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

Platelet aggregation in Klinefelter syndrome is not aggravated by testosterone replacement therapy: A longitudinal follow-up study

BACKGROUND

Men with Klinefelter syndrome (KS) are routinely offered testosterone replacement therapy (TRT) suggested to potentially promote platelet aggregation and increase cardiovascular risk.

OBJECTIVE

We investigated platelet aggregation in men with KS before and during TRT.

MATERIALS AND METHODS

Forty-one adult men with KS participated, of which 20 had no history of TRT at baseline, with 15 completing follow-up after 18 months TRT. Further, we included 21 adult men with KS on long-term TRT (>10 years) and a male reference population. We assessed platelet impedance aggregometry using adenosine diphosphate (6.5 μM), thrombin-receptor-activating-peptide-6 (TRAP 32 μM), and arachidonic acid (ASPI 0.5 mM) as agonists in KS compared to a male reference population and stratified by route of TRT administration.

RESULTS

Platelet aggregation among men with KS at baseline or during TRT was not increased compared with the male reference population. For all three agonist, no change was seen in platelet aggregation in KS at follow-up compared with baseline (p ≥ 0.2). Platelet aggregation was not associated with total testosterone and furthermore, platelet count was not affected by treatment with testosterone. Men with KS treated with testosterone gel showed slightly increased TRAP- and ASPI-induced platelet aggregation compared with those treated with testosterone injection (p = 0.02 and p = 0.04, respectively).

DISCUSSION AND CONCLUSIONS

We observed normal platelet aggregation in men with KS before TRT and following both short and long term treatment. Our findings do not support an independent role of platelets in driving the cardiovascular risk in KS.

Impact of frozen thawed embryo transfer in hormone substituted cycles on thrombotic risk markers

INTRODUCTION

Fertility treatment with frozen thawed embryo transfer (FET) is widely used. Women treated in artificial cycles (AC-FET) receive high doses of estrogen in contrast to natural cycles (NC-FET), where no estrogen is administered. Estrogen substitution may be associated with increased risk of thromboembolism. Our aim is therefore to characterize changes in blood coagulation parameters defined as surrogate thrombotic risk markers in women undergoing estrogen substitution during AC-FET.

MATERIALS

In our prospective cohort study, we enrolled 34 women in either: AC-FET (n = 19) or NC-FET (n = 15). Women were recruited at the Department of Obstetrics and Gynaecology, Horsens Fertility Clinic, Denmark, from August 2019 - November 2020. Blood samples were obtained at four timepoints. Thrombin generation, platelet aggregation and fibrinolysis were evaluated as thrombotic risk markers.

RESULTS

Within the AC-FET group, we found a significantly shorter lagtime (p < 0.05) and time to peak (TTP) (p < 0.001) after hormone substitution compared to baseline. Furthermore, a significantly higher mean peak (p < 0.0001) and larger endogenous thrombin potential (ETP) (p < 0.0001) was observed. When compared to the NC-FET group, women receiving AC-FET had a significantly shorter mean TTP (p < 0.005), higher mean peak (p < 0.0001) and larger ETP (p < 0.05). Additionally, we demonstrated a significantly prolonged lysis time within the AC-FET group (p < 0.001).

CONCLUSION

Our results indicate that women receiving AC-FET have a significantly increased thrombin generation which may increase the thromboembolic risk in women being estrogen substituted.

Estrogens as regulator of hematopoietic stem cell, immune cells and bone biology

Hematopoietic stem cells provide continuous supply of all the immune cells, through proliferation and differentiation decisions. These decisions are controlled by local bone marrow environment as well as by long-range signals for example endocrine system. Sex dependent differential immunological responses have been described under homeostasis and disease conditions. Females show higher longevity than male counterpart that seems to depend on major female sex hormone, estrogen. There are four estrogens - Estrone (E1), estradiol (E2), Estriol (E3) and Estetrol (E4) that spatially and temporarily present during different female reproductive phases. In this review, we discussed recent updates describing the effects of estrogen on HSC, immune cells and in bone biology. Estradiol (E2) being a major/abundant estrogen is extensively investigated, while effects of other estrogens E1, E3 and E4 are started to unravel recently. Furthermore, clinical effect of estrogen as hormone therapy is discussed in HSC and immune cells perspectives. The data presented in this review is compiled by searches of PubMed, database of American Cancer Society (ACS). We have included article from September 1994 to March 2020 as covering all article in chronological order is not fissile so we included relevant article with substantial information in this specific area of research by using the search term (alone or in combination) estrogen, hematopoietic stem cell, immune cells, gender difference, estrone, estriol, estetrol, therapeutic application, pregnancy, effect on bone.

