Haemostatic actions of the folkloric medicinal plant extract Ankaferd Blood Stopper.

Ankaferd Blood Stopper (ABS), a standardized mixture of five plants, has been used historically as a haemostatic agent but its mechanism of action remains unknown. This study investigated the in vitro effects of ABS on haemostatic parameters. When added to plasma or serum, ABS induced the very rapid formation of a protein network and erythrocyte aggregation. The levels of coagulation factors II, V, VII, VIII, IX, X, XI, and XIII were not affected by ABS. Plasma fibrinogen activity and antigen levels were decreased following the addition of ABS, in parallel with the prolonged thrombin time. Total protein, albumin, and globulin levels decreased after the addition of ABS. Our findings suggest that ABS stimulates the formation of an encapsulated protein network that provides focal points for erythrocyte aggregation. ABS has the therapeutic potential to be used for the management of haemorrhage and this agent should be investigated further in clinical trials.

Circulating thrombomodulin levels in familial Mediterranean fever.

Increments in circulating thrombomodulin levels reflect endothelial cell injury. Thrombomodulin can also be synthesized by several inflammatory cells including monocytes, neutrophils, and thrombomodulin itself can modulate the inflammatory response. In this study, we assessed circulating thrombomodulin concentrations in patients with familial Mediterranean fever (FMF). Twenty-five patients with FMF (F/M: 14/11) (mean age: 31.1 +/- 9.7 years) and 25 healthy controls (F/M: 13/12) (mean age: 34.6 +/- 7.0 years) were involved in the study. Thrombomodulin levels were measured by commercially available enzyme-linked immunosorbant assay (ELISA) (Immunoassay of thrombomodulin Diagnostica Stago, Asnieres-Sur-Seine, France). Twenty of the patients were in attack-free period and the remaining five had been during acute FMF attacks. Thrombomodulin levels were higher in the study group (20.9 +/- 12.1 ng/ml) than healthy controls (14.1 +/- 8.4 ng/ml) (p < 0.05). Circulating thrombomodulin levels were also higher in attack-free FMF patients (22.4 +/- 12.9 ng/ml) than controls. This study disclosed for the first time significantly higher increments in the circulating levels of thrombomodulin in FMF. This observation could be a consequence of injured endothelium and/or activated inflammatory cells.

The plasma levels of prostanoids and plasminogen activator inhibitor-1 in primary and secondary thrombocytosis.

An elevated platelet count is a common finding in both hospitalized and ambulatory patients. Thrombosis and bleeding complications are more frequently observed in patients with clonal thrombocytosis than secondary thrombocytosis. The aim of this study was to investigate the behaviors of plasminogen activator inhibitor type 1 (PAI-1), the inhibitor of fibrinolysis; and thromboxane A2 and 6-keto-PGF1 alpha, the products of endoperoxides, in 16 patients affected with clonal thrombocytemia as compared with 16 patients with reactive thrombocytosis and 15 normal controls. In the clonal thrombocytemia group, plasma levels of PAI-1 antigen and activity were significantly higher than both reactive thrombocytosis and control group. Plasma levels of 6-keto-PGF1alpha were significantly higher in the clonal thrombocytemia group than the other two groups and also higher in the reactive thrombocytosis group than the control group, which was also significant. This study confirms that arachidonate metabolism is frequently deranged in patients with thrombocytosis and hypofibrinolysis due to increased PAI-1 plasma levels as shown in the clonal thrombocytosis group. This may explain the thrombotic tendency in myeloproliferative disorders.

Increased plasminogen activator inhibitor-1 activity in offspring of type 2 diabetic patients: lack of association with plasma insulin levels.

OBJECTIVE: To determine whether a dysregulation of the fibrinolytic system exists in normal glucose tolerant offspring of type 2 diabetic patients. RESEARCH DESIGN AND METHODS: In this cross-sectional study, 32 offspring of type 2 diabetic patients and 26 subjects with no family history of diabetes were studied. With respect to the metabolic parameters, plasma fasting and 2-h postload (75 g glucose) glucose and insulin levels, total cholesterol, triglycerides, and HDL cholesterol concentrations were determined. To evaluate the status of hemostatic factors, fibrinogen, tissue plasminogen activator (tPA) antigen level, plasminogen activator inhibitor-1 (PAI-1) antigen level, and PAI-1 activity were assessed. The statistical analyses included the Mann-Whitney U test to check the significance of differences between variables in the two groups and Spearman's rank correlation tests to check the interrelationships between the hemostatic and metabolic parameters in the offspring group. RESULTS: All subjects had normal glucose tolerance according to the American Diabetes Association criteria. Plasma fasting and postload insulin concentrations were significantly higher in offspring compared with control group (P<0.00001 and P<0.01, respectively). Plasma fasting and postload glucose, fibrinogen, tPA antigen, total cholesterol, and BMI were comparable between the groups. The offspring had significantly higher waist-to-hip ratio (WHR) (P = 0.03), higher triglycerides (P = 0.01), and lower HDL cholesterol (P<0.01) compared with the control group. PAI-1 antigen level and PAI-1 activity were higher in the offspring (P = 0.05 and P = 0.04, respectively). In the offspring group, PAI-1 activity was correlated with plasma PAI-1 antigen level (r = 0.40, P = 0.02), fibrinogen (r = 0.45, P = 0.01), and HDL cholesterol (r = -0.36, P = 0.04). However, tPA antigen level, fasting and postload plasma glucose and insulin, total cholesterol, triglycerides, WHR, and BMI did not correlate with PAI-1 activity. CONCLUSIONS: These data suggest that normal glucose tolerant offspring of type 2 diabetic subjects have elevated PAI-1 activity indicating to hypofibrinolysis in this group. The elevated PAI-1 activity has no association with plasma insulin concentration.

