Age-related renal disease in female Dahl salt-sensitive rats is attenuated with 17²-estradiol supplementation by modulating nitric oxide synthase expression

Background: The incidence of chronic renal disease in women increases with aging, especially after menopause, suggesting that loss of sex hormones may contribute to the development and progression of renal disease. However, the mechanisms by which sex hormones, particularly estrogens, contribute to the disease process are unclear.Objective: The present study examined the effects of ovariectomy (OVX) with or without 17²-estradiol (E₂) supplementation (OVX+E₂) on the expression of inducible (iNOS) and endothelial (eNOS) nitric oxide synthase in the kidney.Methods: The study was performed in young (4 months [4M]) and aged (12 months [12M]) female Dahl salt-sensitive rats fed a low-sodium (0.1% NaCl) diet. At 3 months of age, the animals were either subjected to sham surgery, OVX, or OVX with implantation of an E₂ silastic pellet. The treatments were administered for either 1 or 9 months, rendering the animals 4 months of age or 12 months of age at the time of sacrifice, respectively. Renal expression of NOS isoforms was measured by Western blotting and immunohistochemistry.Results: OVX in the aged rats was associated with 35% and 25% decreases in medullary iNOS (mean [SEM] relative optical density [ROD]: 4M OVX, 1.81 [0.14] vs 12M OVX, 1.17 [0.16]; P < 0.05) and eNOS (mean ROD: 4M OVX, 1.91 [0.09] vs 12M OVX, 1.43 [0.15]; P < 0.05) protein expression, respectively, and a 25-fold increase in the abundance of CD68-positive cells, indicating macrophage infiltration (mean cells/mm²: 4M OVX, 1.18 [0.09] vs 12M OVX, 30.0 [0.74]; P < 0.001). E₂ supplementation either partially or completely attenuated these changes in iNOS (mean ROD: 4M OVX+E₂, 2.26 [0.08] vs 12M OVX+E₂, 1.70 [0.09]; P < 0.05), eNOS (mean ROD: 4M OVX+E₂, 2.03 [0.07] vs 12M OVX+E₂, 1.77 [0.11]; P = NS) and CD68 (mean cells/mm²: 4M OVX+E₂, 1.46 [0.07] vs 12M OVX+E₂, 6.87 [1.6]; P < 0.01) associated with OVX in the aging kidney.Conclusions: These data suggest that ovarian E₂ loss with aging may contribute to the development of age-related renal disease through downregulation of iNOS and eNOS protein abundance and increased renal inflammation in this animal model. Furthermore, E2 supplementation may be protective in the aging kidney by attenuating these changes.     

Effects of estrogen deprivation on brain estrogen and progestin receptor levels and the activation of female sexual behavior

Ovariectomy (OVX) in rats is followed by a decline in behavioral sensitivity to combined estrogen and progesterone therapy. The purpose of this study was to further characterize this behavioral change, and to explore its biochemical basis in terms of estrogen and progesterone receptor concentrations in the brain. Sexually inexperienced female rats were used 5 (short-term) or 35 (long-term) days after OVX. Short- and long-term OVX animals were injected with estradiol-17β (E₂; 36 μg/kg body wt, iv) then subjected to one of the following three treatment schedules. (1) Animals were treated with progesterone (1 mg, sc in oil) 20–21 hr after E₂ injection, then tested at 24 hr for female sexual behavior. (2) One or twelve hours after the E₂, cell nuclear estrogen receptors (ER_n) were measured in the pituitary (PIT) and pooled preoptic area and mediobasal hypothalamus (POA-MBH). (3) Twenty-four hours after E₂, progestin receptor (PR_c) concentrations were measured in cytoplasmic fractions prepared from PIT and POA-MBH. Long-term OVX animals showed a reduced capacity to exhibit proceptive and receptive sexual behavior, and a lower PR_c level in the PIT and POA-MBH 24 hr after E₂ injection than animals that had been OVX for only 5 days. However, no differences were observed between long- and short-term OVX rats with respect to ER_n concentrations in PIT and POA-MBH cell nuclei 1 or 12 hr after E₂. Thus, it appears that the decline in behavioral responsiveness to E₂ which occurs after ovariectomy cannot be attributed to a decrease in the ability of E₂ to translocate estrogen receptors into POA-MBH cell nuclei, but is more probably associated with a change in the biochemical processes subsequent to ER_n binding. One of these processes may well be the induction of cytoplasmic progestin receptors.     

