Cardiovascular protection by oestrogen--a calcium antagonist effect?

Estradiol and norgestimate: a review of their combined use as hormone replacement therapy in postmenopausal women

The focus of this review is hormone replacement therapy (HRT) with continuous administration of micronised, oral 17beta-estradiol 1 mg/day (herein referred to as continuous estradiol) plus micronised, oral norgestimate 90 microg/day administered for 3 days then withdrawn for 3 days in a 6-day repeating sequence (herein referred to as intermittent norgestimate). According to data from randomised, comparative trials of 1 year's duration, continuous estradiol 1 mg/day plus intermittent norgestimate 90 microg/day relieves climacteric symptoms (vasomotor symptoms and vulvovaginal atrophy) in postmenopausal women. Continuous estradiol 1 mg/day plus intermittent norgestimate 90 microg/day appeared as effective as estradiol 1 mg/day alone or continuous estradiol 2 mg/day plus continuous norethisterone acetate 1 mg/day in the treatment of postmenopausal women with vasomotor symptoms. Continuous estradiol 1 mg/day plus intermittent norgestimate 90 microg/day was as effective as continuous estradiol 1 mg/day in causing the maturation of vaginal epithelial cells. In a randomised, double-blind study, bone mineral density (BMD) increased to a significantly greater extent and the rate of bone turnover was slower in postmenopausal women treated with continuous oral estradiol 1 mg/day plus intermittent norgestimate 90 microg/day than in placebo-treated patients. Two randomised, double-blind studies indicated that the addition of norgestimate 90 microg/day to continuous estradiol 1 mg/day did not attenuate the beneficial effects of estradiol on lipid parameters. Continuous estradiol 1 mg/day plus intermittent norgestimate 90 microg/day was associated with increases in mean serum high density lipoprotein (HDL)-cholesterol levels and decreases in total cholesterol, low density lipoprotein (LDL)-cholesterol and lipoprotein (a) levels, compared with baseline. There was no statistically significant increase in triglyceride levels. In comparative trials, continuous oral estradiol 1 mg/day plus intermittent oral norgestimate 90 microg/day was well tolerated. Headache, breast pain or discomfort, abdominal pain or discomfort, uterine bleeding, dysmenorrhoea, oedema, nausea and depression were the most commonly reported adverse events. Continuous estradiol 1 mg/day plus intermittent oral norgestimate 90 microg/day was associated with a favourable uterine bleeding profile that improved over time. In a randomised trial, 80% of women were free from bleeding (irrespective of spotting) during month 12 of treatment. Norgestimate 90 microg/day was effective in protecting postmenopausal women against induction of endometrial hyperplasia by continuous estradiol 1 mg/day. In conclusion, data from a limited number of randomised studies indicate that HRT with continuous estradiol 1 mg/day plus intermittent norgestimate 90 microg/day is effective in relieving climacteric symptoms, increasing BMD and slowing the rate of bone turnover in postmenopausal women. This HRT regimen is well tolerated and is associated with a similar incidence of adverse events to that reported in recipients of continuous estradiol 1 mg/day. The norgestimate component of the regimen provides good endometrial protection and is associated with a favourable bleeding profile. Long-term studies investigating the associated risk of breast cancer and thromboembolic events in recipients of continuous estradiol plus intermittent norgestimate are needed. In the meantime, continuous oral estradiol plus intermittent oral norgestimate can be regarded as an effective new option for HRT in postmenopausal women.

Hormone replacement therapy to improve left ventricular diastolic functions in healthy postmenopausal women

OBJECTIVES

To investigate the effects of estrogen and estrogen plus progesterone replacement therapy on left ventricular systolic and diastolic function parameters in healthy postmenopausal women.

METHODS

Forty-six healthy consecutive postmenopausal women were prospectively enrolled. Hormone replacement therapy (HRT), which was either 0.625 mg/day conjugated equine estrogen (CEE) alone, or with 2.5 mg/day medroxyprogesterone acetate (MPA) was administered depending on the hysterectomy status. Left ventricular systolic and diastolic function parameters were evaluated with echocardiography before and after 6 months of HRT. The paired t-test was used for statistical analysis.

RESULTS

Estrogen or estrogen plus progesterone did not significantly alter the left ventricular dimensions and systolic function parameters. However, significant improvements were noted in several diastolic function parameters including late diastolic mitral flow velocity, ratio of early to late mitral flow velocity and isovolumic relaxation time (P=0.003, P=0.001 and P=0.005, respectively, for the CEE group; all P<0.001 for the CEE+MPA group).

CONCLUSIONS

Estrogen or estrogen plus progesterone replacement therapy may significantly improve left ventricular diastolic functions in healthy postmenopausal women.

Glycaemic control and plasma lipoproteins in menopausal women with Type 2 diabetes treated with oral and transdermal combined hormone replacement therapy

AIMS

To compare the effect of a fixed combination of an oestrogen (17-beta oestradiol) with a cyclical progestagen (norethisterone) on glycaemic control, plasma lipoproteins and haemostatic factors in women with Type 2 diabetes.

METHODS

Oral and transdermal hormone replacement therapy (HRT) were compared to no HRT treatment in 33 postmenopausal women with Type 2 diabetes, in a 12-week randomised prospective open parallel group study.

RESULTS

In the 11 women who received 12 weeks of oral HRT, there was a significant fall in total cholesterol (5.9+/-1.0 (S.D.) to 4.7+/-1.0 mmol l(-1), P=0.005), low density lipoprotein cholesterol (3.44+/-0.89 to 2.77+/-0.92 mmol l(-1), P=0.005) and triglyceride values (median (range)), (2.46 (0.96-5.52) to 2.29 (1.00-3.87) mmol l(-1), P<0.05). Oral HRT improved glycated haemoglobin (HbA(1c)) (7.4+/-1.4 to 6.8+/-1.2%, P< or =0.005). Oral HRT additionally reduced the cell adhesion factor E-selectin (82+/-33 to 60+/-20 microg l(-1), P<0.01) and factor VII (143+/-25 to 109+/-24% pooled plasma activity, P<0.01). No improvement in any of these parameters, except E-selectin (65+/-19 to 58+/-18 microg l(-1), P<0.01), occurred in the nine women receiving transdermal HRT, and no improvement occurred in the 13 controls randomised to no treatment.

CONCLUSION

In women with Type 2 diabetes, cyclical oestrogen and progestagen taken orally for 12 weeks significantly improved glycaemic control and lipoprotein concentrations. These metabolic benefits were not apparent when a similar HRT preparation was administered transdermally.

Hypertension, heart rate, use of antihypertensives, and incident prostate cancer

PURPOSE

Recent studies have reported conflicting results on a possible relationship between hypertension, heart rate, and prostate cancer. A model has been developed suggesting that high blood pressure and high heart rate may both be markers for increased central sympathetic nervous activity, which may result in androgen-mediated stimulation of prostate cancer growth.

METHODS

In this study we examined the associations between hypertension, heart rate, use of antihypertensive medications, and incident prostate cancer in a cohort of 2442 men. Data from the Cardiovascular Health Study (CHS), an NHLBI-sponsored observational study of adults age 65 or older in four U.S. communities, were analyzed using Cox proportional hazards regression. Seated systolic and diastolic blood pressures were measured using a standardized protocol at the initial clinical examination and annually at follow-up visits. Medications data were transcribed by trained interviewers from prescription medication containers brought into the clinic by participants.

RESULTS

A total of 209 cases of incident prostate cancer were identified from either an ICD-9 code of 185 in hospital medical records (n = 130) or by self-report from annual surveillance interviews (n = 79). An average of 5.6 years of follow-up was available for analyses. No associations between blood pressure measures at entry into the study and prostate cancer were found, although these results may have been affected by subsequent treatment of hypertension. An association between resting heart rate (HR) equal to or greater than 80 beats per minute and incident prostate cancer was found compared to men with a rate of less than 60 beats per minute (HR: 1.6, 95% confidence interval [CI]: 1.03-2.5). An inverse association was found between risk of incident prostate cancer and use of any antihypertensive medication (HR: 0.7, 95% CI: 0.5-0.9). A test of heterogeneity found no difference between use of the specific classes of antihypertensive medication and the association with prostate cancer risk.

CONCLUSIONS

These data tend to support the hypothesized causal pathway between vascular disease markers and prostate cancer.

Tamoxifen is an acute, estrogen-like, coronary vasodilator of porcine coronary arteries in vitro

Tamoxifen is a mixed estrogen antagonist and agonist. Observational data from breast cancer studies associate tamoxifen use with lesser rates of myocardial infarction. The authors sought to determine the acute vasoactive properties of tamoxifen compared with estradiol. Isolated coronary ring segments from female pigs were studied in organ baths. KCl-precontracted ring segments were exposed to increasing doses of both tamoxifen and estradiol (log-9-log-5 M ). Ring segments were also exposed to tamoxifen and estradiol in the presence of inhibitors of nitric oxide, glybenclamide, the hormone receptor antagonists ICI 182,780 and flutamide, and after de-endothelialization. Tamoxifen caused acute dilation of coronary arteries but less than estradiol. Tamoxifen-and estradiol-induced acute vasodilation was not nitric oxide- or endothelium-dependent, but was adenosine triphosphate-sensitive potassium channel-dependent. Tamoxifen-induced vasorelaxation was inhibited by antagonism of the classic estrogen receptor and antagonism of the androgen receptor with flutamide, whereas estrogen-induced vasorelaxation was inhibited partially by classic estrogen receptor antagonism but not by androgen receptor antagonism. Tamoxifen attenuated both the sensitivity of vasoconstriction to endothelin-1 and the maximal response. Tamoxifen and estradiol are both acute coronary vasodilators, with similar mechanisms of action. Tamoxifen also attenuates coronary vasoconstriction. Such properties may account for some of the observed cardiovascular clinical benefits seen in observational studies of tamoxifen use.

