Cardiovascular protection by oestrogen--a calcium antagonist effect?

Protective action of 17beta-estradiol in cardiac cells: implications for hyperkalemic cardioplegia

BACKGROUND

Hyperkalemic cardioplegic solutions effectively arrest the heart, but may also induce intracellular Ca2+ loading and cellular hypercontracture, which could contribute to ventricular dysfunction associated with global surgical ischemia. Recently, it has been proposed that 17beta-estradiol may possess protective properties in the ischemic myocardium. The purpose of the present study was to examine the action of 17beta-estradiol on cardiac cells exposed to hyperkalemic stress.

METHODS

Single ventricular cardiomyocytes, a preparation devoid of vascular and neuronal elements, were isolated from guinea pig hearts, loaded with a Ca2+-sensitive fluorescent probe, and imaged by digital epifluorescent microscopy. The emitted fluorescence of the probe, a measure of intracellular Ca2+ concentration, and cell length were simultaneously recorded during hyperkalemic challenge, in the absence or presence of 17beta-estradiol.

RESULTS

In control cardiomyocytes, the cytosolic concentration of Ca2+ was 138+/-11 nmol/L and cell length 93+/-11 microm. Exposure to high K+ (+16 mmol/L KCl) significantly increased cytosolic Ca2+ to 2,191+/-87 nmol/L (p < 0.001), and produced cell shortening (length at 39+/-5 microm; p < 0.001). 17beta-Estradiol (10 micromol/L) acutely prevented high K+ to induce either intracellular Ca2+ loading (144+/-13 nmol/L, p < 0.001) or hypercontracture (91+/-10 microm, p < 0.001). Tamoxifen (10 micromol/L), an antiestrogen, abolished the protective effect of 17beta-estradiol.

CONCLUSIONS

We conclude that 17beta-estradiol prevents hyperkalemia-induced Ca2+ loading and hypercontracture through a direct and tamoxifen-sensitive action in cardiomyocytes. This study raises the possibility that 17beta-estradiol should be considered as a cardioprotective adjunct toward a safer hyperkalemic cardioplegia.

Effect of estradiol on rat ileum

1. Sex hormones may influence gastrointestinal motility and thus may be responsible for symptoms that are common during pregnancy or hormone replacement therapy. The purpose of this study was to evaluate the effect of estradiol on the gut. 2. Segments of rat ileum (n=9) were suspended in an organ bath and exposed to increasing concentrations of carbachol, in the presence or absence of 17beta-estradiol. 17beta-estradiol markedly reduced the force developed by the ileum in response to carbachol. 3. These results suggest that estradiol reduces gastrointestinal motility.

Prospective randomized study of the effect of "add-back" hormone replacement on vascular function during treatment with gonadotropin-releasing hormone agonists

BACKGROUND

Gonadotropin-releasing hormone agonists (GnRHas) are a group of drugs that with long-term use induce a pseudomenopausal state in which estrogen production is suppressed. They are commonly used in the treatment of sex steroid-dependent conditions. "Add-back" hormone replacement therapy is used to prevent menopause-like symptoms and bone loss during GnRHa treatment, but it is also recognized that hypoestrogenism adversely affects vascular function. The aim of this study was to examine the effect of GnRHa and add-back therapy on vascular reactivity. This model serves as a paradigm for the effect of hormone replacement therapy in postmenopausal women.

METHODS AND RESULTS

Measurements of endothelium-dependent and endothelium-independent vascular reactivity were compared in 2 groups of women treated with a GnRHa for 6 months. One group received estrogen/progestogen add-back therapy during the second 3 months of GnRHa treatment. Vascular reactivity was examined by use of ultrasound measurements of changes in brachial artery diameter. Endothelium-dependent changes were assessed during reactive hyperemia, whereas endothelium-independent changes were measured after the administration of glyceryl trinitrate sublingual spray. Treatment with the GnRHa alone had an inhibitory effect on endothelium-dependent relaxation. However, endothelium-dependent relaxation significantly improved in the group receiving add-back therapy (14.6%) compared with the group treated with GnRHa alone (8.6%) (P<0.01). There were no significant endothelium-independent changes in either group.

CONCLUSIONS

These results suggest that the administration of add-back therapy has a protective effect on vascular function in GnRHa-induced hypoestrogenism. As a model for the menopause, these results also suggest that the long-term administration of hormone replacement therapy would result in endothelium-dependent arterial relaxation, an observation previously attributed only to the acute administration of estrogen.

Cardiovascular disease in postmenopausal women

With many risk factors for cardiovascular disease, myocardial infarction in particular now being well defined, it becomes increasingly clear that a majority of these factors are not only age, but also gender specific. Confidential risk factors such as smoking, hypertension, diabetes mellitus, overweight and hyperlipaemia, might have a different impact in women than in men. Moreover, there are substantial clinical differences between male and female ischaemic heart disease, both as to presentation, as well as to diagnosis, therapy and prognosis. In addition to a discussion to the risk factors mentioned above, the cardioprotective actions of oestrogens will be reviewed.

Hormone replacement therapy in postmenopausal women with specific risk factors for coronary artery disease

Hormone replacement therapy (HRT) in postmenopausal women is associated with a reduction in the risk of developing coronary artery disease (CAD) of about 50%. Women with an elevated risk for CAD appear to benefit most by HRT. The HRT-associated cardiovascular protection may be related to favourable changes in several important cardiovascular risk estimators, such as circulating blood concentrations of cholesterol, lipoprotein(a) (Lp(a)) and homocysteine. This paper reviews the literature presently available on the effects of HRT on cholesterol, Lp(a) and homocysteine concentrations, and special attention will be given to the effects on their elevated concentrations. The effect of HRT in women with hypertension is reviewed as well. From this overview it can be concluded that risk factors such as cholesterol, Lp(a), and homocysteine can be favourably modulated by HRT, and especially, that the strongest reductions can be achieved in those women with the highest concentrations. Although clinical trials still need to demonstrate the impact of lowering concentrations of Lp(a) and homocysteine, HRT appears to be a promising risk reduction strategy in this respect.

Plant derived estrogens relax rat mesenteric artery in vitro

The aim of this study was to investigate whether plant derived estrogens have the same relaxing effects in vitro as estradiol-17beta on arterial smooth muscle. The mesenteric arterial rings of female and male Wistar rats were studied. The relaxing effects of estradiol-17beta, genistein, daidzein and beta-sitosterol were determined, with particular focus on the role of endothelium. B-sitosterol had no relaxing effect on the arteries. Estradiol-17beta, genistein and daidzein relaxed noradrenaline, potassium chloride and calcium chloride precontracted arterial rings endothelium-independently. The relaxation responses were also independent of gender. Neither the removal of endothelium, nor the inhibition prostacyclin or nitric oxide synthesis, had any effect on the relaxation responses. The exact mechanism of these findings is still unclear.