Effect of estrogen on the expression of GnRH and kisspeptin in the hypothalamus of rats during puberty

The aim of this study was to assess whether changes in kisspeptin and GnRH levels could be attributed to sex steroids at puberty onset. We used the ovariectomy (OVX) model in rats treated with 17β-estradiol (E₂; OVX + E₂), or oil (OVX + oil), and in intact rats treated with E₂ (intact + E₂) or oil only (intact + oil) to determine gene expression changes of Kiss1 and Gnrh1 in the hypothalamus and protein expression of kisspeptin and GnRH in the different areas of the hypothalamus. In the intact + E₂ and OVX + E₂ rats on the day of the onset of puberty, GnRH-immunoreactive (ir) cell numbers decreased (P < 0.05) in the arcuate nucleus but were increased in the preoptic area; Kisspeptin-ir cells increased (P < 0.05) in the arcuate nucleus, periventricular nucleus, and preoptic area; no difference (P > 0.05) was found in the paraventricularis nucleus for GnRH-ir or kisspeptin-ir cells. Additionally, levels of Kiss1 and Gnrh1 messenger RNA in the hypothalamus were significantly higher (P < 0.05) in the OVX + E₂ or intact + E₂ rats than in the OVX + oil or intact + oil animals, respectively. In the OVX + oil rats, OVX significantly increased (P < 0.05) levels of Gnrh1 and Kiss1 messenger RNA and the expression of GnRH and kisspeptin in the hypothalamus compared to intact + oil animals. These results suggest that kisspeptin and GnRH play major roles in modulating the activity of estrogen circuits at the onset of puberty.     

Bone Sparing Effect of a Novel Phytoestrogen Diarylheptanoid from Curcuma comosa Roxb. in Ovariectomized Rats

Phytoestrogens have been implicated in the prevention of bone loss in postmenopausal osteoporosis. Recently, an active phytoestrogen from Curcuma comosa Roxb, diarylheptanoid (DPHD), (3R)-1,7-diphenyl-(4E,6E)-4,6-heptadien-3-ol, was found to strongly promote human osteoblast function in vitro. In the present study, we demonstrated the protective effect of DPHD on ovariectomy-induced bone loss (OVX) in adult female Sprague-Dawley rats with 17β-estradiol (E₂, 10 µg/kg Bw) as a positive control. Treatment of OVX animals with DPHD at 25, 50, and 100 mg/kg Bw for 12 weeks markedly increased bone mineral density (BMD) of tibial metaphysis as measured by peripheral Quantitative Computed Tomography (pQCT). Histomorphometric analysis of bone structure indicated that DPHD treatment retarded the ovariectomy-induced deterioration of bone microstructure. Ovariectomy resulted in a marked decrease in trabecular bone volume, number and thickness and these changes were inhibited by DPHD treatment, similar to that seen with E₂. Moreover, DPHD decreased markers of bone turnover, including osteocalcin and tartrate resistant acid phosphatase (TRAP) activity. These results suggest that DPHD has a bone sparing effect in ovariectomy-induced trabecular bone loss and prevents deterioration of bone microarchitecture by suppressing the rate of bone turnover. Therefore, DPHD appears to be a promising candidate for preserving bone mass and structure in the estrogen deficient women with a potential role in reducing postmenopausal osteoporosis.     