Raloxifene reduces impedance to flow within the uterine artery in early postmenopausal women: a 2-year randomized, placebo-controlled, comparative study

OBJECTIVE

We sought to investigate the long-term effect of raloxifene and continuous combined hormone replacement therapy (ccHRT) on impedance to flow within the uterine artery in postmenopausal women.

STUDY DESIGN

A prospective, randomized, double-blind, placebo-controlled 2-year study was performed in 95 postmenopausal women. They received either 60 mg of raloxifene daily (raloxifene 60 group), 150 mg of raloxifene daily (raloxifene 150 group), ccHRT, or placebo. At baseline and thereafter every 6 months, color Doppler ultrasonography was used to measure the pulsatility index (PI) of the uterine artery.

RESULTS

After 24 months of treatment, compared with placebo, significant decreases were found in the PI in the raloxifene 150 group (P = .021) and in the ccHRT group (P = .007). In the raloxifene 150 group compared with the placebo group, after 6 and 24 months, decreases were observed in median PI of -5% and -15%, respectively, and in the ccHRT group decreases of -2% and -19%, respectively, were found.

CONCLUSION

Long-term use of 150 mg of raloxifene daily or ccHRT reduces impedance to flow within the uterine artery. This indicates that high-dose raloxifene may exert cardiovascular protection.

[Estradiol enhances endothelium-dependent vasodilation via a nitric oxide pathway]

BACKGROUND AND AIM

The mechanisms by which estradiol dilates arterial vessels are still unclear. Our aim was to study if estradiol enhances endothelium-dependent vasodilation in an experimental model of human arteries in vitro, and if this effect is nitric oxide mediated.

METHODS

Using organ bath chambers, we studied 18 arterial rings obtained from left internal mammary arteries during coronary artery bypass grafting surgery. Response to acetylcholine was evaluated at baseline and after the addition of estradiol 10-6 mol/l to the medium, both in the presence or absence of a nitric oxide synthase inhibitor (L-NNA 10-4 mol/l).

RESULTS

Estradiol significantly enhanced the relaxation of the arterial rings in response to acetylcholine (52 +/- 20% after estradiol versus 42 +/- 22% at baseline; n = 10; p = 0.02). However, endothelium-dependent vasodilation relaxation after estradiol addition was not enhanced in the presence of L-NNA (47 +/- 25% after estradiol versus 38 +/- 22% at baseline; n = 8; p = NS).

CONCLUSIONS

Estradiol in vitro enhances endothelium-dependent vasodilation of internal human mammary artery rings; this effect is blunted after the addition to the medium of a nitric oxide inhibitor. Therefore, the vasodilator properties of estradiol at the studied dosage depend on the nitric oxide pathway.

Sex hormone modulation of serotonin-induced coronary vasodilation in isolated heart

The present study was designed to evaluate the differences in the coronary vasodilator actions of serotonin (5-HT) in isolated heart obtained from naive or castrated male and female rats that were treated with either estrogen or testosterone. Hearts from 12 groups of rats were used: male and female naive animals, castrated, castrated and treated with 17beta-estradiol (0.5 microg kg(-1) day(-1)) for 7 or 30 days, and castrated and treated with testosterone (0.5 mg kg(-1) day(-1)) for 7 or 30 days. After treatment, the vascular reactivity of the coronary bed was evaluated. Baseline coronary perfusion pressure (CPP) was determined and dose-response curves to 5-HT were generated. Baseline CPP differed between male (70 +/- 6 mmHg, N = 10) and female (115 +/- 6 mmHg, N = 12) naive rats. Maximal 5-HT-induced coronary vasodilation was higher (P<0.05) in naive female than in naive male rats. In both sexes, 5-HT produced endothelium-dependent coronary vasodilation. After castration, there was no significant difference in baseline CPP between hearts obtained from male and female rats (75 +/- 7 mmHg, N = 8, and 83 +/- 5 mmHg, N = 8, respectively). Castration reduced the 5-HT-induced maximal vasodilation in female and male rats (P<0.05). Estrogen treatment of castrated female rats restored (P<0.05) the vascular reactivity. In castrated male rats, 30 days of estrogen treatment increased (P<0.05) the responsiveness to 5-HT. The endothelium-dependent coronary vasodilator actions of 5-HT are greater in female rats and are modulated by estrogen. A knowledge of the mechanism of action of estrogen on coronary arteries could aid in the development of new therapeutic strategies and potentially decrease the incidence of cardiovascular disease in both sexes.

Vascular inhibitory actions of 17beta-oestradiol in rat portal vein

1. We have examined the effects of 17beta-oestradiol on spontaneous spikes and contractions to noradrenaline in rat portal vein. 2. The 17beta-oestradiol (10 microM) significantly reduced the maximum height of spontaneous spike contractions and significantly reduced the maximum contraction to noradrenaline (10 microM) in portal vein from both male and female rats. 3. The protein synthesis inhibitor cycloheximide (10 microM) did not significantly affect the inhibitory actions of 17beta-oestradiol (10 microM) against spontaneous spike contractions and contractions to noradrenaline. 4. In summary, 17beta-oestradiol diminishes spontaneous spike contractions and the contractile response to noradrenaline in rat portal vein, by a non-genomic action.

Effect of estrogen and progestin replacement on arterial stiffness indices in postmenopausal women

Our objectives were to investigate whether long-term estrogen replacement therapy (ERT) is associated with a reduction in age-associated increases in arterial stiffness and blood pressure (BP), and whether the addition of progestin modifies the effects of estrogen. ERT has been found to have beneficial effects on cardiovascular risk. There are few data, however, delineating the effects of ERT on BP and arterial stiffness, and their age-associated changes. BP and aorto-femoral pulse wave velocity (PWV) were measured in 134 postmenopausal volunteers, aged 51 to 90 years, from the Baltimore Longitudinal Study of Aging, screened to exclude clinical and occult cardiovascular disease, and classified as ERT non-users (N=57) or ERT users (N=77). The latter group was further substratified according to the use of estrogen alone (N=32) or a combination of estrogen and progestins (N=45). ERT users showed similar body habitus, physical activity, and plasma lipids compared to non-ERT users. ERT was associated with an average 9.8 mmHg lower systolic BP (p<0.001), and a 6.3 mmHg lower pulse pressure (p<0.01) than in non-users. Multiple regression analysis showed that ERT was an independent predictor of lower SBP and PP (p<0.05). By analysis of covariance, ERT predicted a reduced age-associated increase in SBP, PP, and PWV (p<0.05). When systolic BP was >130 mmHg, the combination of ERT and progestins predicted a higher PWV than ERT alone. In conclusion, ERT in postmenopausal women can beneficially affect the vascular system, by reducing BP and the age-associated increase in arterial stiffness. The addition of progestins to ERT may reduce these beneficial effects.

The effect of 17beta-estradiol on isolated omental arteries from preeclamptic women

OBJECTIVE

To study the effect of 17beta-estradiol on isolated omental arteries from preeclamptic women.

STUDY DESIGN

Rings of omental artery with intact endothelium were mounted in organ chambers for isometric tension recording. We studied the effect of pharmacological concentrations of 17beta-estradiol on potassium chloride-induced tension and the concentration-contraction relationships for norepinephrine and calcium.

RESULTS

Cumulative application of 17beta-estradiol, in a concentration-dependent manner, relaxed potassium chloride contracted rings. Sixty minutes of incubation with 17beta-estradiol (10(-5)mol/l) attenuated the tension developed in response to potassium chloride, norepinephrine and calcium. Tamoxifen (10(-6)mol/l) did not antagonize the inhibitory actions of 17beta-estradiol.

CONCLUSIONS

Pharmacological concentrations of 17beta-estradiol retain the capability for relaxing omental artery rings from preeclamptic women. The loss of refractoriness to norepinephrine, increased responsiveness to calcium ions and decreased ability of 17beta-estradiol to inhibit calcium-induced tension may be responsible for increased vascular reactivity in preeclampsia.

