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

Estrogen-induced signalling and the renal contribution to salt and water homeostasis

The kidney is considered to be one of the most estrogen-responsive, not reproductive organs in the body. Different estrogen receptors (ERs) show sex-specific differences in expression along the nephron and the expression of different ERs also changes with the estrous cycle of the female. The kidney becomes more estrogen-sensitive when estradiol levels are at their highest, just prior to ovulation. This review discusses the different mechanisms by which estradiol can modify the salt and water conservation processes of the kidney through transporter regulation to support the fluid and electrolyte homeostasis changes required in mammalian reproduction. The kidney plays a critical role in regulating blood pressure by controlling fluid homeostasis, and so protects the female cardiovascular system from dramatic changes in whole body fluid volume that occur at critical points in the human menstrual cycle and in pregnancy. This is augmented by the direct actions of estradiol on the cardiovascular system, for example through the direct stimulation of endothelial nitric oxide (NO) synthase, which releases NO to promote vasodilation. This and other mechanisms are less evident in the male and give women a degree of cardiovascular protection up until menopause, when the risks of cardiovascular disease and chronic kidney disease begin to match the risks experienced by males.

Endogenous sex hormones homeostasis disruption combined with exogenous phthalates exposure increase the risks of childhood high blood pressure: A cohort study in China

BACKGROUND

The structural similarity between sex hormones and exogenous phthalates (PAEs) enabled them as disrupters in regulating childhood blood pressure (BP). We aim to explore the association of sex hormones homeostasis and PAEs metabolites with childhood high BP (HBP).

METHODS

A cohort study was conducted with 1416 children aged 7-13 years at baseline and with 824, 819, and 801 children completing three waves' follow up. Serum testosterone (TT) and estradiol (E2) in children during three consecutive waves of surveys were measured by radioimmunoassay, and then TT/E2 ratio calculated as TT divided by E2 were used to represent sex hormones homeostasis. Seven urinary PAEs metabolites were measured in children of first wave. The BP Z-Scores and HBP across waves were obtained by sex, age, and height specific percentiles. Log-binomial regression models with adjusted risk ratios (aRR) after adjusting for confounders were utilized.

RESULTS

The prevalence of HBP at the baseline survey was 25.5%, and increased from 26.3% in the first wave of survey to 35.0% in the third wave of survey. PAEs were negatively correlated with E2, while positively correlated with TT and TT/E2 ratio. A positive association of the serum TT levels, TT/E2 ratio, and total PAEs was found with HBP prevalence (in wave 1, 2 and 3 with TT (aRR): 1.63, 1.37 and 1.45; with TT/E2: 1.63, 1.42 and 1.20; with PAEs: 1.40, 1.32 and 1.32), persistent HBP (with TT (aRR): 2.19; TT/E2: 2.16; PAEs: 2.57), occasional HBP (with TT (aRR): 1.94; TT/E2: 1.72; PAEs: 1.38), and new HBP incidence (with TT (aRR): 1.44; TT/E2: 1.57; PAEs: 1.67), but E2 had a negative association with HBP phenotypes (HBP prevalence in wave 1, 2 and 3 (aRR): 0.77, 0.93, and 1.10; persistent HBP: 0.47; occasional HBP: 0.96; new HBP incidence: 0.81). The E2 and PAEs had antagonistic effects on HBP risks in children, particularly in girls and those with high BMI group, but the TT levels, TT/E2 ratio and PAEs had synergistic effects on HBP risks in children, particularly in boys and those with high BMI group.

CONCLUSION

Exogenous PAEs exposure and endogenous sex hormones homeostasis disruption independently increase the risks of HBP. Moreover, the exogenous PAEs exposure could disrupt the endogenous sex hormones homeostasis in children, thereby combinedly increased risks of childhood HBP.

Sex Difference in MasR Expression and Functions in the Renal System

Renin-angiotensin system (RAS), as a critical system for controlling body fluid and hemostasis, contains peptides and receptors, including angiotensin 1-7 (Ang 1-7) and Mas receptor (MasR). Ang 1-7 implements its function via MasR. Ang II is another peptide in RAS that performs its actions via two Ang II type 1 and 2 receptors (AT1R and AT2R). The functions of AT2R and MasR are very similar, and both have a vasodilation effect, while AT1R has a vasoconstriction role. MasR affects many mechanisms in the brain, heart, blood vessels, kidney, lung, endocrine, reproductive, skeletal muscle, and liver and probably acts like a paracrine hormone in these organs. The effect of Ang 1-7 in the kidney is complex according to the hydroelectrolyte status, the renal sympathetic nervous system, and the activity level of the RAS. The MasR expression and function seem more complex than Ang II receptors and have interacted with Ang II receptors and many other factors, including sex hormones. Also, pathological conditions including hypertension, diabetes, and ischemia-reperfusion could change MasR expression and function. In this review, we consider the role of sex differences in MasR expression and functions in the renal system under physiological and pathological conditions.

Lipids and diastolic dysfunction: Recent evidence and findings

AIM

Diastolic dysfunction is the decreased flexibility of the left ventricle due to the impaired ability of the myocardium to relax and plays an important role in the pathogenesis of heart failure. Lipid metabolism is a well-known contributor to cardiac conditions, including ventricular function. In this article, we aimed to review the literature addressing the connections between lipids, their storage, and metabolism with left ventricular diastolic dysfunction.

DATA SYNTHESIS

We searched Google scholar, Pubmed, Embase and Researchgate for our keywords: "Diastolic function", "Fat" and "Lipid profile". Initially, 250 articles were selected by title and 84 of them were chosen as most relevant and directly reviewed.

CONCLUSIONS

Alterations of lipid metabolism in cardiac muscle and cardiac lipid content can occur in many conditions, including consumption of a high-fat diet, obesity, metabolic syndrome, and non-alcoholic fatty liver disease (NAFLD). These conditions induce alterations in myocardial lipid metabolism, increase myocardial fat content and epicardial fat thickness and increase inflammation and oxidative stress which ultimately lead to cardiac lipotoxicity and diastolic dysfunction. The effects of lipids on diastolic function can differ based on gender. Lipid profile and metabolism are as important in the pathogenesis of diastolic dysfunction as they are in other cardiovascular disorders. A more careful look at cardiac lipid metabolism in molecular, histological and gross levels results in more precise understanding of its role in myocardial function and leads to development of potential treatments for diastolic dysfunction.

Toward personalized management of chronic hypertension in pregnancy

Chronic hypertension complicates 1% to 2% of pregnancies, and it is increasingly common. Women with chronic hypertension are an easily recognized group who are in touch with a wide variety of healthcare providers before, during, and after pregnancy, mandating that chronic hypertension in pregnancy be within the scope of many practitioners. We reviewed recent data on management to inform current care and future research. This study is a narrative review of published literature. Compared with normotensive women, women with chronic hypertension are at an increased risk of maternal and perinatal complications. Women with chronic hypertension who wish to be involved in their care can do by measuring blood pressure at home. Accurate devices for home blood pressure monitoring are now readily available. The diagnostic criteria for superimposed preeclampsia remain problematic because most guidelines continue to include deteriorating blood pressure control in the definition. It has not been established how angiogenic markers may aid in confirmation of the diagnosis of superimposed preeclampsia when suspected, over and above information provided by routinely available clinical data and laboratory results. Although chronic hypertension is a strong risk factor for preeclampsia, and aspirin decreases preeclampsia risk, the effectiveness specifically among women with chronic hypertension has been questioned. It is unclear whether calcium has an independent effect in preeclampsia prevention in such women. Treating hypertension with antihypertensive therapy halves the risk of progression to severe hypertension, thrombocytopenia, and elevated liver enzymes, but a reduction in preeclampsia or serious maternal complications has not been observed; however, the lack of evidence for the latter is possibly owing to few events. In addition, treating chronic hypertension neither reduces nor increases fetal or newborn death or morbidity, regardless of the gestational age at which the antihypertensive treatment is started. Antihypertensive agents are not teratogenic, but there may be an increase in malformations associated with chronic hypertension itself. At present, blood pressure treatment targets used in clinics are the same as those used at home, although blood pressure values tend to be inconsistently lower at home among women with hypertension. Although starting all women on the same antihypertensive medication is usually effective in reducing blood pressure, it remains unclear whether there is an optimal agent for such an approach or how best to use combinations of antihypertensive medications. An alternative approach is to individualize care, using maternal characteristics and blood pressure features beyond blood pressure level (eg, variability) that are of prognostic value. Outcomes may be improved by timed birth between 38 0/7 and 39 6/7 weeks' gestation based on observational literature; of note, confirmatory trial evidence is pending. Postnatal care is facilitated by the acceptability of most antihypertensives (including angiotensin-converting enzymes inhibitors) for use in breastfeeding. The evidence base to guide the care of pregnant women with chronic hypertension is growing and aligning with international guidelines. Addressing outstanding research questions would inform personalized care of chronic hypertension in pregnancy.

Impact of new definitions of preeclampsia at term on identification of adverse maternal and perinatal outcomes

BACKGROUND

Any definition of preeclampsia should identify women and babies at greatest risk of adverse outcomes.

OBJECTIVE

This study aimed to investigate the ability of the American College of Obstetricians and Gynecologists and International Society for the Study of Hypertension in Pregnancy definitions of preeclampsia at term gestational age (≥37 0/7 weeks) to identify adverse maternal and perinatal outcomes.

