these molecular changes to premature reproductive aging. Fischer rats were exposed daily for 12 consecutive days to vehicle (dimethylsulfoxide), estradiol benzoate (EB) (1 mg/kg), and MXC (low dose, 20 μg/kg or high dose, 100 mg/kg), beginning on embryonic d 19 through postnatal d 7. The perinatally exposed females were aged to 16-17 months and monitored for reproductive senescence. After euthanasia, hypothalamic regions [preoptic area (POA) and medial basal hypothalamus] were dissected for real-time PCR of gene expression or pyrosequencing to assess DNA methylation of the Esr1 gene. Using a 48-gene PCR platform, two genes (Kiss1 and Esr1) were significantly different in the POA of endocrine-disrupting chemical-exposed rats compared with vehicle-exposed rats after Bonferroni correction. Fifteen POA genes were up-regulated by at least 50% in EB or high-dose MXC compared with vehicle. To understand the epigenetic basis of the increased Esr1 gene expression, we performed bisulfite conversion and pyrosequencing of the Esr1 promoter. EB-treated rats had significantly higher percentage of methylation at three CpG sites in the Esr1 promoter compared with control rats. Together with these molecular effects, perinatal MXC and EB altered estrous cyclicity and advanced reproductive senescence. Thus, early life exposure to endocrine disruptors has lifelong effects on neuroendocrine gene expression and DNA methylation, together with causing the advancement of reproductive senescence.

Topics: Animals; Animals, Newborn; Base Sequence; Body Weight; CpG Islands; DNA Methylation; Endocrine Disruptors; Estradiol; Estrogen Receptor alpha; Estrous Cycle; Female; Gene Expression Profiling; Gene Expression Regulation; Kisspeptins; Maternal-Fetal Exchange; Menopause, Premature; Methoxychlor; Molecular Sequence Data; Pregnancy; Preoptic Area; Progesterone; Promoter Regions, Genetic; Rats; Rats, Inbred F344; Regulatory Sequences, Nucleic Acid; Up-Regulation

Previously, pretreatment with estradiol benzoate (EB) was found to modulate the response of hypothalamic-pituitary-adrenal (HPA) axis and gene expression in several catecholaminergic neuronal locations in ovariectomized (OVX) rats exposed to single immobilization stress (IMO). Here, we investigated the role of estrogen receptor (ER) subtypes, using selective agonists for ERalpha (propyl pyrazole triol, PPT) or ERbeta (WAY-200070) in two major central noradrenergic systems and the HPA axis after exposure to single and repeated IMO. OVX female rats received 21 daily injections of either EB (25 mug/kg), PPT (10 mg/kg), WAY-200070 (10 mg/kg), or vehicle. Injections of EB and PPT, but not WAY-200070, elicited reduced body weight and increased uterine weight, showing their selectivity. Both EB and PPT increased corticosterone levels about two- to threefold, but prevented any further rise with either single or repeated IMO, indicating an ERalpha (ESR1)-, but not ERbeta (ESR2)-, mediated mechanism. In the locus coeruleus (LC), the rise in dopamine-beta-hydroxylase (Dbh) mRNA with both stress paradigms was abrogated in EB- or PPT-injected animals. However, WAY-200070 blocked the response of DBH mRNA to single IMO but not to repeated IMO. In the nucleus of the solitary tract (NTS), the rise in tyrosine hydroxylase and DBH mRNAs with both IMOs was absent, or greatly attenuated, in EB- or PPT-treated rats. In most cases, WAY-200070 inhibited the response to single IMO but not to repeated IMO. The results demonstrate that pretreatment with estradiol, or ER-selective agonists, modulates the stress-triggered induction of gene expression of norepinephrine biosynthetic enzymes in LC and NTS, with ER selectivity depending on duration of the stress.

Topics: Adrenal Cortex Hormones; Animals; Body Weight; Dopamine beta-Hydroxylase; Estradiol; Female; Locus Coeruleus; Ovariectomy; Oxazoles; Phenols; Pyrazoles; Rats; Rats, Sprague-Dawley; Receptors, Estrogen; Restraint, Physical; Solitary Nucleus; Stress, Physiological; Tyrosine 3-Monooxygenase

We evaluated the interplay among estrogen, leptin and thyroid function in the regulation of body mass in female rats. Adult female rats were divided into four groups: control (C, sham-operated), ovariectomized (OVX), ovariectomized treated with estradiol benzoate (Eb) 0.7 or 14microg/100gbw per day, during 21 days. OVX led to an increase in body mass, food intake and food efficiency (change in body mass as function of the amount of food ingested) which were normalized by the lower Eb dose, and decreased significantly when the higher dose was given. Serum leptin levels were increased more than two-fold in all ovariectomized groups. Serum T4 levels of the Eb treated OVX were significantly lower than in the controls. Serum T3 and TSH were unaffected by OVX or by Eb treatment. Uterine type 2 iodothyronine deiodinase (D2) activity changed in parallel with serum estradiol: decreased after OVX, returned to control levels after the lower E2 treatment, and increased significantly after the high Eb dosage. The hypothalamic D2 activity was reduced around 30% in all castrated groups, treated or not with estrogen, whereas in the brown adipose tissue the enzyme was not changed. Interestingly, although estrogen-treated OVX rats had lower body weight, serum leptin was high, suggesting that estrogen increases leptin secretion. Our results show that estradiol is necessary for the hypothalamic action of leptin, since the increase in leptin levels observed in all ovariectomized rats was associated with a decrease in food intake and food efficiency only in the rats treated with estrogen.

Topics: Animals; Body Weight; Eating; Estradiol; Female; Leptin; Ovariectomy; Rats; Rats, Wistar; Thyroid Function Tests; Thyroid Gland; Thyroxine

Estrogens affect body fluid balance, including sodium ingestion. Recent findings of a population of neurons in the hindbrain nucleus of the solitary tract (NTS) of rats that are activated during sodium need suggest a possible central substrate for this effect of estrogens. We used immunohistochemistry to label neurons in the NTS that express 11-β-hydroxysteroid dehydrogenase type 2 (HSD2), an enzyme that promotes aldosterone binding, in male rats, and in ovariectomized (OVX) rats given estradiol benzoate (EB) or oil vehicle (OIL). During baseline conditions, the number of HSD2 immunoreactive neurons in the NTS immediately rostral to the area postrema was greater in EB-treated OVX rats compared to those in OIL-treated OVX and male rats. A small number of HSD2 immunoreactive neurons was also labeled for dopamine-β-hydroxylase (DBH), an enzyme involved in norepinephrine biosynthesis. Double-labeled neurons in the NTS were located primarily in the more lateral portion of the HSD2 population, at the level of the area postrema in all three groups, with no sex or estrogen-mediated differences in the number of double-labeled neurons. These results suggest that two subpopulations of HSD2 neurons are present in the NTS. One subpopulation, which does not colocalize with DBH and is increased during conditions of elevated estradiol, may contribute to the effects of estrogens on sodium ingestion. The role of the other, smaller subpopulation, which colocalizes with DBH and is not affected by estradiol, remains to be determined, but one possibility is that these latter neurons are part of a larger network of catecholaminergic input to neuroendocrine neurons in the hypothalamus.