Modulation of Platelet Functions Assessment during Menstruation and Ovulatory Phases

During menstruation, endometrial hemostasis is achieved by platelet aggregation, fibrin deposition, and thrombus formation that interact with local endocrine and immunological factors which cause termination of menstrual bleeding. Interactions between steroidal sex hormones and platelet functions are not well understood. The aim of this study was to evaluate the effect of platelet function during the menstrual cycle and luteal phase in women of reproductive age. The cross-sectional study on women of reproductive age included 44 healthy women. Platelet function was assessed by PFA-100TM analyzer with collagen/epinephrine and collagen/ADP cartridges during the menstrual cycle and luteal phase. There were no significant differences in platelet function between menstruation and ovulatory phase. Platelet activity in Arab collagen/epinephrine cartridge increased during menstruation compared to non-Arab ethnic subjects and no significant differences in platelet function were found when using collagen/ADP cartridge. This study suggested modulation in platelet functions during menstruation and luteal phase in women of reproductive age. Further studies, including a large number of subjects, platelet genetic and progesterone factors change in platelet clotting associated to menstrual cycle should be conducted.

Non-genomic effects of nuclear receptors: insights from the anucleate platelet

Nuclear receptors (NRs) have the ability to elicit two different kinds of responses, genomic and non-genomic. Although genomic responses control gene expression by influencing the rate of transcription, non-genomic effects occur rapidly and independently of transcriptional regulation. Due to their anucleate nature and mechanistically well-characterized and rapid responses, platelets provide a model system for the study of any non-genomic effects of the NRs. Several NRs have been found to be present in human platelets, and multiple NR agonists have been shown to elicit anti-platelet effects by a variety of mechanisms. The non-genomic functions of NRs vary, including the regulation of kinase and phosphatase activity, ion channel function, intracellular calcium levels, and production of second messengers. Recently, the characterization of mechanisms and identification of novel binding partners of NRs have further strengthened the prospects of developing their ligands into potential therapeutics that offer cardio-protective properties in addition to their other defined genomic effects.

Sex and Gender Differences in Ischemic Heart Disease: Endocrine Vascular Disease Approach (EVA) Study Design

Improvements in ischemic heart disease (IHD) management have been unbalanced between sexes, with coronary microvascular dysfunction considered the likely underlying reason. The Endocrine Vascular disease Approach (EVA) is an observational study (Clinicaltrial.gov NCT02737982) aiming to assess sex and gender interactions between coronary circulation, sexual hormones, and platelet function. Consecutive patients with IHD undergoing coronary angiography will be recruited: (1) to assess sex and gender differences in angiographic reperfusion indexes; (2) to evaluate the effects of estrogen/androgen on sex-related differences in myocardial ischemia; (3) to investigate the platelet biology differences between men and women with IHD; (4) to verify sex- and gender-driven interplay between response to percutaneous coronary intervention, platelets, sex hormones, and myocardial damage at baseline and its impact on 12-month outcomes. The integration of sex and gender in this translational project on IHD will contribute to the identification of new targets for further innovative clinical interventions.

The interaction of β2-glycoprotein I with lysophosphatidic acid in platelet aggregation and blood clotting

