Effect of oestrogens on human platelet behaviour

Membrane lipid rafts and estrogenic signalling: a functional role in the modulation of cell homeostasis

It has become widely accepted that along with their ability to directly regulate gene expression, estrogens also influence cell signalling and cell function via rapid membrane-initiated events. Many of these signalling processes are dependent on estrogen receptors (ER) localized to the plasma membrane. However, the mechanisms by which ER are able to trigger cell signalling when targeted to the membrane surface have to be determined yet. Lipid rafts seem to be essential for the plasma membrane localization of ER and play a critical role in their membrane-initiated effects. In this review, we briefly recapitulate the localization and function of ER in different cell types and mostly discuss the possible role of lipid rafts in this context. Further studies in this field may disclose new promising therapeutic avenues by the disruption of lipid rafts in those diseases in which membrane ER activation has been demonstrated to play a pathogenetic role.

The effect of menstrual cycle on platelet aggregation in reproductive-age women

Our aim was to assess the change in platelet activity along the menstrual cycle. We conducted a prospective observational study. The study group included 16 healthy women with regular menstrual cycles, which were compared to a control group of 14 healthy males. Exclusion criteria were age <18 years or >45 years, use of oral contraceptives or any other forms of hormonal therapy and medical disorders or medications that might affect platelet aggregation. Blood samples were taken from each of the women at four different phases of the menstrual cycle: day 1 +/- 1, day 7 +/- 1, day 14 +/- 1, and day 21 +/- 1. A single blood sample was taken from the males. Platelet aggregation was assessed in whole blood samples using the Multiplate analyzer with three different agonists (ADP, arachidonic acid (AA), and thrombin-receptor activating peptide (TRAP)). Platelet aggregation for each of the women at each of the phases of the menstrual cycle was expressed as the percentage change from the day 1 +/- 1 value. A total of 390 aggregation assays were performed. The mean aggregation activity was significantly higher in females compared with males, irrespective of the agonist used. For the TRAP and the ADP agonists, the relative platelet activity decreased along the menstrual cycle from day 1 towards day 21 and from day 7 towards day 21, respectively, although differences reached statistical significance only for day 21 (-12.4% +/- 3.2%, P < 0.05 for TRAP, and -9.5% +/- 3.9%, P < 0.05 for ADP). When using AA to induce platelet aggregation, the relative platelet activity was highest around the time of ovulation (11.0% +/- 4.7%) and was significantly lower on day 21 (-8.5% +/- 6.7%, P < 0.05). In conclusion, platelet aggregation activity is higher in females compared with males. The association between the phase of the menstrual cycle and platelet activity appears to vary with the type of agonist, but platelet aggregation is consistently lowest in the mid-luteal phase irrespective of the agonist used.

The effects of estrone, estradiol and estriol on platelet aggregation induced by adrenaline and adenosine diphosphate

The impact of estrogens on the cardiovascular system and their ability to regulate platelet functions remains controversial. Changes in platelet functions could contribute to thrombotic risk associated with estrogen treatments. Here, we investigated the effects of various forms of estrogen, including estrone (E1), estradiol (E2) and estriol (E3), on platelet aggregation induced by standard agonists (adrenaline and adenosine diphosphate). Platelet-rich plasma (PRP) was prepared from citrated blood donated by 25 normal volunteers. The study on platelet aggregation was carried out in 96-well flat-bottom microtitre plates and assessed using a microplate reader. For studying the effects of each estrogen, PRP was preincubated with 1, 10 and 100 nM of E1, E2 and E3 at 37 degrees C for 20 min, and then coincubated with normal saline (control untreated PRP), adrenaline (ADR) or adenosine diphosphate (ADP) in the microplate. Platelet aggregation was then measured every minute for 8 min. None of the estrogens (E1, E2 and E3) affected platelet aggregation in untreated PRP. Interestingly, only E1 and E3 can synergize the increased platelet aggregation by either ADR or ADP, while the effects of E2 on the increased platelet aggregation by either ADR or ADP depended on internal factors such as endogenous estradiol and platelet aggregated state. Thus, for the rational use of these internal factors for estrogen use, especially E2, in clinical applications, such as hormone replacement therapy, may need evaluation of thrombotic risk.