Topics: 11-beta-Hydroxysteroid Dehydrogenase Type 2; Animals; Body Weight; Cell Count; Contraceptive Agents; Dopamine beta-Hydroxylase; Estradiol; Female; Neurons; Organ Size; Ovariectomy; Rats; Rats, Sprague-Dawley; Solitary Nucleus; Ureter

Demasculinizing action of embryonic estrogen on crowing behavior in male Japanese quails was examined. Eggs were treated with either 20 microg of estradiol benzoate (EB) or vehicle on the 10th day of incubation. Chicks hatched from both groups of eggs were injected daily with either testosterone propionate (TP; 10 microg/g b.w.), 5alpha-dihydrotestosterone (DHT, a non-aromatizable androgen; 10 microg/g b.w.), or vehicle from 11 to 50 days after hatching, and during this period their calling behaviors were observed. Irrespective of embryonic treatments, all birds received posthatching treatment with either TP or DHT, but not with vehicle, emitted crows in place of distress calls in a stress (non-sexual) context of being isolated in a recording chamber. The posthatching TP, but not posthatching DHT, induced crowing in a sexual context (crowing in their home-cages) from much earlier age than posthatching vehicle in the birds received control embryonic treatment with vehicle. The same TP treatment, however, completely eliminated the crowing in a sexual context in the birds received EB during their embryonic life. In the birds treated with either posthatching DHT or posthatching vehicle, the crowing in a sexual context was only slightly decreased by embryonic EB treatment. These data suggest that posthatching estrogen, derived from testosterone aromatization, enhances the demasculinizing action of embryonic estrogen, and thus strongly reduces the sexual motivation for crowing behavior. This demasculinizing action, however, would not influence vocal control system which generates acoustic pattern of crowing in the presence of androgens allowing the birds to crow in a non-sexual context.

Topics: Analysis of Variance; Animals; Body Weight; Cloaca; Coturnix; Dihydrotestosterone; Estradiol; Female; Male; Organ Size; Sexual Behavior, Animal; Stress, Psychological; Testis; Testosterone Propionate; Vocalization, Animal

Previous research has shown that estradiol increases the anorexia associated with serotonin (5-HT) neurotransmission. To examine further the putative relationship between estradiol and 5-HT, we investigated whether estradiol increases the expression of Pet-1 and the 5-HT transporter (5-HTT), two genes implicated in the development and regulation of the 5-HT system. Ovariectomized (OVX) rats (n=5-6/group) were treated with 0, 2, or 10 microg estradiol benzoate (EB) in sesame oil on 2 consecutive days. Food intake and body weight were recorded 2 days later when EB-treated rats typically display signs of behavioral estrus (e.g., reduced feeding). Following the collection of behavioral data, rats were perfused, brains were removed, and coronal sections were cut through the midbrain raphe nuclei. Pet-1 and 5-HTT mRNA levels were quantified throughout the dorsal and median raphe nuclei (DRN and MRN) by conducting in situ hybridization on free-floating tissue sections using (35)S-labeled cDNA probes. As expected, EB treatment decreased food intake and body weight on the day that modeled estrus. At this same time, EB treatment increased Pet-1 and 5-HTT mRNA levels within the DRN and MRN. We conclude that a physiologically relevant regimen of estradiol treatment in OVX rats increases Pet-1 and 5-HTT mRNA levels in the midbrain raphe nuclei at a time when the anorexigenic effect of estradiol is apparent. Further studies are required to determine whether the increased expression of Pet-1 and 5-HTT mRNA plays a causal role in the anorexigenic effect of estradiol.

Topics: Analysis of Variance; Animals; Appetite Depressants; Body Weight; Eating; Estradiol; Estrus; Female; Gene Expression; In Situ Hybridization; Ovariectomy; Raphe Nuclei; Rats; Rats, Long-Evans; RNA, Messenger; Serotonin Plasma Membrane Transport Proteins; Transcription Factors

Previously, a hormone-simulated pregnancy (HSP), and the subsequent 'postpartum' withdrawal in estradiol has been shown to precipitate depressive-like behaviours in the forced swim test in female rats. In this study, we used the HSP and 'postpartum' withdrawal to investigate the impact on sucrose consumption, a model of anhedonia. Rats were assigned to "postpartum", "postpartum"+EB (estradiol benzoate), "postpartum"+IMI (imipramine; a tricyclic antidepressant), "postpartum"+DPN (diarylpropionitrile; an ERbeta agonist), or ovariectomized (OVX) controls and OVX+IMI treatments. All "postpartum" groups received daily hormone injections (estradiol and progesterone) over 23 days to simulate pregnancy, while IMI groups also received daily injections of imipramine. After Day 23, "postpartum" rats were withdrawn from the hormone regimen (mimicking the postpartum decrease in gonadal hormones), and then received daily injections of compounds indicated (DPN, EB, IMI). Rats were tested for consumption of, and preference for, sucrose weekly at baseline, during 'pregnancy' and on 'Postpartum' Days 2-3. During the 'postpartum' period rats in the "postpartum" group had lower sucrose consumption and preference compared to during late-'pregnancy', but no decrease in 'postpartum' consumption or preference was seen in any other groups except "postpartum"+IMI and a decrease in sucrose preference only in the postpartum+EB group from mid-'pregnancy' to 'postpartum'. The OVX +IMI group had decreased sucrose consumption relative to OVX controls, suggesting a negative effect of imipramine on sucrose consumption. Together, these results suggest an important, though complex, role for gonadal hormones in the behavioral changes accompanying this model of depression.

Topics: Analysis of Variance; Animals; Antidepressive Agents; Body Weight; Depression, Postpartum; Disease Models, Animal; Drug Administration Routes; Drug Administration Schedule; Estradiol; Female; Food Preferences; Imipramine; Nitriles; Ovariectomy; Postpartum Period; Pregnancy; Propionates; Rats; Rats, Long-Evans; Substance Withdrawal Syndrome; Sucrose; Sweetening Agents; Time Factors

Binge eating is more common in females than in males. This study investigated the effects of ovarian hormones on binge-eating behavior in a diet-related rat model. Six groups of ovariectomized Sprague-Dawley rats were used (n=13/group). All rats had continuous access to chow and water throughout the study. One half of the rats were injected every fourth day with estradiol benzoate (2 microg/100 microl sesame oil) and progesterone (500 microg/100 microl sesame oil); the other half received only the sesame oil vehicle. Three feeding protocols were tested in each hormone injection condition: (1) chow only: no additional dietary fat access; (2) low-restriction: 1-h fat access every day; (3) high-restriction: 1-h fat access on Monday, Wednesday, and Friday. As previously reported in intact male and female rats, the high-restriction groups exhibited binge-like increases in 1-h energy intake during fat access. The major new finding of this study is that 1-h energy intake was tonically, but not cyclically, reduced in the hormone-treated high-restriction (binge) rats. Specifically, both low- and high-restriction hormone-treated rats consumed significantly less energy than did the oil-treated rats during the 1-h fat period (p<0.0001) and overall (p<0.0001), indicating a tonic inhibition of eating. However, food intake during the 1-h fat access period was also cyclically reduced in the hormone-treated low-restriction rats, but not in the hormone-treated high-restriction rats. These results indicate that the normal cyclic inhibitory influence of ovarian hormones on eating, but not their normal tonic inhibitory influence, is disrupted by conditions leading to binge-type eating.

Topics: Analysis of Variance; Animals; Behavior, Animal; Body Composition; Body Weight; Bulimia; Dietary Fats; Disease Models, Animal; Eating; Energy Intake; Estradiol; Female; Ovariectomy; Progesterone; Rats; Rats, Sprague-Dawley; Time Factors

During the reproductive cycle, fluctuations in circulating estrogens affect multiple homeostatic systems controlled by hypothalamic neurons. Two of these neuronal populations are arcuate proopiomelanocortin and neuropeptide Y neurons, which control energy homeostasis and feeding. Estradiol modulates these neurons either through the classical estrogen receptors (ERs) to control gene transcription or through a G protein-coupled receptor (mER) activating multiple signaling pathways. To differentiate between these two divergent ER-mediated mechanisms and their effects on homeostasis, female guinea pigs were ovariectomized and treated systemically with vehicle, estradiol benzoate (EB) or STX, a selective mER agonist, for 4 wk, starting 7 d after ovariectomy. Individual body weights were measured after each injection day for 28 d, at which time the animals were euthanized, and the arcuate nucleus was microdissected. As predicted, the body weight gain was significantly lower for EB-treated females after d 5 and for STX-treated females after d 12 compared with vehicle-treated females. Total arcuate RNA was extracted from all groups, but only the vehicle and STX-treated samples were prepared for gene microarray analysis using a custom guinea pig gene microarray. In the arcuate nucleus, 241 identified genes were significantly regulated by STX, several of which were confirmed by quantitative real-time PCR and compared with EB-treated groups. The lower weight gain of EB-treated and STX-treated females suggests that estradiol controls energy homeostasis through both ERalpha and mER-mediated mechanisms. Genes regulated by STX indicate that not only does it control neuronal excitability but also alters gene transcription via signal transduction cascades initiated from mER activation.