β₂-Glycoprotein I (β₂-GPI) is a plasma protein that binds to oxidized low-density lipoprotein (LDL) and negatively charged substances, and inhibits platelet activation and blood coagulation. In this study, we investigated the interaction of β₂-GPI with a negatively charged lysophosphatidic acid (LPA) in platelet aggregation and blood clotting. Two negatively charged lysophospholipids, LPA and lysophosphatidylserine, specifically inhibited the binding of β₂-GPI to oxidized LDL in a concentration-dependent manner. Intrinsic tryptophan fluorescence studies demonstrated that emission intensity of β₂-GPI decreases in an LPA-concentration-dependent manner without a shift in wavelength maxima. LPA specifically induced the aggregation of β₂-GPI in phosphate-buffered saline, and in incubated plasma and serum, both of which are known to accumulate LPA by the action of lecithin-cholesterol acyltransferase and lysophospholipase D/autotaxin. β₂-GPI aggregated by LPA did not inhibit activated von Willebrand factor-induced aggregation, and did not prolong the activated partial thromboplastin time in blood plasma, in contrast to non-aggregated β₂-GPI. These results suggest that β₂-GPI aggregated by the binding to LPA fails to inhibit platelet aggregation and blood clotting in contrast to non-aggregated β₂-GPI.

Microparticles reveal cell activation during IVF – a possible early marker of a prothrombotic state during the first trimester

Cell-derived microparticles (MPs) are known to be elevated in a number of diseases related to arterial and venous thromboembolism (VTE), such as acute myocardial infarction, VTE (deep-vein thrombosis and pulmonary embolism) and peripheral arterial disease. IVF-associated pregnancies have previously been shown to be associated with an increased incidence of VTE, mechanisms behind being unknown and sparsely studied. Our objective was to assess cell activation during IVF through analysis of MP levels and phenotype following ovarian stimulation. Thirty-one women undergoing IVF were included and blood samples were collected at down regulation of oestrogen and at high level stimulation with 10- to 100-fold increased endogenous oestrogen levels. MPs were analysed by flow cytometry and phenotyped according to size and protein expression. We found that overall phosphatidylserine positive platelet-, endothelial- and monocyte-derived MPs significantly increased following ovarian stimulation with increased levels of platelet activation markers CD40 ligand and P-selectin. Furthermore, there was an increase in endothelial-derived MPs exposing activation marker E-selectin and monocyte-derived MPs, while neutrophil-derived MPs decreased slightly. In conclusion we found a major increase in MPs and markers indicating cell activation in parallel with the profound oestrogen boost during IVF. To assess whether these changes in MPs are associated with thromboembolic events requires extended longitudinal studies.

Use of SSRI, But Not SNRI, Increased Upper and Lower Gastrointestinal Bleeding: A Nationwide Population-Based Cohort Study in Taiwan

Selective serotonin receptor inhibitor (SSRI) and serotonin-noradrenaline reuptake inhibitor (SNRI) users have been reported to have an increased risk of upper gastrointestinal bleeding (UGIB), but their association with lower gastrointestinal bleeding (LGIB) is less studied. This study aimed to analyze the incidence of UGIB and LGIB among SSRI users, SNRI users, and controls.Using the National Health Insurance Research Database of Taiwan, 9753 subjects who were taking serotonin reuptake inhibitors (8809 with SSRIs, and 944 with SNRIs), and 39,012 age, sex, and enrollment time-matched controls were enrolled at a 1:4 ratio. The log-rank test was used to analyze differences in the cumulative hazard of UGIB and LGIB between groups. Cox proportional hazard regression analysis was used to evaluate the independent risk factors for UGIB and LGIB.During the 10-year follow-up period from 2000 to 2010, SSRI users, but not SNRI users, had significantly higher incidences of UGIB and LGIB than the controls (P < 0.001; log-rank test). The use of SSRIs, but not SNRIs, was independently associated with an increased risk of UGIB (hazard ratio [HR]:1.97; 95% confidence interval [CI]: 1.67-2.31) and LGIB (HR: 2.96, 95% CI: 2.46-3.57) after adjusting for age, sex, underlying comorbidities, and medications.The long-term use of SSRIs significantly increased the risk of UGIB and LGIB, and caused more LGIB than UGIB in the general population after adjusting for possible confounding factors, but the association between SNRIs and GIB is insignificant. Further prospective studies are needed to clarify this important issue.