STUDY DESIGN

In this prospective cohort study at 2 maternity hospitals in England, women attending a routine hospital visit at 35 0/7 to 36 6/7 weeks' gestation underwent assessment that included history; ultrasonographic estimated fetal weight; Doppler measurements of the pulsatility index in the uterine, umbilical, and fetal middle cerebral arteries; and serum placental growth factor-to-soluble fms-like tyrosine kinase-1 ratio. Obstetrical records were examined for all women with chronic hypertension and those who developed new-onset hypertension, with preeclampsia (de novo or superimposed on chronic hypertension) defined in 5 ways: traditional, based on new-onset proteinuria; American College of Obstetricians and Gynecologists 2013 definition; International Society for the Study of Hypertension in Pregnancy maternal factors definition; International Society for the Study of Hypertension in Pregnancy maternal factors plus fetal death or fetal growth restriction definition, defined according to the 35 0/7 to 36 6/7 weeks' gestation scan as either estimated fetal weight <3rd percentile or estimated fetal weight at the 3rd to 10th percentile with any of uterine artery pulsatility index >95th percentile, umbilical artery pulsatility index >95th percentile, or middle cerebral artery pulsatility index <5th percentile; and International Society for the Study of Hypertension in Pregnancy maternal-fetal factors plus angiogenic imbalance definition, defined as placental growth factor <5th percentile or soluble fms-like tyrosine kinase-1-to-serum placental growth factor >95th percentile. Detection rates for outcomes of interest (ie, severe maternal hypertension, major maternal morbidity, perinatal mortality or major neonatal morbidity, neonatal unit admission ≥48 hours, and birthweight <10th percentile) were compared using the chi-square test, and P<.05 was considered significant.

RESULTS

Among 15,248 singleton pregnancies, the identification of women with preeclampsia varied by definition: traditional, 15 of 281 (1.8%; 248); American College of Obstetricians and Gynecologists, 15 of 326 (2.1%; 248); International Society for the Study of Hypertension in Pregnancy maternal factors, 15 of 400 (2.6%; 248); International Society for the Study of Hypertension in Pregnancy maternal-fetal factors, 15 of 434 (2.8%; 248); and International Society for the Study of Hypertension in Pregnancy maternal-fetal factors plus angiogenic imbalance, 15 of 500 (3.3%; 248). Compared with the traditional definition of preeclampsia, the International Society for the Study of Hypertension in Pregnancy maternal-fetal factors plus angiogenic imbalance best identified the adverse outcomes: severe hypertension (40.6% [traditional] vs 66.9% [International Society for the Study of Hypertension in Pregnancy maternal-fetal factors plus angiogenic imbalance, P<.0001], 59.2% [International Society for the Study of Hypertension in Pregnancy maternal-fetal factors, P=.004], 56.2% [International Society for the Study of Hypertension in Pregnancy maternal factors, P=.013], 46.1% [American College of Obstetricians and Gynecologists, P=.449]); P<.0001); composite maternal severe adverse event (72.2% [traditional] vs 100% for all others; P=.046); composite of perinatal mortality and morbidity (46.9% [traditional] vs 71.1% [International Society for the Study of Hypertension in Pregnancy maternal-fetal factors plus angiogenic imbalance, P=.002], 62.2% [International Society for the Study of Hypertension in Pregnancy maternal-fetal factors, P=.06], 59.8% [International Society for the Study of Hypertension in Pregnancy maternal factors, P=.117], 49.4% [American College of Obstetricians and Gynecologists, P=.875]); neonatal unit admission for ≥48 hours (51.4% [traditional] vs 73.4% [International Society for the Study of Hypertension in Pregnancy maternal-fetal factors plus angiogenic imbalance, P=.001], 64.5% [International Society for the Study of Hypertension in Pregnancy maternal-fetal factors, P=.070], 60.7% [International Society for the Study of Hypertension in Pregnancy maternal factors, P=.213], 53.3% [American College of Obstetricians and Gynecologists, P=.890]); birthweight <10th percentile (40.5% [traditional] vs 78.7% [International Society for the Study of Hypertension in Pregnancy maternal-fetal factors plus angiogenic imbalance, P<.0001], 70.1% [International Society for the Study of Hypertension in Pregnancy maternal-fetal, P<.0001], 51.3% [International Society for the Study of Hypertension in Pregnancy maternal factors, P=.064], 46.3% [American College of Obstetricians and Gynecologists, P=.349]).

CONCLUSION

Our findings present an evidence base for the broad definition of preeclampsia. Our data suggest that compared with a traditional definition, a broad definition of preeclampsia can better identify women and babies at risk of adverse outcomes. Compared with the American College of Obstetricians and Gynecologists definition, the more inclusive International Society for the Study of Hypertension in Pregnancy definition of maternal end-organ dysfunction seems to be more sensitive. The addition of uteroplacental dysfunction to the broad definition optimizes the identification of women and babies at risk, particularly when angiogenic factors are included.

The impact of pre-eclampsia definitions on the identification of adverse outcome risk in hypertensive pregnancy - analyses from the CHIPS trial (Control of Hypertension in Pregnancy Study)

OBJECTIVE

To examine the association between pre-eclampsia definition and pregnancy outcome.

DESIGN

Secondary analysis of Control of Hypertension in Pregnancy Study (CHIPS) trial data.

SETTING

International multicentre randomised controlled trial (RCT).

POPULATION

In all, 987 women with non-severe non-proteinuric pregnancy hypertension.

METHODS

We evaluated the association between pre-eclampsia definitions and adverse pregnancy outcomes, stratified by hypertension type and blood pressure control.

MAIN OUTCOME MEASURES

Main CHIPS trial outcomes: primary (perinatal loss or high-level neonatal care for >48 hours), secondary (serious maternal complications), birthweight <10th centile, severe maternal hypertension, delivery at <34 or <37 weeks, and maternal hospitalisation before birth.

RESULTS

Of 979/987 women with informative data, 280 (28.6%) progressed to pre-eclampsia defined restrictively by new proteinuria, and 471 (48.1%) to pre-eclampsia defined broadly as proteinuria or one/more maternal symptoms, signs or abnormal laboratory tests. The broad (versus restrictive) definition had significantly higher sensitivities (range 62-79% versus 36-50%), lower specificities (range 53-65% versus 72-82%), and similar or higher diagnostic odds ratios and 'true-positive' to 'false-positive' ratios. Stratified analyses showed similar results. Addition of available fetoplacental manifestations (stillbirth or birthweight <10th centile) to the broad pre-eclampsia definition improved sensitivity (74-87%).

CONCLUSIONS

A broad (versus restrictive) pre-eclampsia definition better identifies women who develop adverse pregnancy outcomes. These findings should be replicated in a prospective study within routine healthcare to ensure that the anticipated increase in surveillance and intervention in a larger number of women with pre-eclampsia is associated with improved outcomes, reasonable costs and congruence with women's values.

TWEETABLE ABSTRACT

A broad (versus restrictive) pre-eclampsia definition better identifies the risk of adverse pregnancy outcomes.

Swimming training improves cardiovascular autonomic dysfunctions and prevents renal damage in rats fed a high-sodium diet from weaning

NEW FINDINGS

What is the central question of this study? How does swimming exercise training impact hydro-electrolytic balance, renal function, sympathetic contribution to resting blood pressure and cerebrospinal fluid (CSF) [Na⁺ ] in rats fed a high-sodium diet from weaning? What is the main finding and its importance? An exercise-dependent reduction in blood pressure was associated with decreased CSF [Na⁺ ], sympathetically driven vasomotor tonus and renal fibrosis indicating that the anti-hypertensive effects of swimming training in rats fed a high-sodium diet might involve neurogenic mechanisms regulated by sodium levels in the CSF rather than changes in blood volume.

ABSTRACT

High sodium intake is an important factor associated with hypertension. High-sodium intake with exercise training can modify homeostatic hydro-electrolytic balance, but the effects of this association are mostly unknown. In this study, we sought to investigate the effects of swimming training (ST) on cerebrospinal fluid (CSF) Na⁺ concentration, sympathetic drive, blood pressure (BP) and renal function of rats fed a 0.9% Na⁺ (equivalent to 2% NaCl) diet with free access to water for 22 weeks after weaning. Male Wistar rats were assigned to two cohorts: (1) fed standard diet (SD) and (2) fed high-sodium (HS) diet. Each cohort was further divided into trained and sedentary groups. ST normalised BP levels of HS rats as well as the higher sympathetically related pressor activity assessed by pharmacological blockade of ganglionic transmission (hexamethonium). ST preserved the renal function and attenuated the glomerular shrinkage elicited by HS. No change in blood volume was found among the groups. CSF [Na⁺ ] levels were higher in sedentary HS rats but were reduced by ST. Our findings showed that ST effectively normalised BP of HS rats, independent of its effects on hydro-electrolytic balance, which might involve neurogenic mechanisms regulated by Na⁺ levels in the CSF as well as renal protection.

Protective effects of Avena sativa against oxidative stress-induced kidney damage resulting from an estrogen deficiency in ovariectomized Swiss mice model

The aim of this study was to evaluate the antioxidant capacity of Avena sativa and to confirm its protective effects on estrogen deficiency in ovariectomized mice (OVX) model. Animals were treated during 21 and 60 days as follows: negative control, positive control treated with oat, ovariectomized, and ovariectomized receiving hormonal or oat treatments, respectively. 21 days post-surgery, our results showed that ovariectomy increases weight gain and urea level in plasma. After 60 days of treatment, OVX showed a gain in weight, high increases in relative kidney weight, plasmatic creatinine, glutathione peroxidase (GPX) activity, and protein oxidation as shown by elevated protein carbonyl (PCO) and advanced oxidation protein products (AOPP) levels. On the other side, a decrease was detected in catalase activity. Meanwhile, no significant changes in urea level, lipid peroxidation, SOD and GSH activity were detected. Conversely, supplementation with oat reduced weight gain, as well as oxidative stress and oxidation protein in the kidney of OVX mice. PRACTICAL APPLICATIONS: In our study, we removed the two ovaries of adult female mice in order to eliminate the essential source of steroid hormones. Deficiency in these sexual hormones, especially estrogen, leads to several physiological and morphological disturbances that are found in post-menopausal women. The gain in weight and oxidative kidney damages were the main health problems detected in ovariectomized animals. This work explored for the first time the use of oat grains as a safe natural remedy to treat all previous health problems and to avoid carcinogenic effects of the menopausal hormone therapy. Owing to its health benefits, this cereal species has recently gained attention as an important source of antioxidants and fibers. Thanks to these two components, it can be able to restore all indicated disturbances. Therefore, this cereal can be very useful in the prevention of obesity and kidney oxidative damage occurring during menopause.

