Ovarian hormones influence olfactory cue effects on reentrainment in the diurnal rodent, Octodon degus

Octodon degus, a social hystricomorph rodent, responds to olfactory cues from a gonadally intact female entrained to a light-dark cycle (LD) by accelerating reentrainment of running wheel activity following a 6-h phase advance of the LD cycle. In this study, we examined the role of ovarian hormones in the production of and responsiveness to olfactory social cues in females. Experiment 1: intact females were sequentially phase-advanced 6 h with photic cues alone, or in the presence of an intact female donor, ovariectomized (OVX) donor, a castrated male, or a castrated male with testosterone replacement. Acceleration of reentrainment occurred only in the presence of the intact female donor while reentrainment was delayed by OVX donors. Experiment 2: OVX females undergoing a 6-h phase advance did not accelerate reentrainment in the presence of an intact female donor compared to reentrainment with photic cues alone. Thus, ovarian hormones are necessary for both the production of and responsiveness to olfactory cues. Experiment 3: OVX females implanted with estrogen-filled Silastic capsules did not accelerate reentrainment following the 6-h phase advance in the presence of an intact donor, whereas animals implanted with a combination of estrogen- and progesterone-filled capsules (Experiment 4) reduced the length of time needed to reentrain in the presence of an intact donor. Therefore, combined progesterone and estrogen are sufficient for responsiveness to the effective olfactory cue in intact donor females. These data clarify that the sex difference in sensitivity to non-photic odor effects on circadian reentrainment is caused by both the testosterone's inhibitory effects (Octodon degus. J. Biol. Rhythms 18 (2003) 43-50) and the enhancing effects of progesterone and estrogen.     

Effect of ovarian hormones on intestinal mast cell reactivity to substance P

Evidence exists to support the concept that ovarian hormones influence mast cell functioning and related events. Here, we evaluated the constitutive gender difference and the influence of ovarian status on rat mast cell (MC) distribution in jejunum and colon, histamine synthesis and/or its release elicited by Substance P (SP). Higher mast cell (MC) number and histamine release were found in female compared with male. In female rats, hormonal status did not affect the density of resident MC neither in the jejunum nor in the colon. Interestingly, histamine levels released after SP stimulation of jejunal segment was reduced in ovariectomized (OVX) compared with sham OVX rats, and restored in OVX female receiving progesterone. In the colon, OVX resulted in a significant increase in histamine levels released after SP stimulation and a treatment with progesterone did not restore basal histamine levels. Thus, ovarian steroid hormones do not affect jejunal and colonic mast cell number. However, the hormonal status differently influences jejunal and colonic MC sensitivity to SP.     

Influence of gender and estrous cycle on plasma and renal catecholamine levels in rats

Several studies have demonstrated that gonadal hormones show significant effects on the brain and signaling pathways of effector organs/cells that respond to neurotransmitters. Since little information is available concerning the impact of male and female gonadal hormones on the renal and peripheral sympathetic system, the objective of this study was to further assess whether and how the renal content and plasma concentration of catecholamines are influenced by gender and the estrous cycle in rats. To achieve this, males Wistar rats were divided into 4 groups: (i) sham (i.e., control), (ii) gonadectomized, (iii) gonadectomized and nandrolone decanoate replacement at physiological levels or (iv) gonadectomized and nandrolone decanoate replacement at high levels. Female Wistar rats were divided into 6 groups: (i) ovariectomized (OVX), (ii) estrogen replacement at physiological levels and (iii) estrogen replacement at at high levels, (iv) progesterone replacement at physiological levels and (v) progesterone replacement at at high levels, and (vi) sham. The sham group was subdivided into four subgroups: (i) proestrus, (ii) estrus, (iii) metaestrus, and (iv) diestrus. Ten days after surgery, the animals were sacrificed and their plasma and renal catecholamine levels measured for intergroup comparisons. Gonadectomy led to an increase in the plasma catecholamine concentration in females, as well as in the renal catecholamine content of both male and female rats. Gonadectomized males also showed a lower level of plasma catecholamine than the controls. The urinary flow, and the fractional excretion of sodium and chloride were significantly increased in gonadectomized males and in the OVX group when compared with their respective sham groups.     