Topics: Animals; Arcuate Nucleus of Hypothalamus; Body Weight; Energy Metabolism; Estradiol; Estrogens; Estrone; Female; Gene Expression; Gene Expression Profiling; Guinea Pigs; Homeostasis; Models, Biological; Oligonucleotide Array Sequence Analysis; Ovariectomy; Receptors, Estrogen; Reverse Transcriptase Polymerase Chain Reaction; Signal Transduction

Ingestion of propranolol at 10 and 15 mg kg(-1) body weight for 35 days by adult male mice was investigated for its effects on fertility. Body weight and absolute and relative testes weights were reduced and the average weights of epididymis, ventral prostate and seminal vesicle decreased significantly. A significant decline of spermatogenesis in testes due to a decrease in the number of primary, secondary spermatocytes and spermatids in the treatment group 2 (15 mg kg(-1)) is attributed to a significant decrease in testosterone, LH and FSH. Sperm motility and density were also significantly decreased in the cauda epididymis and in the testes of group 2 treated male mice. In addition, the treatment markedly increased the number of fetal resorptions in female mice impregnated by the group 2 males, thereby reducing their fertility.

Topics: Animals; Body Weight; Epididymis; Estradiol; Female; Fertility; Male; Mice; Organ Size; Pregnancy; Propranolol; Prostate; Reproduction; Seminal Vesicles

The specific roles of estrogen receptor (ER) subtypes alpha and beta in mediating estrogen's influences on lupus autoimmunity are unknown. Herein we found that ovariectomized NZB/NZW F1 mice treated with propyl pyrazole triol (ERalpha-selective agonist) had significantly shorter survival, earlier development of albuminuria, higher serum concentrations of total IgG and prolactin, increased serum levels of anti-DNA IgG3, IgG2a and IgG2b and decreased anti-DNA IgG1 level compared to vehicle controls. In contrast, diarylpropionitrile (ERbeta-selective agonist) administration significantly decreased serum anti-DNA IgG2b level but did not significantly affect serum levels of other anti-DNA IgG subclasses, serum total IgG or prolactin concentration, mortality or the occurrence of albuminuria. These findings suggest that ERalpha activation plays the predominant and immunostimulatory role in estrogen-mediated modulation of lupus while ERbeta activation appears to have a slightly immunosuppressive effect on this disease. ERalpha activation coincidentally increased serum prolactin concentrations and may accelerate lupus disease activity also through this mechanism.

Topics: Albuminuria; Animals; Antibodies, Antinuclear; Blood Urea Nitrogen; Body Weight; Disease Models, Animal; Estradiol; Estrogen Receptor alpha; Estrogen Receptor beta; Female; Immune System; Immunoglobulin G; Immunologic Factors; Lupus Erythematosus, Systemic; Mice; Mice, Inbred NZB; Nitriles; Ovariectomy; Phenols; Prolactin; Propionates; Pyrazoles; Receptors, Estrogen; Survival Analysis

This study examined the influence of oestrogen on cardiovascular responses to hypotension produced by administration of isoproterenol (Isop) and on neural activation in hindbrain nuclei mediating these responses. We first measured mean arterial pressure (MAP) and heart rate (HR) after administration of isoproterenol, a beta-adrenergic agonist that increases circulating levels of AngII, in ovariectomized (OVX) rats treated with oestradiol benzoate (EB). We then evaluated EB effects on Isop-induced Fos immunoreactivity (Fos-IR) in the hindbrain baroreflex circuit. To control for weight loss associated with oestrogen replacement in OVX rats, we food restricted a separate group of OVX rats and evaluated Isop-induced changes in MAP, HR and Fos-IR. The depressor response to Isop was significantly attenuated by EB, which also produced a disproportionate increase in HR. These effects were not secondary to loss of body weight after EB treatment, because cardiovascular responses to Isop in food restricted rats were similar to those in OVX rats treated with the oil vehicle. Isop significantly increased Fos-IR in the nucleus of the solitary tract (NTS), area postrema (AP), rostral ventrolateral medulla (RVLM), and lateral parabrachial nucleus (lPBN); however, EB significantly attenuated the increase in the AP and in the lPBN. Again, these effects were not secondary to body weight loss, because food restricted rats had the same pattern of Fos-IR as did rats treated with the oil vehicle. These results suggest that EB modifies cardiovascular responses to Isop, possibly by decreasing activation of the AP and lPBN.

Topics: Adrenergic beta-Agonists; Animals; Area Postrema; Baroreflex; Blood Pressure; Body Weight; Estradiol; Estrogen Replacement Therapy; Female; Heart Rate; Isoproterenol; Medulla Oblongata; Neurons; Ovariectomy; Proto-Oncogene Proteins c-fos; Rats; Rats, Sprague-Dawley; Rhombencephalon; Solitary Nucleus

The avian neurohypophysial hormone arginine vasotocin (AVT) is an important regulatory hormone involved in many physiological processes including fluid balance, blood pressure regulation, stress responses and reproductive events including oviposition. The mechanisms by which AVT stimulates myometrial contraction during oviposition are not well established in birds. In the present study, immunohistochemistry and in situ hybridization were used to localize AVT and the oxytocin-like VT3 receptor in the shell gland of Japanese quail (Coturnix coturnix japonica). Using an AVT-specific antibody, immunoreactive AVT (ir-AVT) was observed in the myometrium of both photosensitive and photorefractory birds. Similarly, VT3 receptor gene transcripts were detected in the myometrial layer of the shell gland of both photosensitive and photorefractory birds. Body mass, shell gland mass and length of mucosal folds of the shell gland of photosensitive birds was higher compared to that of photorefractory birds. Treatment of photorefractory birds with estrogen increased shell gland activity (mass and length of mucosal folds) and levels of both AVT and VT3 receptor mRNA, whereas treatment of photosensitive birds with the estrogen antagonist tamoxifen decreased shell gland activity and levels of both AVT and VT3 receptor mRNA. Our results suggest that shell gland contractility in response to AVT may be regulated during the reproductive cycle of the Japanese quail and that, in part, this regulation is estrogen-dependent.

Topics: Animals; Body Weight; Coturnix; Endometrium; Estradiol; Estrogen Antagonists; Female; Myometrium; Organ Size; Oviposition; Photoperiod; Receptors, Vasopressin; RNA, Messenger; Tamoxifen; Time Factors; Uterine Contraction; Uterus; Vasotocin

D-003 is a mixture of long-chain fatty acids purified from sugarcane wax that inhibits both cholesterol synthesis prior to mevalonate formation, and lipid peroxidation. D-003 has been shown to prevent bone loss and bone resorption in ovariectomized rats, and significantly improves bone resorption markers in postmenopausal women with reduced bone mineral density. As hormone-replacement therapy, D-003 displays cholesterol-lowering and anti-resorptive effects. We have studied its potential oestrogenic activity in-vivo using the uterotrophic assay. Rats were randomly distributed into five groups: a sham-operated group and four groups of ovariectomized rats, one treated with vehicle, one with D-003 (50 mg kg(-1)), one with oestradiol benzoate (30 microg kg(-1)) and one with D-003 (50 mg kg(-1)) plus oestradiol benzoate (30 microg kg(-1)). Treatments were administered for 14 days. Ovariectomy decreased the values of relative uterus weight, epithelium cell height and endometrial thickness compared with sham-operated rats, and these effects were all significantly reduced with oestradiol benzoate, but not with D-003. Concurrent administration of D-003 and oestradiol benzoate had statistically similar effects on all variables as oestradiol benzoate alone. In conclusions, D-003 orally given at 50 mg kg(-1), a dose that prevents bone loss and bone resorption in ovariectomized rats, did not display oestrogenic/anti-oestrogenic activity in-vivo, as assessed in the uterotrophic assay.