Membrane lipid rafts coordinate estrogen-dependent signaling in human platelets

The impact of estrogens on the viability of cardiovascular system and their ability to regulate platelet function is still an open and debated question. We have previously shown that estrogen is able to significantly potentiate the aggregation induced by low doses of thrombin and to initiate a rapid and reversible signaling pathway mediated by ERbeta-directed activation of the tyrosine kinases Src and Pyk2 at the level of the plasma membrane. Lipid rafts are critical, cholesterol-enriched membrane domains, which play a major role in blood platelet activation processes. In this work, we investigated the role of lipid rafts in 17beta-estradiol signaling in human platelets. We observed that membrane rafts were essential for both 17beta-estradiol-dependent potentiation of platelet aggregation induced by subthreshold concentrations of thrombin and 17beta-estradiol-induced phosphorylation of Src. 17beta-estradiol caused the reversible translocation of ERbeta to the raft fractions and promoted the rapid and transient recruitment to, and activation within the membrane raft domains of the tyrosine kinases Src and Pyk2. The raft integrity was essential with this respect, as these effects of 17beta-estradiol were completely inhibited by cholesterol depletion. This paper provides evidence for the first time that membrane lipid rafts coordinate estrogen signaling in human platelets.

Nongenomic effects of 17β-estradiol in human platelets: potentiation of thrombin-induced aggregation through estrogen receptor β and Src kinase

The impact of estrogens on the cardiovascular system and their ability to regulate platelet function are matters of controversy. The recent finding that estrogen receptors are expressed in human platelets renders these cells an excellent model for studying the nongenomic effects of these hormones. In this work, we investigated 17β-estradiol–dependent signaling in platelets from adult healthy men. 17β-estradiol caused the rapid phosphorylation of the tyrosine kinases Src and Pyk2 and the formation of a signaling complex, which included Src, Pyk2, and the phosphatidylinositol 3-kinase. Both these events were dependent on estrogen receptor β engagement. We found that estrogen receptor β was membrane-associated in platelets. On treatment with 17β-estradiol, Src and Pyk2 activation occurred in the membrane fraction but not in the cytosol. In contrast, no significant activation of phosphatidylinositol 3-kinase was detected in estrogen-treated platelets. 17β-estradiol did not induce any platelet response directly, but it strongly potentiated the activation of integrin αIIbβ3 and the platelet aggregation induced by subthreshold concentrations of thrombin. These effects were dependent on estrogen receptor β recruitment and were associated with a strong synergistic effect with thrombin on Src activation. Taken together, these results indicate that 17β-estradiol can modulate platelet function by exercising a proaggregating role.

A practical concept for preoperative management of patients with impaired primary hemostasis

In a prospective study, 254 of 5649 unselected patients scheduled for surgery at our hospital were identified preoperatively as having either acquired (n=182) or inherited (n=72) impaired primary hemostasis (platelet dysfunction including von Willebrand disease). All patients were initially pretreated with desmopressin (DDAVP). Response to DDAVP or subsequent treatment(s) was defined as correction of any one of the abnormal PFA-100 platelet function tests. The non-responders were additionally treated with tranexamic acid or aprotinin; those with von Willebrand disease (vWD) received factor VIII concentrates with von Willebrand factor (vWF). Those still unresponsive to therapy received conjugated estrogens and, as a last attempt, a platelet transfusion. The administration of DDAVP led to a correction of platelet dysfunction in 229 of the 254 patients treated (90.2%). Tranexamic acid was effective in 12 of 16, aprotinin in 3 of 5, and factor VIII concentrates with vWF in all 4 patients with unresponsive to DDAVP. The remaining 6 patients were pretreated with conjugated estrogens, and 2 of these patients were additionally treated with platelet transfusion. The frequency of blood transfusion was lower, but not statistically significant (9.4% vs. 12.2%: p = 0.202) in preoperatively treated patients with impaired hemostasis than in patients without impaired hemostasis. In a retrospective group, the frequency of blood transfusion was statistically significant higher (89.3% vs. 11.3%: p < 0.001) in patients without preoperative correction of impaired hemostasis than in patients without impaired hemostasis. Preoperative correction of impaired primary hemostasis is possible in nearly all patients affected, and results in a reduction of homologous blood transfusions.