17-beta estradiol can reduce secondary ischemic damage and mortality of subarachnoid hemorrhage

Subarachnoid hemorrhage (SAH) is a unique disorder commonly occurring when an aneurysm ruptures, leading to bleeding and clot formation, with a higher incidence in females. To evaluate the influence of 17-beta estradiol (E2) in the outcome of subarachnoid hemorrhage, SAH was induced by endovascular puncture of the intracranial segment of internal carotid artery in 15 intact females (INT), 19 ovariectomized females (OVX), and 13 ovariectomized female rats with E2 replacement (OVX + E2). Cerebral blood flow was recorded before and after SAH. All animals were decapitated immediately after death or 24 hours after SAH for clot area analysis. Brains were sliced and stained with 2,3,5-triphenyltetrazolium chloride (TTC) for secondary ischemic lesion analysis. The cortical cerebral blood flow (CBF), which was measured by a laser-Doppler flowmeter, decreased to 29.6%+/-17.7%, 22.8%+/-8.3%, and 43.5%+/-22.9% on the ipsilateral side (P = 0.01), and decreased to 63.4%+/-14.1%, 57.4%+/-11.0%, and 66.6%+/-17.9% on the contralateral side (P = 0.26) in INT, OVX, and OVX + E2, respectively. The subcortical CBF, which were measured by the H2 clearance method, were 7.77+/-12.03, 7.80+/-8.65, and 20.58+/-8.96 mL 100 g(-1) min(-1) on the ipsilateral side (P < 0.01), and 21.53+/-2.94, 25.13+/-3.01, and 25.30+/-3.23 mL 100 g(-1) min(-1) on the contralateral side in INT, OVX, and OVX + E2, respectively. The mortality was 53.3%, 68.4%, and 15.4% in INT, OVX, and OVX + E2, respectively (P = 0.01), whereas no significant difference in clot area was noted among the groups. The secondary ischemic lesion volume was 9.3%+/-8.4%, 24.3%+/-16.3%. and 7.0%+/-6.4% in INT, OVX, and OVX + E2, respectively (P < 0.01). This study demonstrated that E2 can reduce the mortality and secondary ischemic damage in a SAH model without affecting the clot volume.

Temporal changes in cardiac function and cerebral blood flow during sequential postmenopausal hormone replacement

OBJECTIVE

The purpose was to assess the temporal changes in cardiac function and cerebral blood flow during postmenopausal administration of estrogen with and without progestogen.

STUDY DESIGN

Sixteen postmenopausal volunteers were assessed during estradiol plus sequential norethindrone acetate and placebo in two 12-week periods. Temporal changes were measured by magnetic resonance flow mapping 8 times.

RESULTS

Systemic vascular resistance was reduced during estradiol (-6.9%; P <.05), declined further during the addition of norethindrone acetate, and was accompanied by an increase in stroke volume (maximum increase, 5.2%; P <.05) without fluid retention. Both systolic (-5 mm Hg; P =.03) and diastolic (-3 mm Hg; P =.03) blood pressure were reduced during estradiol. Cerebral blood flow was reduced after 9 weeks of hormone replacement therapy (-37 mL/min; P =.01) but increased to baseline after the addition of norethindrone acetate.

CONCLUSIONS

Sequential hormone replacement therapy is associated with changes in cardiac function, which are of therapeutic potential in cardiovascular disorders. Sequential hormone replacement therapy exhibits an overall neutral effect on cerebral blood flow.

17beta-estradiol, gender independently, reduces atheroma development but not neointimal proliferation after balloon injury in the rabbit aorta

The aim of the present study was to investigate anti-proliferative and anti-atherogenic properties of 17beta-estradiol in balloon injured female and male rabbit aortae. Thirty-two female and 32 male New Zealand White rabbits where gonadectomised. Vascular injury was performed with a balloon catheter in the lower abdominal aorta. Male and female rabbits were randomised into four groups of eight animals each. Only two of four groups received a 0.5% cholesterol-enriched diet. One cholesterol-diet group and one normal-diet group received intramuscular injections of estradiol valerate (1 mg/kg body weight/week). After 28 days, the denuded part of the abdominal aorta was excised and analysed by morphometry and immunohistochemistry. Estrogen treatment did not show an inhibitory effect on neointimal proliferation in normo-cholesterolemic male or female rabbits. A gender independent inhibitory effect of 17beta-estradiol was seen on atheroma development in cholesterol-fed female and male rabbits, while plasma total cholesterol levels were significantly reduced in male rabbits only. The 17beta-estradiol treatment was associated with a significantly decreased number of luminal endothelial cells in normo and hyper-cholesterolemic female rabbits, as evaluated by immunohistochemical staining for 'von Willebrand factor'. Staining for Ki-67-positive proliferating cells after 28 days showed a statistically significant increased proliferative activity in the neointima of hyper-cholesterolemic female rabbits. The neointimal content of macrophages increased significantly in all hyper-cholesterolemic rabbits. Under 17beta-estradiol treatment, the number of macrophages was increased in female and decreased in male rabbits by tendency. Additionally, the 'classical' vascular estrogen receptor was present in both female and male rabbit aortae without statistically significant differences. In conclusion, 17beta-estradiol did not reduce post-injury neointima formation in normo-cholesterolemic rabbits. However, in hyper-cholesterolemic rabbits, 17beta-estradiol reduced atheroma development gender independently. This effect cannot be explained by lowering of plasma cholesterol levels or endothelium-mediated pathways, and requires further investigation on, for example, antioxidative, antiproliferative or estrogen receptor mediated effects.

The effect of oophorectomy and estrogen replacement therapy on Doppler derived parameters of aortic flow

OBJECTIVES

The immediate consequences of surgical castration and estrogen replacement therapy (ERT) on left ventricular systolic performance as assessed by Doppler-derived parameters of aortic flow were examined.

METHODS

A follow up study comprising two groups: eight premenopausal women who underwent hysterectomy and bilateral oophorectomy and started ERT 1 week after surgery - the study group, and a control group consisted of eight premenopausal women who did not start ERT following hysterectomy. Doppler echocardiography was performed before surgery, 1 week and 1 month post surgery.

RESULTS

In both groups significant increase in heart rate was observed after 1 week, remaining high after 1 month in the control group only. The early post-operative period in all women was characterized by an increase in aortic flow velocity, but was statistically significant in the study group only. After initiation of ERT a significant decrease in peak flow velocity (PFV) and mean acceleration (MA) was recorded.

CONCLUSIONS

Changes in estradiol level may be associated with alterations in left ventricular function. The initial and acute effect of estrogen on the heart muscle after surgical castration is towards a decrease in Doppler-derived parameters of aortic flow. Whether these effects represent a depression of left ventricular function, or alternatively, reflect peripheral vasculature reactivity, requires further evaluation.

Controversial issues in climacteric medicine I. Cardiovascular disease and hormone replacement therapy. International Menopause Society Expert Workshop. 13-16 October 2000, royal society of medicine, London, UK

The clinical benefits of HRT are clearly established for the relief of menopausal symptoms, improving quality of life and the prevention of osteoporosis. Although research on the impact of HRT (oral, transdermal, tibolone, etc.) and on the effects of raloxifene on CVD is still ongoing, with certain unresolved controversies, studies using a variety of different HRT formulations have shown a clear benefit on surrogate markers of CHD and epidemiological and clinical, although not randomized, studies have demonstrated a CHD reduction in HRT-treated women. Today, HRT may be used for the primary prevention of CVD. Conversely, there is no clear reason to commence HRT solely or primarily to confer an immediate cardiovascular benefit in postmenopausal women with established CHD. Equally, there is no compelling evidence for discontinuing--or indeed not initiating--HRT in women without CVD because of concern about cardiovascular risk. In any case, all medical interventions should be individualized to the specific woman's age, characteristics and needs. The ultimate effects of different dosages, schedules and type of hormones used should be clarified, avoiding inferring the effects of one form of HRT to others. The importance of increased attention to life-style factors such as healthy diet, exercise and cessation of smoking should be underlined since these can confer specific benefits also to menopausal women. For women with known risks for CVD, HRT may contribute to the beneficial effects of life-style improvements and well-established therapies (including blood pressure control, cholesterol-lowering drugs, aspirin, etc.). New strategies, including lower dosages, new estrogens, progestins, and new estrogen-like substances may be designed to target specific needs.

Acute effects of 17beta-estradiol on ventricular and vascular hemodynamics in postmenopausal women

Because premenopausal women have lower cardiovascular morbidity than postmenopausal women, it has been proposed that estrogen may have a protective role. Estrogen is involved in smooth muscle relaxation both through its specific receptor as well as through calcium channel blockade. This study examined the acute effect of estradiol on invasive cardiovascular hemodynamics in 18 postmenopausal women (age 62.6 +/- 7.6 years, means +/- SD). The effect of estradiol on left ventricular chamber performance was studied in 9 women using simultaneous left ventricular pressure-volume recordings. In a further group of 9 women, the acute effect of estradiol on arterial function was assessed using input impedance (derived from simultaneous aortic pressure and flow recordings), pressure waveform analysis, and pulse wave velocity. After 2 mg micronized 17beta-estradiol was administered, serum estradiol levels increased from 50.9 +/- 21.9 to 3,190 +/- 2,216 pmol/l, P < 0.0001. There was no effect of estradiol on either left ventricular inotropic or lusitropic function. There was no acute effect of estradiol on arterial impedance, reflection coefficient, augmentation index, or pulse wave velocity. There was a trend to decreased heart rate and cardiac output in both groups of 9 women. Because heart rate and cardiac output were common to both hemodynamic data sets, results for these parameters were pooled. Across all 18 women, there was a small but significant decrease in heart rate (69.2 +/- 10.4 vs. 67.2 +/- 9.9 beats/min, P = 0.02), as well as a significant decrease in cardiac output (4.82 +/- 1.77 vs. 4.17 +/- 1.56 l/min, P = 0.002). Despite achieving supraphysiological serum levels, this study found no significant effect of acute 17beta-estradiol on ventricular or large artery function.