Bone loss in ovariectomized rats: dominant role for estrogen but apparently not for FSH

Estrogen deficiency as the sole factor underlying post‐menopausal osteoporosis was challenged, in light of reports that both follicular stimulation hormone (FSH) receptor and FSHβ knockout mice were resistant to bone loss, suggesting a detrimental role for FSH. We assessed whether lowering FSH levels by gonadotropin realizing (GnRH) analog decapeptyl in ovariectomized female rats (OVX) affects bone. Wistar‐derived 25 days old OVX female rats were injected for 10 weeks with estradiol‐17β (E₂), with GnRH analog (decapeptyl) or with both. FSH and luteinizing hormone (LH) serum levels were markedly increased in OVX rats, with smaller growth plates with disrupted architecture; heavy infiltration of bone marrow with numerous adipocytes and reduced thickness of cortical bone. In OVX rats treated with E₂, FSH, and LH levels were intermediate, the tibia was similar to that of intact rats, but there was reduced thickness of cortical bone. In decapeptyl treated OVX rats, FSH and LH levels were suppressed, the organization of growth plate and the trabecular bone were disrupted, and there were fewer proliferative and chondroblastic cells and a large adipocytes population in bone marrow, but an increased trabecular bone volume (TBV). In the E₂ + decapeptyl treatment, FSH and LH levels were suppressed, with partially restored growth plate architecture and improved TBV. In conclusion, E₂ deficiency is the dominant factor impairing bone loss in OVX and concomitant changes in FSH/LH levels achieved by decapeptyl have some modulating, though complex role in this setting. The role of high FSH levels in post‐menopausal bone loss requires further investigation using combined sub‐optimal doses of the different hormones. J. Cell. Biochem. 112: 128–137, 2011. © 2010 Wiley‐Liss, Inc.     

In vivo 5-HIAA release from the anterior hypothalamus in the ovariectomized and estradiol treated rat following perfusion with progesterone

In the present study the frequency and magnitude of the release of 5-Hydroxyindoleacetic Acid (5-HIAA) was measured from the anterior hypothalamus of ovariectomized (OVX) and OVX rats treated with estradiol (E₂). Female, Holtzman strain rats were maintained on a photoperiod of 14 H light from 0100 to 1500 H and experiments performed from 0900 to 1700 H. Animals exhibiting four-day estrous cycles (250–300 gms) were OVX (20 days recovery) and a push-pull-cannula (PPC) implanted and stereotaxically aimed at the SCN region in the anterior hypothalamus. Following a 7–10 day recovery push-pull-perfusion (PPP) experiments were performed on either OVX females or on OVX females in which a silastic E₂ implant (150 g E₂/ml. sesame oil), was placed sc 48 H prior to PPP. In other experiments progesterone (P₄) was perfused in a pulsatile manner over the SCN region of the anterior hypothalamus. The overall average 5-HIAA release in the OVX treated rats (548±358 pg/10 min.) was similar to that in the OVX E₂ group (694±148 pg/10 min). The average period of 5-HIAA release was (48.2±5.5 min) in the OVX group and (56.0±9.8 min) in the OVX E₂ group. These results indicate that exposure of long term OVX rats (20 days) to E₂ has no effect on the release or period of 5-HIAA release from serotonergic terminals concentrated in the SCN of the anterior hypothalamus. Pulsatile perfusions of P₄ over the SCN region in the OVX E₂ treated rat significantly decreased 5-HIAA release but had no effect on the frequency of 5-HIAA release. This suggests that the pulsatile perfusion of P₄ can modulate serotonergic activity and potentially affect serotonergic dependent neuroendocrine systems.     