The effect of the menstrual cycle and of decompression stress on arachidonic acid-induced platelet aggregation and on intrinsic platelet thromboxane production in women compared with men

Menstrual cycle variations in platelet aggregation and thromboxane production in association with sex steroids have been reported. External stimuli such as decompression sickness have been associated with clotting activity changes, specifically, increased platelet aggregation. Differences in response of platelets from women and men, when subjected to such a stress, have been observed. This study evaluated the ability of washed platelets from women in the proliferative and secretory phases of the menstrual cycle to aggregate in response to arachidonic acid and the aggregation difference between washed platelets from women and men in response to decompression stress and arachidonic acid. Additionally, platelet thromboxane production differences between the assessed platelet populations were compared. Our results indicate no difference in platelet aggregability between phases of the menstrual cycle. A significant aggregation difference between platelets from women and men was noted. Platelets from women were more sensitive to arachidonic acid aggregation. These differences were not affected by decompression stress. No difference in thromboxane B2 production was noted between the platelet populations evaluated.

Management of breast abscesses

Hospital experience of breast abscess is changing as nonpuerperal abscess associated with periductal mastitis assumes increasing importance. Clinical presentation, bacteriology, and management differ notably from acute puerperal abscess, but the latter can still cause severe morbidity. The standard management of puerperal abscess by incision, breaking down loculi, and dependent drainage may still be used, but the author has shown that an alternative approach--curettage and primary obliteration of the cavity under antibiotic cover--can give equally good results with reduced morbidity.

Sex difference in antithrombotic effect of aspirin

A number of clinical trials suggest that the antithrombotic effect of aspirin is limited to men. To test the possibility that this is due to a sex difference in the inhibitory effect of aspirin on platelet behavior, we studied whole-blood platelet aggregation in men and women and in male patients with carcinoma of the prostate receiving hormone therapy. The in vitro inhibitory effect of aspirin on so-called spontaneous platelet aggregation induced by stirring whole blood and monitored by the decrease in the number of singleton platelets was greater in men (mean +/- SD inhibitory ratio 1.54 +/- 0.30 in men, 1.23 +/- 0.22 in women; p less than 0.001). The inhibitory effect of aspirin was reduced in orchiectomized male patients and was restored by the addition of testosterone to blood samples. Estradiol had no detectable influence on the inhibitory effect of aspirin. Testosterone thus seems to influence platelet aggregation and its inhibition by aspirin as assessed by whole-blood in vitro aggregometry. Possible mechanisms for this effect of testosterone and its relevance to the choice of antithrombotic therapy are discussed.

Sex-related differences in platelet aggregation in native whole blood

To clarify discrepant reports about sex-related differences platelet aggregation (PA) was tested by a new impedance method in native whole blood (NWB) and compared to the results of citrated whole blood (CWB) and the turbidometric method (TM). In NWB collagen or ADP-induced PA was stronger in women than men similar to the TM indicating that this is not or not only caused by citrate. With collagen this difference persisted after ingestion of 125 mg acetylsalicylic acid (ASA) which might in part explain the greater therapeutic benefit of ASA for men. The results exclude haematocrit or platelet count as a cause of the differences of PA between women and men. Sodium arachidonate (NaAA)-induced PA was inhibited by 125 mg ASA in all tested methods; since inhibition of ADP-induced PA was not observed in NWB or CWB and the impedance methods failed to show a second wave of ADP-induced PA the significance of the second wave appears doubtful. The impedance method of NWB was found to be more sensitive to collagen, ADP or NaAA than the impedance method of CWB and to collagen or NaAA more sensitive than the TM. The impedance methods in NWB or CWB are not suited to test epinephrine-induced PA.

New embolization method using estrogen: effect of estrogen on microcirculation

To ascertain the mechanism of action of estrogen administered by a new embolization method, developed by the authors as a treatment method for dural arteriovenous malformations, conjugated estrogens were injected into the mesenteric artery of rabbits, and microcirculatory changes in the dominant areas were studied biomicroscopically. Conjugated estrogen induced sludging and stasis in the microcirculation, approximately in proportion to the concentration and dose.