Estrogen replacement therapy and outcome of coronary balloon angioplasty in postmenopausal women

Estrogen replacement therapy (ERT) in women after menopause is associated with prevention of clinical coronary artery disease. However, few studies have investigated possible benefits from ERT in postmenopausal women undergoing treatment for established coronary disease. We therefore retrospectively reviewed the clinical outcomes of 428 postmenopausal women undergoing percutaneous transluminal coronary balloon angioplasty (PTCA) to test the hypothesis that ERT has a beneficial effect in this setting. The women were divided into 2 groups based on ERT status at the time of the procedure. Estrogen users were younger (60 +/- 10 vs 68 +/- 9 years, p <0.001), more commonly had family histories of coronary heart disease (54% vs 41%, p = 0.04), had less incidence of hypertension (63% vs 76%, p = 0.02), and had slightly fewer diseased vessels per patient (1.3 +/- 0.5 vs 1.5 +/- 0.7, p = 0.03) compared with nonusers. No in-hospital deaths occurred in estrogen users compared with 5% hospital mortality in nonusers (p = 0.01). The combined outcome of death or myocardial infarction (MI) also was lower in estrogen users (4% vs 12%, p = 0.04). Of 348 women discharged after successful PTCA, 336 (97%) were able to be contacted at an average follow-up interval of 22 +/- 17 months (range 5 to 82). Estrogen users had superior event-free survival both for death as well as for death or nonfatal MI. Repeat revascularizations were similar in both groups (32% vs 24%, p = 0.15). In a Cox proportional-hazards model, nonusers had 4 times the likelihood of death after angioplasty compared with estrogen users (OR = 4.025, 95% CI = 1.3 to 13.4, p = 0.02). We conclude that estrogen replacement may offer protection against clinical coronary events in postmenopausal women who already have established coronary disease and are undergoing balloon angioplasty. The benefit was independent of age, smoking, presence of diabetes mellitus, or the number of diseased coronary vessels. However, it did not include a reduction in repeat revascularization procedures, suggesting no reduction in restenosis.

The effect of hormone replacement therapy on diastolic left ventricular function in hypertensive and normotensive postmenopausal women

OBJECTIVES

To evaluate the effect of hormone replacement therapy (HRT) on left ventricular diastolic function in a group of hypertensive and normotensive postmenopausal women.

METHODS

Left ventricular diastolic function at rest was evaluated by M-mode, two-dimensional and Doppler echocardiography in 19 postmenopausal women with normal blood pressure and 11 postmenopausal women with mild hypertension, before treatment and during 12 months of HRT. Transdermal estradiol was used in women with a surgical menopause and a sequential regimen of transdermal estradiol and peroral medroxyprogesterone acetate in women with a spontaneous menopause. The parameters assessed were: body mass index, heart rate, ejection fraction of the left ventricle (EF), septal (SW) and posterior wall (PW) dimensions, left ventricular end-systolic (LVsd) and end-diastolic (LVdd) dimensions and volumes (ESV, EDV), total diastolic time (DT), duration of the early (Ei) and of the late (Ai) filling phase, peak velocity of the early (E) and late mitral flow (A), A/E velocity ratio and systolic and diastolic blood pressure. Quantitative data were analyzed using unpaired t-test, MANOVA and multiple regression analysis where appropriate.

RESULTS

Hypertensive postmenopausal women had significantly higher SW (P < 0.05), PW (P < 0.05), A/E (P < 0.05) and A (P < 0.001) than normotensive postmenopausal women, before therapy. After 12 months of HRT a significant decrease in SW, PW, LVsd, ESV and increase in EF, DT, Ei and E was observed in both hypertensive and normotensive postmenopausal women. Heart rate slowed and systolic pressure decreased significantly only in normotensive postmenopausal women on HRT.

CONCLUSION

HRT of 12 months' duration does not deteriorate left ventricular diastolic function of both hypertensive and normotensive postmenopausal women. Improvement in some parameters of diastolic function could be partially explained by the decrease in heart rate and systolic pressure, induced by therapy.

Hormone replacement therapy, heart disease, and other considerations

Multiple observational studies suggest a marked reduction in risk of coronary heart disease (CHD) associated with postmenopausal estrogen use. A new meta-analysis presented here extends these results to estrogen plus progestin regimens. Although the findings from observational studies are strong and consistent, and there are several plausible mechanisms by which estrogen might reduce risk for CHD, most of the known biases would tend to exaggerate estrogen's benefit. Further, estrogen therapy clearly increases risk for endometrial hyperplasia and cancer, venous thromboembolic events and gallbladder disease, and long-term use probably also increases the risk of breast cancer. Therefore, until findings from randomized trials confirm and quantitate the benefit of estrogen therapy for prevention of CHD, we believe it should not be recommended to all postmenopausal women.

Estrogen replacement reverses endothelial dysfunction in postmenopausal women

PURPOSE

To measure the effect of long-term clinical hormone replacement therapy on brachial artery vasomotor responses, and to compare these responses in premenopausal and postmenopausal women.

PATIENTS AND METHODS

We studied 23 postmenopausal women, including 18 who were evaluated prior to starting clinically indicated oral hormone replacement therapy. Twelve postmenopausal women received estrogen alone, the other 6 were treated with estrogen/medroxyprogesterone combinations. Eleven premenopausal volunteers served as a comparison group. Change in brachial artery diameter in response to postischemic hyperemic flow and sublingual nitroglycerin was measured by ultrasound.

RESULTS

The 18 postmenopausal subjects receiving hormone replacement showed a progressive improvement in their postischemic vasodilation. Mean (+/-SD) postischemic vasodilation was 0.4%+/-7.1% prior to estrogen replacement. There were significant increases in postischemic vasodilation of 4.8%+/-6.6% after 1 month and 8.3%+/-3.4% after 6 months of estrogen replacement. The response to nitroglycerin was similar at all time points studied. Women with the most abnormal responses to hyperemic flow at baseline demonstrated the greatest improvement after 6 months of hormone replacement therapy. Premenopausal and postmenopausal subjects differed in their response to hyperemic flow, with premenopausal women showing 5.8% vasodilatation compared with a 0.6% vasodilation in postmenopausal women (P=0.046).

CONCLUSIONS

Endothelial function is abnormal in many postmenopausal women compared with premenopausal women, and in some postmenopausal women it can be enhanced by estrogen replacement therapy. This effect may increase with prolonged use.

Oral estrogen improves serum lipids, homocysteine and fibrinolysis in elderly men

The effects of estrogen on cardiovascular risk factors have been less well defined in men than in women. We measured lipid and lipoprotein concentrations, lipoprotein particle size distributions, lipoprotein (a), homocysteine, and markers of thrombosis and fibrinolysis in 18 [corrected] healthy elderly men (age 74 +/- 3 years, mean +/- S.D.) before and after 9 weeks of treatment with 0.5, 1 or 2 mg/day of oral micronized 17beta-estradiol. LDL-C (-6%), apo B (-9%), triglyceride (-5%), and homocysteine (-11%) concentrations decreased with estradiol, whereas HDL-C (+14%) increased. Intermediate-size VLDL subclass concentrations were lowered and LDL and HDL subclass levels altered in such a way as to cause average LDL and HDL particle size to increase. Lipoprotein (a) did not change. Fibrinogen (-13%) and plasminogen activator inhibitor-1 (PAI-1) concentrations (-26%) decreased, but there were no changes in thrombotic markers including thrombin-antithrombin III complex, prothrombin fragment 1.2, D-dimer, antithrombin activity, protein-C and S and von Willebrand factor antigen. Breast tenderness occurred in four men and heartburn in five but did not require discontinuation of treatment. We conclude that oral estrogen in men reduces homocysteine, fibrinogen, and PAI-1 concentrations and favorably influences VLDL, LDL and HDL subclass levels without increasing markers of thrombotic risk.

A double-blind, placebo controlled study of postmenopausal oestrogen replacement therapy and carotid artery pulsatility index

OBJECTIVE

To determine whether postmenopausal oestrogen replacement therapy affects carotid artery pulsatility index.

DESIGN

A prospective double-blind placebo controlled trial.

SETTING

University associated teaching hospital.

PARTICIPANTS

Twenty-eight postmenopausal women who were more than 12 months postmenopausal and who had not taken exogenous oestrogen.

INTERVENTIONS

Independent randomisation to receive oral oestradiol (2 mg daily) or placebo for 20 to 24 weeks.

MAIN OUTCOME MEASURES

Internal carotid artery Doppler pulsatility index, measured within one centimetre of the carotid bifurcation.