Calcium regulates estrogen increase in permeability of cultured CaSki epithelium by eNOS-dependent mechanism

Estrogen increases baseline transepithelial permeability across CaSki cultures and augments the increase in permeability in response to hypertonic gradients. In estrogen-treated cells, lowering cytosolic calcium abrogated the hypertonicity-induced augmented increase in permeability and decreased baseline permeability to a greater degree than in estrogen-deprived cells. Steady-state levels of cytosolic calcium in estrogen-deprived cells were higher than in estrogen-treated cells. Increases in extracellular calcium increased cytosolic calcium more in estrogen-deprived cells than in estrogen-treated cells. However, in estrogen-treated cells, increasing cytosolic calcium was associated with greater increases in permeability in response to hypertonic gradients than in estrogen-deprived cells. Lowering cytosolic calcium blocked the estrogen-induced increase in nitric oxide (NO) release and in the in vitro conversion of L-[(3)H]arginine to L-[(3)H]citrulline. Treatment with estrogen upregulated mRNA of the NO synthase isoform endothelial nitric oxide synthase (eNOS). These results indicate that cytosolic calcium mediates the responses to estrogen and suggest that the estrogen increase in permeability and the augmented increase in permeability in response to hypertonicity involve an increase in NO synthesis by upregulation of the calcium-dependent eNOS.

Serum lipids and arterial plaque load are altered independently with high-dose progesterone in hypercholesterolemic male rabbits

Antiatherogenic effects of sex steroids in premenopausal women are not well defined. Therefore, we employed an established rabbit model for atherosclerosis to study the effects of exogenous estrogen and a progesterone analogue (P) on serum lipids and aortic plaque load. Serum cholesterol (C) and triglyceride (T) levels and atherosclerotic plaque loads were compared in 5 groups of male New Zealand White rabbits fed a 12-week, C-rich diet: 1 control group (CG) and 4 groups treated with estriol (E), haloperidol (H), low-dose 17-hydroxyprogesterone (LDP), or high-dose 17-hydroxyprogesterone (HDP). Serum P was measured in the LDP and HDP groups. Serial histologic sections (15 each of 27 ascending aortas) were studied by light microscopy and computerized morphometric analysis. Plaque load is defined as the ratio of intimal area to medial area (I/M). Exogenous E (p<0.001), H (P = 0. 02), LDP and HDP (P<0.001, each) were found to be significantly associated with less aortic plaque load than controls. In a multivariate analysis, after controlling for the differences in serum C and T levels, HDP (p = 0.014) was found to be associated with less aortic plaque load than controls, and this association approached statistical significance in the E (p = 0.052) and H (p = 0.069) groups. These data suggest that the mechanism(s) involved with the antiatherogenic effect of HDP in this animal model is, or are, independent of an alteration in serum lipids.

Chronic and acute effects of oestrogens on vascular contractility

In addition to their role as sex hormones, it has been known for many years that oestrogens have protective effects on the vasculature. These have been implicated in the reduced incidence of cardiovascular disorders in premenopausal women and in post-menopausal women receiving oestrogen replacement therapy. This protection has been found to be due, in part at least, to direct effects of oestrogens on blood vessels. This review will summarize the available literature regarding oestrogenic effects on vascular contractility. Two major influences of oestrogens will be discussed; first the genomic effects induced by chronic administration of steroid hormones, and second, the rapid effects on vascular smooth muscle by non-genomic, and as yet not fully identified, mechanisms. In so doing, the diversity of oestrogenic actions on vascular contractility will be highlighted and the protective role of these agents against adverse cardiovascular events discussed.

Plant-derived estrogens relax coronary arteries in vitro by a calcium antagonistic mechanism

OBJECTIVES

To investigate the potential for plant derived estrogens (phytoestrogens) genistein, phloretin, biochanin A and zearalanone to relax rabbit coronary arteries in vitro and to determine the mechanism(s) of such relaxation.

BACKGROUND

Epidemiological data suggests a reduction in the incidence of coronary heart disease in humans who have a high intake of phytoestrogens.

METHODS

Isolated rabbit coronary artery rings were suspended in individual organ baths, precontracted with potassium chloride (30 mM), and the relaxing effects and mechanisms of relaxation to genistein, phloretin, biochanin A and zearalanone were determined by measurement of isometric tension.

RESULTS

Genistein, phloretin and biochanin A induced significant gender-independent relaxation in rings with and without endothelium. Inhibition of nitric oxide and prostaglandin synthesis with L-NAME and indomethacin had no effect on genistein-induced relaxation. Relaxation was unaffected by the specific estrogen receptor antagonist ICI 182,780, the ATP-sensitive potassium channel inhibitor glibenclamide and the potassium channel inhibitor, barium chloride. Calcium concentration-dependent contraction curves in high potassium depolarization medium were significantly shifted to the right and downward after incubation with genistein and zearalanone. An inhibitory effect of genistein (2 microM) on L-type calcium current in guinea-pig ventricular myocytes confirmed a calcium antagonist relaxing mechanism of action. In healthy volunteers, plasma genistein levels of approximately 2 microM are achieved after ingestion of a commercially available soy protein drink (Supro) containing 37 mg genistein.

CONCLUSIONS

This study demonstrates that phytoestrogens induce endothelium-independent relaxation of coronary arteries; the mechanism involves calcium antagonism. These mechanisms may contribute to the potential long-term cardiovascular protective effect of these substances.

Cardiovascular effects of droloxifene, a new selective estrogen receptor modulator, in healthy postmenopausal women

Selective estrogen receptor modulators, like tamoxifen and related compounds, have mixed estrogen agonistic/antagonistic effects. Tamoxifen may confer significant cardiovascular benefits without the estrogen-associated risks of endometrial and breast cancer. Droloxifene, a structural analogue of tamoxifen, has estrogen agonistic effects on bone and antagonistic effects on endometrial and breast tissue. Its cardiovascular effects in women are unknown. We enrolled 24 healthy postmenopausal women in a randomized, double-blind, 2-period crossover trial comparing the effects of droloxifene (60 mg/d) with conjugated estrogen (0.625 mg/d). Plasma lipids, coagulation and fibrinolytic factors, and brachial flow-mediated vasodilator responses were measured at the beginning and end of each treatment period. Droloxifene and estrogen resulted in 16.6% and 12.0% reductions, respectively, in low density lipoprotein cholesterol (P<0.001) and 13.2% and 9.5% reductions, respectively, in lipoprotein(a) (P<0.05). In contrast, estrogen, but not droloxifene, increased high density lipoprotein (18.5%, P<0.001). Droloxifene also reduced fibrinogen by 17.8% versus a 7.3% reduction with estrogen (P=0.004) but produced no estrogen-like changes in plasminogen, plasminogen activator inhibitor-1, or tissue plasminogen activator. Droloxifene and estrogen produced 36.4% and 27.3% increases, respectively, in flow-mediated vasodilation (percent change from baseline, P<0.05 for both). Droloxifene has estrogen agonistic properties regarding low density lipoprotein and lipoprotein(a) metabolism, certain coagulation factors, and endothelium-dependent vasodilation but, unlike estrogen, has no effect on high density lipoprotein/triglyceride metabolism and the fibrinolytic cascade. It remains unknown whether droloxifene can confer a true cardiovascular benefit.

Sex-specific triggers for right ventricular outflow tract tachycardia

BACKGROUND

Right ventricular outflow tract tachycardia (RVOT-VT) is a common arrhythmia in young patients without heart disease. The arrhythmia is characterized by repetitive bursts and premature ventricular contractions with a left bundle branch block, inferior-axis QRS morphology, and symptoms of palpitations. Although more frequent in women, sex-specific triggers for symptomatic RVOT-VT have not been identified.

METHODS AND RESULTS

We interviewed 34 women and 13 men referred for ablation of RVOT-VT to determine if predictable but sex-specific exacerbations in symptomatic RVOT-VT exist. After a general query asking if there was predictability to what triggered palpitations, we then specifically queried all patients about symptomatic RVOT-VT initiation with exercise, stress, caffeine, fatigue, and, in women only, periods of recognized hormonal flux. The times identified as states of hormonal flux included premenstrual, gestational, perimenopausal, and coincident with the administration of birth control pills. In response to the completed interview, the most common recorded trigger for RVOT-VT in women was recognized states of hormonal flux with 20 (59%) of 34 women responding positively and 14 (41%) of the 34 indicating that states of hormonal flux were the only recognizable triggers. Men were more likely than women to report that their RVOT-VT was predictably triggered by exercise, stress, or caffeine: 12 (92%) of 13 men versus 14 (41%) of 34 women (P <.01).

CONCLUSIONS

Triggers for RVOT-VT initiation are sex specific. Women have RVOT-VT initiation with recognized states of hormonal flux. Men more commonly have RVOT-VT initiated by exercise or stress. These data have important implications related to patient education and counseling in the setting of RVOT-VT and may influence the timing of drug treatment and electrophysiologic evaluation in selected patients.