Topics: Administration, Oral; Animals; Body Weight; Endometrium; Epithelial Cells; Estradiol; Fatty Acids; Female; Organ Size; Ovariectomy; Random Allocation; Rats; Rats, Sprague-Dawley; Uterus

In male Japanese quail, crowing behavior is considered to be strictly androgen-dependent. It was previously shown that in chicks, treatment with either testosterone or 5alpha-dihydrotestosterone (5alpha-DHT; a non-aromatizable androgen) induced crowing with motivation for distress calling in acutely isolated conditions. Many studies, however, have shown that the potencies of testosterone and 5alpha-DHT in activating crowing in castrated males are different. To clarify the effects of androgenic and estrogenic actions on the production of crows and distress calls, we injected quail daily from 11 to 42 days after hatching (Day 11 to 42) with testosterone propionate (TP), 5alpha-DHT, estradiol benzoate (EB) or vehicle and examined their calling behaviors both in a recording chamber (acutely isolated conditions) and in their home-cages (well-acclimated conditions). Both TP- and 5alpha-DHT-treated birds began to crow by Day 13 when isolated in the recording chamber. The TP-treated birds, however, crowed less frequently than 5alpha-DHT-treated ones. This, combined with the observations that distress calling was strongly inhibited in EB-treated birds, suggests that estrogen converted from testosterone may inhibit the motivation for distress calling. On the other hand, after chronic treatment of TP, but not of 5alpha-DHT, birds began to crow intensely in their home-cages earlier than vehicle treated controls, suggesting that estrogen is needed to initiate crowing behavior in sexually active males. Taken together, it is suggested that estrogenic actions affect the motivation underlying vocal behaviors, while the androgenic action is indispensable in generating crowing.

Topics: Aggression; Aging; Androgens; Animals; Body Weight; Cloaca; Coturnix; Dihydrotestosterone; Estradiol; Estrogens; Female; Male; Organ Size; Sexual Behavior, Animal; Sexual Maturation; Testis; Testosterone Propionate; Vocalization, Animal

With the aim of establishing a sensitive model for the detection of weak effects of endocrine disrupting chemicals on thyroid carcinogenesis, thyrotrophic and tumor-promoting influences of beta-estradiol-3-benzoate (EB) in combination with representative antithyroidal agents (goitrogens), sulfadimethoxine (SDM), propylthiouracil (PTU), potassium perchlorate (PPC), iopanoic acid (IOP) or an iodine-deficient diet were evaluated in a short-term (7-day) experiment without N-bis(2-hydroxypropyl)nitrosamine (DHPN) initiation and a long-term (30-week) experiment with DHPN initiation in ovariectomized F344 rats. In the short-term experiment, the most remarkable thyrotrophic effects were found in the PTU-treated group, followed by the SDM and PPC cases. EB treatment alone caused slight increases in thyroidal weights but no apparent morphological changes. Concomitant treatment with EB and antithyroidal agents enhanced the changes in thyroid weights, histopathological findings and/or serum thyroid hormone levels in the SDM (30 and 100 p.p.m), PTU (5 and 30 p.p.m) and PPC (100 p.p.m), IOP (30 and 100 mg/kg) or iodine-deficient diet groups. In the long-term experiment after DHPN initiation, EB alone slightly increased small numbers of animals with follicular hyperplasias, adenomas and adenocarcinomas. Simultaneous treatment with antithyroidal chemicals was associated with an increase in the incidences of focal hyperplasias, adenomas and/or adenocarcinomas. The enhancement was most remarkable with PTU (5 p.p.m), followed by PTU (2 p.p.m), SDM (100 p.p.m) and PPC (100 p.p.m). The results showed that EB has only a marginal promoting effect on DHPN-induced rat thyroid carcinogenesis and that antithyroidal chemicals, particularly PTU, are effective as co-promoting agents.

Topics: Animals; Antithyroid Agents; Body Weight; Carcinogenicity Tests; Cell Transformation, Neoplastic; Estradiol; Estrogens; Female; Models, Animal; Molecular Structure; Organ Size; Ovariectomy; Proliferating Cell Nuclear Antigen; Rats; Rats, Inbred F344; Thyroid Neoplasms; Time Factors

The aim of this study was to evaluate, by morphologic techniques, the effects of sex steroid deficiency on mandible bone remodeling of female rats, in groups of different experimental periods and to compare the results with 90-day orquiectomized males. Female and male Wistar rats, 3 months old, were divided into experimental groups and at the end of each experimental period were killed, and mandibles were extracted. The left mandibles were prepared with rote technique bone and examined by a light microscope. Morphological analyses of the mandibles demonstrated resorption signals in the alveolar bone, after 30 days in ovariectomized females, but it was more intense 90 days after castration. The orquiectomized group exhibited some signals of resorption similar to the ovariectomized group of 60 days. Morphometric analysis of alveolar bone thickness in females after 60 days was in agreement with morphological results. However, the analysis of periodontal ligament thickness did not show any significant difference. There were variations in sexual hormone deficiency in the mandibles of males and females and they seemed to be more precocious in ovariectomized than in orquiectomized rats. It is important for a health professional to have knowledge about bone metabolism to improve the quality of life of postmenopaused and old people.

Topics: Alveolar Bone Loss; Alveolar Process; Animals; Body Weight; Bone Remodeling; Bone Resorption; Cephalometry; Collagen; Dental Cementum; Estradiol; Estrogen Replacement Therapy; Estrogens; Female; Image Processing, Computer-Assisted; Male; Mandible; Orchiectomy; Ovariectomy; Periodontal Ligament; Rats; Rats, Wistar; Testosterone; Time Factors

Epidemiological data reveal that the incidence of liver cancer is markedly higher in men than women. To clarify the mechanism responsible for the induction of higher incidence of liver tumors in male animals, we investigated the modifying effect of sex hormones in diethylnitrosamine (DEN)-induced rat hepatocarcinogenesis. F344 male rats (n=120) were divided into two experiments, experiment I (Exp I) and experiment II (Exp II). In each experiment, 60 rats were randomly allocated into four groups. The mini-osmotic pumps containing doses of 47.5 mg (Exp I) or 23.75 mg (Exp II) of DEN were inserted into the abdominal cavity of each animal to initiate liver carcinogenesis. Animals in group 2 were castrated one week prior to DEN treatment, and animals in groups 3 and 4 were treated with 1 or 10 microg of estradiol-3-benzoate (EB), respectively, one week prior to DEN treatment. Animals in group 1 were treated with DEN alone and sham-operated at the same time. All animals were sacrificed 26 weeks after DEN treatment. In Exp I, liver tumor incidence of group 3 decreased significantly compared with that of group 1 (p<0.05), and tumor multiplicities of groups 2, 3 and 4 were decreased significantly compared to that of group 1 (p<0.01). In Exp II, tumor incidence of group 3 was significantly different (p<0.05) when compared to that of group 1. Immunohistochemical expression of ERalpha was shown in normal appearing cells, but not in tumor cells. Western blot analysis confirmed that ERalpha expression was higher in normal liver tissue compared to tumor tissues. Taken together, we conclude that castration or EB treatment has an inhibitory effect in DEN-induced hepatocarcinogenesis in F344 rats. The reason for ERalpha loss in tumor cells should be further elucidated.