Sex differences in cardiac and renal responses to a high salt diet in Sprague-Dawley rats

High dietary salt intake is an important risk factor for cardiovascular and renal diseases. However, sexual disparity exists in the response of target organs to high salt diet (HSD). To determine how sex affects cardiac and renal functions' response to HSD, 20 weanling Sprague-Dawley rats (10 males and 10 females) were divided into 4 groups of 5 rats each. The rats were fed a normal diet (0.3% NaCl) or HSD (8% NaCl) for 12 weeks. Fluid balance (FB) was determined from 24 hrs water intake and voided urine. Blood pressure (BP) was measured via arterial cannulation under anesthesia (25% w/v urethane and 1% w/v α-chloralose; 5 ml/kg, i.p). Serum levels of troponin I, aminotransaminases, creatinine, urea, uric acid and electrolytes as well as urinary concentration of albumin, creatinine, and electrolytes were measured using appropriate assay kits. Values are presented as mean ± S.E.M, compared by two-way ANOVA and Bonferroni post Hoc test. In the male rat, HSD significantly increased BP, serum: Troponin I, LDH and sodium (p < 0.05), urinary: albumin, sodium, potassium and FB (p < 0.05). In the female rat, HSD increased BP, serum: troponin I, LDH, sodium and creatinine clearance (p < 0.05), urinary: albumin, sodium and potassium (p < 0.01). However, HSD increased more, the BP, serum: Troponin I, LDH, urinary albumin and FB in male rats, while HSD increased urinary sodium more in female rats. Basal values in male vs. female of serum LDH and urinary albumin were significantly different. Thus, sex plays an important role in the response of the heart and kidney to salt stress.

Chronic Estrogen Supplementation Prevents the Increase in Blood Pressure in Female Intrauterine Growth-Restricted Offspring at 12 Months of Age

Low birth weight is associated with a greater prevalence of hypertension and an earlier age at menopause in women in later life. Yet, the association between birth weight and blood pressure (BP) in women as they age is not well defined. In a rodent model of low birth weight induced by placental insufficiency, intrauterine growth restriction programs a significant increase in BP by 12 months of age in female growth-restricted offspring that is associated with early reproductive senescence, increased testosterone, and a shift in the hormonal milieu. Thus, this study tested the hypothesis that increased BP in female growth-restricted offspring is abolished by chronic estradiol supplementation. Placebo or 17β-estradiol valerate mini pellets (1.5 mg for 60-day release) were administered at 12 months of age for 6 weeks. BP, measured in conscious catheterized rats, was significantly increased in placebo-treated growth-restricted relative to placebo-treated control. However, BP was not elevated in estradiol-treated growth-restricted relative to placebo-treated growth-restricted. Estradiol mediates its effects on BP via its receptors and the renin-angiotensin system. BP was decreased in growth-restricted offspring treated with a G-protein coupled receptor agonist, G1 (400 mg/kg for 2 weeks). Renal AT1aR (angiotensin type 1a receptor) and AT1bR (angiotensin type 1b receptor) and renal AR (androgen receptor) mRNA expression were elevated in vehicle-treated growth-restricted offspring, but not in G1-treated growth-restricted. Therefore, these data suggest that chronic estradiol supplementation prevents the increase in BP that develops in female growth-restricted offspring via actions that may involve its G-protein coupled receptor and the renin-angiotensin system.

Sex-dependent expression of brain medullary MAP and PI3 kinases in adult sheep with antenatal betamethasone exposure

Antenatal betamethasone (BM) therapy for women in jeopardy of premature delivery accelerates the lung development in preterm infants and reduces infant mortality rates, but may induce early programming events with chronic cardiovascular consequences. In a sheep model of fetal programming, in utero BM-exposed (BMX) offspring as adults exhibit elevated mean arterial pressure (MAP), decreased baroreflex sensitivity (BRS) for the control of heart rate and insulin resistance accompanied by dysregulation of the brain renin-angiotensin (Ang) system (RAS). However, the status of signaling mechanisms in the brain dorsomedial medulla (DMM) of the BMX sheep that comprise both the mitogen activated protein kinase (MAPK) and phosphoinositide 3-kinase (PI3K) cellular pathways is unknown. Given the importance of these signaling pathways in the actions of Ang peptides as well as baroreflex function and autonomic integration, we applied both a kinase signaling array and associated individual immunoblots of the dorsomedial brain medulla from adult female and male sheep with antenatal BMX. MAPK and PI3K pathways were altered significantly in the BMX sheep in a sex-dependent manner. A protein array for kinases (PathScan® Intracellular Signaling Array Kit, Cell Signaling) and subsequent verification by immunoblot revealed that within the DMM, female BMX sheep exhibit lower expression of proteins in the PI3K pathway, while male BMX sheep show greater expression of p-MAPK pathway proteins extracellular signal regulated kinase (ERK) 1/2. We conclude that maladaptive changes in these two kinase pathways in the DMM may contribute to the chronic dysregulation of blood pressure in this model of fetal programming.

GPCRs in context: sexual dimorphism in the cardiovascular system

Cardiovascular disease (CVD) remains the largest cause of mortality worldwide, and there is a clear gender gap in disease occurrence, with men being predisposed to earlier onset of CVD, including atherosclerosis and hypertension, relative to women. Oestrogen may be a driving factor for female-specific cardioprotection, though androgens and sex chromosomes are also likely to contribute to sexual dimorphism in the cardiovascular system (CVS). Many GPCR-mediated processes are involved in cardiovascular homeostasis, and some exhibit clear sex divergence. Here, we focus on the G protein-coupled oestrogen receptor, endothelin receptors ET_A and ET_B and the eicosanoid G protein-coupled receptors (GPCRs), discussing the evidence and potential mechanisms leading to gender dimorphic responses in the vasculature. The use of animal models and pharmacological tools has been essential to understanding the role of these receptors in the CVS and will be key to further delineating their sex-specific effects. Ultimately, this may illuminate wider sex differences in cardiovascular pathology and physiology.

LINKED ARTICLES

This article is part of a themed section on Molecular Pharmacology of GPCRs. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175.21/issuetoc.

Role of Kidneys in Sex Differences in Angiotensin II-Induced Hypertension

The significance of kidneys in regulation of sodium and water balance and hemodynamics has been demonstrated both in patients and animal models. In the present study, we tested our hypothesis that kidneys play an essential role in control of sex differences in angiotensin II (Ang II)-dependent hypertension. Kidney transplantations (KTXs) were performed between male (M) and female (F) C57BL/6 mice (donor→recipient: F→F, M→M, F→M, and M→F). Radiotelemetry transmitters were implanted for measurement of mean arterial pressure during the infusion of Ang II (600 ng·kg^-1·min^-1). Gene expressions and inflammatory responses in the transplanted grafts were assessed. We found that same-sex-KTX mice still exhibited sex differences in Ang II-dependent hypertension (31.3±0.8 mm Hg in M→M versus 12.2±0.6 mm Hg in F→F), which were reduced between males and females when they received kidneys of the opposite sex (32.9±1 mm Hg in M→F versus 22.3±0.7 mm Hg in F→M). The sex differences in gene expressions, including AT₁R (angiotensin II receptor, type 1), AT₁R/AT₂R, ET-1 (endothelin-1), ETA (endothelin receptor type A), NHE3 (sodium-hydrogen exchanger 3), α-ENaC (α-epithelial sodium channel), and γ-ENaC, were unaltered in same-sex KTXs and much lessened in cross-sex KTXs. In addition, the cross-sex KTXs exhibited more robust inflammatory responses reflected by higher expression of IL-6 (interleukin 6), TNFα (tumor necrosis factor α), and KC (keratinocyte-derived chemokine) than same-sex KTX. Our results indicate that kidneys play an essential role in sex differences of Ang II-dependent hypertension. KTX of male kidneys to females augmented the blood pressure response, whereas KTX of female kidneys to males attenuated the blood pressure response. The host's extrarenal systems modulate expressions of many genes and inflammatory response, which may also contribute to the sex differences in blood pressure regulation.