Pharmacodynamics of oestrogens and progestogens

The ovaries cyclically secrete estradiol and progesterone. Cyclic ovarian estradiol secretion is associated with a bone-saving and vascular protection effect. Endogenous progesterone does not modify the vasodilator effect of oestrogens. At physiological concentrations, the natural sex steroids have low antigonadotropic effects. More potent synthetic derivatives with more antigonadotropic effects were synthesized in the 1950s. After the menopause, there is no longer any need to use hormonal steroids as antigonadotropics. In addition, vascular contraindications are more common in an older population. Contraceptive steroids (particularly ethinyl estradiol) are therefore rarely used. The oestrogen that is most widely prescribed for post-menopausal replacement is a complex formulation of conjugated oestrogens of equine origin that is administered orally in a single daily dose. Improvements in hormone replacement therapy may result from the use of parenteral estradiol (providing sufficient doses are reached) and of a progestogen chemically more similar to progesterone.

Estrogen as a neuroprotectant in stroke

Recent evidence suggests that reproductive steroids are important players in shaping stroke outcome and cerebrovascular pathophysiologic features. Although women are at lower risk for stroke than men, this native protection is lost in the postmenopausal years. Therefore, aging women sustain a large burden for stroke, contrary to a popular misconception that cancer is the main killer of women. Further, the value of hormone replacement therapy in stroke prevention or in improving outcome remains controversial. Estrogen has been the best studied of the sex steroids in both laboratory and clinical settings and is considered increasingly to be an endogenous neuroprotective agent. A growing number of studies demonstrate that exogenous estradiol reduces tissue damage resulting from experimental ischemic stroke in both sexes. This new concept suggests that dissecting interactions between estrogen and cerebral ischemia will yield novel insights into generalized cellular mechanisms of injury. Less is known about estrogen's undesirable effects in brain, for example, the potential for increasing seizure susceptibility and migraine. This review summarizes gender-specific aspects of clinical and experimental stroke and results of estrogen treatment on outcome in animal models of cerebral ischemia, and briefly discusses potential vascular and parenchymal mechanisms by which estrogen salvages brain.

Estradiol exerts neuroprotective effects when administered after ischemic insult

BACKGROUND AND PURPOSE

17beta-Estradiol (E2) has been reported to exert neuroprotective effects when administered before an ischemic insult. This study was designed to determine whether E2 treatment after ischemia exerts the same effects and, if so, how long this therapeutic window remains open, and whether the effects are related to changes in cerebral blood flow (CBF).

METHODS

Female Sprague-Dawley rats were subjected to permanent middle cerebral artery occlusion (MCAO). In protocol 1, E2 was administered (100 microg/kg IV followed immediately by subcutaneous implantation of crystalline E2 in a silicone elastomer tube) to ovariectomized females (OVX+E2) at 0.5 (n=8), 1 (n=6), 2 (n=7), 3 (n=6), or 4 (n=9) hours after MCAO. Intact (INT; n=6) and ovariectomized females (OVX; n=12) were subjected to MCAO and received vehicle instead of E2. Two days after MCAO the animals were killed, and ischemic lesion volume was determined by 2,3,5-triphenyltetrazolium chloride staining. In protocol 2, CBF was monitored before and at 1, 24, and 48 hours in a group of animals receiving E2 or vehicle 0.5 hour after ischemia induction (INT, n=6; OVX, n=8; OVX+E2, n=6).

RESULTS

Lesion volume was 20.9+/-2.2% and 21.8+/-1.2% in the INT and OVX groups, respectively. E2 was found to decrease lesion volume significantly when administered within 3 hours after MCAO. The lesion volumes were 6.3+/-0.5%, 10.3+/-2.1%, 11.8+/-1.8%, 13.5+/-1.6%, and 17.9+/-2.8% when E2 was administered at 0.5, 1, 2, 3, or 4 hours after MCAO, respectively. CBF decreased to 43.1+/-2.2% and 25.4+/-1.0% in the INT and OVX animals, respectively, at 5 minutes after MCAO. In comparison to OVX rats, CBF was not different at 1 hour after E2 administration but was increased significantly in the OVX+E2 group 1 and 2 days after E2 administration.

CONCLUSIONS

E2 exerts neuroprotective effects when administered after ischemia, with a therapeutic window in a permanent focal cerebral ischemia model of approximately 3 hours. This effect of estradiol was associated with no immediate change in blood flow but with a delayed increase in CBF.

Effects of a single dose of oral estrogen on left ventricular diastolic function in hypertensive postmenopausal women with diastolic dysfunction

OBJECTIVE

To evaluate the acute effects of a single dose of oral estrogen on left ventricular diastolic function in hypertensive postmenopausal women with diastolic dysfunction.

DESIGN

Prospective, double-blind, placebo-controlled, clinical study.

SETTING

Cardiology and postmenopausal outpatient clinics of a university hospital.

PATIENT(S)

Thirty postmenopausal women with hypertension (diastolic blood pressure of >90 mm Hg) and left ventricular diastolic dysfunction (mitral E/A ratio [the ratio of peak velocity of early mitral diastolic filling to late diastolic filling] of <1 and isovolumic relaxation time of >100 ms) were included in the study. Thirty normotensive postmenopausal women with normal left ventricular diastolic function served as the control group.

INTERVENTION(S)

Conjugated equine estrogen (0.625 mg) was given orally. Left ventricular diastolic function was assessed by Doppler echocardiography at baseline and 3 hours after the administration of estrogen.

MAIN OUTCOME MEASURE(S)

Left ventricular diastolic filling as assessed by Doppler echocardiography.

RESULT(S)

Estrogen had no effect on heart rate or blood pressure in either study group. The baseline E/A ratios were 0.72 +/- 0.26 and 1.22 +/- 0.30, and the isovolumic relaxation times were 122 +/- 18 ms and 89 +/-14 ms in the hypertensive and normotensive groups, respectively. Estrogen had no significant effect on any of the Doppler parameters in the normotensive group. In the hypertensive group, there was a trend toward normalization of the E/A ratio (from 0.73 +/- 0.11 to 0.84 +/- 20) and a significant improvement in the isovolumic relaxation time (from 124 +/- 20 ms to 105 +/- 13 ms) in response to the administration of estrogen compared with placebo.

CONCLUSION(S)

A single dose of oral estrogen caused a significant improvement in left ventricular diastolic filling in hypertensive postmenopausal women with diastolic dysfunction.

Sequentially combined hormone replacement therapy reduces impedance to flow within the uterine and central retinal arteries in healthy postmenopausal women

OBJECTIVE

The purpose of this study was to investigate the long-term effects of combined hormone replacement therapy on the impedances of the uterine, central retinal, and ophthalmic arteries in healthy postmenopausal women.

STUDY DESIGN

In a prospective controlled study we randomly assigned 30 healthy postmenopausal women (mean age, 52 +/- 3 years) to 2 groups. Women in the hormone replacement therapy group (n = 15) received 1 mg micronized 17beta-estradiol daily sequentially combined with 5 or 10 mg dydrogesterone for 14 days of each 28-day cycle during 12 months and 2 mg 17beta-estradiol combined with 10 mg dydrogesterone thereafter for a period of 3 months. The control group (n = 15) received no treatment. Color Doppler ultrasonography was used to measure the impedance to flow (pulsatility index) within the uterine, central retinal, and ophthalmic arteries in the 17beta-estradiol phase at baseline and after 3, 12, and 15 months.

RESULTS

With respect to values in the control group, 12 months of hormone replacement therapy was associated with a significantly lower (by 39%) mean pulsatility index of the uterine artery (decrease from baseline of 25% in hormone replacement therapy group and increase of 14% in control group) and a significantly lower (by 29%) mean pulsatility index of the central retinal artery (decrease of 9% in hormone replacement therapy group and increase of 20% in control group). After 3 months this effect was already evident. During hormone replacement therapy the reductions in mean pulsatility index values of the uterine and central retinal arteries with respect to baseline were larger (both P =.002) in the women with high pretreatment pulsatility index values than in those with low pretreatment values. The baseline pulsatility index of the uterine artery correlated positively with age and with duration of amenorrhea (r = 0.42, P =. 01; r = 0.48, P =.008; respectively).

CONCLUSION

These results suggest that 12 months of sequentially combined hormone replacement therapy with a low dose of estradiol (1 mg) lowers arterial impedance in specific vascular territories. These data may help in understanding the effects of hormone replacement therapy on the cerebral circulation.