Topics: Animals; Blotting, Western; Body Weight; Diethylnitrosamine; Estradiol; Estrogen Receptor alpha; Immunohistochemistry; Liver; Liver Neoplasms, Experimental; Male; Orchiectomy; Organ Size; Prostate; Random Allocation; Rats; Rats, Inbred F344; Testosterone

Sex differences in the ingestion of food and concentrated NaCl solutions by rats have been investigated for more than a quarter of a century, though the underlying mechanism(s) and the role of reproductive hormones remain the subject of debate. We hypothesized that sex differences in the ingestion of sucrose and NaCl solutions are attributable, in part, to sex differences in taste responses/taste perception. We employed short-access, 10-s tests along with 18-h, two-bottle preference tests to examine sex differences in sensitivity to and ingestion of sucrose and NaCl solutions. To evaluate the role of estrogen, we ovariectomized (OVX) female rats and then used an estrogen-replacement schedule that mimics the pattern of fluctuation of estrogen levels in intact female rats. We observed striking sex differences in the rate of licking NaCl mixed in a dilute sucrose solution. Compared to males, OVX rats with or without estrogen licked at higher rates to more concentrated NaCl solutions, suggesting that female rats are less sensitive to concentrated NaCl solutions. Although less pronounced, we also observed sex differences in the rate of licking to sucrose, particularly at lower concentrations. Compared to males, OVX rats with or without estrogen licked less, suggesting that female rats are less sensitive to lower concentrations of sucrose. Estrogen appeared to play, at most, a small role in mediating taste responses to specific concentrations of sucrose in these testing procedures. Nonetheless, sex differences in taste responses were clear, and it seems likely that such differences underlie, in part, observed differences in ingestion.

Topics: Animals; Body Weight; Eating; Estradiol; Female; Food Preferences; Male; Ovariectomy; Perception; Rats; Sex Factors; Sodium Chloride, Dietary; Sucrose; Taste

Of the various environmental factors influencing reproduction, food availability plays a particularly significant role, and an insufficient supply of oxidizable metabolic fuels inhibits reproduction in female mammals. When ovariectomized, steroid-primed hamsters are food deprived for 48 h, estrous behavior is suppressed. However, the specific neuroendocrine alterations that mediate the suppression of estrous behavior are unknown. Several conditions that inhibit female sexual behavior are thought to be associated with altered neuropeptide Y (NPY) activity in the brain. Intracerebroventricular (ICV) infusion of NPY inhibits estrous behavior in ovariectomized steroid-primed rats and hamsters. Furthermore, food-deprived rats have an increase in NPY mRNA in the arcuate nucleus (ARC) of the hypothalamus. Unlike rats, studies in Syrian hamsters have failed to detect any alterations in ARC NPY mRNA following food deprivation. Here we show that ARC NPY immunoreactivity and mRNA is increased in food-deprived hamsters but not in hamsters given other metabolic challenges that inhibit estrous behavior. These findings support the hypothesis that NPY contribute to, but not be critical for, the nutritional inhibition of sexual receptivity.

Topics: Animals; Antimetabolites; Arcuate Nucleus of Hypothalamus; Behavior, Animal; Body Weight; Cell Count; Cold Temperature; Cricetinae; Deoxyglucose; Eating; Epoxy Compounds; Estradiol; Estrus; Female; Food Deprivation; Hypoglycemic Agents; Immunohistochemistry; In Situ Hybridization; Mesocricetus; Neurons; Neuropeptide Y; Ovariectomy; Posture; Progesterone; Propionates; RNA, Messenger; Sexual Behavior, Animal

The prolonged modulatory effects of beta-estradiol 3-benzoate (EB), a synthetic estrogenic compound, were investigated in a rat two-stage thyroid tumorigenesis model. One week after a single subcutaneous (s.c.) injection of N-bis(2-hydroxypropyl)nitrosamine, gonadectomized F344 rats of both sexes were s.c. implanted with fused pellets containing EB for 32 weeks. Doses of EB at 0, 0.004, 0.02 and 0.1mg were achieved by varying the ratio of EB to cholesterol in the pellet. Major organs including the thyroid, pituitary, liver, kidneys, uterus and brain were weighed and histopathological observation was performed. Serum was assayed for triiodothyronine (T(3)), thyroxine (T(4)) and thyroid-stimulating hormone (TSH). Thyroid weights were increased by the EB pellet implantation in a dose-dependent manner and significantly (P<0.05) elevated in the 0.1mg EB male group and in the 0.02 and 0.1mg EB female groups. The EB treatments dose-dependently suppressed serum T(4) levels and inversely elevated serum TSH levels in both sexes but without statistical significance in females. Histopathologically, EB increased the occurrence of thyroid proliferative lesions in males and showed a tendency for increase in females. Interestingly, the effect of EB was more intensive in males than in females, even the lowest dose inducing a follicular carcinoma in a male. These results, thus indicate the possible contribution of prolonged EB stimulation at lower doses to thyroid tumorigenesis without additional promotive condition.

Topics: Animals; Body Weight; Carcinogens; Cholesterol; Dose-Response Relationship, Drug; Estradiol; Estrogens; Female; Male; Nitrosamines; Organ Size; Rats; Rats, Inbred F344; Thyroid Neoplasms; Thyrotropin; Thyroxine; Triiodothyronine

Estrogen produces both beneficial and adverse effects on cardiovascular health via mechanisms that remain unclear. Stroke-prone spontaneously hypertensive rats (SHRSP) maintained on Stroke-Prone Rodent Diet and 1% NaCl drinking water (starting at 8 wk of age) rapidly develop stroke and malignant nephrosclerosis that can be prevented, despite continued hypertension, by drugs targeting angiotensin II and aldosterone actions. This study evaluated estrogen's effects in the SHRSP model. Female SHRSP that were sham operated (SHAM), ovariectomized (OVX) at 4 wk of age, or OVX and treated with estradiol benzoate (E2,30 microg x kg-1 x wk-1) were studied. In a survival protocol, OVX rats lived significantly longer (15.1 +/- 0.3 wk) compared with SHAM (13.6 +/- 0.2 wk) or OVX+E2 rats (12.4 +/- 0.2 wk). In a protocol in which animals were matched for age, at 11.5 wk, terminal systolic blood pressure and urine protein excretion were elevated in SHAM and OVX+E2 rats compared with OVX rats; blood urea nitrogen, renal microvascular and glomerular lesions, and plasma renin concentration were elevated in OVX+E2 relative to SHAM or OVX rats. In a survival protocol using intact female SHRSP, treatment with an antiestrogen (tamoxifen, 7 mg.kg-1.wk-1) prolonged survival by >2 wk compared with controls (P < 0.01). The data indicate that estrogen promotes microangiopathy in the kidney and stroke in saline-drinking SHRSP.