Cardiovascular Autonomic Responses in the VCD Rat Model of Menopause: Effects of Short- and Long-Term Ovarian Failure

After menopause, hypertension elevates the risk of cardiac diseases, one of the major causes of women's morbidity. The gradual depletion of ovarian follicles in rats, induced by 4-vinylcyclohexene diepoxide (VCD), is a model for studying the physiology of menopause. 4-Vinylcyclohexene diepoxide treatment leads to early ovarian failure (OF) and a hormonal profile comparable to menopause in humans. We have hypothesized that OF can compromise the balance between sympathetic and parasympathetic tones of the cardiovascular system, shifting toward dominance of the former. We aimed to study the autonomic modulation of heart and blood vessels and the cardiovascular reflexes in rats presenting short-term (80 days) or long-term (180 days) OF induced by VCD. Twenty-eight-day-old Wistar rats were submitted to VCD treatment (160 mg/kg, intraperitoneally) or vehicle (control) for 15 consecutive days and experiments were conducted at 80 or 180 days after the onset of treatment. Long-term OF led to an increase in the sympathetic activity to blood vessels and an impairment in the baroreflex control of the heart, evoked by physiological changes in arterial pressure. Despite that, long-term OF did not cause hypertension during the 180 days of exposure. Short-term OF did not cause any deleterious effect on the cardiovascular parameters analyzed. These data indicate that long-term OF does not disrupt the maintenance of arterial pressure homeostasis in rats but worsens the autonomic cardiovascular control. In turn, this can lead to cardiovascular complications, especially when associated with the aging process seen during human menopause.

Breaking the Cycle: Estrous Variation Does Not Require Increased Sample Size in the Study of Female Rats

Despite the striking differences between male and female physiology, female physiology is understudied. In response, the National Institutes of Health is promulgating new policies to increase the use of female organisms in preclinical research. Females are commonly believed to have greater variability than males because of the estrous cycle, but recent studies call this belief into question. Effects of estrous cycling on mean arterial pressure were assessed in female Dahl S rats using telemetry and vaginal cytometry and found that estrous cycling did not affect mean arterial pressure magnitude or variance. Data from the PhysGen arm of the Program for Genomic Applications was used to compare male and female variance and coefficient of variation in 142 heart, lung, vascular, kidney, and blood phenotypes, each measured in hundreds to thousands of individual rats from over 50 inbred strains. Seventy-four of 142 phenotypes from this data set demonstrated a sex difference in variance; however, 59% of these phenotypes exhibited greater variance in male rats rather than female. Remarkably, a retrospective power analysis demonstrated that only 16 of 74 differentially variable phenotypes would be detected when using an experimental cohort large enough to detect a difference in magnitude. No overall difference in coefficient of variation between male and female rats was detected when analyzing these 142 phenotypes. We conclude that variability of 142 traits in male and female rats is similar, suggesting that differential treatment of males and females for the purposes of experimental design is unnecessary until proven otherwise, rather than the other way around.

GPER activation ameliorates aortic remodeling induced by salt-sensitive hypertension

The mRen2 female rat is an estrogen- and salt-sensitive model of hypertension that reflects the higher pressure and salt sensitivity associated with menopause. We previously showed that the G protein-coupled estrogen receptor (GPER) mediates estrogenic effects in this model. The current study hypothesized that GPER protects against vascular injury during salt loading. Intact mRen2 female rats were fed a normal (NS; 0.5% Na(+)) or high-salt diet (HS; 4% Na(+)) for 10 wk, which significantly increased systolic blood pressure (149 ± 5 vs. 224 ± 8 mmHg;P< 0.001). Treatment with the selective GPER agonist G-1 for 2 wk did not alter salt-sensitive hypertension (216 ± 4 mmHg;P> 0.05) or ex vivo vascular responses to angiotensin II or phenylephrine (P> 0.05). However, G-1 significantly attenuated salt-induced aortic remodeling assessed by media-to-lumen ratio (NS: 0.43; HS+veh: 0.89; HS+G-1: 0.61;P< 0.05). Aortic thickening was not accompanied by changes in collagen, elastin, or medial proliferation. However, HS induced increases in medial layer glycosaminoglycans (0.07 vs. 0.42 mm(2);P< 0.001) and lipid peroxidation (0.11 vs. 0.51 mm(2);P< 0.01), both of which were reduced by G-1 (0.20 mm(2)and 0.23 mm(2); both P< 0.05). We conclude that GPER's beneficial actions in the aorta of salt-loaded mRen2 females occur independently of changes in blood pressure and vasoreactivity. GPER-induced attenuation of aortic remodeling was associated with a reduction in oxidative stress and decreased accumulation of glycosaminoglycans. Endogenous activation of GPER may protect females from salt- and pressure-induced vascular damage.

Differences in angiotensin (1-7) between men and women

In experimental animal models of hypertension, angiotensin (1-7) [ANG-(1-7)] is higher in females compared with males; however, it is less clear whether the same applies to humans. Therefore, this study sought to compare circulating concentrations of ANG-(1-7) in apparently healthy men and women under normal physiological conditions. With the use of a cross-sectional experimental design, blood was collected in EDTA anticoagulant from 42 volunteers (21 men and 21 women; and age range, 19-48 yr) for analysis of plasma concentrations of ANG-(1-7) and ANG II. Blood pressure was measured and vascular endothelial function was determined (n = 25) using the brachial artery flow-mediated dilation (FMD) test. As a result, women exhibited a higher circulating concentration of ANG-(1-7) (P = 0.04) compared with men, whereas values of ANG II were similar between groups. Baseline arterial diameter, peak diameter, and shear rate were significantly greater (P < 0.02) in men compared with women. No significant differences in FMD, FMD normalized for shear, or time to peak dilation were observed between men and women. In addition, a positive correlation between ANG-(1-7) and FMD (P = 0.04) and negative association between ANG-(1-7) with ANG II (P = 0.01) were only identified in men, whereas a positive relationship between ANG-(1-7) and diastolic blood pressure (P = 0.03) was observed in women.

IN CONCLUSION

, women exhibit significantly higher plasma concentrations of ANG-(1-7) compared with men. In addition, this study describes a relationship between ANG-(1-7), vascular function, and diastolic blood pressure that appears to be sex dependent.

Pressor responsiveness to angiotensin II in female mice is enhanced with age: role of the angiotensin type 2 receptor

Background

The pressor response to angiotensin II (AngII) is attenuated in adult females as compared to males via an angiotensin type 2 receptor (AT₂R)-dependent pathway. We hypothesized that adult female mice are protected against AngII-induced hypertension via an enhanced AT₂R-mediated pathway and that in reproductively senescent females this pathway is no longer operative.

Methods

Mean arterial pressure was measured via telemetry in 4-month-old (adult) and 16-month-old (aged) and aged ovariectomized (aged-OVX) wild-type and AT₂R knockout (AT₂R-KO) female mice during baseline and 14-day infusion of vehicle (saline) or AngII (600 ng/kg/min s.c.). Real-time reverse transcription polymerase chain reaction (RT-PCR) was used to determine renal gene expression of angiotensin receptors and angiotensin-converting enzyme 2 in response to 14-day treatment with vehicle or AngII.

Results

Basal mean arterial pressure was similar between the groups. The pressor response to AngII was augmented in adult AT₂R-KO compared to adult wild-type mice (29 ± 3 mmHg versus 10 ± 4 mmHg, respectively, on day 14 as compared to basal mean arterial pressure, P = 0.002). In wild-type mice, pressor responsiveness to AngII was augmented with age, such that the pressor response to AngII was similar between aged AT₂R-KO and wild-type female mice (31 ± 4 mmHg versus 34 ± 3 mmHg, respectively, on day 14, P = 0.9). There were no significant differences in pressor responsiveness to AngII between aged and aged-OVX mice. Vehicle-treated aged wild-type mice had a lower renal AT₂R/AT₁R balance as compared to adult counterparts. In response to AngII, the renal AT₂R/AT₁R balance in aged wild-type females was greater than that observed in vehicle-treated aged wild-type females and adult wild-type females, yet the protective effects of AT₂R activation were not restored.

Conclusions

The protective role of the AT₂R depressor pathway is lost with age in female mice. Therefore, targeting deficits in AT₂R expression and/or signaling may represent a novel anti-hypertensive approach in aged females.

Sex- and age-related differences in the chronic pressure-natriuresis relationship: role of the angiotensin type 2 receptor

Sex hormones regulate the renin-angiotensin system. For example, estrogen enhances expression of the angiotensin type 2 receptor. We hypothesized that activation of the angiotensin type 2 receptor shifts the chronic pressure-natriuresis relationship leftward in females compared with males and that this effect is lost with age. Mean arterial pressure was measured by radiotelemetry in adult (4 mo old) and aged (14 mo old) wild-type and angiotensin type 2 receptor knockout male and female mice. Chronic pressure-natriuresis curves were constructed while mice were maintained on a normal-salt (0.26%) diet and following 6 days of high salt (5.0%) diet. Mean arterial pressure was lower in adult wild-type females than males (88 ± 1 and 97 ± 1 mmHg, respectively), a difference that was maintained with age, but was absent in adult knockout mice. In wild-type females, the chronic pressure-natriuresis relationship was shifted leftward compared with knockout females, an effect that was lost with age. In males, the chronic pressure-natriuresis relationship was not influenced by angiotensin type 2 receptor deficiency. Compared with age-matched females, the chronic pressure-natriuresis relationships in male mice were shifted rightward. Renal expression of the angiotensin type 2 receptor was fourfold greater in adult wild-type females than males. With age, the angiotensin type 2 receptor-to-angiotensin type 1 receptor balance was reduced in females. Conversely, in males, angiotensin receptor expression did not vary significantly with age. In conclusion, the angiotensin type 2 receptor modulates the chronic pressure-natriuresis relationship in an age- and sex-dependent manner.

Gender differences in the relationship between blood pressure and body mass index during adolescence

OBJECTIVE

In adults, gender and obesity play significant roles in the regulation of blood pressure (BP). This study investigated the effects of gender and body mass index (BMI) on BP during adolescence.

DESIGN AND SETTING

A cross-sectional and longitudinal study involving 6838 students under twenty years old (median, eighteen years old; male, 4624; female, 2214) at Osaka University visited the Healthcare Center for their matriculation health examination from April to May in the years 2008, 2009, and 2010, and re-visited the Healthcare Center for their student health examination from May to June in the years 2011, 2012, and 2013.