Sexual Dimorphism in Development of Kidney Damage in Aging Fischer-344 Rats

BackgroundAging kidneys exhibit slowly developing injury and women are usually protected compared with men, in association with maintained renal nitric oxide.ObjectivesOur purpose was to test 2 hypotheses: (1) that aging intact Fischer-344 (F344) female rats exhibit less glomerular damage than similarly aged males, and (2) that loss of female ovarian hormones would lead to greater structural injury and dysregulation of the nitric oxide synthase (NOS) system in aging F344 rat kidneys.MethodsWe compared renal injury in F344 rats in intact, ovariectomized, and ovariectomized with estrogen replaced young (6 month) and old (24 month) female rats with young and old intact male rats and measured renal protein abundance of NOS isoforms and oxidative stress.ResultsThere was no difference in age-dependent glomerular damage between young or old intact male and female F344 rats, and neither ovariectomy nor estrogen replacement affected renal injury; however, tubulointerstitial injury was greater in old males than in old females. These data suggest that ovarian hormones do not influence these aspects of kidney aging in F344 rats and that the greater tubulointerstitial injury is caused by male sex. Old males had greater kidney cortex NOS3 abundance than females, and NOS1 abundance (alpha and beta isoforms) was increased in old males compared with both young males and old females. NOS abundance was preserved with age in intact females, ovariectomy did not reduce NOS1 or NOS3 protein abundance, and estrogen replacement did not uniformly elevate NOS proteins, suggesting that estrogens are not primary regulators of renal NOS abundance in this strain. Nicotinamide adenine dinucleotide phosphate oxidase-dependent superoxide production and nitrotyrosine immunoreactivity were increased in aging male rat kidneys compared with females, which could compromise renal nitric oxide production and/or bioavailability.ConclusionsThe kidney damage expressed in aging F344 rats is fairly mild and is not related to loss of renal cortex NOS3 or NOS1 alpha.     

Mechanisms of 17beta-estradiol on the production of ET-1 in ovariectomized rats

In order to clarify the mechanism underlying the possible preventive effect of estrogen on atherogenesis, we investigated the role of 17beta-estradiol (E2) in the regulation of endothelin-1 (ET-1) production in ovariectomized rats, which may contribute to atherogenesis. Female Spragure-Dawly rats were randomly divided into three groups: sham-operated group (sham), ovariectomized group (OVX) and 17beta-estradiol replacement group (OVX + E2, 20 microg(-1).kg.d(-1),s.c.). 4 weeks after operation, the plasma concentration of ET-1, clearance of ET-1, functional ECE activity and preproET-1 mRNA expression in aorta were measured. Concentration of plasma ET-1 change from 107.8 +/- 18.3 pg/ml (sham) and 135.5 +/- 27.6 pg/ml (OVX + E2) to 190.7 +/- 25.5 pg/ml (OVX ) (n = 8, p < 0.05). There was no significant difference in the clearance of 125IET-1 among three groups (p > 0.05). Functional ECE activity was increased in OVX group in comparison to that in sham group (p < 0.05). The OVX increased the preproET-1 mRNA expression in sham, whereas treatment with estrogen reversed these changes (p < 0.05). The present study have shown that estrogen down-regulates plasma ET-1 levels by inhibiting the preproET-1 mRNA expression and functional ECE activity. Clearance of ET-1 was not affected. Inhibition of ET-1 production mediated by modulating ECE activity may be one of the novel mechanisms of the protective of estrogens on the cardiovascular system.     

17Beta-estradiol inhibits ovariectomy-induced expression of inducible nitric oxide synthase in rat aorta in vivo

The objective of this study was to elucidate a role of ovarian steroid hormones in the production of immunologic nitric oxide (NO) synthases in the female rat aorta in vivo. Aortic homogenates were analyzed by using western blot with isoform-specific antibodies against endothelial NOS (eNOS) and inducible NOS (iNOS). Two weeks after ovariectomy (OVX), rats (10-week-old) were treated with 17beta-estradiol (E2) and/or progesterone (P4) for 5 days, and aortae were obtained from these rats on the following day. OVX markedly increased the levels of iNOS protein in abdominal aorta, whereas treatment with E2 or a combination of E2 and P4 inhibited the induction of iNOS in the aorta. The present findings indicate that endogeneous estrogen negatively regulates the expression of iNOS in abdominal aorta, and suggest that changes in the levels of circulating estrogen may affect vascular function.     