Topics: Angiotensin I; Animals; Blood Pressure; Body Weight; Capillaries; Estradiol; Estrogen Antagonists; Estrogen Replacement Therapy; Estrogens; Female; Kidney; Neovascularization, Pathologic; Organ Size; Ovariectomy; Rats; Rats, Inbred SHR; Receptors, Estrogen; Renin; Sodium Chloride; Stimulation, Chemical; Stroke; Survival Analysis; Tamoxifen

Tamoxifen, a nonsteroidal antiestrogen, is used widely in the treatment of breast cancer and is undergoing evaluation as a chemopreventive agent. In this study, we investigated several long-term effects of tamoxifen in intact adult female rats following acute treatment at various dosages. The effects of tamoxifen on somatic growth, growth hormone (GH) levels, thyroid hormone levels, and on hepatic cytochrome P450 (P450) expression were compared with those of fulvestrant (ICI 182,780), 17beta-estradiol-3-benzoate, and 4-hydroxytamoxifen under the same experimental conditions. Each compound was injected s.c. for two consecutive days, and rats were killed 37 days after treatment. Tamoxifen decreased body weight and serum triiodothyronine (T3) levels at dosages ranging from 0.5 to 200 mg/kg. Ovary weight, uterus weight, peak plasma GH concentration, and hepatic CYP2A1 content were decreased 37 days after treatment with tamoxifen at a dosage of 20 mg/kg, but expression of other P450 enzymes was not affected. However, tamoxifen and 4-hydroxytamoxifen could not be detected in plasma by high performance liquid chromatography analysis at this time, which suggests that the effects of tamoxifen were mediated indirectly. 4-Hydroxytamoxifen exhibited effects similar to those of tamoxifen, indicating that this metabolite contributes to the in vivo activity of tamoxifen. Estradiol benzoate decreased CYP2A1 and increased CYP3A hepatic levels, but had no effect on serum T3 concentration. In contrast, treatment with ICI 182,780 had little or no effect on the endpoints measured. In summary, 2-day tamoxifen treatment of intact adult female rats resulted in persistent suppression of somatic growth, serum T3 levels, and hepatic CYP2A1 expression.

Topics: Animals; Aryl Hydrocarbon Hydroxylases; Body Weight; Cytochrome P-450 Enzyme System; Dose-Response Relationship, Drug; Estradiol; Female; Gene Expression Regulation, Enzymologic; Liver; Organ Size; Ovary; Rats; Rats, Long-Evans; Steroid Hydroxylases; Tamoxifen; Testosterone; Thyroxine; Time Factors; Triiodothyronine; Uterus

Modifying effects of beta-estradiol 3-benzoate (EB) and methoxychlor (MXC), a pesticide which possesses weak estrogenic activity, on 7,12-dimethylbenz(a)anthracene (DMBA)-induced mammary carcinogenesis were investigated in ovariectomized or intact female Sprague-Dawley rats. Twenty-eight weeks after a single DMBA (100 mg / kg body weight) initiation, when the incidence of mammary tumor-bearing rats had reached 75%, a number of the animals were subjected to ovariectomy in order to obtain 3 groups: i) tumor-bearing, ovariectomized group; ii) tumor-bearing, intact group; iii) no-tumor, ovariectomized group. Subsequently animals of each group were subjected to subcutaneous implantation of 0.5 mg EB or given diet containing 1000 ppm MXC for 13 weeks. Although the incidences, multiplicities and volumes of the palpable tumors gradually decreased after ovariectomy, EB treatment stimulated tumor growth in the tumor-bearing, ovariectomized group thereafter. A similar effect of EB treatment was also observed in the no-tumor, ovariectomized group. However, MXC did not show any effect in the tumor-bearing, or no-tumor ovariectomized groups, except that the multiplicity of tumors was significantly decreased by MXC treatment in the tumor-bearing, intact group. The results of our study suggest that MXC has no promotion / progression effect, but rather possesses a weak inhibitory effect, whereas the strongly estrogenic substance EB clearly enhanced DMBA-induced mammary tumorigenesis.

Topics: 9,10-Dimethyl-1,2-benzanthracene; Animals; Body Weight; Disease Progression; Estradiol; Female; Mammary Neoplasms, Animal; Methoxychlor; Ovary; Rats; Rats, Sprague-Dawley; Time Factors

In order to improve the sensitivity of our previously established thyroid carcinogenesis model and to clarify whether endocrine disrupting chemicals with weak estrogenic activity have any modifying effects on the development of thyroid proliferative lesions, 6-week-old female castrated F344 rats were first given a single subcutaneous injection of 2000 mg/kg body weight of N-bis(2-hydroxypropyl)nitrosamine. From 1 week later, they received diets with: no supplement (basal diet (BD) group); cholesterol pellets containing 0.5 mg 17 beta-estradiol 3-benzoate (EB); or diet admixed with 1000 ppm methoxychlor (MXC) or 10,000 ppm bisphenol A (BPA) for 20 weeks. Furthermore, additional groups were administered 200 ppm sulfadimethoxine (SDM) in the drinking water simultaneously with the BD, EB, MXC or BPA treatments. Thyroid follicular cell hyperplasias, adenomas and/or carcinomas were induced only in the EB+SDM group, the incidences of non-malignant lesions being significantly increased, as compared with the BD+SDM group values. Furthermore, the serum level of thyroid stimulating hormone (TSH) was significantly increased in this group. No significant variation in quantitative values for thyroid proliferative lesions or TSH levels were observed in the other treated groups. The results of the present study convincingly indicate that EB, with strong estrogenic activity, but not MXC and BPA, with weak estrogenic activities, exerts promoting effects on thyroid carcinogenesis in rats. The present modified rat two-stage thyroid carcinogenesis model appears to have advantages over our previous model for screening purposes.

Topics: Adenoma; Animals; Benzhydryl Compounds; Body Weight; Carcinogens; Cholesterol; Disease Models, Animal; Endocrine System; Estradiol; Estrogens, Non-Steroidal; Female; Methoxychlor; Nitrosamines; Organ Size; Ovariectomy; Phenols; Rats; Rats, Inbred F344; Sulfadimethoxine; Thyroid Gland; Thyroid Neoplasms; Thyrotropin

Polychlorinated biphenyls (PCBs) are persistent environmental contaminants that have the potential to disrupt reproduction through a variety of different pathways. In the present study, we investigated the effects of fetal and lactational PCB exposure on reproductive behavior in male and female laboratory rats. These pregnant rats were injected daily with either 2,4,2',4'-tetrachlorobiphenyl (PCB 47) at the dosage of 1 or 20 mg/kg body weight or 3,4,3',4'-tetrachlorobiphenyl (PCB 77) at the dosage of 0.25 or 1 mg/kg body weight or sesame oil (control group) from gestational days 7 to 18. Offspring were then tested for sexual behavior as adults. Exposure to both PCB 77 and PCB 47 reduced the level of sexual receptivity in the female offspring, but had no detectable effects on the sexual behavior of the male offspring. In addition to changes in adult sexual behavior in the females, both PCBs produced a significant increase in the females' anogenital distance, suggesting a modification of androgen responsiveness in females resulting from PCB exposure during development. Similar effects were not seen with the males.

Topics: Analysis of Variance; Animals; Body Weight; Dose-Response Relationship, Drug; Environmental Pollutants; Estradiol; Female; Male; Ovariectomy; Polychlorinated Biphenyls; Posture; Pregnancy; Prenatal Exposure Delayed Effects; Rats; Rats, Long-Evans; Reaction Time; Sex Factors; Sexual Behavior, Animal

We evaluated the mechanism of action by the phytoestrogen genistein in the prepubertal rat uterus, when administered pharmacologically or physiologically. Female rats were injected with genistein (500 microg/g body weight), estradiol benzoate (EB) (500 ng/g body weight) or vehicle, dimethylsulfoxide (DMSO), on days 16, 18, and 20 postnatal. In 21-day-old rats, both compounds increased circulating estradiol and decreased progesterone concentrations. Uterine estrogen receptor alpha (ER-alpha) and androgen receptor (AR) proteins were reduced, and progesterone receptors (PR) were increased, as measured by western blot analyses. Immunohistochemistry for ER-alpha was confirmatory. Reverse transcription-polymerase chain reaction (RT-PCR) analyses indicated a decrease in ER-alpha, but not in ER-beta, PR and AR mRNA levels following genistein treatment. In prepubertal rats exposed perinatally to 250 mg genistein per kg AIN-76A diet or 250 microg estradiol per kg diet, uterine ER-alpha, AR, and PR proteins were not altered significantly. We conclude that pharmacologic, but not physiologic concentrations of genistein can modulate sex steroid receptor expression in the rat uterus.