METHODS

Height, body weight, and BP were measured in students both on and 3 years after admission to Osaka University.

RESULTS

On admission, the slope of the regression line for BMI and systolic BP (SBP) in non-underweight students was significantly different between genders. SBP and diastolic BP (DBP) increased in both genders during the observation period. Among male students who had a normal BMI on admission, those who had an increase in BMI of over 4% during the observation period showed a greater increase in SBP than those who had a change in BMI of -4% to 4%. On the other hand, female students showed no change in BP with the increase in BMI.

CONCLUSIONS

The magnitude of BP elevation with increased BMI was associated with gender during adolescence. This may be a cause of the higher prevalence of hypertension in adult males.

Role of estrogen in diastolic dysfunction

The prevalence of left ventricular diastolic dysfunction (LVDD) sharply increases in women after menopause and may lead to heart failure. While evidence suggests that estrogens protect the premenopausal heart from hypertension and ventricular remodeling, the specific mechanisms involved remain elusive. Moreover, whether there is a protective role of estrogens against cardiovascular disease, and specifically LVDD, continues to be controversial. Clinical and basic science have implicated activation of the renin-angiotensin-aldosterone system (RAAS), linked to the loss of ovarian estrogens, in the pathogenesis of postmenopausal diastolic dysfunction. As a consequence of increased tissue ANG II and low estrogen, a maladaptive nitric oxide synthase (NOS) system produces ROS that contribute to female sex-specific hypertensive heart disease. Recent insights from rodent models that mimic the cardiac phenotype of an estrogen-insufficient or -deficient woman (e.g., premature ovarian failure or postmenopausal), including the ovariectomized congenic mRen2.Lewis female rat, provide evidence showing that estrogen modulates the tissue RAAS and NOS system and related intracellular signaling pathways, in part via the membrane G protein-coupled receptor 30 (GPR30; also called G protein-coupled estrogen receptor 1). Complementing the cardiovascular research in this field, the echocardiographic correlates of LVDD as well as inherent limitations to its use in preclinical rodent studies will be briefly presented. Understanding the roles of estrogen and GPR30, their interactions with the local RAAS and NOS system, and the relationship of each of these to LVDD is necessary to identify new therapeutic targets and alternative treatments for diastolic heart failure that achieve the cardiovascular benefits of estrogen replacement without its side effects and contraindications.

Update on the Angiotensin converting enzyme 2-Angiotensin (1-7)-MAS receptor axis: fetal programing, sex differences, and intracellular pathways

The renin-angiotensin-system (RAS) constitutes an important hormonal system in the physiological regulation of blood pressure. Indeed, dysregulation of the RAS may lead to the development of cardiovascular pathologies including kidney injury. Moreover, the blockade of this system by the inhibition of angiotensin converting enzyme (ACE) or antagonism of the angiotensin type 1 receptor (AT1R) constitutes an effective therapeutic regimen. It is now apparent with the identification of multiple components of the RAS that the system is comprised of different angiotensin peptides with diverse biological actions mediated by distinct receptor subtypes. The classic RAS can be defined as the ACE-Ang II-AT1R axis that promotes vasoconstriction, sodium retention, and other mechanisms to maintain blood pressure, as well as increased oxidative stress, fibrosis, cellular growth, and inflammation in pathological conditions. In contrast, the non-classical RAS composed of the ACE2-Ang-(1-7)-Mas receptor axis generally opposes the actions of a stimulated Ang II-AT1R axis through an increase in nitric oxide and prostaglandins and mediates vasodilation, natriuresis, diuresis, and oxidative stress. Thus, a reduced tone of the Ang-(1-7) system may contribute to these pathologies as well. Moreover, the non-classical RAS components may contribute to the effects of therapeutic blockade of the classical system to reduce blood pressure and attenuate various indices of renal injury. The review considers recent studies on the ACE2-Ang-(1-7)-Mas receptor axis regarding the precursor for Ang-(1-7), the intracellular expression and sex differences of this system, as well as an emerging role of the Ang1-(1-7) pathway in fetal programing events and cardiovascular dysfunction.

Estrogen therapy, independent of timing, improves cardiac structure and function in oophorectomized mRen2.Lewis rats

OBJECTIVE

mRen2.Lewis rats exhibit exacerbated increases in blood pressure, left ventricular (LV) remodeling, and diastolic impairment after the loss of estrogens. In this same model, depletion of estrogens has marked effects on the cardiac biopterin profile concomitant with suppressed nitric oxide release. With respect to the establishment of overt systolic hypertension after oophorectomy (OVX), we assessed the effects of timing long-term 17β-estradiol (E2) therapy on myocardial function, myocardial structure, and the cardiac nitric oxide system.

METHODS

OVX (n = 24) or sham operation (Sham; n = 13) was performed in 4-week-old female mRen2.Lewis rats. After randomization, OVX rats received E2 immediately (OVX + E2-early; n = 7), E2 at 11 weeks of age (OVX + E2-late; n = 8), or no E2 at all (OVX; n = 9).

RESULTS

E2-early was associated with lower body weight, less hypertension-related cardiac remodeling, and decreased LV filling pressure compared with OVX rats without E2 supplementation. E2-late similarly attenuated the adverse effects of ovarian hormone loss on tissue Doppler-derived LV filling pressures and perivascular fibrosis, and significantly improved myocardial relaxation or mitral annular velocity (e'). Early and late exposures to E2 decreased dihydrobiopterin, but only E2-late yielded significant increases in cardiac nitrite concentrations.

CONCLUSIONS

Although there are some similarities between E2-early and E2-late treatments in relation to preservation of diastolic function and cardiac structure after OVX, the lusitropic potential of E2 is most consistent with late supplementation. The cardioprotective effects of E2-late are independent of blood pressure and may have occurred through regulation of cardiac biopterins and nitric oxide production.

Testosterone reduces vascular relaxation by altering cyclic adenosine monophosphate pathway and potassium channel activation in male Sprague Dawley rats fed a high-salt diet

OBJECTIVES

Male gender and high-salt diet are risk factors for hypertension. The effect of chronic exposure to testosterone is an increase in vascular tone but its influence upon responses induced by other vasoactive agents is not clear. We considered the possibility of interactions between testosterone and a high-salt diet in the mechanisms that are involved in the regulation of vascular tone. Therefore, we designed experiments to assess the involvement of the cyclic adenosine monophosphate (cAMP) pathway and potassium channel activation on vascular relaxation elicited by testosterone deficiency that was induced by orchidectomy in Sprague Dawley rats on a normal or high-salt diet.

METHOD

Weanling male rats were randomly divided into eight groups (n = 6 each) that were either orchidectomized or sham operated with or without testosterone replacement (10 mg/kg body weight of Sustanon 250 intramuscularly, Organon, Holland) and were placed on a normal or high-salt (0.3% or 8% NaCl) diet, respectively, for 6 weeks. Arterial blood pressure was determined before and weekly throughout the experiment using the tail-cuff method. Relaxation responses to forskolin and diazoxide were studied in noradrenaline (0.1 µM) precontracted aortic rings.

RESULTS

There was an increase in the systolic blood pressure of rats placed on a high-salt diet compared with control or orchidectomized rats. Orchidectomy elicited a reduction in the systolic blood pressure while testosterone replacement restored systolic blood pressure to values seen in intact rats. A high-salt diet reduced the relaxation response to forskolin and diazoxide but not in orchidectomized rats while testosterone replacement re-established the blunted relaxation response to forskolin and diazoxide.

CONCLUSION

Inhibition of potassium channel or adenylyl cyclase activation appears to contribute to the mechanisms by which a high-salt diet increases vascular tone. These effects were counteracted by orchidectomy in male Sprague Dawley rats.

Relaxation response of abdominal aorta to androgens in orchidectomised Sprague-Dawley rats fed a high-salt diet

Previous studies have demonstrated the acute relaxant effects of androgens on normal arterial beds, but not on any with underlying or induced pathologies. This study investigated whether the status of the gonads affects the direct actions of androgens on isolated abdominal aorta from male Sprague-Dawley rats fed a high-salt diet. A high-salt diet reduced the relaxation response to exogenous testosterone, but not to dehydroepiandrosterone (DHEA). Orchidectomy reduced the relaxation response to both testosterone and DHEA, while testosterone replacement restored the acute vasorelaxant effect of testosterone and DHEA in both normal and high-salt diet fed rats. Gonadal status appears to be important in the acute vasorelaxant effect of androgens.

Sexual dimorphism in urinary angiotensinogen excretion during chronic angiotensin II-salt hypertension

BACKGROUND

The intrarenal renin-angiotensin system contributes to hypertension by regulating sodium and water reabsorption throughout the nephron. Sex differences in the intrarenal components of the renin-angiotensin system have been involved in the greater incidence of high blood pressure and progression to kidney damage in males than females.

OBJECTIVE

This study investigated whether there is a sex difference in the intrarenal gene expression and urinary excretion of angiotensinogen (AGT) during angiotensin II (Ang II)-dependent hypertension and high-salt (HS) diet.

METHODS

Male and female Sprague-Dawley rats were divided into 5 groups for each sex: Normal-salt control, HS diet (8% NaCl), Ang II-infused (80 ng/min), Ang II-infused plus HS diet, and Ang II-infused plus HS diet and treatment with the Ang II receptor blocker, candesartan (25 mg/L in the drinking water). Rats were evaluated for systolic blood pressure (SBP), kidney AGT mRNA expression, urinary AGT excretion, and proteinuria at different time points during a 14-day protocol.