Postmenopausal women have an increased maximal platelet reactivity compared to men despite dual antiplatelet therapy

Dual antiplatelet medication with acetylsalicylic acid (ASA) and clopidogrel is the main therapy for patients with stable coronary vessel disease (CVD) after percutaneous coronary intervention (PCI). Despite platelet inhibition subgroups of patients have been shown to exhibit an increase of risk for adverse cardiovascular events. The aim of our study was to elucidate the influence of sex on platelet reactivity in patients with CVD under medication with ASA and clopidogrel. Two hundred and thirty patients with CVD on combined therapy with ASA (100 mg/day) and clopidogrel (75 mg/day) were included into our study. These patients were divided into a male (n = 128) and female (n = 102) group. Platelet reactivity was assessed by impedance aggregometry. Women demonstrated a significantly higher thrombin receptor-activating peptide (TRAP)-induced platelet reactivity than men (male 79.43 ± 28.55 U vs. female 89.3 ± 30.69 U; P < 0.05). The ADP-induced (male 19.81 ± 15.51 U vs. female 23.73 ± 17.68 U; P > 0.05) or arachidonic acid-induced (male 10.3 ± 12.87 U vs. female 12.76 ± 14.44 U; P > 0.05) platelet aggregation did not differ significantly between women and men. A multivariate linear regression model revealed female sex to be a significant prognostic marker for an increased TRAP-induced platelet reactivity, independent of the ASA and clopidogrel-associated platelet function inhibition. Sex differences did not influence the effectiveness of ASA or clopidogrel-mediated platelet function inhibition. Nevertheless, women had a significantly increased maximal platelet reactivity compared to men despite antiplatelet therapy.

Reference intervals for platelet aggregation assessed by multiple electrode platelet aggregometry

INTRODUCTION

Analyses of platelet aggregation in hirudin whole blood using Multiplate® was validated. Reference intervals for the most commonly used agonists were established, and the association between platelet aggregation, age, gender and haematological values was analysed.

MATERIAL AND METHODS

We included 121 healthy individuals to establish reference intervals and six healthy individuals for evaluation of the day-to-day variation. Platelet aggregation was evaluated on hirudin whole blood employing Multiplate® induced by arachidonic acid, ADP, collagen and ristocetin (RISTOlow and RISTOhigh). Measurements of haematological values were performed employing Sysmex K-4500.

RESULTS

We found no association between platelet aggregation and age (p>0.57 for all agonists, except RISTOlow: p=0.05). Platelet aggregation was significantly higher in women compared to men for all agonists (p<0.0003), except RISTOlow (p=0.05). A reference interval is presented as 95% confidence interval suitable for any age and both sex. Day-to-day variation was <11% for all agonists except for RISTOlow. No association was found between platelet aggregation and haematocrit or red blood cell count after adjusting for age and gender except for RISTOhigh. A positive significant association was found between platelet count and platelet aggregation (p<0.04). Finally, a significant positive association was found between platelet aggregation and white blood cell count for all agonists (p<0.05) except RISTOlow and RISTOhigh (p>0.05).

CONCLUSION

Reference intervals for platelet aggregation in healthy individuals (age: 17 to 66 years) were established in hirudin whole blood measured by Multiplate® employing the most commonly used agonists.

Large-scale prediction and testing of drug activity on side-effect targets

Discovering the unintended 'off-targets' that predict adverse drug reactions is daunting by empirical methods alone. Drugs can act on several protein targets, some of which can be unrelated by conventional molecular metrics, and hundreds of proteins have been implicated in side effects. Here we use a computational strategy to predict the activity of 656 marketed drugs on 73 unintended 'side-effect' targets. Approximately half of the predictions were confirmed, either from proprietary databases unknown to the method or by new experimental assays. Affinities for these new off-targets ranged from 1 nM to 30 μM. To explore relevance, we developed an association metric to prioritize those new off-targets that explained side effects better than any known target of a given drug, creating a drug-target-adverse drug reaction network. Among these new associations was the prediction that the abdominal pain side effect of the synthetic oestrogen chlorotrianisene was mediated through its newly discovered inhibition of the enzyme cyclooxygenase-1. The clinical relevance of this inhibition was borne out in whole human blood platelet aggregation assays. This approach may have wide application to de-risking toxicological liabilities in drug discovery.