Ovariectomy worsens secondary hyperparathyroidism in mature rats during low-Ca diet

Estrogen deficiency impairs intestinal Ca absorption and induces bone loss, but its effects on the vitamin D-endocrine system are unclear. In the present study, calciotropic hormones levels, renal vitamin D metabolism, 1,25-dihydroxyvitamin D3 [1,25(OH)2D3]-dependent intestinal calcium absorption, and bone properties in 3-mo-old sham-operated (sham) or ovariectomized (OVX) rats fed either a normal-Ca (NCD; 0.6% Ca, 0.65% P) or a low-Ca (LCD; 0.1% Ca, 0.65% P) diet for 2 wk were determined. LCD increased serum 1,25(OH)2D3 levels in both sham and OVX rats. Serum parathyroid hormone [PTH(1-84)] levels were highest in OVX rats fed LCD. Renal 25-hydroxyvitamin D1alpha-hydroxylase (1-OHase) protein expression was induced in both sham and OVX rats during LCD, while renal 1-OHase mRNA expression was highest in OVX rats fed LCD. Renal vitamin D receptor (VDR) and mRNA expressions in rats were induced by ovariectomy in rats fed NCD but suppressed by ovariectomy in rats fed LCD. The induction of intestinal calcium transporter-1 and calbindin-D9k mRNA expressions by LCD were not altered by ovariectomy. As expected, bone Ca content, cancellous bone mineral density, and bone strength index in proximal metaphysis of rat tibia were reduced by both ovariectomy and LCD (P<0.05) as analyzed by two-way ANOVA. Taken together, the data demonstrate that ovariectomy alters the responses of circulating PTH levels, renal 1-OHase mRNA expression, and renal VDR expression to LCD. These results suggest that estrogen is necessary for the full adaptive response to LCD mediated by both PTH and 1,25(OH)2D3.     

Regulation of leptin by steroid hormones in rat adipose tissue.

We investigated if steroid hormones regulate the secretion and the expression of leptin in female and male rat adipose tissue fragments in vitro. Dexamethasone time and dose-dependently increased the secretion and mRNA expression of leptin with a half-maximal stimulation of approximately 1 nM. A time-course revealed a maximal stimulatory effect of 17 beta-estradiol after 24 hours. In male adipose tissue 17 beta-estradiol increased leptin secretion (32% by 50 nM 17 beta-estradiol, P = 0.07 and 34% by 500 nM 17 beta-estradiol, P < 1780.05) after 24 hours. An additional effect of estrogen was seen in the dexamethasone (50 nM) stimulated cells (38% with 50 nM 17 beta-estradiol, P < 0.05 and 48% by 500 nM 17 beta-estradiol, P < 0.05). Basal secretion of leptin was equal in female and male adipose tissue, whereas the effects of 17 beta-estradiol (50 nM) and dexamethasone were significantly increased in female as compared with male adipose tissue. Progesterone, testosterone, dihydrotestosterone and dehydroepiandrostendione-sulfate neither affected leptin secretion in male nor female adipose tissue in vitro. Furthermore, to investigate the effect of estrogen female rats were ovariectomized (OVX) and the adipose tissue was incubated in vitro and compared with adipose tissue leptin secretion from sham operated rats (SHAM), and with ovariectomized rats treated with 17 beta-estradiol (EST). A decreased basal and dexamethasone-stimulated leptin secretion from OVX rats compared with SHAM rats was found (P < 0.005) whereas 17 beta-estradiol treatment of ovariectomized rats maintained a normal leptin secretion. However, the dexamethasone stimulation was equally increased above basal levels in SHAM, OVX and EST rats (3.7 +/- 1.2, 2.9 +/- 0.8, 4.2 +/- 1.4, NS, ANOVA) respectively.     