Estrogen dependence of the renal vasodilatory effect of nicotine in rats: role of α7 nicotinic cholinergic receptor/eNOS signaling

AimsWe recently reported that acute exposure to nicotine vasodilates the renal vasculature of male rats via facilitation of endothelial nitric oxide synthase (eNOS). In this study, we investigated whether this effect of nicotine is sexually dimorphic and the role of estrogen in modulating the nicotine effect.Main methodsNicotine-evoked vasodilation was evaluated in phenylephrine-preconstricted perfused kidneys obtained from male, proestrus female, ovariectomized (OVX) and estrogen-replaced OVX (OVXE₂) rats.Key findingsNicotine infusion (5 × 10^? 5, 1 × 10^? 4, and 5 × 10^? 4 M) produced greater concentration-dependent reductions in the renal perfusion pressure (RPP) in an isolated kidney from proestrus females than from males. Inhibition of NOS by N^G-nitro-l-arginine abolished the nicotine-evoked reduction in RPP and abolished the gender difference in the nicotine effect. Nicotine vasodilation was also attenuated in kidneys isolated from OVX and diestrus rats, models characterized by reduced estrogen levels. Further, estrogen or l-arginine supplementation in OVX rats largely restored the renal vasodilatory response to nicotine. Estrogen receptor blockade by tamoxifen abrogated the enhanced nicotine-evoked vasodilation elicited by E₂ in OVX rats. The nitrite/nitrate levels and protein expressions of eNOS and α₇ nicotinic cholinergic receptor (α₇ nAChRs) were significantly higher in renal tissues of OVXE₂ compared with OVX rats, suggesting a facilitatory effect for E₂ on α₇ nAChRs/eNOS signaling.SignificanceEstrogen-dependent facilitation of NOS signaling mediates the enhanced vasodilator capacity of nicotine in the renal vasculature of female rats. Preliminary evidence also suggests a potential role for α₇ nAChRs in this estrogen-dependent phenomenon.     

The effects of estrogen on thermoregulation,heart rate,and activity in the female rat with comparisons to males

Intact female (SHAM), ovariectomized (OVX), OVX with estradiol (E2), and male (MALE) rats, had core temperature (T_c), heart rate (HR), and activity (ACT) measured every 5 min for 10 days. E2 lowered T_c (SHAM > MALE ⩾ OVX > E2) and increased ACT (E2 > all other groups). Diurnal and mean 24 h HR was reduced in resting animals by E2 (OVX > SHAM > E2 > MALE). Significant differences in T_c and HR were quantified without the need to align the SHAM female data by estrus cycle phase. Telemetered female rats provide a sensitive model with which to measure the effects of subtle thermoeffectors on temperature regulation.     

MicroRNA-23a Participates in Estrogen Deficiency Induced Gap Junction Remodeling of Rats by Targeting GJA1

Increased incidence of arrhythmias in women after menopause has been widely documented, which is considered to be related to estrogen (E₂) deficiency induced cardiac electrophysiological abnormalities. However, its molecular mechanism remains incompletely clear. In the present study, we found cardiac conduction blockage in post-menopausal rats. Thereafter, the results showed that cardiac gap junctions were impaired and Connexin43 (Cx43) expression was reduced in the myocardium of post-menopausal rats. The phenomenon was also observed in ovariectomized (OVX) rats, which was attenuated by E₂ supplement. Further study displayed that microRNA-23a (miR-23a) level was significantly increased in both post-menopausal and OVX rats, which was reversed by daily E₂ treatment after OVX. Importantly, forced overexpression of miR-23a led to gap junction impairment and Cx43 downregulation in cultured cardiomyocytes, which was rescued by suppressing miR-23a by transfection of miR-23a specific inhibitory oligonucleotide (AMO-23a). GJA1 was identified as the target gene of miR-23a by luciferase assay and miRNA-masking antisense ODN (miR-Mask) assay. We also found that E₂ supplement could reverse cardiac conduction blockage, Cx43 downregulation, gap junction remodeling and miR-23a upregulation in post-menopausal rats. These findings provide the evidence that miR-23a mediated repression of Cx43 participates in estrogen deficiency induced damages of cardiac gap junction, and highlights a new insight into molecular mechanism of post-menopause related arrhythmia at the microRNA level.     