Effect of 17-beta estradiol on pre-existing atherosclerotic lesions: role of the endothelium

The atheroprotective effects of estrogen during the process of atherogenesis is well documented, whereas limited information is available about the effect of estrogen on pre-existing atherosclerotic lesions. After bilateral ovariectomy, 24 New Zealand White rabbits were randomized into three groups of eight animals each and subsequently fed a 0.5% cholesterol diet. In group I, the vessels were excised at day 84, whereas in group II, the cholesterol diet was continued for a total of 168 days. In group III, the animals were first fed with a cholesterol diet for 84 days; in the second phase of the experiment, the cholesterol diet was continued for a further 84 days with a combined estrogen treatment (1 mg estradiol valerate per kg body weight per week intramuscularly). At the end of the experiment, the proximal aortic arch, right carotid artery, thoracical aorta and abdominal aorta of each animal were excised and prepared for histological and immunohistological examination. By day 168, morphometrical analysis displayed a significantly lower plaque development under estrogen therapy in the carotid artery (0.08+/-0.18 mm(2) vs. 0.60+/-0.39 mm(2)), the thoracic aorta (0.56+/-0.94 mm(2) vs. 3.63+/-2.06 mm(2)), and in the abdominal aorta (0.55+/-0.70 mm(2) vs. 1.71+/-1.05 mm(2)) in comparison with the corresponding 168 day control group. However, estrogen treatment has failed to reduce further atherosclerotic plaque development in the aortic arch (9.42+/-1.79 mm(2) vs. 11. 64+/-3.29 mm(2)). Immunohistological detection of the 'anti-human factor VIII related antigen', i.e. the 'von Willebrand factor' (vWF), showed a significantly lower number of luminal cells positive for vWF in the aortic arch in the 84-day cholesterol group, compared with the corresponding controls of normocholesterolemic rabbits (65. 9+/-12.4% vs. 83.1+/-6.2%; P<0.05). Estradiol was able to inhibit the further progression of atherosclerosis when moderate vessel wall alterations were present, whereas pre-existing severe atherosclerosis was associated with a failure of the anti-atherosclerotic estrogen action. As suggested by the in situ detection of vWF as a morphological marker for endothelial cells, an intact endothelial layer might play an important role in mediating the beneficial effect of estrogen in the process of atherosclerosis.

A randomized trial on effects of hormone therapy on ambulatory blood pressure and lipoprotein levels in women with coronary artery disease

OBJECTIVE

To investigate 1-year effects of hormone replacement therapy (HRT) on ambulatory blood pressure (ABP) and lipoprotein levels in postmenopausal women with coronary artery disease (CAD).

METHODS

Sixty patients at a mean age (+/- SD) of 59 +/- 7 years were randomized into three groups: conjugated equine oestrogens (CEE) 0.625 mg daily (n = 20), 50 microg 17beta-oestradiol transdermally (TTSE) per 24 h (n = 20) or placebo (n = 20) for 18 days, then combined with medroxyprogesterone acetate 5 mg for 10 days. Each cycle of 28 days was repeated for one year.

RESULTS

Night-time systolic ABP had decreased by 9.6% (P= 0.0075) in 15 of 18 women in the CEE group and by 22% in 12 of 13 women (P = 0.0034) in the placebo group after 1 year. In the CEE group, a 4.6% rise in daytime systolic ABP (P< 0.05) and a 4.2% rise in night-time systolic ABP (P< 0.05) appeared from baseline to 6 months in 13 of 18 women. In the CEE group (14 women analysed), high-density lipoprotein levels showed a 15.8% increase (P= 0.0018) in 13 women, low-density lipoprotein levels a 15.2% decrease (P= 0.0129) in 12 women and total cholesterol levels a 7.5% decrease (P = 0.057) in 11 women after 1 year. Triglyceride levels showed no changes. In the TTSE group and in the placebo group, with 12 and 13 women analysed respectively, no significant changes appeared.

CONCLUSIONS

One year of HRT in patients with CAD does not influence ABP. Oral HRT induces beneficial effects on lipoprotein levels.

Positive inotropism induced by androgens in isolated left atrium of rat: evidence for a cAMP-dependent transcriptional mechanism

Steroid hormones exert their biological actions via intracellular receptors modulation of transcription. In addition, a number of molecular interactions, and the existence of membrane receptors in several tissues, support the hypothesis of nongenomic action of steroids. The androgens, 5alpha- and 5beta-dihydrotestosterone (0.1 to 100 microM), induce a rapid positive inotropism in the isolated left atrium of male Wistar rats whose time course of response might suggest that it is a non-genomic effect. However, the fact that the facilitation of contractility was inhibited by actinomycin D (5 microg/ml) and cycloheximide (10 microg/ml) indicates that a transcriptional component might play a role. The existence of a rapid functional genomic role would be somewhat surprising. However, rapid transcriptional mechanisms were also observed in certain cAMP-dependent responses. In the left atrium of rat, Rp-cAMPS (10 microM), a cAMP-dependent protein kinase inhibitor, antagonized 5alpha- but not 5beta-dihydrotestosterone-induced positive inotropism. The inhibition by Rp-cAMPS of isoproterenol- and forskolin-induced positive inotropism, and the fact that these cAMP-dependent effects were also inhibited by actinomycin D and cycloheximide, suggest that a cAMP-dependent transcriptional component may be partly involved in the positive inotropism induced by 5alpha-dihydrotestosterone. In addition, 5alpha-dihydrotestosterone might increase the basal adenylyl cyclase activity by acting on unoccupied beta-adrenoceptor-G-protein-adenylyl cyclase complexes, since the elicited inotropism was inhibited by a beta-blocker, atenolol (1 microM), a G-protein inhibitor, pertussis toxin (2 microg/ml, 3 h), and an adenylyl cyclase inhibitor, dideoxy-adenosine (10 microM).

Acute activation of Maxi-K channels (hSlo) by estradiol binding to the beta subunit

Maxi-K channels consist of a pore-forming alpha subunit and a regulatory beta subunit, which confers the channel with a higher Ca(2+) sensitivity. Estradiol bound to the beta subunit and activated the Maxi-K channel (hSlo) only when both alpha and beta subunits were present. This activation was independent of the generation of intracellular signals and could be triggered by estradiol conjugated to a membrane-impenetrable carrier protein. This study documents the direct interaction of a hormone with a voltage-gated channel subunit and provides the molecular mechanism for the modulation of vascular smooth muscle Maxi-K channels by estrogens.

Calcium antagonistic effect of 17 alpha-estradiol derivatives: in vitro examinations

The calcium antagonistic effect of 17 alpha-estradiol derivatives was investigated in vitro in human aortic smooth muscle cells. The substances tested were 17 alpha-estradiol, 17 alpha-ethinylestradiol, the scavestrogens J811 and J861, and 17 beta-estradiol. Examinations were carried out by measuring 45Ca influx into the cells. All compounds showed a significant inhibition of calcium influx at the concentration of 10(-6) M. The strongest effect could be registered for the scavestrogens. Since these substances are virtually devoid of estrogenic activity, they may offer advantages over 17 beta-estradiol in the therapy and prevention of cardiovascular disease.

Estradiol inhibits Ca2+ and K+ channels in smooth muscle cells from pregnant rat myometrium

The purpose of this study was to investigate the actions of 17beta-estradiol on the electrical activity of pregnant rat myometrium. The longitudinal layer of the myometrium was dissected from pregnant rats (17 to 19 days of gestation), and single cells were isolated by enzymatic digestion. Calcium currents and potassium currents were recorded by the whole-cell voltage-clamp method, and the single calcium-dependent potassium current was recorded by the outside-out patch-clamp method. The effects of 17beta-estradiol on these currents were investigated. When a myometrial cell was held at -50 mV, depolarization to a potential more positive than -30 mV produced an inward current followed by a slowly developing outward current. Application of tetraethylammonium inhibited the outward current while the inward current was completely abolished in a calcium-free solution. Estradiol at high concentrations (> 3 microM) inhibited both inward and outward currents in a voltage-dependent manner. Removal of estradiol restored the amplitude of the outward but not of the inward current. Estradiol (30 microM) also inhibited the activity of single calcium-dependent potassium channels without changing single channel conductance. In conclusion, estradiol at high concentrations inhibited: (1) voltage-dependent calcium, (2) calcium-dependent potassium and (3) voltage-dependent potassium currents. These actions of estradiol would prevent action potential generation and after-hyperpolarizations. Suppression of the after-hyperpolarization might further prevent spike generation due to slowing of the calcium channel's recovery from the inactivated state.

Augmentation and suppression of action potentials by estradiol in the myometrium of pregnant rat

The purpose of this study was to investigate the actions of estradiol on spontaneous and evoked action potentials in the isolated longitudinal smooth muscle cells of the pregnant rat. Single cells were obtained by enzymatic digestion from pregnant rat longitudinal myometrium. Action potentials and currents were recorded by whole-cell current-clamp and voltage-clamp methods, respectively. The acute effects of 17β-estradiol on action potentials and inward and outward currents were investigated. The following results were obtained. The average resting membrane potential of single myometrial cells was -54 mV (n = 40). In many cells, an electrical stimulation evoked a membrane depolarization, and action potentials were superimposed on the depolarization. In some cells, spontaneous action potentials were observed. Estradiol (30 µM) slightly depolarized the membrane (ca. 5 mV) and attenuated the generation of action potentials by reducing the frequency and amplitude of the spikes. Afterhyperpolarization was also attenuated by estradiol (30 µM). On the other hand, in 5 of 35 cells, estradiol increased the first spike amplitude and action potential duration, while frequency of the spike generation and afterhyperpolarization were inhibited. In voltage-clamped muscle cells, estradiol inhibited both inward and outward currents. Acute inhibition or augmentation of spike generation by estradiol is due to the balance of inhibition of inward and outward currents. Inhibition of both currents also prevented afterhyperpolarization, causing potential-dependent block of Ca spikes.Key words: estradiol, progesterone, rat myometrium, action potential, channel current.