Effects of diosgenin on myometrial matrix metalloproteinase-2 and -9 activity and expression in ovariectomized rats

Diosgenin, a traditional Yam extraction, has been used in hormone replacement for menopausal women. We aimed to investigate the influences of diosgenin administration upon the MMP-2 and -9 activity and expression and reproductive hormones of ovariectomized (OVX) rats, a model of menopausal status. Seven-week old female Wistar rats with bilateral OVX or sham operation (controls) were divided and administered different dosages of diosgenin (0, 10, 50, or 100 mg/kg/day) for 8 weeks. Serum was then sampled for progesterone (P4) and estradiol (E2) assay and uterine horns harvested. Myometrial MMP-2 and -9 activity and expression were surveyed and myometrial collagen expression was also assayed. The results show higher body weight in OVX rats across the 8 weeks post surgery and no significant differences were noted among OVX or Sham rats with diosgenin supplements. There were lower P4 and E2 concentrations in OVX rats compared to Sham rats, and higher P4 concentration of Sham rats post diosgenin supplement. MMP-2 and -9 mRNA expression and activity was lower in OVX rats, although higher MMP-2 and lower MMP-9 activity/mRNA expression was observed in OVX rats post diosgenin supplementation. Collagen mRNA expression was higher in OVX rats compared to Sham controls, and diosgenin administration decreased collagen mRNA expression in OVX rats. In conclusion, diosgenin is associated with gelatinase expression and collagen metabolism in OVX rats. Diosgenin administration can partially reverse the effects of OVX upon MMP functions and hormone status. Adequate diosgenin supplement might modulate myometrial gelatinase expression and collagen metabolism in menopausal subjects.     

Differential regulation of the bumetanide-sensitive cotransporter (NKCC2) by ovarian hormones

The Na-K-2Cl cotransporter (NKCC2) regulates sodium transport along the thick ascending limb of Henle's loop and is important in control of sodium balance, renal concentrating ability and renin release. To determine if there are sex differences in NKCC2 abundance and/or distribution, and to evaluate the contribution of ovarian hormones to any such differences, we performed semiquantitative immunoblotting and immunoperoxidase immunohistochemistry for NKCC2 in the kidney of Sprague Dawley male, female and ovariectomized (OVX) rats with and without 17-β estradiol or progesterone supplementation. Intact females demonstrated greater NKCC2 protein in homogenates of whole kidney (334 ± 29%), cortex (219 ± 20%) and outer medulla (133 ± 9%) compared to males. Ovarian hormone supplementation to OVX rats regulated NKCC2 in the outer medulla only, with NKCC2 protein abundance decreasing slightly in response to progesterone but increasing in response to 17-β estradiol. Immunohistochemistry demonstrated prominent NKCC2 labeling in the apical membrane of thick ascending limb cells. Kidney section NKCC2 labeling confirmed regionalized regulation of NKCC2 by ovarian hormones. Localized regulation of NKCC2 by ovarian hormones may have importance in controlling sodium and water balance over the lifetime of women as the milieu of sex hormones varies.     

Differential effects of sex steroids in young and aged female mRen2.Lewis rats: A model of estrogen and salt-sensitive hypertension

Background: Male-female differences in the expression of hypertension and in end-organ damage are evident in both experimental models and human subjects, with males exhibiting a more rapid onset of cardiovascular disease and mortality than do females. The basis for these male-female differences is probably the balance of the complex effects of sex steroids (androgens, estrogen, progesterone) and their metabolites on the multiple regulatory systems that influence blood pressure (BP). A key target of estrogen and other steroids is likely to be the different components of the renin-angiotensin-aldosterone system (RAAS).Objective: The aim of this study was to review the current experimental evidence on the protective effects of estrogen in hypertensive models.Methods: The search terms estrogen , renin-aangiotensin-aldosterone system, renin receptor, salt-sensitivity, endorgan damage, hypertension, kidney, mRen2.Lewis, and injury markers were used to identify relevant publications in the PubMed database (restricted to the English language) from January 1990 to October 2007.Results: In a new congenic model that expresses the mouse renin 2 gene (mRen2.Lewis), estrogen depletion (via ovariectomy [OVX ]) in young rats was found to have a marked stimulatory effect on the progression of increased BP and cardiac dysfunction. Moreover, estrogen depletion exacerbated salt-sensitive hypertension and the extent of salt-induced cardiac and renal injury in young mRen2.Lewis rats, which probably reflected the inability to appropriately regulate various components of the RAAS. However, OVX in aged mRen2.Lewis rats conveyed renal protective effects from a high-salt diet compared with intact hypertensive littermates (64 weeks), and these effects were independent of changes in BP.Conclusion: These studies in hypertensive mRen2.Lewis rats underscored the influence of ovarian hormones on BP and tissue injury, as well as the plasticity of this response, apparently due to age and salt status.     