RESULTS

Both male and female rats exhibited similar increases in urinary AGT, with increases in SBP during chronic Ang II infusion. HS diet greatly exacerbated the urinary AGT excretion in Ang II-infused rats; males had a 9-fold increase over Ang II alone and females had a 2.5-fold increase. Male rats displayed salt-sensitive SBP increases during Ang II infusion and HS diet, and female rats did not. In the kidney cortex, males displayed greater AGT gene expression than females during all treatments. During Ang II infusion, both sexes exhibited increases in AGT gene message compared with same-sex controls. In addition, HS diet combined with Ang II infusion exacerbated the proteinuria in both sexes. Concomitant Ang II receptor blocker treatment during Ang II infusion and HS diet decreased SBP and urinary AGT similarly in both sexes; however, the decrease in proteinuria was greater in the females.

CONCLUSION

During Ang II-dependent hypertension and HS diet, higher intrarenal renin-angiotensin system activation in males, as reflected by higher AGT gene expression and urinary excretion, indicates a mechanism for greater progression of high blood pressure and might explain the sex disparity in development of salt-sensitive hypertension.

Prenatal testosterone exposure leads to hypertension that is gonadal hormone-dependent in adult rat male and female offspring

Prenatal testosterone exposure impacts postnatal reproductive and endocrine function, leading to alterations in sex steroid levels. Because gonadal steroids are key regulators of cardiovascular function, it is possible that alteration in sex steroid hormones may contribute to development of hypertension in prenatally testosterone-exposed adults. The objectives of this study were to evaluate whether prenatal testosterone exposure leads to development of hypertension in adult males and females and to assess the influence of gonadal hormones on arterial pressure in these animals. Offspring of pregnant rats treated with testosterone propionate or its vehicle (controls) were examined. Subsets of male and female offspring were gonadectomized at 7 wk of age, and some offspring from age 7 to 24 wk received hormone replacement, while others did not. Testosterone exposure during prenatal life significantly increased arterial pressure in both male and female adult offspring; however, the effect was greater in males. Prenatal androgen-exposed males and females had more circulating testosterone during adult life, with no change in estradiol levels. Gonadectomy prevented hyperandrogenism and also reversed hypertension in these rats. Testosterone replacement in orchiectomized males restored hypertension, while estradiol replacement in ovariectomized females was without effect. Steroidal changes were associated with defective expression of gonadal steroidogenic genes, with Star, Sf1, and Hsd17b1 upregulation in testes. In ovaries, Star and Cyp11a1 genes were upregulated, while Cyp19 was downregulated. This study showed that prenatal testosterone exposure led to development of gonad-dependent hypertension during adult life. Defective steroidogenesis may contribute in part to the observed steroidal changes.

Activation of GPR30 attenuates diastolic dysfunction and left ventricle remodelling in oophorectomized mRen2.Lewis rats

AIMS

GPR30 is a novel oestrogen receptor expressed in various tissues, including the heart. We determined the role of GPR30 in the maintenance of left ventricular (LV) structure and diastolic function after the surgical loss of ovarian hormones in the female mRen2.Lewis rat, a model emulating the cardiac phenotype of the post-menopausal woman.

METHODS AND RESULTS

Bilateral oophorectomy (OVX) or sham surgery was performed in study rats; the selective GPR30 agonist, G-1 (50 µg/kg/day), or vehicle was given subcutaneously to OVX rats from 13-15 weeks of age. Similar to the cardiac phenotype of sham rats, G-1 preserved diastolic function and structure relative to vehicle-treated OVX littermates independent of changes in blood pressure. G-1 limited the OVX-induced increase in LV filling pressure, LV mass, wall thickness, interstitial collagen deposition, atrial natriuretic factor and brain natriuretic peptide mRNA levels, and cardiac NAD(P)H oxidase 4 (NOX4) expression. In vitro studies showed that G-1 inhibited angiotensin II-induced hypertrophy in H9c2 cardiomyocytes, evidenced by reductions in cell size, protein content per cell, and atrial natriuretic factor mRNA levels. The GPR30 antagonist, G15, inhibited the protective effects of both oestradiol and G-1 on this hypertrophy.

CONCLUSION

These data show that the GPR30 agonist G-1 mitigates the adverse effects of oestrogen loss on LV remodelling and the development of diastolic dysfunction in the study rats. This expands our knowledge of the sex-specific mechanisms underlying diastolic dysfunction and provides a potential therapeutic target for reducing the progression of this cardiovascular disease process in post-menopausal women.

Restoration of the blood pressure circadian rhythm by direct renin inhibition and blockade of angiotensin II receptors in mRen2.Lewis hypertensive rats

BACKGROUND

Alterations in the circadian arterial pressure rhythm predict cardiovascular mortality. We examined the circadian arterial pressure rhythm and the effect of renin-angiotensin system blockade in congenic mRen2.Lewis hypertensive rats, a renin-dependent model of hypertension derived from the backcross of transgenic hypertensive [mRen-2]27 rats with Lewis normotensive ones.

METHODS

Twenty-nine mRen2.Lewis hypertensive rats were randomly assigned to drink tap water (vehicle; n = 9), valsartan (30 mg/kg/day; n = 10), or valsartan (30 mg/kg/day) combined with aliskiren given subcutaneously (50 mg/kg/day; n = 10) for 2 weeks. Arterial pressure, heart rate, and locomotive activity were recorded with chronically implanted radiotelemetry probes. The awake/asleep ratio was calculated as [awake mean arterial pressure (MAP) mean - asleep MAP mean)] / (awake MAP mean) x 100. Plasma renin activity (PRA) and concentration (PRC), and plasma and kidney angiotensin II (Ang II) were measured by radioimmunoassay (RIAs).

RESULTS

Untreated hypertensive rats showed an inverse arterial pressure rhythm, higher at day and lower at night, accompanied by normal rhythms of heart rate and locomotive activity. Treatment with valsartan or aliskiren and valsartan normalized the elevated arterial pressure and the arterial pressure rhythm, with the combination therapy being more effective in reducing MAP and in restoring the awake/asleep ratio. While PRA and PRC increased with the treatments, the addition of aliskiren to valsartan partially reversed the increases in plasma Ang II levels. Valsartan and the aliskiren and valsartan combination markedly reduced the renal cortical content of Ang II.

CONCLUSION

The altered circadian arterial pressure rhythm in this renin-dependent hypertension model uncovers a significant role of Ang II in the desynchronization of the circadian rhythm of arterial pressure, heart rate, and locomotive activity.

Blood pressure and mesenteric vascular reactivity in spontaneously hypertensive rats 7 months after gonadectomy

OBJECTIVE

Sexual dimorphism in the degree of high blood pressure (BP) has been observed in both animal and human hypertension. However, the mechanisms are still poorly understood. We tested the hypothesis that long-term loss of sex steroids promotes changes in mesenteric vascular reactivity that impact the maintenance of hypertension in the spontaneously hypertensive rats (SHR).

METHODS

Male SHR were sham operated (M-SHAM) or castrated (M-CX), and female SHR were sham-operated (F-SHAM) or ovariectomized (F-OVX) at 3 weeks of age. Seven months later, BP was measured in anesthetized rats, and vascular responsiveness was evaluated in the isolated perfused mesentery.

RESULTS

Mean arterial BP (mm Hg) was significantly greater in M-SHAM (186 ± 6) compared with F-SHAM (159 ± 5). Gonadectomy reduced BP in male SHR (M-CX: 160 ± 4) but had no significant effect in female SHR (F-OVX: 153 ± 7). Norepinephrine-induced constriction was similar in all groups. Gonadectomy attenuated serotonin-induced vasoconstriction in the mesentery. Acetylcholine (ACh)- and isoproterenol (ISO)-induced vasodilation was greater in female than male SHR. Ovariectomy of female SHR blunted ACh and ISO dilatory responses. ISO dose-response curves were shifted to the left in castrated male SHR.

CONCLUSIONS

Gonadectomy exerts long-term effects on mesenteric vascular reactivity and hypertension in the SHR.

Vasodilation in response to the GPR30 agonist G-1 is not different from estradiol in the mRen2.Lewis female rat

Our studies in the mRen2.Lewis female rat, an angiotensin II- and estrogen-dependent model of hypertension, revealed that chronic activation of estrogen receptor GPR30 markedly reduces blood pressure in ovariectomized females. The present studies measured acute vasodilation to the selective GPR30 agonist G-1 and 17-β-estradiol (10(-9)-10(-5.5) M) in isolated aortic rings and mesenteric arteries from intact mRen2.Lewis females. Maximal relaxation was greater in mesenteric vessels versus the aorta for both G-1 (47% ± 8% vs 80% ± 5% of phenylephrine preconstriction, P < 0.001) and estradiol (42% ± 7% vs 83% ± 4% of phenylephrine preconstriction, P < 0.001). The GPR30 antagonist G15 attenuated the response to both estradiol and G-1. Removal of the endothelium or pretreatment with Nitro-L-arginine methyl ester (L-NAME) partially attenuated vasorelaxation. Responses were not altered in mesenteric vessels from ovariectomized females. Immunohistochemical analysis revealed GPR30 expression in mesenteric endothelial and smooth muscle cells, and smooth muscle expression was confirmed in cultured cells. We conclude that estradiol-induced relaxation in conduit and resistance vessels from mRen2.Lewis females may be mediated by the novel estrogen receptor GPR30. The direct vasodilatory response of G-1 in resistance vessels presents one mechanism for the reduction in blood pressure induced by chronic G-1 administration.