Prostaglandins and ischemic heart disease

There is an abundance of information suggesting that prostaglandins are involved in the development and clinical expression of atherosclerosis. Many studies demonstrate a relationship between prostaglandins and the risk factors for peripheral and coronary artery disease. Thus, part of the mechanism by which hyperlipidemia, diabetes mellitus, smoking, hypertension, sex hormones, age, heredity, emotional stress and diet contribute to the development and progression of atherosclerosis may be through an imbalance between thromboxane A2 and prostaglandin I2. Recent studies show a temporal relationship between acute ischemic events (specifically, unstable angina) and a transcardiac increase in thromboxane B2, while others demonstrate a salutary effect of disaggregatory and vasodilatory prostaglandins in such patients. If prostaglandins and thromboxane prove important in ischemic vascular disease, attention will be directed at the correction of their pathologic imbalance. This may be accomplished by dietary manipulation as well as by the development of prostaglandin receptor antagonists or inhibitors of specific prostaglandin pathways.

Testosterone inhibits prostacyclin production by rat aortic smooth muscle cells in culture

The effects of testosterone on cell proliferation and prostacyclin production were investigated using rat aortic smooth muscle cells in culture. Testosterone at 10(-10)-10(-6) M did not have any significant effect on cell proliferation, but it significantly inhibited prostacyclin production by the cells. Maximal inhibition of prostacyclin production (70%) was observed when cells were treated with a physiological concentration of 19(-8) M testosterone for 5 consecutive days. These results suggest that testosterone may stimulate thrombus formation and accelerate atherosclerosis by suppressing prostacyclin production in arterial smooth muscle cells.

Appropriate contraception for middle-aged women

The United States Food and Drug Administration and the International Planned Parenthood Federation recommend that women over the age of 40 should utilize forms of contraception other than the pill. This decision was reached as a result of the 1975 clinical papers by Mann and his associates (Mann et al., 1975; Mann & Inman, 1975) and the epidemiological reports of the Royal College of General Practitioners (1977), Mann, Inman & Thorogood (1976) and Vessey, McPherson & Johnson (1977). Several authoritative bodies believed it prudent to suggest that the age limit for oral contraceptive use be lowered to 35, and even to 30 years (Anon, 1977; Planned Parenthood memorandum, 1977). The investigations of Inman & Vessey (1968) point to a precarious rise in mortality figures for women over age 35 on oral contraceptives.

Quantitative changes in platelet aggregation due to physiological and pathological factors and medication

Quantitative measurements of platelet aggregation in samples of venous blood were made in altogether 66 healthy volunteers by a modified version of the method of Wu and Hoak. The formation of aggregates was found to be unaffected or at the most barely affected by such factors as sex, age, smoking, fatty food, physical exertion and medication with isoprenaline or ovulation inhibitors. No difference in the number of aggregates formed was noted between 12 control patients and 16 patients with myocardial infarcts or 14 with other conditions predisposing to arterial thrombosis. Anticoagulant therapy had no effect on aggregation. It is suspected that aggregation in vitro due to methodological factors may obscure any quantitative alterations in the formation of aggregation present in vivo.

Hemostasis by premedication with estrogen in hair-transplant surgery

Premedication with water-soluble conjugated estrogens administered the previous day and a half-hour before operation diminished bleeding and allows for a drier field, better vision and quicker work. Post-operative bleeding is negligible. Their short-term use has not led to feminization nor presented cardiovascular problems.

Serum naphythylamidase isoenzymes during hormonal treatment. Electrophoretic and quantitative studies

Alterations in serum naphthylamidase isoenzymes were studied by electrophoretic and quantitative methods in women treated with oral contraceptives and women treated with naturally occurring conjugated estrogens for climacteric symptoms. In women treated with oral contraceptives the appearance of extra isoenzyme components was accompanied by a distinct and significant increase in the total serum naphthylamidase activity, whereas in treatment with conjugated estrogens no such increase was found. The result suggests that combined oral contraceptives and natural estrogens affect the serum naphthylamidase pattern in different ways.

The effect of premarin on blood loss attending open heart surgery

Premarin was administered prophylactically to every other patient in a series of 148 consecutive cases of open intracardiac surgery. Of these, 132 patients were matched to analyse the results of Premarin administration and postoperative blood loss. There were 67 patients who were given Premarin and 65 who did not receive this drug; both groups were identical in respect of age and sex. Matching was undertaken according to history of previous cardiac operations and anticoagulation, type of valve surgery or repair of congenital anomaly, duration of perfusion, platelet count and the use of fresh blood and epsilon-aminocaproic acid in the postoperative period. The prophylactic use of Premarin was not associated with a reduction in postoperative bleeding.