RESULTS

Replicate data were available from 27 women. The mean pulsatility index decreased by -0.11 in 15 women receiving oestradiol, compared with a mean rise of 0.05 in the 12 women who received placebo (P = 0.006, 95% CI for treatment difference 0.06-0.31).

CONCLUSIONS

Oestrogen replacement decreases postmenopausal carotid artery pulsatility index, probably reflecting decreased peripheral vascular resistance. This is a further mechanism whereby hormone replacement therapy may impart cardiovascular protection.

Physiological concentrations of 17beta-estradiol inhibit the synthesis of nitric oxide synthase in macrophages via a receptor-mediated system

We investigated the effect of estrogen on inducible nitric oxide synthase (iNOS), which is not well understood, in contrast to the known effect of estrogen on endothelial nitric oxide synthase (eNOS). When J774 cells, a murine macrophage cell line, were incubated with interferon-gamma and lipopolysaccharide, iNOS was induced, and a large amount of NO was released. Pre- or coincubation with 17beta-estradiol inhibited this induction of iNOS protein and NO release; however, 17beta-estradiol did not have a direct effect on enzyme activity of iNOS. The analog, 17alpha-estradiol, did not have such an effect. Tamoxifen, an antiestrogen, and ICI182780, an estrogen-receptor antagonist, inhibited the influence of 17beta-estradiol on iNOS. Thus 17beta-estradiol inhibited the induction of iNOS by a classic receptor-mediated pathway. The inhibition of the NO release from iNOS by 17beta-estradiol is in contrast to the reported augmentation of continuous NO release from eNOS. These harmonious effects of estrogen on iNOS and eNOS may have some role in the antiatherosclerotic effects of 17beta-estradiol.

Short-term estrogen administration ameliorates dobutamine-induced myocardial ischemia in postmenopausal women with coronary artery disease

OBJECTIVES

This study was designed to examine whether short-term estrogen administration ameliorates dobutamine-induced myocardial ischemia in postmenopausal women with coronary artery disease (CAD).

BACKGROUND

Estrogen replacement therapy in postmenopausal women is associated with a marked reduction in the risk of CAD. Estrogen has been reported to have both short- and long-term effects on the cardiovascular system. However, it remains to be examined whether short-term estrogen administration ameliorates myocardial ischemia caused by increased myocardial oxygen demand in postmenopausal women with CAD.

METHODS

Eight postmenopausal women with proved CAD underwent dobutamine stress echocardiography (DSE). DSE was performed three times in a placebo-controlled, double-blind manner: 1) 30 min after intravenous administration of saline solution (placebo) and after 2) a low dose (1.25 mg) and 3) a high dose (10 mg) of conjugated estrogen. The effects of estrogen were compared at the maximal comparable stage of DSE, which was the maximal DSE level that the same patient achieved in all three examinations.

RESULTS

Estrogen dose-dependently ameliorated the dobutamine-induced worsening of symptoms (prolonging time to onset of symptoms by 52% [low dose] and 72% [high dose]), electrocardiographic findings (decreasing the magnitude of summed ST segment changes by 36% [low dose] and 76% [high dose]) and left ventricular wall motion (reducing the wall motion score index by 50% [low dose] and 77% [high dose], all p < 0.01 by analysis of variance). There was no significant difference in blood pressure, heart rate or rate-pressure product among the three examinations at the maximal comparable stage of DSE.

CONCLUSIONS

Estrogen has short-term anti-ischemic effects on the myocardial ischemia induced by increased myocardial oxygen demand in postmenopausal women with CAD.

Short-term anti-ischemic effect of 17beta-estradiol in postmenopausal women with coronary artery disease

BACKGROUND

Short-term administration of 17beta-estradiol improves effort-induced myocardial ischemia in female patients with coronary artery disease. 17Beta-estradiol also has direct and indirect coronary vascular smooth muscle relaxing properties. The aim of the present study was to evaluate the effect of short-term administration of 17beta-estradiol on pacing-induced myocardial ischemia by means of continuous monitoring of coronary sinus pH in 16 postmenopausal female patients with coronary artery disease.

METHODS AND RESULTS

Patients underwent incremental atrial pacing starting at a rate of 100 bpm and increments of 20 bpm every 2 minutes up to 160 bpm before and 20 minutes after either 17beta-estradiol (1 mg sublingual, 9 patients) or placebo (sublingual, 7 patients). The time to the onset of myocardial ischemia during pacing was significantly increased by 17beta-estradiol (mean+/-SD, 254+/-36 versus 298+/-23 seconds; P<.02) but not by placebo (262+/-45 versus 256+/-34 seconds; P=NS) The pH shift was significantly reduced by 17beta-estradiol but not by placebo at every step of the pacing protocol. The maximum pH shift at peak pacing was significantly reduced by the administration of 17beta-estradiol by 0.022 pH units (95% CI, 0.001, 0.043; P<.04) but not by sublingual placebo (-0.002 pH units; 95% CI, -0.0073, 0.0021; P=NS). The maximum pH shift at maximum comparable pacing was also reduced by 17beta-estradiol by 0.015 pH units (95% CI, 0.012, 0.017; P<.001) but not by placebo (-0.0022 pH units; 95% CI, -0.006, 0.0015; P=NS).

CONCLUSIONS

17Beta-estradiol reduces the degree of pacing-induced myocardial ischemia in postmenopausal patients with coronary artery disease. The reduction of pacing-induced coronary sinus pH shift is consistent with an anti-ischemic effect of the hormone and is not due to preconditioning, as evidenced by the absence of improvement after placebo.

Effects of a pure antiestrogen and progesterone on estrogen-mediated alterations of blood flow and progesterone receptor expression in the aorta of ovariectomized rabbits

There is ample evidence from epidemiological studies that estrogen-replacement therapy protects postmenopausal women against cardiovascular disease. One explanation for this beneficial effect could be the improvement of blood flow under estrogen therapy. By using ultrasound and Doppler color flow mapping we demonstrated in the aorta of ovariectomized rabbits a significant dose-dependent increase in blood flow after treatment with 17beta-estradiol. An increase in blood flow was already observed within 1 h of estradiol treatment and lasted until the end of a 14-day treatment phase. Progesterone did not attenuate the effects of 17beta-estradiol on aortic blood flow. The pure estrogen receptor antagonist ZM 182780, however, dose-dependently reversed the effect of 17beta-estradiol on blood flow after the 14-day treatment phase, but was not able to antagonize the rapid 17beta-estradiol effect on blood flow after 1 h. After killing the animals mRNA and protein expression of the progesterone receptor (PR), a known estrogen-responsive gene in classic target organs, were examined. Analogous to the blood flow results the PR mRNA level increased dose-dependently after 17beta-estradiol treatment, whereas ZM 182780 was able to reverse this effect. Immunohistochemical localization of PR in the aortic wall revealed an increase in immunoreactivity in fibroblasts of the adventitia after 17beta-estradiol treatment. ZM 182780, and to a lesser degree progesterone, reversed the 17beta-estradiol-induced increase in PR immunoreactivity. PR immunoreactivity was further detected in endothelial and smooth muscle cells, but the various hormonal treatments had no discernible effect on the PR mRNA level in these cellular compartments. Our findings in the aorta of OVX rabbits suggest that (a) 17beta-estradiol exhibits a rapid effect on arterial tone, (b) the pure estrogen receptor antagonist ZM 182780 inhibits the 17beta-estradiol effect on blood flow and PR mRNA and (c) progesterone does not attenuate the beneficial effect of estrogens on arterial tone.

Effect of acute administration of estradiol 17 beta on aortic blood flow in menopausal women

Acute administration of estradiol 17beta increases aortic blood flow velocity in menopausal women. This suggests that the effect of the ovarian hormone on cardiac dynamics is mainly dependent on a reduction in peripheral vascular resistances.