Tetrahydrobiopterin restores diastolic function and attenuates superoxide production in ovariectomized mRen2.Lewis rats

After oophorectomy, mRen2.Lewis rats exhibit diastolic dysfunction associated with elevated superoxide, increased cardiac neuronal nitric oxide synthase (nNOS) expression, and diminished myocardial tetrahydrobiopterin (BH₄) content, effects that are attenuated with selective nNOS inhibition. BH₄ is an essential cofactor of nNOS catalytic activity leading to nitric oxide production. Therefore, we assessed the effect of 4 wk BH₄ supplementation on diastolic function and left ventricular (LV) remodeling in oophorectomized mRen2.Lewis rats compared with sham-operated controls. Female mRen2.Lewis rats underwent either bilateral ovariectomy (OVX) (n = 19) or sham operation (n = 13) at 4 wk of age. Beginning at 11 wk of age, OVX rats were randomized to receive either BH₄ (10 mg/kg · d) or saline, whereas the sham rats received saline via sc mini-pumps. Loss of ovarian hormones reduced cardiac BH₄ when compared with control hearts; this was associated with impaired myocardial relaxation, augmented filling pressures, increased collagen deposition, and thickened LV walls. Additionally, superoxide production increased and nitric oxide decreased in hearts from OVX compared with sham rats. Chronic BH₄ supplementation after OVX improved diastolic function and attenuated LV remodeling while restoring myocardial nitric oxide release and preventing reactive oxygen species generation. These data indicate that BH₄ supplementation protects against the adverse effects of ovarian hormonal loss on diastolic function and cardiac structure in mRen2.Lewis rats by restoring myocardial NO release and mitigating myocardial O₂⁻ generation. Whether BH₄ supplementation is a therapeutic option for the management of diastolic dysfunction in postmenopausal women will require direct testing in humans.

Neuronal nitric oxide synthase inhibition improves diastolic function and reduces oxidative stress in ovariectomized mRen2.Lewis rats

OBJECTIVE

The loss of estrogen in mRen2.Lewis rats leads to an exacerbation of diastolic dysfunction. Because specific neuronal nitric oxide synthase (nNOS) inhibition reverses renal damage in the same model, we assessed the effects of inhibiting neuronal nitric oxide on diastolic function, left ventricular remodeling, and the components of the cardiac nitric oxide system in ovariectomized (OVX) and sham-operated mRen2.Lewis rats treated with N5-(1-imino-3-butenyl)-L-ornithine (L-VNIO; 0.5 mg/kg per day for 28 d) or vehicle (saline).

METHODS

Female mRen2.Lewis rats underwent either bilateral oophorectomy (OVX; n = 15) or sham operation (or surgical procedure) (sham; n = 19) at 4 weeks of age. Beginning at 11 weeks of age, the rats were randomized to receive either L-VNIO or vehicle.

RESULTS

The surgical loss of ovarian hormones, particularly estrogen, led to exacerbated hypertension, impaired myocardial relaxation, diminished diastolic compliance, increased perivascular fibrosis, and increased relative wall thickness. The cardiac tetrahydrobiopterin-to-dihydrobiopterin levels were lower among OVX rats compared with sham-operated rats, and this altered cardiac biopterin profile was associated with enhanced myocardial superoxide production and decreased nitric oxide release. L-VNIO decreased myocardial reactive oxygen species production, increased nitrite concentrations, attenuated cardiac remodeling, and improved diastolic function.

CONCLUSIONS

Impaired relaxation, diastolic stiffness, and cardiac remodeling were found among OVX mRen2.Lewis rats. A possible mechanism for this unfavorable cardiac phenotype may have resulted from a deficiency in available tetrahydrobiopterin and subsequent increase in nNOS-derived superoxide and reduction in nitric oxide synthase metabolites within the heart. Selective nNOS inhibition with L-VNIO attenuated cardiac superoxide production and limited remodeling, leading to improved diastolic function in OVX mRen2.Lewis rats.

Long-term systemic angiotensin II type 1 receptor blockade regulates mRNA expression of dorsomedial medulla renin-angiotensin system components

In Fischer 344 (F344) rats, renin-angiotensin system (RAS) blockade for 1 yr with the angiotensin II type 1 (AT(1)) receptor blocker L-158,809 prevents age-related impairments in metabolic function, similar to transgenic rats with low glial angiotensinogen (Aogen). Brain RAS regulation may contribute to the benefits of long-term systemic AT(1) antagonism. We assessed the mRNA of RAS components in the dorsomedial medulla of F344 rats at 3 (young; n = 8) or 15 mo of age (old; n = 7) and in rats treated from 3 to 15 mo of age with 20 mg/l of the AT(1) receptor antagonist L-158,809 (Old+L; n = 6). Aogen and renin mRNA were lower in the young compared with old group. Angiotensin-converting enzyme (ACE) mRNA was lower in the old and Old+L compared with the young group. ACE2 and neprilysin expression were significantly higher in Old+L compared with young or old rats. AT(1b), AT(2), and Mas receptor mRNA were higher with treatment. Leptin receptor mRNA was lower in the old rats and this was prevented by L-158,809 treatment. Dual-specificity phosphatase 1 (DUSP1) mRNA was highest in the Old+L group. Aggregate correlate summation revealed a positive relationship for Mas receptor mRNA with food intake. The findings provide evidence for regulation of dorsomedial medullary renin and Aogen mRNA during aging. Long-term AT(1) receptor blockade increases the mRNA of the enzymes ACE2 and neprilysin and the MAS receptor, which could potentially shift the balance from ANG II to ANG-(1-7) and prevent age-related declines in the leptin receptor and its signaling pathway.

Orchidectomy attenuates impaired endothelial effects of a high-salt diet in Sprague–Dawley rats

The effect of sex hormones on vascular reactivity is considered one of the underlying factors contributing to gender differences in cardiovascular functions and diseases. Experiments were designed to investigate the role of androgens in salt-induced hypertension by assessing the relaxation response of isolated aortic rings to acetylcholine and sodium nitroprusside in the presence or absence of l-nitroarginine methyl ester in Sprague–Dawley rats. The rats were either orchidectomized or sham-operated, with or without testosterone replacement, and were placed on a normal or high-salt diet for 6 weeks. The results indicate a significant increase (p < 0.001) in the mean arterial blood pressure of rats on the high-salt diet, when compared with control or orchidectomized rats. Orchidectomy elicited a reduction in mean arterial blood pressure (p < 0.01), while testosterone replacement normalized mean arterial blood pressure to values seen in intact rats on the high-salt diet. The high-salt diet reduced the relaxation response to acetylcholine both in the presence and absence of inhibition of endothelial nitric oxide synthase with l-nitroarginine methyl ester. Bilateral orchidectomy attenuated the impaired endothelial function induced by the high-salt diet in rats, but this was reversed by concomitant administration of testosterone, suggesting a role for androgens in enhancing long-term vascular smooth muscle tone and hence maintenance of high blood pressure in salt-induced hypertension.

Attenuation of salt-induced cardiac remodeling and diastolic dysfunction by the GPER agonist G-1 in female mRen2.Lewis rats

INTRODUCTION

The G protein-coupled estrogen receptor (GPER) is expressed in various tissues including the heart. Since the mRen2.Lewis strain exhibits salt-dependent hypertension and early diastolic dysfunction, we assessed the effects of the GPER agonist (G-1, 40 nmol/kg/hr for 14 days) or vehicle (VEH, DMSO/EtOH) on cardiac function and structure.

METHODS

Intact female mRen2.Lewis rats were fed a normal salt (0.5% sodium; NS) diet or a high salt (4% sodium; HS) diet for 10 weeks beginning at 5 weeks of age.

RESULTS

Prolonged intake of HS in mRen2.Lewis females resulted in significantly increased blood pressure, mildly reduced systolic function, and left ventricular (LV) diastolic compliance (as signified by a reduced E deceleration time and E deceleration slope), increased relative wall thickness, myocyte size, and mid-myocardial interstitial and perivascular fibrosis. G-1 administration attenuated wall thickness and myocyte hypertrophy, with nominal effects on blood pressure, LV systolic function, LV compliance and cardiac fibrosis in the HS group. G-1 treatment significantly increased LV lusitropy [early mitral annular descent (e')] independent of prevailing salt, and improved the e'/a' ratio in HS versus NS rats (P<0.05) as determined by tissue Doppler.

CONCLUSION

Activation of GPER improved myocardial relaxation in the hypertensive female mRen2.Lewis rat and reduced cardiac myocyte hypertrophy and wall thickness in those rats fed a high salt diet. Moreover, these advantageous effects of the GPER agonist on ventricular lusitropy and remodeling do not appear to be associated with overt changes in blood pressure.

Rosiglitazone reduces blood pressure in female Dahl salt-sensitive rats

Postmenopausal women (PMW) are at greater risk for salt-sensitive hypertension and insulin resistance than premenopausal women. Peroxisome-proliferator-activated receptor-gamma (PPARgamma) agonists reduce blood pressure (BP) and insulin resistance in humans. As in PMW, ovariectomy (OVX) increases salt sensitivity of BP and body weight in Dahl salt-sensitive (DS) rats. This study addressed whether rosiglitazone (ROSI), a PPARgamma agonist, attenuates salt-sensitive hypertension in intact (INT) and OVX DS rats, and if so, whether insulin resistance, nitric oxide (NO), oxidative stress, and/or renal inflammation were contributing mediators. Telemetric BP was similar in OVX and INT on low salt diet (0.3% NaCl), but was higher in OVX than INT on high salt (8% NaCl). ROSI reduced BP in OVX and INT on both low and high salt diet, but only attenuated salt sensitivity of BP in OVX. Nitrate/nitrite excretion (NO(x); index of NO) was similar in INT and OVX on low salt diet, and ROSI increased NO(x) in both groups. High salt diet increased NO(x) in all groups but ROSI only increased NO(x) in OVX rats. OVX females exhibited insulin resistance, increases in body weight, plasma leptin, cholesterol, numbers of renal cortical macrophages, and renal MCP-1 and osteopontin mRNA expression compared to INT. ROSI reduced cholesterol and macrophage infiltration in OVX, but not INT. In summary, PPARgamma activation reduces BP in INT and OVX females, but attenuates the salt sensitivity of BP in OVX only, likely due to increases in NO and in part to reductions in renal resident macrophages and inflammation.