Comparison of the effects of ethinyl oestradiol and conjugated equine oestrogens in oophorectomized women

Seventeen oophorectomized women were treated for 3 month periods, in random sequence, with ethinyl oestradiol 20 and 50 mug daily and conjugated equine oestrogens (Premarin)0-625 and 1-25 mg daily. The serum cholesterol, clot lysis time, plasma fibrinogen, platelet adhesiveness and activated partial thromboplastin time remained unchanged throughout the different oestrogen regimes. There was a significant rise of serum triglyceride levels on both doses of ethinyl oestradiol but no significant change with Premarin. Serum luteinizing hormone levels were depressed most by ethinyl oestradiol 50 mug daily, although no down to the levels in premenopausal women.

Metabolic effects of oestrogen treatment in patients with carcinoma of prostate: a comparison of stilboestrol and conjugated equine oestrogens

Serum cholesterol and triglyceride levels were estimated and oral glucose tolerance tests performed on 16 patients with carcinoma of the prostate before treatment and while receiving stilboestrol in doses of 1 mg, 7.5 mg, and 15 mg daily and conjugated equine oestrogens (Premarin) 15 mg daily. Serum triglyceride levels were greater than 170 mg/100 ml in nearly all the patients while receiving Premarin or stilboestrol 7.5 mg and 15 mg daily. In six out of 10 patients who were given stilboestrol 1 mg daily the serum triglycerides remained within the normal range. No significant effects on serum cholesterol levels or glucose tolerance tests were observed with the various oestrogen regimens. The results support previous suggestions that a daily dose of 1 mg of stilboestrol should be regularly used in the treatment of carcinoma of the prostate.

The interaction of some oral contraceptive steroids with lipid monolayers and with Erythrocytes

Some steroids used in oral contraceptive combinations have been found to interact with cholesterol and lecithin spread as monolayers on water and to protect erythrocytes against haemolysis. No simple relation between steroid structure and these interactions was found, although in general the more water-soluble members of a group of structurally related compounds interacted to a lesser extent. No distinction could be observed in the behaviour of progestogens and oestrogens in the systems studied. It is suggested in the light of the evidence presented here and from data in the literature that these steroids may adsorb at lipid surfaces and may penetrate lipid membranes. This gives substance to the hypothesis that some steroids adsorb at platelet surfaces and alter the surface properties or the permeability of the platelet membrane sufficiently to cause increased platelet aggregation.

An evaluation of the use of stilboestrol and antibiotics in the early management of acute puerperal breast abscess

One hundred and seventy-five cases of acute breast abscess treated surgically have been described. The supposed rationale for the early use of stilboestrol and antibiotics in this condition has been reviewed. Neither stilboestrol nor antibiotics confers any benefit with regard to rate of healing or recurrent abscess formation after incision. Whilst full evaluation of these drugs in breast abscess awaits a prospective trial, it is suggested that, in the case of stilboestrol, there are sufficient potential dangers to make its routine prescription undesirable, if not indefensible. In the case of antibiotics since no apparent benefit is conferred it might reasonably be concluded that administration is merely wasteful.

Involuntary movements in patients taking oral contraceptives

Involuntary movements developed in five women taking oral contraceptives. In one, the sudden onset of a unilateral disturbance suggested a cerebral thrombosis; this case is considered to be a further example of the increased risk of cerebrovascular disease associated with oral contraception. The four other patients suffered a relapse of Sydenham's chorea between one and four months after starting an oral contraceptive regimen. Possibly an underlying vascular mechanism was responsible for these relapses.

Platelet aggregation during oral contraception

Platelet aggregation has been found to be significantly accelerated with the coagulation-induced Chandler's tube technique in women taking combined oestrogen-progestin oral contraceptives, though this was less than in the third trimester of pregnancy. Women taking the pure progestogen, chlormadinone acetate, have not shown this change up to the sixth month of study. In contrast the accelerated platelet aggregation resulting from conventional oral contraception became normal one month after changing to the progestogen. There was no change in the platelet aggregation response to adenosine diphosphate (A.D.P.) during oral contraception.