Influence of gonadal hormones and social housing conditions on agonistic,copulatory, and related socio-sexual behaviour in the Mongolian gerbil (Meriones unguiculatus)

The Mongolian gerbil is colonial, but its social organization within its colonies is not known. Pair formation has been suggested by breeders and has been observed under semi-natural conditions. Family units remain stable under such conditions. In the solitary-living hamster (Cricetus auratus), agonistic behaviour decreases in male-female encounters during female heat. This report concerns the influence of female and male gonadal hormones on agonistic behaviour in gerbils studied in cagemate and non-cagemate encounters. Further, the occurrence of mating, marking, and drumming was studied in the same situations. No effects were found of either the female or the male endocrine condition on the low amount of agonistic behaviour between cagemates. A reduction in the high amount of agonistic responses in encounters between non-cagemates was indicated. It was related to the castrated-male and induced-oestrous female conditions. Copulatory behaviour was not influenced by social maintenance conditions. Marking and drumming were most frequent in females in oestrous and intact males. The occurences in the females were influenced by the individual's endocrine condition, but not by the opponent's. Intact males in encounters with non-cagemates marked more frequently when the females were in anoestrous. Drumming in the intact males increased in tests with oestrous versus anoestrous females but occurred more frequently in encounters with non-cagemates than in those with cagemates. The behaviour of castrated males was not influenced by the endocrine or by social housing conditions. The limited variation in agonistic behaviour relative to the endocrine conditions may reflect a non-solitary social organization.     

Effect of a postnatal high-fat diet exposure on puberty onset,estrous cycle regularity,and kisspeptin expression in female rats

Kisspeptin, encoded by Kiss1, plays a key role in pubertal maturation and reproduction as a positive upstream regulator of the hypothalamic-pituitary-gonadal (HPG) axis. To examine the role of high-fat diet (HFD) on puberty onset, estrous cycle regularity, and kisspeptin expression, female rats were exposed to HFD in distinct postnatal periods. Three groups of rats were exposed to HFD containing 60% energy from fat during the pre-weaning period (postnatal day (PND) 1–16, HFD PND 1–16), post-weaning period (HFD PND 21–34), or during both periods (HFD PND 1–34). Puberty onset, evaluated by vaginal opening, was monitored on days 30–34. Leptin, estradiol (E₂), Kiss1 mRNA levels, and number of kisspeptin-immunoreactive cells in the anteroventral periventricular nucleus (AVPV) and arcuate nucleus (ARC) were measured at day 34. Body weight increased only in rats exposed to HFD during post-weaning period, whereas the timing of vaginal opening was unaffected in all three groups. Leptin, Kiss1 mRNA levels, and number of kisspeptin-immunoreactive cells at day 34 were not affected by HFD. Additionally, the estrous cycle regularity was monitored in rats exposed to HFD for 40 days from weaning. Leptin, E₂, and Kiss1 mRNA levels in the AVPV and ARC were measured after the HFD exposure. Thirty-three percent of rats exposed to HFD exhibited irregular estrous cycles and a two-fold increase in leptin. By contrast, E₂ level and Kiss1 mRNA levels were not affected by the treatment. These data show that postnatal HFD exposure induced irregular estrous cycles, but had no effect on puberty onset or kisspeptin.     

Estrogen and n-3 polyunsaturated fatty acid supplementation have a synergistic hypotriglyceridemic effect in ovariectomized rats