The structures and inhibitory effects of Buame [N-(3-hydroxy-1,3,5(10)-estratrien-17β-yl)-butylamine] and Diebud [N,N'-bis-(3-hydroxy-1,3,5(10)-estratrien-17β-yl)-1,4-butanediamine] on platelet aggregation

Compounds with estrogenic effects that also inhibit platelet aggregation might be useful in reducing thrombotic events associated with estrogenic therapy. In this study, two aminoestrogens, Buame [N-(3-hydroxy-1,3,5(10)-estratrien-17β-yl)-butylamine] and Diebud [N,N'-bis-(3-hydroxy-1,3,5(10)-estratrien-17β-yl)-1,4-butanediamine], were synthesized and characterized using common analytical methods and spectrophotometric analyses. The location and orientation of these molecules on the estrogenic receptor α (ERα) were also evaluated. Platelet inhibitory effects were elucidated ADP-induced platelet aggregation and ADP- and collagen-induced ATP release. Molecular docking demonstrated that Buame can reach and bind to the ERα in the ligand binding domain (LBD) similar to 17β-estradiol (co-crystallized ligand). On the other hand, Diebud binds only to the surface of ERα due to its high molecular volume compared to 17β-estradiol and Buame.

Platelet-rich plasma: a milieu of bioactive factors

Platelet concentrates such as platelet-rich plasma (PRP) have gained popularity in sports medicine and orthopaedics to promote accelerated physiologic healing and return to function. Each PRP product varies depending on patient factors and the system used to generate it. Blood from some patients may fail to make PRP, and most clinicians use PRP without performing cell counts on either the blood or the preparation to confirm that the solution is truly PRP. Components in this milieu have bioactive functions that affect musculoskeletal tissue regeneration and healing. Platelets are activated by collagen or other molecules and release growth factors from alpha granules. Additional substances are released from dense bodies and lysosomes. Soluble proteins also present in PRP function in hemostasis, whereas others serve as biomarkers of musculoskeletal injury. Electrolytes and soluble plasma hormones are required for cellular signaling and regulation. Leukocytes and erythrocytes are present in PRP and function in inflammation, immunity, and additional cellular signaling pathways. This article supports the emerging paradigm that more than just platelets are playing a role in clinical responses to PRP. Depending on the specific constituents of a PRP preparation, the clinical use can theoretically be matched to the pathology being treated in an effort to improve clinical efficacy.

Decreased serotonin content and reduced agonist-induced aggregation in platelets of patients chronically medicated with SSRI drugs

BACKGROUND

Chronic treatment with selective serotonin reuptake inhibitors (SSRIs) reduces the risk and severity of cardiovascular diseases. SSRIs block the serotonin transporter, thereby inhibiting serotonin (5-HT) uptake into presynaptic neurons as well as into platelets where 5-HT is stored in dense granules. When 5-HT is released in response to agonists it enhances platelet aggregation induced by injury-related signals. Chronic administration of SSRIs may thus reduce platelet aggregability secondary to depletion of platelets' serotonin stores.

METHODS

The study included ten DSM-IV-TR major depression (MDD) and four obsessive compulsive disorder (OCD) patients and fourteen healthy untreated age- and sex-matched controls. The patients were chronically medicated (6-108 months) with various SSRIs. Platelet serotonin content was assessed in fresh samples of platelet rich plasma (PRP) using radioimmunoassay. ADP, collagen, arachidonic acid and epinephrine were used as inducers of platelet aggregation measured in PRP by turbometric method in a microplate reader.

RESULTS

Lower platelet serotonin content (66%; p<0.05) and lower ADP, collagen or epinephrine-induced platelet aggregation (10-52%; p<0.05) were detected in PRP of SSRI-medicated patients, while no such effect was obtained with arachidonic acid.

LIMITATIONS

The small sample size and the co-treatment with non-SSRI drugs such as benzodiazepines.

CONCLUSION

Patients chronically medicated with SSRIs exhibit lower platelet 5-HT content and reduced platelet aggregation induced by ADP, collagen and epinephrine, but not by arachidonic acid. Our observations may explain the increased bleeding risk associated with chronic SSRI treatment as well as the reported beneficial effect of SSRIs in prevention of recurrent myocardial infarction.