Topics: Animals; Body Weight; Estradiol; Estrogens, Non-Steroidal; Female; Gene Expression Regulation; Genistein; Immunohistochemistry; Isoflavones; Organ Size; Ovariectomy; Ovary; Phytoestrogens; Plant Preparations; Progesterone; Rats; Rats, Sprague-Dawley; Receptors, Steroid; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Sexual Maturation; Testosterone; Uterus

Brief exposure of rats to high doses of natural estrogens early in life results in permanent alterations of the prostate gland, which include differentiation defects, altered gene expression, and dysplasia with aging. Whether low-dose treatments can cause similar effects in the developing prostate remains controversial. The current project was designed to determine the dose-response relationship of the prostate gland to estradiol exposure during the developmentally critical neonatal period in the rat. Male Sprague-Dawley (SD) rats were treated on Days 1, 3, and 5 of life by s.c. injections of a 7-log range of doses (0.015 microg/kg to 15.0 mg/kg) of beta-estradiol-3-benzoate (EB) in 25 microl of peanut oil (Arachis) as vehicle. In a separate block, neonatal Fisher 344 (F344) rats received 0.15, 15.0, or 1500.0 microg EB/kg. Rats were killed on Postnatal Day (PND) 35 or 90, and the prostates were microdissected, weighed, and frozen for immunohistochemistry. Preputial separation and hepatic testosterone hydroxlase activities were monitored and measured to determine the onset of puberty. On PND 35, there was an increase in prostate weights of SD rats treated with low doses of EB and a decrease in prostate weights of SD rats treated with high doses. The low-dose effect was entirely abolished by PND 90, and only high-dose suppression of organ sizes was found. The transient nature of the effect in low-dose animals suggests an advancement of puberty as the cause for increased reproductive organ weights on PND 35. F344 rats were more sensitive than SD rats to the suppressive effects of high doses of neonatal EB on PND 90. Despite this heightened responsiveness in the F344 rats, a low-dose estrogenic effect on adult prostate weights was not observed. Thus, in the rat model a sustained effect at low doses of natural estrogens is not present in the prostate glands.

Topics: Aging; Animals; Animals, Newborn; Body Weight; Cell Differentiation; Dose-Response Relationship, Drug; Estradiol; Male; Organ Size; Prostate; Rats; Rats, Inbred F344; Rats, Sprague-Dawley; Receptors, Androgen; Sexual Maturation

The two genes coding for thyroid hormone receptors (TR) alpha 1 and beta have opposite effects on female sex behaviors. Deletion of TRalpha 1 reduced them, whereas deletion of TRbeta actually increased them. These results could not be attributed to altered levels of hormones in the blood, general alterations in estrogen responsiveness or altered general activity. Instead, they indicate a previously unknown molecular mechanism upon which the two TR genes exert opposite influences.

Topics: Animals; Body Weight; Estradiol; Estrogens; Female; Gene Deletion; Male; Mice; Mice, Inbred Strains; Mice, Knockout; Organ Size; Oxytocin; Paraventricular Hypothalamic Nucleus; Posture; Preoptic Area; Progesterone; Receptors, Estrogen; Receptors, Thyroid Hormone; Sexual Behavior, Animal; Thyroxine; Triiodothyronine; Uterus; Vasopressins

As part of a collaborative project to assess whether a 2-weeks administration period is sufficient to detect testicular toxicity of various compounds, male rats were subcutaneously administered 0, 5, 20, 50 or 100 micrograms/kg of estradiol benzoate (E2B), a known testicular toxicant, daily for 2 or 4 weeks. After 4-weeks, suppression of body weight gain, increase in the weight of the adrenal gland, and gross changes such as decrease in size of the prostate and seminal vesicles, and increase in size of the adrenal gland were observed in the 5, 20, 50 and 100 micrograms/kg groups. On histopathological examination, degeneration/necrosis of Pachytene spermatocytes, atrophy of Leydig cells, mature spermatid retention (Lee, et al., 1993) at stages IX, X and XI, and atrophy of ducts of the epididymides were also observed in the 5, 20, 50 and 100 micrograms/kg groups. After 2-weeks, the same changes were also observed with 20, 50 and 100 micrograms/kg, but not 5 micrograms/kg. These results indicate that the toxic effects of E2B are detectable by administration for 2 weeks at an appropriate dose level.

Topics: Adrenal Glands; Animals; Body Weight; Dose-Response Relationship, Drug; Estradiol; Genitalia, Male; Injections, Subcutaneous; Male; Organ Size; Pituitary Gland; Rats; Rats, Sprague-Dawley; Specific Pathogen-Free Organisms; Testis; Time Factors; Toxicity Tests

Reproductive behavior is sexually differentiated in quail: The male-typical copulatory behavior is never observed in females even after treatment with high doses of testosterone (T). This sex difference in behavioral responsiveness to T is organized during the embryonic period by the exposure of female embryo to estrogens. We showed recently that the sexually dimorphic medial preoptic nucleus (POM), a structure that plays a key role in the activation of male copulatory behavior, is innervated by a dense steroid-sensitive network of vasotocin-immunoreactive (VT-ir) fibers in male quail This innervation is almost completely absent in the female POM and is not induced by a chronic treatment with T, suggesting that this neurochemical difference could be organizational in nature. This idea was tested by injecting fertilized quail eggs of both sexes on day 9 of incubation with either estradiol benzoate (EB) (25 microg, a treatment that suppresses the capacity to show copulatory behavior in adulthood) or the aromatase inhibitor R76713 (10 microg, a treatment that makes adult females behaviorally responsive to T), or with the solvents as a control (C). At 3 weeks posthatch, all subjects were gonadectomized and later implanted with Silastic capsules filled with T. Two weeks later, all birds were perfused and brain sections were processed for VT immunocytochemistry. Despite the similarity of the adult endocrine conditions of the subjects (all were gonadectomized and treated with T Silastic implants providing the same plasma level of steroid to all subjects), major qualitative differences were observed in the density of VT-ir structures in the POM of the different groups. Dense immunoreactive structures (fibers and a few cells) were observed in the POM of C males but not females; EB males had completely lost this immunoreactivity (and lost the capacity to display copulatory behavior); and, conversely, R76713 females displayed a male-typical VT-ir system in the nucleus (and also high levels of copulatory behavior). Similar changes in immunoreactivity were seen in the nucleus of the stria terminalis and in the lateral septum (VT-ir fibers only in this case) but not in the magnocellular vasotocinergic system. These neurochemical changes closely parallel the effects of the embryonic treatments on male copulatory behavior. The vasotocinergic system of the POM can therefore be considered an accurate marker of the sexual differentiation of brain circuits mediating this beh

Topics: Analysis of Variance; Animals; Aromatase Inhibitors; Body Weight; Brain Chemistry; Cloaca; Coturnix; Embryo, Nonmammalian; Estradiol; Female; Immunohistochemistry; Male; Neurons; Preoptic Area; Sex Characteristics; Sexual Behavior, Animal; Testosterone; Triazoles; Vasotocin

The aim of this study was to find out whether mifepristone, known mainly as a substance with an antiprogesterone and antiglucocorticoid effect, also has an in vivo antiestrogenic activity on the adenohypophysis of the rat. Male Wistar rats were given chronically either estradiol-benzoate (EB, 1 mg s.c. twice a week) for a period of 12 days, or the non steroidal antiestrogen tamoxifen (1 mg/day/rat), or mifepristone (1 mg/day/rat), or EB together with mifepristone or tamoxifen. The hypertrophic effect of the EB on the weight of the adenohypophysis (AP) was significantly suppressed both by tamoxifen and by mifepristone. Mifepristone and tamoxifen reduced the increased content of PRL in the estrogenized adenohypophysis. Mifepristone but not tamoxifen significantly increased the content of the LH in the adenohypophysis of estrogen treated rats. Mifepristone and tamoxifen suppressed the increased concentration of cyclic nucleotides cAMP and cGMP in the estrogenized adenohypophysis. Mifepristone given alone increased serum levels of corticosterone, but when given together with EB deepened inhibiting effect EB on them. The results of our preliminary study show that mifepristone exerts a weak antiestrogenic activity on the level of hypophysis, however the pharmacology is not identical to tamoxifen.