17β—雌二醇下调血管平滑肌内皮素A型受体的表达

为进一步探讨雌激素对心血管的保护作用,实验在双侧卵巢去势大鼠模型和培养的血管平滑肌细胞（VSMCs)上,观察17β－雌二醇（E2）对血管反应性及VSMCs增殖的影响,以RT－PCR和Western blot检测内皮素受体（ETAR）的表达,结果显示：去势雌性大鼠血管对内皮素（ET－1）的反应性明显增高,ETAR特异性受体阻断剂BQ123能完全阻断ET－1对VSMCs增殖的影响,E2能明显抑制ET－1对VSMCs增殖的作用,RT－PCR结果显示E2能抑制ETAR mRNA的表达,Western blot进一步证实E2能抑制ETAR蛋白表达,E2受体阻断剂Tamoxifen能部分抑制ET－1对VSMCs的增殖及ETAR的mRNA和蛋白 的表达。以上结果提示;ET－1促VSMCs增殖的效应主要是由ETAR介导的,雌激素能通过下调ETAR来抑制ET－1对VSMCs 促增殖的作用和血管对ET－1的反应,且此作用与雌激素受体有关。     

Effect of estrogen on calcium-handling proteins, beta-adrenergic receptors, and function in rat heart

Regulation of cellular Ca(2+) cycling is central to myocardial contractile function. Loss of Ca(2+) regulation is associated with cardiac dysfunction and pathology. Estrogen has been shown to modify contractile function and to confer cardioprotection. Therefore, we investigated the effect of estrogen on expression of rat heart myocardial Ca(2+)-handling proteins and beta-adrenergic receptor (beta(1)-AR) and examined functional correlates. Female rats were sham-operated (SHAM) or ovariectomized. Two weeks after ovariectomy rats were injected (i.p.) daily with estradiol benozoate (OVX+EB) or sesame oil (OVX) for 2 weeks. Protein abundance was measured by immunoblotting and mRNA was quantified by real-time RT-PCR. OVX significantly decreased estrogen and progesterone levels and EB replacement returned both estrogen and progesterone to physiological levels. OVX induced a 75% reduction of uterine weight and a gain in body weight. Replacement restored weights to SHAM level. OVX increased and estrogen-replacement normalized abundance of beta(1)-AR and L-type Ca(2+) channel (Cav1.2) protein. OVX decreased sodium-Ca(2+) exchange protein (NCX) and estrogen restored protein abundance to SHAM levels. Sarcoplasmic reticular ATPase (SERCA), phospholamban (PLB), and ryanodine receptor (RyR) abundance was not altered by hormone status. Levels of mRNA encoding for beta(1)-AR, Cav1.2, and NCX were not influenced by OVX or estrogen replacement. OVX had no effect on SERCA and PLB mRNA level but estrogen replacement elicited a significant increase compared to OVX and SHAM. Estrogen-dependent changes in Ca(2+)-handling proteins and beta(1)-AR are theoretically consistent reduced myocellular Ca(2+) load. However, hormone-dependent alterations in protein were not associated with changes in contractile function.     