The cardiovascular safety of triphasic contraceptive steroids

It was hypothesized that estrogen-induced cardioprotection is mediated by up-regulation and down-regulation of expression of nitric oxide (NO) and P-selectin, respectively. Published data on circulating levels of the vasodilator NO, atherogenic glycoprotein P-selectin, and lipoprotein-a [Lp(a)] in users of triphasic contraceptive steroids are lacking. A total of 30 healthy women (nonusers, controls) and 82 women using oral triphasic contraceptive steroids (ethinyl estradiol and levonorgestrel: Triovlar, Schering AG) for 18 to 24 cycles participated in this study. Fasting blood samples were obtained from users and nonusers for the determination of P-selectin and Lp(a) by enzyme immunoassay and NO by a colorimetric method. The serum Lp(a) levels in OC users were significantly higher than those of nonusers. On the other hand, the serum NO levels in OC users were significantly elevated when compared to nonusers. Plasma P-selectin was significantly lowered in OC users p < 0.005. These results demonstrate the beneficial effects of ethinyl estradiol in the triphasic contraceptive regimen. Ethinyl estradiol may afford a degree of anti-atherogenic-cardioprotective effect by up-regulation of the expression of the vasodilator NO and down-regulation of the expression of the atherogenic P-selectin. This may outweigh the cardiovascular risk of the increased atherogenic Lp(a). This study may explain the very low rate of mortality from venous thromboembolism in OC users, which compares favorably with the risks that many people accept in daily life.

Effect of hormone replacement therapy on non-invasive cardiovascular haemodynamics

OBJECTIVE

To determine the detailed effects of hormone replacement therapy (HRT) on non-invasive haemodynamics, including an assessment of the effect on the pulsatile afterload assessed in terms of the augmentation index and pulse-wave velocity.

DESIGN

A cross-sectional study of healthy postmenopausal women using carotid and radial tonometry and pulse-wave velocity measurements.

SETTING

Community-based ambulatory women attending the menopause centre at a tertiary hospital.

PATIENTS

Seventy postmenopausal women divided into those not currently being administered HRT (n = 38, aged 46-72 years) and those who were being administered a variety of HRT (n = 32, aged 49-67 years).

METHODS

Central arterial pressure waveforms were measured using carotid applanation tonometry to derive the augmentation index and ejection duration. The arterial pulse-wave velocity was assessed using paired carotid, radial and dorsalis tonometry waveforms.

RESULTS

Women being administered HRT had a significantly lower augmentation index (20.4 +/- 8.6 versus 27.0 +/- 10.2%, P = 0.005) and shorter ejection times (320 +/- 17 versus 329 +/- 18 ms, P = 0.037). There was no significant difference in brachial blood pressure (131/76 versus 129/77 mmHg). Women being administered HRT exhibited a greater reversal in the age-related loss of amplification which occurs owing to arterial stiffening. This amplification between central and peripheral systolic blood pressures was greater among women being administered HRT (5.3 +/- 6.2 versus 2.2 +/- 4.0 mmHg, P = 0.014). There was no difference in pulse-wave velocity between the two groups.

CONCLUSIONS

HRT appears to improve the pulsatile vascular afterload by decreasing the augmentation of the late systolic blood pressure. This effect is not apparent from routine brachial cuff measurements, which, as a result, may underestimate haemodynamic benefits. Such effects may help to explain a portion of the improvement in cardiovascular morbidity found in other trials.

Fibrinogen and plasminogen modifications during oral estradiol replacement therapy

OBJECTIVE

To assess the effects of oral E2 replacement therapy on various hemostatic parameters and cardiovascular risk factors in healthy, postmenopausal women.

DESIGN

A double-blind, randomized, prospective study comparing the effect of a placebo and of oral micronized E2 (2 mg daily) during a 6-month period. Evaluations were performed before treatment and after 3 and 6 months.

SETTING

Departments of Gynecology, Hemostasis, and Nutrition, Hôtel-Dieu, Paris, France.

PATIENT(S)

Thirty-six healthy women with natural or surgical menopause.

RESULT(S)

Compared with placebo, oral E2 replacement therapy resulted in a significant decrease in fibrinogen and apo B and a significant increase in plasminogen.

CONCLUSION(S)

Besides the effects on lipoproteins, oral estrogen replacement therapy modifies parameters involved in coagulation and fibrinolysis.

Acute hemodynamic effects of estrogen administration in postmenopausal women

The hemodynamic effects of estrogens in replacement doses have not been fully clarified; therefore, we studied the acute hemodynamic changes after 0.625 and 1.25 mg of conjugated estrogens, administered intravenously, using a thermodilution catheter, in postmenopausal women without structural heart disease. Pulmonary and systemic pressures and resistances and stroke volume did not change compared with baseline, but heart rate and cardiac output decreased significantly, which may be associated with estrogen's previously described calcium-blocking effect or with a more recently contemplated beta-blocking action.

Mechanism of vascular smooth muscle relaxation by estrogen in depolarized rat and mouse aorta. Role of nuclear estrogen receptor and Ca2+ uptake

17 beta-Estradiol induces vasodilation in vitro and in vivo, which has been suggested to contribute to the cardiovascular protection by this ovarian steroid hormone. However, the exact mechanism of vasorelaxation by estrogens remains to be elucidated. In this study, we analyzed the potential role of genomic mechanisms involving the nuclear estrogen receptor and inhibition of entry of extracellular Ca2+ in 17 beta-estradiol-induced vasorelaxation in depolarized aortic rings, isolated from male and female rats and male mice. In both male and female rat aortic rings without endothelium and in intact male mouse aortic rings treated with NG-nitro-L-arginine, 17 beta-estradiol caused dose-dependent (0.3 to 30 mumol/L) relaxation of contraction evoked by high-K+ depolarization (30 and 45 mmol/L KCl, respectively). The estrogen receptor antagonist ICI 164384 had no effect on 17 beta-estradiol-induced relaxations. 125I-17 beta-estradiol binding studies showed the presence of high-affinity cytosolic-nuclear estrogen receptors in control male mouse aortas. Comparable relaxations of aortic rings isolated from control and estrogen receptor-deficient transgenic mice provided direct evidence that the nuclear estrogen receptor is not involved in this response. 17 beta-Estradiol-induced relaxation of rat aortic rings could not be prevented by cycloheximide or actinomycin D, suggesting that the response was not mediated by de novo protein synthesis or gene transcription. In rat aortic rings, 17 beta-estradiol inhibited the increase of 45Ca uptake by 30 mmol/L KCl at concentrations (10 and 30 mumol/L) that caused vasorelaxation in the same tissue, suggesting that inhibition of Ca2+ entry contributes to the response. 17 alpha-Estradiol was less effective, and estrone was devoid of vasorelaxing activity. Vasorelaxation by estrogens in female and male rat aortas was similar, indicating no gender difference in vascular responses under these conditions.

Increased expression of the cardiac L-type calcium channel in estrogen receptor-deficient mice

Steroid hormones control the expression of many cellular regulators, and a role for estrogen in cardiovascular function and disease has been well documented. To address whether the activity of the L-type Ca2+ channel, a critical element in cardiac excitability and contractility, is altered by estrogen and its nuclear receptor, we examined cardiac myocytes from male mice in which the estrogen receptor gene had been disrupted (ERKO mice). Binding of dihydropyridine Ca2+ channel antagonist isradipine (PN200-110) was increased 45.6% in cardiac membranes from the ERKO mice compared to controls, suggesting that a lack of estrogen receptors in the heart increased the number of Ca2+ channels. Whole-cell patch clamp of acutely dissociated adult cardiac ventricular myocytes indicated that Ca2+ channel current was increased by 49% and action potential duration was increased by 75%. Examination of electrocardiogram parameters in ERKO mice showed a 70% increase in the QT interval without significant changes in PQ or QRS intervals. These results show that the membrane density of the cardiac L-type Ca2+ channel is regulated by the estrogen receptor and suggest that decreased estrogen may lead to an increase in the number of cardiac L-type Ca2+ channels, abnormalities in cardiac excitability, and increased risk of arrhythmia and cardiovascular disease.