Topics: Animals; Body Weight; Corticosterone; Drug Combinations; Estradiol; Estrogen Antagonists; Injections, Subcutaneous; Male; Mifepristone; Organ Size; Pituitary Gland, Anterior; Rats; Rats, Wistar; Tamoxifen

Adipocyte hormone leptin (OB protein) is considered to be an "adiposity signal" regulating body weight homeostasis and energy balance. We have previously reported that oestrogens (oestradiol-benzoate) significantly decrease the body weight in male rats, increase anterior pituitary and serum levels of the intracellular messenger cAMP, which activates cAMP-dependent protein kinase A, their targets include hormone-sensitive lipase and they influence the brain sympathetic system. The present study tested our hypothesis that oestrogens could influence serum leptin levels in male mice. We found that chronic administration of oestradiol-benzoate significantly attenuated serum levels of leptin, in the dependence on the duration of its administration, and simultaneously decreased body weight. We suppose that oestrogens affect leptin levels interacting with the signal transmission system of cAMP, possibly at the genome level. Our observations that the food consumption of mice with simultaneously decreased body weight and levels of serum leptin support the idea that there exists a satiety factor that counters the effect of low leptin.

Topics: Adipocytes; Animals; Body Weight; Estradiol; Leptin; Male; Mice; Proteins

In order to examine the optimal administration period and parameters for male fertility assessment, male rats were subcutaneously administered 0.2, 2 or 20 micrograms/kg of estradiol benzoate (E2B), a known testicular toxicant, for 4 weeks or 9 weeks before mating. After 4 weeks administration, suppression of body weight gain and food consumption, decreases in prostate and seminal vesicle weights, atrophy of Leydig cells, and mature spermatid retention at stages IX, X and XI were observed in the 2 and 20 micrograms/kg groups. In the 20, micrograms/kg group, decreases in epididymides weight and copulation index were also found but the number of sperm and sperm motility were not affected. In the 0.2 micrograms/kg group, no changes were noted in any parameters. After 9 weeks administration, decreases in testis weight and the number and motility of sperm were observed in the 20, micrograms/kg group, in addition to the changes found after 4 weeks administration. These results suggest that detailed histopathological evaluation and determination of accessory sex organ weights are sensitive for evaluating the effects of E2B on male fertility. Results with the 4-weeks treatment were comparable to those with the 9-weeks treatment in terms of these parameters.

Topics: Animals; Body Weight; Cesarean Section; Dose-Response Relationship, Drug; Drug Administration Schedule; Eating; Estradiol; Female; Fertility; Genitalia, Male; Infertility, Male; Longevity; Male; Organ Size; Pregnancy; Rats; Rats, Sprague-Dawley; Spermatozoa

To investigate interactions between circulating sex hormones, dietary fructose and magnesium on bone mineral density and numbers of trabeculae, 10 weeks old orchiectomized and sham-orchiectomized rats were studied. One-third of the orchiectomized animals were injected with beta-oestradiol-3-benzoate twice per week in sesame oil; another one-third, testosterone cypionate; the remaining one-third as well as the sham-orchiectomized animals, sesame oil only. All animals were fed either fructose or cornstarch without added magnesium. After 14 weeks, a 24 h urine sample was collected for measurements of calcium, magnesium, phosphorus, and cAMP. Blood was collected for determinations of calcium, magnesium, phosphorus, 25-monohydroxy and 1,25-dihydroxycholecalciferols, oestrogen, testosterone, and parathyroid hormone. Femurs were used for measurements of bone mineral density, and tibiae, for numbers of trabeculae. Exogenous testosterone interacted with starch and magnesium deficiency to decrease serum calcium concentration significantly, which increased circulating parathyroid hormone. High circulating parathyroid hormone raised urinary cAMP and serum 1,25-dihydroxycholecalciferol. Increased parathyroid hormone, cAMP and 1,25-dihydroxycholecalciferol may be responsible for bone resorption which was noted in reductions of bone mineral density and the numbers of trabeculae in the group. In contrast, exogenous oestrogen interacted with fructose and magnesium deficiency to increase serum calcium concentration which caused a reduction of circulating parathyroid. Low parathyroid hormone, reduced 1,25-dihydroxycholecalciferol and cAMP may explain the increased bone mineral density and the numbers of trabeculae in this group.

Topics: Animals; Body Weight; Bone Density; Bone Diseases, Metabolic; Calcifediol; Calcitriol; Calcium; Cyclic AMP; Estradiol; Fructose; Magnesium; Magnesium Deficiency; Male; Orchiectomy; Parathyroid Hormone; Phosphorus; Rats; Starch; Testosterone

The influence of cyclic ovarian hormone replacement therapy on the satiety effect of exogenous CCK-8 was determined to investigate the mechanism mediating the preestrous decrease in meal size in female rats. Once weekly, food-deprived ovariectomized rats were IP injected with 0.5-4 micrograms/kg CCK-8 and offered 0.4-0.8 M sucrose 52 h after the second of two daily SC injections of 2.5 or 10 micrograms estradiol benzoate or vehicle and 4 h after 500 mg progesterone or vehicle. In each of three tests, estradiol significantly increased CCK-8's inhibitory effect on sucrose intake. In contrast, progesterone alone or in combination with estradiol did not consistently influence the satiating potency of CCK-8. The interaction of estradiol and CCK-8 was clearest for the dose of 4 micrograms/kg CCK-8. The interaction occurred during diurnal tests and during dark-onset tests in which estradiol did not decrease baseline sucrose intake. These results demonstrate that a cyclic regimen of estradiol replacement in ovariectomized rats is sufficient to enhance the satiating effect of exogenous CCK-8 and that simultaneous progesterone treatment does not influence this effect. Potentiation of the satiating effect of CCK released from the small intestine by ingested food may be one of the mechanisms by which food intake decreases during the period of high estrogen concentration in the estrus cycle.

Topics: Animals; Appetite; Body Weight; Dose-Response Relationship, Drug; Eating; Estradiol; Estrus; Female; Food Preferences; Ovariectomy; Rats; Rats, Sprague-Dawley; Satiety Response; Sincalide

In three experiments (2 on females, 1 on males), we determined the blood flow in the tibia and the distal part of the femur, together with cardiac output (by means of 85Sr-microspheres), tibial bone density and tibial ash weight related to bone volume. We found that 1) the bone blood flow always fell significantly after oestradiol benzoate, 2) no change occurred after norethisterone in doses corresponding to those of oestradiol benzoate, but the blood flow showed a tendency to fall after doses one order higher (it decreased significantly in one case only), 3) the density of the tibia and tibial ash weight related to bone volume rose nonsignificantly after oestradiol benzoate, but fell (mostly statistically significantly) after norethisterone. The lowering of the bone mineral indexes in rat bones after norethisterone is a surprising and potentially significant finding requiring further verification.

Topics: Animals; Body Weight; Bone and Bones; Bone Density; Dose-Response Relationship, Drug; Estradiol; Female; Femur; Male; Norethindrone; Rats; Regional Blood Flow; Tibia

Topics: Body Composition; Body Weight; Castration; Estradiol; Female; Humans; Male; Metabolism; Orchiectomy; Pharmacology; Rats; Research