The n-3 polyunsaturated fatty acids (PUFAs), EPA and DHA, as well as estrogen have been shown to decrease circulating levels of triglyceride (TG), but their underlying mode of action is unclear. The purpose of this study was to determine the effects of n-3 PUFA consumption and estrogen injection on TG metabolism. Rats (n = 48) were fed a modified AIN-93G diet with 0, 1, or 2 % EPA + DHA relative to the total energy intake during 12 weeks. At 8 weeks, rats were ovariectomized (OVX), and after a 1-week recovery, rats were injected with either 17β-estradiol-3-benzoate (E₂) or corn oil for the last 3 weeks. The n-3 PUFA consumption and E₂ injection independently decreased the hepatic expressions of sterol regulatory element-binding protein 1, acetyl-CoA carboxylase 1, fatty acid synthase (FAS), and diacylglycerol acyltransferase 2 (DGAT2) (P < 0.05). There were interactions between n-3 PUFA consumption and E₂ injection on hepatic expression of FAS and DGAT2. In addition, n-3 PUFA consumption and E₂ injection up-regulated the expression of AMP-activated protein kinase (AMPK), phosphorylated AMPK, peroxisomal proliferator-activated receptor α, and carnitine palmitoyltransferase 1 in liver and skeletal muscle. E₂ injection increased the expression of estrogen receptor α and β in skeletal muscle and liver, but n-3 PUFA consumption increased the expression of both receptors only in skeletal muscle. The present study suggests that the hypotriglyceridemic effects of n-3 PUFA consumption and E₂ injection could be due to the down-regulation of hepatic TG synthesis and up-regulation of TG oxidation in liver and skeletal muscle in OVX rats.     

Effects of 17β-Estradiol and Vitamin E Treatments on Blood Trace Element and Antioxidant Enzyme Levels in Ovariectomized Rats

We investigated the effect of 17β-estradiol (E₂) alone and separately vitamin E treatment on trace element status of rats following an ovariectomic operation. Forty rats were equally divided into four groups: Group 1, control, non-ovariectomized rats; Group 2, (OVX) rats, ovariectomized under general anesthesia; Group 3, (OVX+E₂) rats, the group received a 40 μg kg⁻¹ subcutan dose of E₂ per day after ovariectomy; and Group 4, (OVX + E₂ + vitamin E) rats, received the same E₂ treatment, but with an additional 100 mg kg⁻¹ intraperitoneal dose of vitamin E per day after ovariectomy. At the end of the 30-day experiment, the rats were sacrificed and their blood was collected for the measurement of zinc, copper, iron, phosphorus, selenium, magnesium, calcium, manganese, and chromium; copper–zinc superoxide dismutase (SOD); manganese-superoxide dismutase (Mn-SOD); glutathione peroxidase (Se-GSH-Px); and catalase (CAT). The levels of zinc, copper, iron, phosphorus, selenium, calcium, chromium, and manganese and activities of SOD, Mn-SOD, Se-GSH-Px, and CAT were lower in the OVX than in the control group, but magnesium level was unaffected. However, zinc, copper, iron, phosphorus, selenium, calcium, chromium, and manganese levels and SOD, Mn-SOD, Se-GSH-Px, and CAT activities were higher under separate E₂ and E₂ + vitamin E treatments. The level of magnesium in the treated-OVX groups was not different than in the OVX group. In conclusion, E₂ treatment has an ameliorating effect on the trace element status in OVX, and this effect may be enhanced with the addition of vitamin E.     

High-Altitude Pulmonary Hypertension and Signal Transduction in the Cardiovascular System

Estrogen plays a cardioprotective role in female rat hearts subjected to ischemia/reperfusion injury. The its effects are, at least partially, associated with decreased cardiomyocyte contraction and increased expression of β₂-adrenoceptor (β₂-AR). We tested whether β₂-AR could be involved in cardioprotection against ischemic damage and whether the roles of β₂-AR were dependent on estrogenic environment. We first determined the effects of hypoxia/reoxygenation (H/R) on cardiomyocyte shortening in female rats. We then determined the roles of β₂-AR in cardiomyocyte shortening, lactate dehydrogenase (LDH) release in culture medium, and cell death during hypoxia in isolated myocytes from female rats. We further determined the effects of estrogen on the roles of β₂-AR during hypoxia. H/R induced short-term hibernation and stunning at the level of ventricular myocytes from normal female rats. Inhibition of β₂-AR with ICI118,551 significantly elevated adrenergic contractile reserve, myocardial injury, and cell death in normal female rats during hypoxia, whereas ovariectomy (OVX) prominently enhanced myocyte contraction, myocardial injury, and cell death, and deprived the alternations in normal female rats. These changes were restored to normal by estrogen replacement (OVX+E₂). These data suggest that β₂-AR may be involved in the cardioprotection against ischemic damage, and the cardioprotection may depend on estrogenic environment.     