Short-term estrogen replacement therapy reduces platelet marker levels in Malaysian postmenopausal women

OBJECTIVES

In healthy postmenopausal women (PMW) increased platelet activation has been associated with adverse cardiovascular events. There is much debate about the relationship between platelet function and serum estradiol level in PMW. This study assessed the effect of short-term oral estrogen replacement therapy (ERT) on platelet activation markers (CD62P and PAC-1) and its correlation with age and body mass index (BMI) among healthy PMW.

METHODS

A prospective intervention study was conducted at Hospital University Sains Malaysia, involving 48 healthy PMW who were evaluated for platelet activation marker levels as determined by flow cytometry, before and after two weeks of oral ERT with 0.625 mg of conjugated equine estrogen once daily. The pre- and post-ERT platelets activation markers difference was analysed by paired t-test.

RESULTS

The pre-ERT, mean ± SD percentage levels of CD62P and PAC-1 were significantly reduced from 7.00 ± 5.91 and 41.75 ± 26.85 to 3.05 ± 2.47 and 20.86 ± 19.02, respectively, after two weeks of ERT (P value < 0.001). The correlation of platelet activation markers was significant with estradiol but not with age and BMI.

CONCLUSION

Short-term ERT leads to reduction in platelet activity, which might contribute to protection against cardiovascular diseases in healthy PMW.

Calcium mobilization by the plant estrogen ferutinin does not induce blood platelet aggregation

Platelet activation is closely associated with an increase in intracellular Ca(2+) concentration. Various compounds including Ca(2+) ionophores are able to trigger platelet aggregation by increasing intracellular Ca(2+) concentration in platelets. In the present study, we monitored the effect of the phytoestrogen ferutinin, which acts as a Ca(2+) ionophore in human blood platelets; its ionophore-like properties include upregulation of [Ca(2+)](in), activation of fibrinogen receptors and increased fibrinogen binding. Using spectrofluorometry and triple-color flow cytometry, we demonstrate that ferutinin increases [Ca(2+)](in) in both isolated platelets and platelets in whole blood from humans. This effect was almost completely blocked by the Ca(2+) chelator EGTA and was not sensitive to either Gd(3+) or econazole, which inhibit VOC and SOC channels, respectively. Nor was the effect sensitive to thapsigargin, an inhibitor of endoplasmic reticulum Ca(2+) ATPases. Ferutinin stimulated the expression of the active form of the GPIIb-IIIa complex and whole blood platelet aggregation only weakly and had no statistically significant effect on the binding of fibrinogen. These results demonstrate apparently inconsistent effects of ferutinin, which raises intraplatelet Ca(2+) concentration but fails to have an effect on spontaneous blood platelet aggregation. This pattern of responses may be caused by the combination of ferutinin's Ca(2+) ionophoric and estrogenic properties.

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.

Platelet function recovery after cessation of aspirin: preliminary study of volunteers and surgical patients

BACKGROUND AND OBJECTIVE

Recent evidence indicates that platelet function may recover more rapidly after cessation of aspirin therapy than previously thought. The present study evaluated the effect of aspirin on platelet function using platelet aggregometry in healthy individuals and in aspirin-treated patients scheduled for surgery.

METHODS

Platelet aggregation in response to arachidonic acid, epinephrine, and adenosine diphosphate was determined in 14 male volunteers during and after 10 days' aspirin administration (100 mg) and in 58 aspirin-treated patients during intake, on days 3, 4 or 6 after drug cessation, and on day 10 after drug cessation, prior to elective surgery. Urine thromboxane (11-dehydro-thromboxane B2) concentrations were also measured.

RESULTS

Platelet aggregation in response to arachidonic acid and epinephrine was significantly decreased in both volunteers and patients during aspirin administration. The aggregation normalized within 3 days of aspirin cessation in the volunteers and within 4-6 days in the patients. Urine concentration of 11-dehydro-thromboxane B2 was about three times lower with aspirin treatment than without, although in two patients concentrations were higher with aspirin.

CONCLUSION

Platelet aggregometry with arachidonic acid is a sensitive test for the evaluation of the effects of aspirin on platelet function. In most aspirin-treated patients, platelet function recovers 4 days after drug cessation, although the process is sometimes prolonged. Therefore, the time of aspirin cessation before scheduled surgery should be determined individually.