Influence of estrogen depletion and salt loading on renal angiotensinogen expression in the mRen(2).Lewis strain

The mRen(2).Lewis (mRen2) strain is an ANG II-dependent model of hypertension expressing marked sex differences in blood pressure and tissue injury that also exhibits estrogen and salt sensitivity. Because estrogen and salt influence angiotensinogen (AGT), circulating and renal expression of the protein were assessed in the mRen2 using a sensitive and specific ELISA. Hemizygous female and male mRen2 were placed on normal (1% NaCl, NS)- or high (8% NaCl, HS)-salt diets from 5 to 15 wk of age while a separate NS cohort was ovariectomized (OVX). The OVX mRen2 exhibited higher blood pressure (184 +/- 6 vs. 149 +/- 5 mmHg, n = 6), a 16-fold increase in urinary AGT (uAGT) (0.2 +/- 0.02 vs. 0.01 +/- 0.01 microg x kg(-1) x day(-1), P < 0.01), but no change in proteinuria (PROT). Excretion of AGT was correlated with blood pressure and PROT in the female groups. The HS diet led to higher blood pressure (224 +/- 8 mmHg), a 180-fold increase in uAGT (1.8 +/- 0.2 microg x kg(-1) x day(-1)), and increased PROT (98 +/- 9 vs. 7 +/- 1 mg x kg(-1) x day(-1)). Compared with females, NS males expressed higher excretion of uAGT (3.0 +/- 0.4 microg x kg(-1) x day(-1)) and PROT (32 +/- 5 mg x kg(-1) x day(-1)); both were increased eightfold with HS (uAGT: 23 +/- 3 microg x kg(-1) x day(-1); PROT: 285 +/- 28 mg x kg(-1) x day(-1)) without a change in blood pressure. Although uAGT was markedly higher in the OVX and HS groups, neither renal cortical AGT mRNA or protein expression was increased. Moreover, AGT release in cortical slices was similar for the NS and HS females. We conclude that the increase in uAGT with estrogen depletion or HS likely may be a biomarker for glomerular damage reflecting filtration of the circulating protein in the mRen2.

Refractory blood pressure in female SHR to increased oxidative stress is not mediated by NO or by upregulation of renal antioxidant enzymes

There is a sex difference in the blood pressure (BP) responses to prooxidants and antioxidants in the spontaneously hypertensive rat (SHR). In contrast to males, BP in female SHR does not decrease in response to antioxidants, such as tempol or apocynin, or increase in response to the prooxidant, molsidomine. Molsidomine decreases BP and increases expression of antioxidants in male Wistar-Kyoto rats (WKY), but not male SHR. The present study tested the hypothesis that the mechanism responsible for the lack of a pressor response to molsidomine in females is due to higher endogenous nitric oxide (NO) or to compensatory upregulation of renal antioxidant enzymes. Female SHR were treated with molsidomine in the presence or absence of nitro-L-arginine methyl ester (L-NAME) for 2 wk. Molsidomine increased nitrate/nitrite (NO(x)) and F2-isoprostane (F2-IsoP) excretion, whereas L-NAME reduced NO(x) but increased F-Isop. Molsidomine and L-NAME together further reduced NO(x) and increased F2-IsoP. Molsidomine alone had no effect on BP; L-NAME alone increased BP. The combination of molsidomine and L-NAME did not increase BP above L-NAME alone levels. Whole body and renal oxidative stress increased, while renal cortical Cu,Zn-SOD expression was downregulated and catalase was upregulated by molsidomine; glutathione peroxidase expression was unaffected. These data support our previous studies suggesting that BP in female SHR is independent of either increases or decreases in oxidative stress. The mechanisms responsible for the sex difference in BP response to increase or decrease of oxidative stress are not due to increased NO in females or to compensatory upregulation of antioxidant enzymes in response to increases in oxidants.

STIM and Orai proteins: players in sexual differences in hypertension-associated vascular dysfunction?

Sex-associated differences in hypertension have been observed repeatedly in epidemiological studies; however, the mechanisms conferring vascular protection to females are not totally elucidated. Sex-related differences in intracellular Ca(2+) handling or, more specifically, in mechanisms that regulate Ca(2+) entry into vascular smooth muscle cells have been identified as players in sex-related differences in hypertension-associated vascular dysfunction. Recently, new signalling components that regulate Ca(2+) influx, in conditions of intracellular store depletion, were identified: STIM1 (stromal interaction molecule 1), which works as an intracellular Ca(2+) sensor; and Orai1, which is a component of the CRAC (Ca(2+) release-activated Ca(2+)) channels. Together, these proteins reconstitute store-operated Ca(2+) channel function. Disturbances in STIM1/Orai1 signalling have been implicated in pathophysiological conditions, including hypertension. In the present article, we analyse evidence for sex-related differences in Ca(2+) handling and propose a new hypothesis where sex-related differences in STIM/Orai signalling may contribute to hypertension-associated vascular differences between male and female subjects.

Estradiol modulates uterine 18 kDa translocator protein gene expression in uterus and kidney of rats

We examined the effect of ovariectomy, with and without estradiol treatment, on 18 kDa translocator protein (TSPO) gene expression and its binding density in the uterus and kidney of rats. Ovariectomy causes a significant decrease in uterine, but not renal TSPO binding density, while estradiol treatment of ovariectomized rats restored TSPO binding density in the uterus. These TSPO density levels did not correlate with steady state or new RNA transcription. Our in vivo study suggests that estradiol is responsible for the maintenance of uterine TSPO density via transcriptional mechanisms. Our in vivo study also suggests that in the kidney estradiol appears to operate via post-transcriptional mechanisms to maintain TSPO density.

Effect of 17beta-oestradiol replacement on vascular responsiveness in ovariectomized diabetic rats

1. Women with functional ovaries exhibit a gender advantage in terms of the prevalence of cardiovascular diseases. However, whether this gender bias pertains in diabetes is unknown. 2. The aim of the present study was to examine the effects of 17beta-oestradiol (E2) on vascular responsiveness in normal and diabetic ovariectomized (OVX) rats. Aged-matched female rats were divided into four groups as follows: (i) OVX; (ii) OVX + E2 treated; (iii) diabetic OVX; and (iv) diabetic OVX + E2 treated. Bilateral ovariectomy was performed and streptozotocin was used to induce experimental diabetes. Rats were treated with 1 mg/kg per day, p.o., E2 for 8 weeks. 3. Although E2 treatment had no effect on blood glucose levels in normal and diabetic OVX rats, it significantly reduced systolic blood pressure and prevented diabetes-induced loss of bodyweight gain. 4. In segments of the thoracic aorta, concentration-dependent vasoconstrictor responses to KCl and phenylephrine were significantly attenuated following E2 treatment in both the normal and diabetic groups. The sarcoplasmic/endoplasmic reticulum calcium ATPase inhibitor thapsigargin (10(-6) mol/L) and the Ca(2+) channel blocker nifedipine (10(-6) mol/L) inhibited the transient vasoconstriction to PE in all groups. The constrictor effect of PE was increased by the nitric oxide synthase inhibitor N(G)-nitro-l-arginine methyl ester (l-NAME; 10(-6) mol/L), but was reduced by superoxide dismutase (SOD; 100 U/mL) and the cyclo-oxygenase inhibitor indomethacin (10(-6) mol/L) in all groups. Responses to acetylcholine (ACh; 10(-6) mol/L) demonstrated reduced endothelium-dependent relaxation in non-E2-treated groups. Relaxation responses to ACh were increased by 100 U/mL SOD and 10(-6) mol/L indomethacin, but were reduced by 10(-6) mol/L l-NAME in all groups. There were no differences among the four groups in terms of relaxation responses to sodium nitroprusside (10(-11) to 10(-6) mol/L). 5. In conclusion, the results of the present study suggest that oestrogen treatment has beneficial effects on vascular function in both diabetic and non-diabetic OVX rats due to Ca(2+) regulation and anti-oxidation.

Sex differences in control of blood pressure: role of oxidative stress in hypertension in females

In general, blood pressure is higher in normotensive men than in age-matched women, and the prevalence of hypertension in men is also higher until after menopause, when the prevalence of hypertension increases for women. It is likely then that the mechanisms by which blood pressure increases in men and women with aging may be different. Although clinical trials to reduce blood pressure with antioxidants have typically not been successful in human cohorts, studies in male rats suggest that oxidative stress plays an important role in mediating hypertension. The exact mechanisms by which oxidative stress increases blood pressure have not been completely elucidated. There may be several reasons for the discrepancies between clinical and animal studies. In this review, the data obtained in selected clinical and animal studies are discussed, and the hypothesis is put forward that oxidative stress may not be as important in mediating hypertension in females as has been shown previously in male rats. Furthermore, it is likely that differences in genetics, age, length of time with hypertension, endothelial dysfunction, and sex are all factored in to modulate the responses to antioxidants in humans. As such, future clinical trials should be designed and powered to evaluate the effects of oxidative stress on blood pressure separately in men and women.