Influence of Exercise on Bone Remodeling-Related Hormones and Cytokines in Ovariectomized Rats: A Model of Postmenopausal Osteoporosis

This study aims to explore the effects of exercise on postmenopausal osteoporosis and the mechanisms by which exercise affects bone remodeling. Sixty-three Wistar female rats were randomly divided into five groups: (1) control group, (2) sham-operated group, (3) OVX (Ovariectomy) group, (4) DES-OVX (Diethylstilbestrol-OVX) group, and (5) Ex-OVX (Exercise-OVX) group. The rat osteoporosis model was established through ovariectomy. The Ex-OVX rats were made to run 251.2 meters every day, 6 d/wk for 3 months in a running wheel. Trabecular bone volume (TBV%), total resorption surface (TRS%), trabecular formation surface (TFS%), mineralization rate (MAR), bone cortex mineralization rate (mAR), and osteoid seam width (OSW) were determined by bone histomorphometry. The mRNA and protein levels of interleukin-1β (IL-1β₂), interleukin-6 (IL-6), and cyclooxygenase-2 (Cox-2) were determined by in situ hybridization and immunohistochemistry, respectively. Serum levels of estrogen estradiol (E₂), calcitonin (CT), osteocalcin (BGP), and parathyroid hormone (PTH) were determined by ELISA assays. The investigation revealed that compared to the control and the sham-operated groups, the OVX group showed significantly lower levels of TBV%, E₂, and CT, but much higher levels of TRS%, TFS%, MAR, OSW, BGP, and PTH. The Ex-OVX group showed increased TBV% and serum levels of E₂ and CT compared to the OVX group. Ovariectomy also led to a significant increase in IL-1β mRNA and protein levels in the bone marrow and IL-6 and Cox-2 protein levels in tibias. In addition, the Ex-OVX group showed lower levels of IL-1 mRNA and protein, IL-6 mRNA, and Cox-2 mRNA and protein than those in the OVX group. The upshot of the study suggests that exercise can significantly increase bone mass in postmenopausal osteoporosis rat models by inhibiting bone resorption and increasing bone formation, especially in trabecular bones.     

Identification of a regulatory loop for the synthesis of neurosteroids: a steroidogenic acute regulatory protein-dependent mechanism involving hypothalamic-pituitary-gonadal axis receptors

Brain sex steroids are derived from both peripheral (primarily gonadal) and local (neurosteroids) sources and are crucial for neurogenesis, neural differentiation and neural function. The mechanism(s) regulating the production of neurosteroids is not understood. To determine whether hypothalamic‐pituitary‐gonadal axis components previously detected in the extra‐hypothalamic brain comprise a feedback loop to regulate neuro‐sex steroid (NSS) production, we assessed dynamic changes in expression patterns of steroidogenic acute regulatory (StAR) protein, a key regulator of steroidogenesis, and key hypothalamic‐pituitary‐gonadal endocrine receptors, by modulating peripheral sex hormone levels in female mice. Ovariectomy (OVX; high serum gonadotropins, low serum sex steroids) had a differential effect on StAR protein levels in the extrahypothalamic brain; increasing the 30‐ and 32‐kDa variants but decreasing the 37‐kDa variant and is indicative of cholesterol transport into mitochondria for steroidogenesis. Treatment of OVX animals with E₂, P₄, or E₂ + P₄ for 3 days, which decreases OVX‐induced increases in GnRH/gonadotropin production, reversed this pattern. Suppression of gonadotropin levels in OVX mice using the GnRH agonist leuprolide acetate inhibited the processing of the 37‐kDa StAR protein into the 30‐kDa StAR protein, confirming that the differential processing of brain StAR protein is regulated by gonadotropins. OVX dramatically suppressed extra‐hypothalamic brain gonadotropin‐releasing hormone 1 receptor expression, and was further suppressed in E₂‐ or P₄‐treated OVX mice. Together, these data indicate the existence of endocrine and autocrine/paracrine feedback loops that regulate NSS synthesis. Further delineation of these feedback loops that regulate NSS production will aid in developing therapies to maintain brain sex steroid levels and cognition.     