Oestrogen and vascular disease

Cardiovascular disease (CVD) is the leading cause of morbidity and mortality in postmenopausal women. Epidemiological studies consistently suggest that oestrogen administered to postmenopausal women confers an estimated 30-50% reduction in risk of development and progression of CVD. The long term effect on the cardiovascular system of the addition of a progestogen to the replacement regimen is currently unknown. In addition, it may be argued that it remains to be proven whether the magnitude of the oestrogen-induced cardioprotective effect demonstrated in these observational studies is a real biological phenomenon. No prospective, randomised, controlled studies examining the effect of oestrogen on primary and secondary prevention of CVD have been completed. However, a large number of biologically plausible mechanisms have been identified which provide evidence to support the proposed oestrogen-induced cardioprotection. These include oestrogen mediated favourable changes in metabolic profile, in particular changes in lipid metabolism, insulin resistance and the fibrinolytic system. In addition, recent data have shown that oestrogen may affect vascular structure and function by a variety of mechanisms. It has been shown that oestrogen may induce acute and chronic coronary and cerebral vasodilation through both direct (vascular smooth muscle) and indirect (endothelium dependent) mechanisms. Oestrogen also has recently been shown to have complex anti-atherogenic and antioxidant properties. Much less is known of the vascular effects of progestogens. Progestogens currently in clinical use have androgenic properties and may attenuate the beneficial effects of oestrogen by neutralising or opposing the lipid lowering, vasodilatory and anti-atherogenic actions of oestrogen. Thus further studies are required to elucidate the effects on arterial physiology and CVD outcome of the oestrogens and progestogens of different types, doses and routes of administration which are collectively referred to as postmenopausal 'hormone replacement therapy'.

Estrogen induces nitric oxide-mediated vasodilation of human mammary arteries in vitro

Human internal mammary arteries (IMA) are relatively protected from atherosclerosis. Estrogen plays a protective role in cardiovascular disease. It causes in vitro and in vivo vasodilatation, but the mechanisms are contradictory. To investigate the in vitro vasomotor effect of estrogen on IMA and the role of endothelium, we studied 30 IMA segments harvested from 10 men during coronary artery bypass grafting surgery. Patients with diabetes mellitus, hypercholesterolemia, hypertension, and smoking were excluded. Twenty IMA rings had intact endothelium ((+)Endo) and 10 rings were denuded of endothelium ((-)Endo). Vasomotor response of each ring was expressed as the percentage of maximal response to norepinephrine (NE). Acetylcholine (10(-8)-10(-5) M) given to (+)Endo and (-)Endo rings induced vasorelaxation of 72 +/- 30.4% and vasoconstriction of 48.5 +/- 20.1%, respectively. 17-Beta-estradiol (10(-8)-10(-5) M) given after maximal precontraction with NE induced marked relaxation in (+)Endo (80.9 +/- 39.2%), but no significant vasomotor effect in (-)Endo rings (P < 0.0001). Vasorelaxation to 17-beta-estradiol (10(-6) M) in (+)Endo rings was 64.5 +/- 18.4 and 8.6 +/- 8.4%, before and after 15-min treatment with nitric oxide synthase inhibitor, L-nitroarginine methyl ester, respectively (n = 14, P < 0.0001). Tamoxifen (10(-6) M) decreased 17-beta-estradiol (10(-7) M)-induced relaxation by 71%. In conclusion, 17-beta-estradiol induces endothelium-dependent NO-mediated vasodilation of human mammary arteries in vitro. This response is mediated through estrogen receptors.

Antiarrhythmic effect and its underlying ionic mechanism of 17beta-estradiol in cardiac myocytes

1. The effects of oestrogens on action potential and membrane currents were examined in single guinea-pig atrial myocytes. 2. 17Beta-estradiol (3-10 microM) shortened the action potential duration without significant changes in the resting membrane potential. E-4031 (1 microM) markedly prolonged the action potential duration and induced early afterdepolarization, and 17beta-estradiol (10 microM) abolished it. 3. When cells were perfused in isoproterenol-containing solution, action potentials due to abnormal automaticity caused by membrane depolarization developed, and were also inhibited by 17beta-estradiol. 4. Under voltage clamp conditions, the voltage-dependent Ca2+ currents consisted of both T-(I(Ca,T)) and L-type (I(Ca,L)). 17Beta-estradiol reduced I(Ca,L) concentration-dependently, while it (10 microM) suppressed I(Ca,T) only by approximately 10%. 17Beta-estradiol did not affect time courses of I(Ca,L) inactivation, but it shifted the steady-state inactivation curve to more negative potentials. 5. 17Beta-estradiol (10 microM) did not affect the time-dependent K+ current (I(K)), referred to as I(Kr) and I(Ks) and inwardly rectifying K+ current. However, 17beta-estradiol (30 microM) or diethylstilbestrol (10 microM) inhibited K+ currents. 6. DES and ethinylestradiol (EES) also suppressed I(Ca,L), but testosterone and progesterone failed to inhibit I(Ca,L) The potency of the inhibitory effect on I(Ca,L) was DES> EES> 17beta-estradiol. 7. 17Beta-estradiol and DES also inhibited the cyclic AMP-enhanced I(Ca,L), but cyclic GMP in the pipette or pretreatment of L-NAME could not block the effects of oestrogen on I(Ca,L). 8 These results suggest that oestrogen specifically has antiarrhythmic effects, possibly by acting the L-type Ca2+ channels. The antiarrhythmic effects of oestrogens may contribute to the cardioprotective actions of oestrogens.

Antagonistic effects of 17 beta-estradiol, progesterone, and testosterone on Ca2+ entry mechanisms of coronary vasoconstriction

The clinical observation that coronary artery disease is more common in men and postmenopausal women than in premenopausal women has suggested cardioprotective effects of female sex hormones including hormone-mediated coronary vasodilation. The purpose of this study was to investigate whether the sex hormone-induced coronary relaxation is caused by inhibition of Ca2+ mobilization into coronary smooth muscle. The effects of 17beta-estradiol, progesterone, and testosterone on vascular reactivity and 45Ca2+ influx were tested in deendothelialized coronary artery strips isolated from castrated male pigs. Prostaglandin F2alpha (PGF2alpha) (10(-5) mol/L) caused significant, maintained contraction of coronary artery strips. Caffeine (25 mmol/L), an activator of Ca2+ release from intracellular stores, caused transient contraction in Ca2+-free solution whereas membrane depolarization by 96 mmol/L KCl, an activator of Ca2+ entry, caused maintained contraction in the presence of external Ca2+. The 3 sex hormones caused significant and concentration-dependent relaxation of PGF2alpha- and 96 mmol/L KCl-induced contractions with 17beta-estradiol being the most effective. The sex hormones did not significantly affect the transient caffeine contraction in Ca2+-free solution. In contrast, the sex hormones significantly inhibited the PGF2alpha- and KCl-induced 45Ca2+ influx. 17beta-Estradiol caused similar inhibition of PGF2alpha- and KCl-induced contractions, suggesting inhibition of the same Ca2+ entry mechanism. However, progesterone and testosterone caused greater relaxation of PGF2alpha-induced contraction than of KCl-induced contraction. We conclude that in coronary arteries of castrated male pigs, sex hormones inhibit Ca2+ entry from extracellular space but not Ca2+ release from intracellular stores. 17beta-Estradiol mainly inhibits Ca2+ entry, whereas progesterone and testosterone cause coronary relaxation by inhibiting other mechanisms in addition to Ca2+ entry.

Cycling of inducibility of paroxysmal supraventricular tachycardia in women and its implications for timing of electrophysiologic procedures

Arrhythmias in women may be affected by phases of the menstrual cycle. This study was designed to determine the prevalence of perimenstrual clustering of spontaneous episodes of paroxysmal supraventricular tachycardia (SVT) in women. It also tested the hypothesis that women with this temporal pattern of events have an altered probability of induction of paroxysmal SVT during electrophysiologic testing at higher estrogen states (midcycle or with estrogen replacement therapy) than at low estrogen states (perimenstrual or without estrogen replacement). A structured history of the relation of spontaneous paroxysmal SVTs to phases of the menstrual cycle was obtained prospectively among 42 women referred during a 3-year period. Patients with cyclical patterns of spontaneous tachycardias, who had had negative electrophysiologic studies at midcycle or while receiving estrogen replacement therapy, had repeat procedures (1) when premenstrual or at the onset of menses, or (2) after stopping estrogen replacement therapy. Seventeen of 42 consecutive female patients (40%) had histories of perimenstrual clustering of arrhythmias. Six women (4 with normal menstrual cycles, 2 on estrogen replacement therapy), who qualified for paired electrophysiologic studies because of a negative initial electrophysiologic study that included provocation with isoproterenol, had inducibility into SVTs during the second study. All 6 had dual atrioventricular (AV) nodal pathway physiology, 4 had AV nodal reentrant tachycardia (AVNRT) induced, 1 had both AVNRT and reciprocating AV tachycardias, and 1 had nonsustained AVNRT and an atrial tachycardia induced. Successful ablation procedures were performed in 5 of the 6 patients. Thus, among women with a history of perimenstrual clustering of paroxysmal SVT and among those receiving estrogen replacement therapy, scheduling of elective electrophysiologic procedures at times of low estrogen levels (premenstrual or off estrogen replacement therapy) may facilitate the probability of a successful procedure.

Withdrawal of hormonal therapy for 4 weeks decreases arterial compliance in postmenopausal women

BACKGROUND

We demonstrated in a previous cross-sectional study that arterial compliance is elevated in postmenopausal women taking estrogen-containing hormonal therapy, which may partially account for the reduction in cardiovascular risk observed.