Estrogen-induced increases in coronary blood flow are antagonized by inhibitors of nitric oxide synthesis

OBJECTIVE

Estrogen receptors have been found in coronary arterial endothelial and vascular smooth muscle cells. Therefore the present study was designed to determine if estradiol-17 beta can increase coronary blood flow and if so whether the changes are mediated by nitric oxide.

STUDY DESIGN

Five oophorectomized non-pregnant sheep were chronically instrumented to measure blood pressure, heart rate, cardiac output, left circumflex coronary blood flow and central venous pressure. Animals received estradiol-17 beta (1.0 micrograms/kg) and cardiovascular responses were followed for 135 min.

RESULTS

Estradiol-17 beta (1.0 micrograms/kg) increased left circumflex (coronary) blood flow 28 +/- 3%, cardiac output 15 +/- 1% and heart rate by 13 +/- 3%. Coronary vascular resistance decreased 23 +/- 5%, systemic vascular resistance decreased by 12 +/- 2% while blood pressure did not change significantly. Administration of the nitric oxide synthetase inhibitor L-nitroarginine methylester (L-NAME), had no effect on basal coronary blood flow but completely reversed estradiol-17 beta induced increases in coronary blood flow.

CONCLUSION

These results demonstrate that estrogen increases coronary blood flow in the non-pregnant sheep and that L-NAME, an inhibitor of nitric oxide, is able to reverse the estrogen induced flow changes.

Menopause and post-menopause

From the endocrine point of view, menopause is considered a deficiency state and oestrogen therapy regarded as restoring the pre-menopausal endocrine milieu. Oestrogen therapy alleviates acute climacteric symptoms and also reduces the risk of cardiovascular disease, osteoporosis and Alzheimer's disease. Cardiovascular protection seems to be the major benefit of oestrogen replacement: it reduces morbidity and mortality from coronary heart disease by approximately 50%. The mechanisms are complex and not fully under-stood. In this review we discuss currently available data on the effects of hormone replacement therapy on serum lipids and lipoproteins, the vessel wall (endothelium dependent and endothelium independent), blood flow, cardiac function, blood pressure, haemostasis, insulin sensitivity and direct anti-atherosclerotic effect as possible mechanisms of cardioprotection. Oestrogen therapy reduces the rate of post-menopausal bone loss, increases bone mineral density (BMD) and decreases fracture rate. Recent evidence suggests that initiation of oestrogen therapy in older women produces larger increases in BMD which might provide a significant protective effect at the time when fracture is common. The incidence of Alzheimer's disease is reduced by 50% in post-menopausal women taking oestrogen replacement. Limited clinical trials of oestrogen treatment in women with this disease have documented beneficial effects on cognitive function. The results of epidemiological studies of the effects of oestrogens on breast cancer risk are conflicting but recent evidence suggests that the risk is increased in current users after 5 years of use and among older women. In contrast, increase in the risk of venous thromboembolism is most significant within the first 12 months of therapy, strongly suggesting the importance of individual susceptibility.

Sex hormones and vascular reactivity

It is increasingly recognized that sex steroids have, among many other effects, the ability to cause vasodilation. The vasodilatory effects of estradiol have been the best documented and described. At low concentrations, estradiol has the ability to improve impaired endothelium dependent (nitric oxide mediated) relaxation in estrogen deficient subjects. At high concentrations, estradiol causes vasodilation principally by endothelium independent mechanisms, in a gender independent fashion, which appear to involve a number of pathways such as ATP-dependent K+ channels. Testosterone also has ability, at higher doses, to cause vasodilation of the coronary circulation, in a gender independent fashion. The mechanisms of sex steroid-induced vasodilation are reviewed in this article.

Effect on survival of estrogen replacement therapy after coronary artery bypass grafting

We examined the relation between postmenopausal estrogen placement therapy (ERT) and survival in 1,098 women who underwent coronary artery bypass grafting (CABG). Patients were selected for the study if their age was > or = 55 years at the time of preoperative coronary angiography or if they had previously undergone bilateral oophorectomy. Life-table analysis was used to compare survival after surgery in 92 women who received ERT and 1,006 women who did not. Five-year survival was 98.8% in the estrogen users and 82.3% in the non-users. Ten-year survival was 81.4% in the users and 65.1% in the nonusers (p = 0.0001 by Lee Desu test). The women who did not take estrogen were significantly older (p < 0.001), had more vessels with significant stenosis (p = 0.033), lower ejection fractions (p = 0.051), and more prior myocardial infarctions (p = 0.054). However, a Cox proportional-hazards model selected the number of coronary arteries narrowed (RR 1.43, p < 0.0001), estrogen use (RR 0.38, p = 0.001), left main coronary stenosis (RR 1.83, p = 0.001), and diabetes mellitus (RR 1.57, p = 0.003) as the significant independent predictors of survival. These data suggest that ERT improves survival significantly after CABG in postmenopausal women with coronary artery disease.

Effect of chronic treatment with 17beta-estradiol and progesterone on endothelium-dependent and endothelium-independent relaxation in isolated aortic rings from ovariectomized rats

OBJECTIVE

Our purpose was to study the influence of chronic treatment with sex hormones on endothelium-dependent and endothelium-independent relaxation of rat aortic rings.

STUDY DESIGN

Rings of aortas, with and without endothelium, from rats treated with sex hormones or vehicle for 10 days were mounted in organ baths for isometric tension recording. Indomethacin (10(-5) mol/L) and N(omega)-nitro-L-arginine methyl ester (10(-4) mol/L), alone or in combination, were used to block cyclooxygenase and nitric oxide synthase, respectively. Mean data of contraction induced by potassium chloride (60 mmol/L), the relaxation by acetylcholine (10(-6) mol/L) in potassium chloride-contracted rings, tension induced by phenylephrine, and the negative logarithm of the concentration of acetylcholine or 3-morpholinosydnonimine producing a 50% relaxation, and area under the curve were calculated.

RESULTS

Treatment with 17beta-estradiol (10 microg/rat/day) decreased the tension induced by 60 mmol/L potassium chloride and increased the relaxation by acetylcholine in the rings with endothelium precontracted with potassium chloride. Contraction induced by potassium chloride and relaxation induced by acetylcholine were not influenced by the treatment with progesterone (2 mg/rat/day) or estrogen-progesterone combination. Treatment with estradiol, progesterone, or both hormones had no effect on tension developed in intact rings in response to phenylephrine and did not influence endothelium-dependent relaxation to acetylcholine or endothelium-independent relaxation to 3-morpholinosydnonimine in rings contracted with phenylephrine. The inhibition by N(omega)-nitro-L-arginine methyl ester of endothelium-dependent relaxation by acetylcholine was attenuated after the treatment with the sex hormones.

CONCLUSIONS

Chronic treatment with sex hormones did not increase production or release of endothelium-derived relaxing factor and did not change the sensitivity of rat aortic smooth muscle to nitric oxide. The treatment slightly counteracted the inhibition of endothelium-dependent relaxation produced by nitric oxide synthase blocker.