Influence of gonadal hormones on the behaviour of pair-living Mongolian gerbils (Meriones Unguiculatus) towards the cagemate versus a non-cagemate in a social choice test

Laboratory, semi-natural and field observations indicate that the Mongolian gerbil may naturally live in pairs or family groups. Endocrine influence on behaviour towards cagemates and non-cagemates was investigated. The males tested were intact or castrated. The hormonal condition of the females was controlled by gonadectomy and oestrogen and progesterone replacement treatment. The duration and number of visits to the incentive animals were recorded in a choice test, which allowed restricted contact between the experimental and incentive animals. Anoestrous females approached the intact cagemates more than the non-cagemates, while the intact males approached the non-cagemates more often. A comparison of the female behaviour under the different female endocrine conditions tested showed that females significantly increased their response in oestrus towards the strange intact males but not towards their cagemates. Experimental intact males analogously increased their response towards the strange oestrus female but not towards the cagemate. In tests which involved castrated males either as experimentals or incentives, no behavioural change was seen relative to the endocrine condition of the female. The hormonal effects seen were thus connected with the social relationship, as the hormone-induced changes were seen only in behaviour towards a strange animal.     

Effects of two estradiol regimens on anxiety and depressive behaviors and trophic effects in peripheral tissues in a rodent model

Background: With aging and menopause, which are associated with decreases in ovarian steroids such as 17β-estradiol (E₂), women might experience negative psychological symptoms, including anxiety and depression. Some women use E₂-based therapies to alleviate these symptoms, but E₂ has been associated with trophic effects that might increase vulnerability to some steroid-sensitive cancers, such as breast cancer, in both premenopausal and postmenopausal women.Objective: This study investigated the relationships between the possible beneficial effects of E₂ on anxiety and depressive behaviors concurrent with trophic effects using an animal model of E₂ decline and replacement.Methods: Dose-dependent effects of E₂ on affective, sexual, and motor behavior of young adult rats were studied. Ovariectomized (OVX) rats were administered the chemical carcinogen 7,12-dimethylbenz(a) anthracene (DMBA) 1.25 mg or inactive vehicle (vegetable oil; control) by gavage. E₂ (0.03 or 0.09 mg/kg) or vehicle was administered subcutaneously 44 to 48 hours before assessments of anxiety (light—dark transition), depression (forced swim test), sexual (lordosis), and motor (activity monitor) behaviors. Fourteen weeks after carcinogen exposure, E₂ concentrations in plasma and brain regions (cortex, hippocampus, and hypothalamus) were determined. Incidences and numbers of tumors and uterine weight were analyzed.Results: Administration of E₂ (0.09 mg/kg) was associated with significant increases in antianxiety-like behavior in the light—dark transition task, antidepressant-like behavior in the forced swim test, and physiologic circulating and central E₂ concentrations compared with E₂ (0.03 mg/kg) and vehicle. Compared with vehicle, E₂ (0.9 > 0.3 mg/kg) was associated with significant increases in lordosis and uterine weight. Administration of DMBA was associated with significant increases in the incidences and numbers of tumors; this effect was augmented by E₂administration.Conclusions: Based on the findings in this rat model, the hypothesis that E₂ may be effective in reducing anxiety and depressive behaviors and enhance sexual behavior in OVX rats, concurrent with trophic effects in the periphery, was supported. Moderate physiologic levels of E₂ might have beneficial effects on affective and sexual behaviors in female rodents, but regimens including E₂ might increase tumorigenic capacity.