Effects of estradiol and progesterone on body composition, protein synthesis, and lipoprotein lipase in rats

Prior studies suggest that estradiol and progesterone regulate body composition in growing female rats. Because these studies did not consider the confounding effect of changes in food intake, it remains unclear whether ovarian hormones regulate body composition independently of their effects on food intake. We utilized a pair-feeding paradigm to examine the effects of these hormones on body composition. In addition, skeletal muscle protein fractional synthesis rate and adipose tissue lipoprotein lipase activity were measured to examine pathways of substrate deposition into fat and fat-free tissue. Female Sprague-Dawley rats [pubertal: 7-8 wk old; 190 +/- 0.5 (SE) g] were separated into four groups: 1) sham-operated (S; n = 8), 2) ovariectomized plus placebo (OVX; n = 8), 3) ovariectomized plus estradiol (OVX+E; n = 8), and 4) ovariectomized plus progesterone (OVX+P; n = 8). All ovariectomized groups were pair-fed to the S group. Body composition was measured using total body electrical conductivity. The relative increase in fat-free mass was greater (P < 0.01) in the OVX group (31 +/- 2%) than in the S (17 +/- 2%), OVX+E (18 +/- 2%), and OVX+P (22 +/- 2%) groups. The fractional synthetic rates of gastrocnemius muscle protein paralleled changes in fat-free mass: OVX had a higher (P < 0.05) synthesis rate (21 +/- 3%/day) than S (12 +/- 2%/day), OVX+E (11 +/- 2%/day), and OVX+P (8 +/- 1%/day) groups. Body fat increased in the S group (31 +/- 7%; P < 0.01), whereas the OVX groups lost fat (OVX: -10 +/- 7%; OVX+E: -15 +/- 7%; OVX+P: -13 +/- 7%). No differences in lipoprotein lipase were found. Our results suggest that estradiol and progesterone may regulate the growth of fat and fat-free tissues in female rats. Moreover, ovarian hormones may influence skeletal muscle growth through their effects on skeletal muscle protein synthesis.     

Anatomically distinct activation of endothelin-3 and the L-arginine/nitric oxide pathway in the kidney with advanced aging

Aging is associated with spontaneous degenerative changes of renal function and structure. The aim of this study was to determine changes of the endothelin (ET) system and NO tissue bioactivity during the physiological aging process. Renal protein expression of ET-1 and ET-3, ETA, and ETB receptor mRNA expression, ET receptor binding and distribution, and tissue NO metabolite content were determined in adult, middle-aged, and senescent normotensive female Wistar rats. In senescent animals, medullary ET-3 content increased 3.4-fold (p<0.05 vs. adult), whereas aging did not affect ET-3 levels in the cortex. Local NO bioavailability, determined by NO metabolite tissue measurements, decreased in the cortex only. ET receptor binding capacity--predominantly due to ETB receptor binding--was lower in medulla than in cortex. Aging had no effect on ET-1 binding capacity or ET receptor distribution, whereas with advanced age gene expression of both receptors decreased. In conclusion, aging causes distinctive expressional changes of the renal endothelin system in otherwise healthy rats. The pronounced increase of endothelin-3 in the renal medulla is associated with preservation of local NO metabolite levels, changes not observed in the cortex. These findings could be important for pathologies and possibly therapy associated with renal aging.     

Estrogen upregulates renal angiotensin II AT1 and AT2 receptors in the rat

We studied renal AT1 and AT2 receptors in male, female, ovariectomized and ovariectomized-estrogen-treated Wistar-Hanover and Wistar-Kyoto rats. AT1 receptors and AT1A receptor mRNA predominated, with no significant differences between males and females. AT2 receptor expression was restricted in female rats to the capsule, the transition zone between outer and inner medulla, the endothelium lining the papilla, and arcuate arteries and veins. There were no AT2 receptors in male rats, while male mice express substantial numbers of estrogen-dependent AT2 receptors. Arcuate arteries and veins expressed AT1B mRNA in males and females, and AT2 mRNA in females only. AT1 receptor and AT2 receptor expression were estrogen-dependent, with increases in AT1 and AT2 receptor expression after estrogen treatment in ovariectomized rats. Estrogen treatment increased prostaglandin E2 (PGE2) and cGMP concentrations in the renal medulla, and eNOS expression in cortical arteries. In rodents, expression of renal Angiotensin II receptor types is estrogen-dependent, with significant species, strain and area differences. Our results support an important role for AT2 receptors in the regulation of renal function and in the protective effects of estrogen in the kidney.