Non-genomic mechanism of 17 beta-oestradiol-induced inhibition of contraction in mammalian vascular smooth muscle

17 beta-Oestradiol (E2) at 0.1-10 microM directly inhibited various tonic and phasic smooth muscle contractions. The mechanism(s) of oestrogen-induced inhibition of contraction was studied using intact and permeabilized strips and isolated single cells of smooth muscle. 2. In endothelium-denuded vascular smooth muscle, E2 attenuated high K(+)-induced force development and myosin light chain phosphorylation, and produced rapid and reversible relaxation. There were no significant differences in these inhibitory effects between tissue types (femoral artery vs. portal vein), species (rat vs. rabbit) or sexes. 3. The inhibitory potencies of several steroidal and non-steroidal oestrogen analogues were examined and their effects were for the most part stereo-specific. However, two steroids with negligible affinities for the nuclear oestrogen receptor also strongly inhibited high K(+)-induced contraction. 4. Genomic modulators including a protein synthesis inhibitor, an RNA synthesis inhibitor, and oestrogen receptor antagonists did not affect the inhibitory actions of E2. Inhibitors of cyclic nucleotide-dependent protein kinases did not reduce the E2 effect. 5. Ca2+ release from intracellular stores by agonists and by inositol 1,4,5-trisphosphate (IP3) does not appear to be modulated by E2. Neither pretreatment with ryanodine nor with thapsigargin affected the E2-induced inhibition of high K(+)-induced contraction. 6. E2 had no effect on either normal or GTP gamma S-increased Ca2+ sensitivity of the regulatory and contractile apparatus. 7. E2 and its analogues rapidly inhibited voltage-dependent L-type Ca2+ channel currents in isolated smooth muscle cells. Repetitive stimulation was not required for E2-induced inhibition of the currents. 8. This study strongly suggests that at pharmacological concentrations oestrogen primarily reduces Ca2+ influx through inhibition of L-type Ca2+ channels in a non-genomic manner and decreases myosin light chain phosphorylation and contraction of smooth muscle.

Long-term estradiol replacement decreases contractility of guinea pig coronary arteries to the thromboxane mimetic U46619

BACKGROUND

Estradiol replacement therapy reduces the incidence of coronary artery disease. Current evidence suggests that estradiol may stimulate the production of endothelium-derived NO and thereby reduce the contractile response of vascular smooth muscle. We investigated the effect of long-term replacement of estradiol on NO release and its effect on coronary artery contractility.

METHODS AND RESULTS

Female guinea pigs were ovariectomized and allowed to recover for 100 days. Pellets containing 17 beta-estradiol (0.25, 0.5, 1.5, and 7.5 mg released over 21 days) were placed subcutaneously for 19 to 20 days. Animals were then anesthetized, and the coronary arteries were excised and cut into ring segments. Rings were placed in small-vessel myographs for measurement of isometric force. Contractile responses of coronary arteries to cumulative addition of U46619 (10(-10) to 10(-5) mol/L), a thromboxane mimetic, were measured in the presence and absence of nitro-L-arginine (LNA), a selective NO synthase inhibitor, and methylene blue, a guanylate cyclase inhibitor. Low (0.25-mg) but not high (0.5-, 1.5-, or 7.5-mg) doses of estradiol inhibited the maximal contractile responses to U46619 compared with arteries from untreated castrated animals. In addition, both LNA and methylene blue potentiated contractile responses to U46619 of arteries from animals receiving 0.25 and 0.5 mg but not 1.5 and 7.5 mg estradiol. Negative log EC50 values were significantly inhibited at 0.25 and 7.5 mg but unaffected at 0.5 and 1.5 mg estradiol compared with castrated animals.

CONCLUSIONS

Estradiol at low doses may protect against vasospasm by stimulating endothelium-derived NO release and inhibiting coronary artery contractility.

Effects of estrogen replacement therapy on thrombin generation

The aim of this study was to investigate the hemostatic system in menopausal women before and after three months of treatment with transdermal estradiol (TTS 50, 50 micrograms/die, n = 13) or coniugated equine estrogen (CEE, 0.625 mg/die, n = 9) by evaluating : beta-thromboglobulin, platelet factor 4, factor VIIag, factor VIIc, fibrinopeptide A-FPA-, thrombin-antithrombin-TAT-complexes, antithrombin-AT-activity, protein C, plasma fibrinolytic activity (euglobulin clot lysis time), plasminogen and antiplasmin activity. FPA levels significantly increased during TTS 50 treatment (p < 0.001) while protein C showed a slight but significant decrease in both treatments (TTS 50 p < 0.001, CEE p < 0.05). TAT complexes and AT were found unaltered. Platelet function and fibrinolytic activity did not significantly change. A significant relationship between FPA and estradiol levels, which were significantly increased during. TTS 50 therapy, was found (r = 0.40, p < 0.05). These findings indicate that unopposed estradiol given by transdermal route induces a slight but significant blood clotting activation, which seems strictly related to its biological activity.

Hormone replacement therapy and cardioprotection: basic concepts and clinical considerations

A large body of epidemiological evidence shows that estrogen use after the menopause reduces the incidence of cardiovascular disease up to 50%. The use of progestin as co-medication in HRT appears not to attenuate the cardioprotective effects of estrogen. Menopause-related changes in metabolic cardiovascular risk factors are identifiable, as are HRT-related changes in these factors. Estrogens may act in a gender-specific way on vascular endothelial cells and other components of the vessel wall enhancing the synthesis and release of NO and other vasodilators and by inhibiting the synthesis and release of vasoconstricting agents, thus favoring vasodilation. Angiographic studies demonstrated in postmenopausal women with ischemic heart disease a reduction in coronary stenosis by estrogen monotherapy. Several studies, including the PEPI-trial, failed to demonstrate any major effect of HRT on blood pressure. The information on HRT and cardioprotection which is available so far is very promising and merits recommending HRT not only in healthy women but also in women with cardiovascular disease as well as in women with increased risk for this disease.

The mythology of hormone replacement therapy

OBJECTIVE

To evaluate the literature on contraindications contained in pharmaceutical data sheets of five currently available oestrogen replacement preparations (HRT). These contraindications include cardiovascular disease, diabetes, liver diseases, otosclerosis, endometriosis, melanoma and hormone-dependent tumours.

DESIGN

Systematic review.

INTERVENTIONS

Oestrogen replacement regimens.

RESULTS

The contraindications to the five HRT preparations have been taken uncritically from the data sheets of oral contraceptives. In some of these conditions not only is HRT not contraindicated, it is indicated. The data sheets for the HRT preparations all state that cardiovascular disease is a contraindication, but systematic review shows that ischaemic heart disease, hypertension and hyperlipidaemia are not contraindications, and in ischaemic heart disease HRT may actually be indicated. Similarly, systematic review shows that diabetes, chronic liver disease, endometriosis, some cases of treated cancer of the endometrium and breast, melanoma and otosclerosis are not contraindications to HRT.

CONCLUSIONS

The information in the pharmaceutical data sheets of HRT regimens should be modified as more accurate information could influence how these preparations are prescribed by doctors as well as affect patient compliance.

Estrogen replacement therapy and exercise performance in postmenopausal women with coronary artery disease

We treated 10 postmenopausal women with stable angina, positive exercise test, and documented coronary artery disease with oral conjugated equine estrogen (0.625 mg/day of Premarin) or placebo for 4 weeks, in random order, with crossover after a 4-week washout period. Exercise tests, performed after each treatment period while the patients were taking their usual antianginal drugs showed no differences; thus, short-term estrogen does not improve exercise-induced ischemia compared with placebo.