OBJECTIVE

To investigate the effects of withdrawal and recommencement of hormonal therapy, each for 4 weeks, on arterial compliance.

METHODS

Seventeen postmenopausal women [aged 56 +/- 4 years (mean +/- SD)] taking long-term hormonal therapy (+HT group) were studied at baseline, 4 weeks after withdrawal of hormonal therapy and again 4 weeks after recommencement. Systemic arterial compliance (SAC), pulse wave velocity (PWV) in the aorto-femoral and femoral-dorsalis pedis regions, and hemodynamic variables were measured at baseline, and at the end of each study intervention. As a time-control, seventeen postmenopausal women (aged 63 +/- 7 years) not taking hormonal therapy (-HT group) were also investigated.

RESULTS

SAC significantly decreased from 0.47 +/- 0.06 to 0.40 +/- 0.05 arbitrary compliance units (mean +/- SEM; P < 0.05) after 4 weeks withdrawal from hormonal therapy. PWV in the femoral-dorsalis pedis region was elevated significantly by the withdrawal of hormonal therapy (8.4 +/- 0.4 to 9.4 +/- 0.5 m/s; P < 0.05), but PWV in the aortofemoral region did not change. After therapy had been recommenced for 4 weeks, SAC and PWV in the femoral-dorsalis pedis region were restored to baseline values. The -HT group showed no difference in SAC or PWV, and mean arterial pressure did not change in either group throughout the study period.

CONCLUSION

These data suggest that hormonal modulation of distal arterial vascular tone may account for short-term changes in arterial compliance associated with estrogen-containing hormonal therapy.

The effects of different types and doses of oestrogen replacement therapy on clinic and ambulatory blood pressure and the renin-angiotensin system in normotensive postmenopausal women

OBJECTIVE

The effect on blood pressure of oral replacement' doses of exogenous oestrogen may depend on the type and dose of oestrogen administered. This study was designed to compare with placebo the effect of once daily treatment with a 'natural' oestrogen, piperazine oestrone sulphate, in two different doses and a semisynthetic oestrogen, ethinyloestradiol, on clinic and ambulatory blood pressure and the renin-angiotensin system in postmenopausal women.

DESIGN AND METHODS

Twenty-four normotensive postmenopausal women (median age 54 years, range 47-60 years) participated in the study which used a double-blind crossover design. For each subject there were four randomized treatment phases, each lasting 4 weeks. The separate treatments administered once daily were 0.625 mg oestrone sulphate, 2.5 mg oestrone sulphate, 0.02 mg ethinyloestradiol and matching placebo. Clinic blood pressure, heart rate and weight were measured weekly with the mean values of weeks three and four of each phase used for analysis. Ambulatory blood pressure and biochemical measurements were performed in the final week of each phase.

RESULTS

Twenty-four subjects entered and 22 completed the randomized phases of the study. Compared with the placebo phase, end-of-phase mean clinic diastolic blood pressure was reduced in subjects taking the semisynthetic oestrogen (P < 0.01) but was unchanged in those taking the 'low' and 'high' dose natural oestrogen. Mean clinic systolic blood pressure was also unchanged by any of the oestrogen treatments. Ambulatory night-time systolic, diastolic and mean arterial blood pressures were reduced with the low-dose natural and semisynthetic oestrogen treatments compared with placebo (P < 0.01), whereas there was no significant effect of the oestrogen treatments on ambulatory daytime blood pressures. A reduction in clinic and ambulatory heart rate was observed with the high-dose oestrone and semisynthetic oestrogen treatments. There was a dose-dependent increase in plasma renin substrate and decrease in plasma renin concentration with all active treatments; however, there was no change in plasma renin activity or plasma aldosterone concentration.

CONCLUSION

In normotensive postmenopausal women, replacement doses of natural and semisynthetic oestrogen reduce night-time ambulatory blood pressure with either no change or a small reduction in clinic blood pressure. Reduction in blood pressure is not explained by reduced activity of the renin-angiotensin system but could have a component of reduced central sympathetic drive consistent with the decreased heart rate.

Effect of estrogen on aortic function in postmenopausal women

We hypothesized that estrogen may alter aortic elastic properties. The aortic pressure-diameter relation was obtained in 20 postmenopausal women, 10 without (group 1) and 10 with (group 2) proven coronary artery disease, before and after intravenous administration of 10 micrograms of 17beta-estradiol. Instantaneous aortic diameter was measured by an intravascular catheter developed in our institution simultaneously with aortic pressure at the same aortic level with a catheter-tipped micromanometer. At baseline, elastic properties of the aorta were decreased in group 2 compared with group 1. Compared with baseline, aortic distensibility was increased in both groups (P < 0.01 and P < 0.05 for groups 1 and 2, respectively) after estrogen administration, whereas the pressure-diameter loop was shifted downward along a different hypothetical line of elasticity, suggesting active changes in the aortic elastic properties. Furthermore, a significant reduction in wave reflection was found in both groups (P < 0.001). This action may contribute to the beneficial effects of estrogen on the cardiovascular system and may have future therapeutic implications in postmenopausal women.

Effect of acute testosterone on myocardial ischemia in men with coronary artery disease

The effect of acute testosterone administration on exercise-induced myocardial ischemia was assessed in 14 men with coronary artery disease and low plasma testosterone concentrations in a study of randomized, double-blind, crossover design. Testosterone increased time to 1-mm ST-segment depression compared with placebo by 66 (15 to 117) seconds (p = 0.016), suggesting a beneficial effect of testosterone on myocardial ischemia in these patients.

Effect of acute and long-term treatment with 17-beta-estradiol on the vasomotor responses in the rat aorta

1. This study sought to evaluate whether the effects of acute and long-term treatment with 17-beta-estradiol on the vasomotor responses in rat aortic rings are mediated through the same mechanism. 2. Ovariectomized rats were treated daily with either 17-beta-estradiol-3-benzoate (100 microg kg(-1)) or vehicle for 1 week. 3. The effect of long-term 17-beta-estradiol treatment on the responses to cumulative doses of phenylephrine, 5-HT, calcium, potassium and 17-beta-estradiol was determined in aortic rings. In the same rings, the effect of acute exposure to 17-beta-estradiol (5 and 10 microM) on the dose response curves for phenylephrine, 5-HT, calcium, potassium and acetylcholine were estimated. The measurements were made in rings with and without intact endothelium. The tone-related basal release of nitric oxide (NO) was measured in rings with intact endothelium. 4. Long-term 17-beta-estradiol treatment reduced the maximum developed contraction to all contracting agents studied. This effect was abolished in endothelium denuded vessels. Acute 17-beta-estradiol treatment also reduced maximal contraction. This effect, however, was independent of the endothelium. 5. Long-term 17-beta-estradiol treatment significantly increased the ability of the rings to dilate in response to acetylcholine whereas acute exposure to 17-beta-estradiol had no effect. The tone-related release of NO was significantly increased after long-term exposure to 17-beta-estradiol. 6. In conclusion, this study indicate that the acute and long-term effects of 17-beta-estradiol in the rat aorta are mediated through different mechanisms. The long-term effect is mediated through the endothelium most likely by increasing NO release. In contrast, the acute effect of 17-beta-estradiol seems to be through an effect on the vascular smooth muscle cells.

Electrocardiogram pattern in hypercholesterolemic women: the influence of hormone replacement therapy

OBJECTIVE

The aim of this study was to delineate electrocardiogram (ECG) patterns in postmenopausal women with hypercholesterolemia and to assess the possible influence of female sex hormones.

STUDY DESIGN

A total of 72 postmenopausal women with moderately elevated total cholesterol levels constituted the case group, of which 48 came from a clinical trial and 24 from a cohort study. Some 236 women aged 50-59 years with normal levels of cholesterol were participants in the same cohort study in the local area. These 236 women had been subdivided into three groups: premenopausal, postmenopausal and postmenopausal with hormone replacement therapy (HRT). Of the 48 women in the clinical study group, 12 patients showed pathological ECG changes. Six of these patients were treated with HRT for 2 years (transdermal estradiol 50 micrograms/day and a daily dose of 5 mg medroxyprogesterone acetate, MPA) and the rest were non-users of HRT.

RESULTS

In the women with hypercholesterolemia, 16 of 72 patients (22%) showed ischemic ECG changes, compared to nine of 88 (10%) with normal cholesterol levels (p = 0.04). We found no significant difference in the prevalence of ECG changes between postmenopausal women with and without HRT in the groups with normal levels of cholesterol. In the hormone treatment group, four of six patients showed an improvement in ECG pattern, in contrast to two of six non-users of HRT.

CONCLUSIONS

This preliminary study revealed a higher prevalence of pathological ECG changes in postmenopausal women who had hypercholesterolemia than in normocholesterolemic women. These findings support the idea that hyperlipidemia contributes to the overall increase in cardiovascular disease, as this is also associated with ECG changes. Transdermal estradiol combined with MPA has a beneficial effect in reversing the process of atherosclerosis, as well as improving the ECG pattern. The prevalence of pathological ECG patterns was similar for HRT users and non-users. This outcome may be affected by several factors. Hence, further research is warranted.