Endogenous estrogen and acetylcholine-induced vasodilation in normotensive women

Acute exogenous estrogen administration enhances endothelial function in postmenopausal women. To evaluate the effect of endogenous estrogen on endothelium-dependent vasodilation, in 10 fertile normotensive women (age range 45 to 51 years) we studied the changes in forearm blood flow (strain-gauge plethysmography) induced by intrabrachial acetylcholine (0.15, 0.45, 1.5, 4.5, 1.5 micrograms.100 mL-1.min-1), an endothelium-dependent vasodilator, or sodium nitroprusside (1, 2, 4 micrograms.100 mL-1.min-1), an endothelium-independent vasodilator, in basal conditions and within 1 month after ovariectomy. As control subjects, 10 matched healthy women were also evaluated. In basal condition, vasodilation to acetylcholine and sodium nitroprusside was similar in patients and control subjects. Ovariectomy was followed by endogenous estrogen deprivation (from 71.6 +/- 31.3 to < 12 pg/mL) and was associated with a significant (P < .01) reduction in acetylcholine-induced vasodilation compared with baseline (maximum percent increase in forearm blood flow: baseline 568.2 +/- 47.1%; ovariectomy 309.5 +/- 37.4%); the response to sodium nitroprusside was unaffected by ovariectomy (maximum percent increase in forearm blood flow: baseline 526.4 +/- 36.5%; ovariectomy 454.7 +/- 47.2%; P = NS). In 6 of 10 patients, the study was repeated after 3 months of estrogen replacement therapy (17 beta-estradiol, 50 micrograms/d by transdermal patches). Exogenous estrogen restored acetylcholine-induced vasodilation (maximum percent increase in forearm blood flow: 548.9 +/- 43.1%; P < .01 versus ovariectomy), which was no longer different from baseline, whereas the response to sodium nitroprusside was not affected (maximum percent increase in forearm blood flow: 480.2 +/- 39.3%; P = NS). These results suggest a protective role of endogenous estrogen on endothelium-dependent vasodilation in the forearm vascular bed of normotensive women.

17-beta-Estradiol therapy lessens angina in postmenopausal women with syndrome X

OBJECTIVES

We sought to investigate the hypothesis that estrogen replacement therapy ameliorates symptoms in postmenopausal women with syndrome X.

BACKGROUND

Syndrome X (angina pectoris, positive findings on exercise electrocardiography and normal results on coronary angiography) frequently occurs in menopausal women. This observation, in conjunction with the known vasoactive properties of estrogens, suggests that estrogen depletion may contribute to the pathogenesis of syndrome X in some women.

METHODS

Twenty-five postmenopausal patients with syndrome X completed a double-blind, placebo-controlled study of the effect of 17-beta-estradiol cutaneous patches (100 micrograms/24 h) on the frequency of chest pain and on exercise tolerance. Patients were randomly assigned to receive either placebo or 17-beta-estradiol patches for 8 weeks and were then crossed over to the other treatment.

RESULTS

During the placebo phase, patients had a mean of 7.3 episodes of chest pain/10 days. A reduction to 3.7 episodes/10 days was observed during the 17-beta-estradiol phase (p < 0.05). No significant differences were observed between the effects of 17-beta-estradiol and placebo on exercise duration or the results of other cardiologic investigations.

CONCLUSIONS

Estrogen replacement reduces the frequency of chest pain and may be a useful new therapeutic option for treating postmenopausal women with syndrome X.

Menopause is associated with endothelial dysfunction in women

To evaluate the effect of endogenous estrogens on endothelial function in humans, we examined whether menopause is associated with impairment in endothelium-dependent vasodilation in normotensive and essential hypertensive women. In 73 normotensive subjects (37 women, 36 men) and 73 hypertensive patients (36 women, 37 men), we studied endothelial function by measuring forearm blood flow modifications (strain-gauge plethysmography) induced by intrabrachial acetylcholine (0.15, 0.45, 1.5, 4.5, and 15 micrograms/100 mL per minute), an endothelium-dependent vasodilator, and sodium nitroprusside (1,2, and 4 micrograms/100 mL per minute), an endothelium-independent vasodilator. Women younger than 45 years had normal menstrual cycles. In essential hypertensive patients, responses to acetylcholine but not to sodium nitroprusside were significantly (P < .001) reduced compared with responses in normotensive subjects. Moreover, in both groups, vasodilation to acetylcholine showed a marked negative correlation with advancing age (normotensive subjects: r = -.88, P < .001; hypertensive patients: r = -.87, P < .001). In contrast, vasodilation to sodium nitroprusside showed a less evident negative correlation with advancing age (normotensive subjects: r = -46, P < .01; hypertensive patients: r = -.48, P < .01). However, in normally menstruating normotensive women, no endothelial dysfunction was observed, and age-related impairment in endothelium-dependent vasodilation was evident only after menopause. In normally menstruating hypertensive women, aging was associated with endothelial dysfunction although the deterioration of endothelium-dependent vasodilation was less marked than that in men. In contrast, after menopause, the age-related endothelial dysfunction in hypertensive women was similar to that observed in men. Finally, no sex-related difference in the response to sodium nitroprusside was observed in either normotensive subjects or essential hypertensive patients. Age-related endothelial dysfunction is attenuated in premenopausal normotensive and hypertensive women compared with men, whereas no sex-induced difference is observed after menopause, suggesting a protective effect of endogenous estrogens on endothelial function.

The menopause and the cardiovascular system

Combining the wealth of epidemiological, metabolic and recent mechanistic data, it would appear biologically plausible that HRT, either oestrogen alone or in combination with progestogen, is cardioprotective. Further research is required, as information is lacking on cardiovascular effects of HRT instigated at an older age. There is a need to identify cardiovascular benefit, indirect and/or direct, of combined oestrogen/progestogen therapy using randomized trials. The various progestogen types and doses also need to be investigated. Studies are also required to investigate the effect of HRT use in higher risk patients with established CVD. There is scant information on the effect of HRT on blood pressure of patients with hypertension. Cardiovascular risk factor profiles and incidence surveys need to be conducted in developing countries to characterize their female population and to identify the prevalence of CVD; this needs to be undertaken before widespread recommendations on CVD prevention and the role of HRT can be made. If HRT is to be used effectively in the future treatment of heart disease in women these questions need to be addressed. At present HRT is indicated for the relief of menopausal symptoms and the prevention of osteoporosis. In women without these indications, ORT may be recommended in those who have had a premature menopause, and possibly in those who have established CHD or who are at high risk of developing CHD. It is too early to suggest a blanket recommendation for the use of HRT in the treatment of the symptoms of women with established CVD, but HRT after the menopause may at least be safely used in the secondary prevention of CHD.

Investigation of the negative inotropic effects of 17 beta-oestradiol in human isolated myocardial tissues

1. The aim of the present study was to evaluate the effects of 17 beta-oestradiol in human myocardium. The effects of 17 beta-oestradiol, progesterone and testosterone on force of contraction were investigated in electrically driven isolated atrial trabeculae and ventricular papillary muscles from human hearts in the presence and absence of Bay K 8644, a calcium channel agonist. In addition, the effects of 17 beta-oestradiol, progesterone and testosterone on binding of [3H]-PN 200 110 were assessed in membranes prepared from human ventricular myocardium. 2. 17 beta-Oestradiol elicited a negative inotropic effect in atrial (IC50: 7.1 mumol 1(-1), confidence interval 3.8 to 13.4, n = 3) and ventricular preparations (IC50: 4.6 mumol 1(-1)), confidence interval 2.2 to 9.4, n = 3) as compared with solvent controls. There was no significant difference (P > 0.05) of IC50 values in the absence and presence of isoprenaline (0.0 mumol 1(-1)) in atrial (IC50: 10.8 mumol 1(-1), confidence interval 9.1 to 12.9, n = 6) and ventricular preparations (IC50: 9.4 mumol 1(-1), confidence interval 7.3 to 11.9, n = 8). 3. 17 beta-Oestradiol at 30 mumol 1(-1) induced a significant rightward shift of the concentration-response curves for the positive inotropic effect of Bay K 8644 in atrial preparations (EC50: 0.13 mumol 1(-1), confidence interval 0.08 to 0.19, n = 6; EC50 with 17 beta-oestradiol: 0.58 mumol 1(-1), confidence interval 0.33 to 0.83, n = 6, P < 0.05) and ventricular preparations (EC50: 0.07 mumol 1(-1), confidence interval 0.04 to 0.11, n = 8; EC50 with 17 beta-oestradiol: 0.3 mumol 1(-1), confidence interval 0.18 to 0.49, n = 8, P < 0.05). Testosterone, progesterone at 30 mumol 1(-1) and the solvent control had no significant effect on the concentration-response curves to Bay K 8644. 4. In membranes prepared from human ventricular myocardium the effect of 17 beta-oestradiol on binding of [3H]-PN 200 110, an antagonist at the 1,4 dihydropyridine binding site, was not different from that observed with progesterone, testosterone or solvent controls. 5. In myocardial membranes no specific oestrogen receptors were demonstrated by [3H]-oestradiol binding studies. 6. Thus, the calcium antagonistic property of 17 beta-oestradiol cannot be attributed to a direct interaction with 1, 4 dihydropyridine binding sites.

Postmenopausal estrogen and progestin use and the risk of cardiovascular disease

BACKGROUND

Estrogen therapy in postmenopausal women has been associated with a decreased risk of heart disease. There is little information, however, about the effect of combined estrogen and progestin therapy on the risk of cardiovascular disease.

METHODS

We examined the relation between cardiovascular disease and postmenopausal hormone therapy during up to 16 years of follow-up in 59,337 women from the Nurses' Health Study, who were 30 to 55 years of age at base line. Information on hormone use was ascertained with biennial questionnaires. From 1976 to 1992, we documented 770 cases of myocardial infarction or death from coronary disease in this group and 572 strokes. Proportional-hazards models were used to calculate relative risks and 95 percent confidence intervals, adjusted for confounding variables.

RESULTS

We observed a marked decrease in the risk of major coronary heart disease among women who took estrogen with progestin (multivariate adjusted relative risk, 0.39; 95 percent confidence interval, 0.19 to 0.78) or estrogen alone (relative risk, 0.60; 95 percent confidence interval, 0.43 to 0.83), as compared with women who did not use hormones [corrected]. However, there was no significant association between stroke and use of combined hormones (multivariate adjusted relative risk, 1.09; 95 percent confidence interval, 0.66 to 1.80) or estrogen alone (relative risk, 1.27; 95 percent confidence interval, 0.95 to 1.69).

CONCLUSIONS

The addition of progestin does not appear to attenuate the cardioprotective effects of postmenopausal estrogen therapy.

Release of vasoactive agents from the isolated perfused human ovary

OBJECTIVE

To investigate local vascular control in the isolated perfused premenopausal human ovary by measuring flow-induced release of vasoactive substances.

DESIGN

Release of adenosine 5' triphosphate (ATP), substance P (SP), endothelin (ET), and vasopressin (AVP) from the ovarian vascular endothelium was estimated in perfusate under basal conditions and during two periods of increased flow.

MAIN OUTCOME MEASURES

Vascular resistance; ATP, SP, ET and AVP release.

RESULTS

The mean ratio (pressure/flow during increased flow):(pressure/flow at basal flow) was 1.27 +/- 0.04 for the first, and 1.15 +/- 0.05 for the second period of increased flow (n = 10), indicating significant vasoconstriction (P < 0.01 and 0.05, respectively), present to a greater extent during the first period of increased flow compared to the second (P < 0.05). ATP release was seen in response to increased flow (n = 8, P < 0.05). From 12 ovarian bed preparations, five released ET and SP and three of these released AVP. Four of the five perfused ovaries that released peptides contained either a developing follicle or a corpus luteum while all those that showed no peptide release were inactive.

CONCLUSIONS

ATP release may play a role in the local control of the human premenopausal ovarian vasculature independent of ovulatory status. Peptides may also contribute to local vascular control in the ovary and their release from predominantly active ovaries suggests a relationship between ovulation and vascular endothelial function.

Different effects of estrogen and progesterone on experimental atherosclerosis in female versus male rabbits. Quantification of cellular proliferation by bromodeoxyuridine

BACKGROUND

The aim of the present study was to compare the effect of estrogen and progesterone on the development of experimental atherosclerosis in female versus male rabbits to assess possible sex-specific differences.

METHODS AND RESULTS

A total of 32 female and 32 male New Zealand White rabbits were ovariectomized or castrated. In addition to a 0.5% cholesterol diet, the rabbits received estradiol alone (1 mg/kg body wt [BW] per week), progesterone alone (25 mg/kg BW per week), or combined estradiol-progesterone in these dosages during 12 weeks. Ovariectomized female and castrated male rabbits served as control groups without hormone treatment. Before excision of the vessels, bromodeoxyuridine labeling was performed to determine the extent of cellular proliferation in the atherosclerotic lesions. The aortic arch was analyzed immunohistologically and morphometrically. An inhibitory effect of estrogen on intimal plaque size was found in female rabbits compared with the ovariectomized control group (0.7 +/- 0.5 versus 3.7 +/- 2.5 mm2, P < .002; proliferating cells, 3.1 +/- 1.8% versus 8.5 +/- 2.6%, P < .002). In combination with progesterone, however, estrogen was not able to reduce intimal plaque size or cellular proliferation. In contrast, estradiol in castrated male rabbits was not associated with an inhibitory effect on cellular proliferation or intimal thickening compared with controls (estrogen treatment, 7.6 +/- 2.1% proliferating cells and 2.8 +/- 1.0 mm2 neointima; control group, 7.2 +/- 2.1% cellular proliferation and 2.9 +/- 1.2 mm2 intimal thickening).

CONCLUSIONS

Our data suggest that the atheroprotective effect of estrogen is probably due to a mechanism that is present in female rabbits only.

Current estrogen-progestin and estrogen replacement therapy in elderly women: association with carotid atherosclerosis. CHS Collaborative Research Group. Cardiovascular Health Study

The cardioprotective effects of combined estrogen/progestin replacement therapy have been questioned. Therefore, we have compared carotid arterial wall thickening and the prevalence of carotid stenosis in elderly women (> or = 65 years old) currently using replacement estrogen/progestins (E + P) with arterial pathology and its prevalence in women using unopposed estrogens (E). This cross-sectional study used baseline data from all 2962 women participating in the Cardiovascular Health Study, a population-based study of coronary heart disease and stroke in elderly adults. Users of hormone replacement therapy (HRT) were categorized as never (n = 1726), past (n = 787), current E (n = 280), or current E + P (n = 73). Maximal intimal-medial thicknesses of the internal and common carotid arteries and stenosis of the internal carotid arteries were measured by ultrasonography. Current E + P users resembled current E users in most respects, although some lifestyle factors were more favorable among E + P users. Current E + P use and current E use (as compared with no use) were associated with smaller internal carotid wall thicknesses (-0.22 mm; P = 0.003; and -0.09 mm; P = 0.05, respectively) and smaller common carotid wall thicknesses (-0.05 mm; P = 0.03; and -0.02 mm; P = 0.1, respectively) and lower odds ratios (OR) for carotid stenosis (> or = 1% vs. 0%); OR = 0.61; 95% confidence interval [CI]: 0.36 to 1.01; and OR = 0.91, 95% CI: 0.67 to 1.24, respectively), after adjustment for current lifestyle and risk factors. When both groups of current HRT users were compared, there were no significant differences in carotid wall thicknesses or prevalence of carotid stenosis. For this sample of elderly women, both current E + P therapy and current E therapy were associated with decreased measures of carotid atherosclerosis. These measures did not differ significantly between the two groups of HRT users.