Activation of blood coagulation in patients with mitral stenosis and sinus rhythm.

The aim of this study was to assess whether there is blood coagulation activation in patients with mitral stenosis (MS) and sinus rhythm (SR) and to investigate the value of left atrial spontaneous echo contrast (LASEC) as a predictive sign of increased coagulation activity. Using thrombin-antithrombin III complexes and prothrombin fragment 1+2 as in vivo hemostatic markers, we concluded that there is a hypercoagulable state in patients with MS and SR when LASEC is present.

Effects of hormone replacement on hemostasis in spontaneous menopause.

OBJECTIVE: To examine the effects of continuous combined estrogen-progesterone replacement therapy on coagulation and natural anticoagulant systems in spontaneous menopause. DESIGN: A randomized, double-blind, placebo-controlled study was conducted during a 6-month period to examine the effect of hormone replacement therapy (HRT) on blood coagulation parameters. One hundred-ten healthy postmenopausal women were randomized into two groups. Those in group 1 were given conjugated estrogen (0.625 mg/d, Premarin) and medroxyprogesterone acetate (5 mg/d, Farlutal), and those in group 2 were given identical tablets of placebo for 6 months. Serum levels of modified activated protein C resistance, antithrombin III, fibrinogen, factor VIIIa, factor VIII, factor IX, activated partial thromboplastin time, prothrombin time, thrombin time, and lipoprotein (a) were measured before and 6 months after the treatment and analyzed for changes in extrinsic and intrinsic coagulation parameters. RESULTS: At the end of the 6-month period, fibrinogen, lipoprotein (a), and activated protein C resistance levels were decreased significantly in the HRT group compared with the control group. Antithrombin III levels were increased, indicating antithrombin activity. Activated partial thromboplastin time, as a measure for intrinsic coagulation cascade, was prolonged in concert with decreased intrinsic coagulation factors, factor VIII, and factor IX (p < 0.05). In the extrinsic coagulation system, prothrombin time was significantly increased, although factor VIIa level was not changed (p > 0.05). CONCLUSION: Significant changes were observed in the coagulation parameters, which may further explain the cardioprotective effect of HRT.

Soluble L-selectin increases in the cerebrospinal fluid prior to meningeal involvement in children with acute lymphoblastic leukemia.

Soluble L-selectin was determined in the CSF samples of 20 children with CNS leukemia at the time they had blasts in CSF and/or clinical findings of CNS involvement; 17 CSF fluid samples were obtained from 17 of these 20 children, 29-91 days before the appearance of CSF cytological and/or clinical findings of CNS involvement; while 15 CSF samples were withdrawn from among the same group of children, after treatment of meningeal leukemia. In addition, CSF sL-selectin was also assayed in 17 children with ALL, who remained in complete remission at least for a year and, as controls, in 12 children without malignant or meningeal disorders. There was no significant difference in CSF sL-selectin levels between the children with ALL without evidence of meningeal involvement and the controls (1.34 +/- 0.21 ng/ml, 1.46 +/- 0.18 ng/ml respectively, p > 0.05). However, in children with CNS leukemia, not only at the time CNS involvement was diagnosed, but also 29-91 days before the diagnosis of CNS leukemia, the concentrations of the CSF sL-selectin (12.41 +/- 2.14 ng/ml, 7.70 +/- 1.60 ng/ml respectively) were significantly higher than those in controls (p < 0.001 and p < 0.01 respectively). After treatment and disappearance of the blasts in CSF, sL-selectin was found to be decreased and even normalized in the majority of children who had meningeal involvement (2.87 +/- 2.14 ng/ml). In 5 children, the CSF sL-selectin remained high, after the blasts in CSF had disappeared and CNS leukemia recurred within 3 months in 4 of these 5 children. In conclusion, assay of sL-selectin in CSF seems to be a good diagnostic tool in the detection of CNS involvement in children with ALL. This method may also be used as an indicator, in prediction of the CNS leukemia, which is going to develop.

Changes of hemostatic factors in children with acute lymphoblastic leukemia receiving combined chemotherapy including high dose methylprednisolone and L-asparaginase.

In this study, protein C (PC), protein S (PS), heparin cofactor II (HCFII), prothrombin fragment 1+2 (PF 1,2), thrombin-antithrombin III complex (TAT), von Willebrand factor (vWF) and thrombomodulin (TM) were investigated in 19 patients with acute lymphoblastic leukemia, (ALL) receiving combined chemotherapy including L-asparaginase (L-ASP) and high dose methylprednisolone (HDMP). HDMP was administered in doses of 30 mg/kg/day for 7 days, and 20 mg/kg/day for another 7 days. In order to evaluate the effect of HDMP on the hemostatic system, the 8 patients studied here received HDMP (30 mg/kg/day) therapy for 4 days before the combined chemotherapy. These parameters were also studied in 12 healthy children as a control group. PC levels were normal in the patients while PS levels were decreased both before and after combined chemotherapies. Patients with ALL have laboratory signs of coagulation activation such as PF 1,2, TAT prior to initiation of chemotherapy. With combined chemotherapy, TAT levels were found to be normal while PF1,2 were not. TM levels were found to be increased both before and after therapies whereas HCFII and vWF levels were not different from those of the control group. The short course of HDMP therapy did not prominently influence these hemostatic parameters. These results indicate that both the malignant process and the drugs used in combined chemotherapy cause a decrease in natural inhibitors and an increase in procoagulant activity and endothelial injury. These hemostatic changes may contribute to a thrombotic tendency in the patients with ALL.

The acute effect of smoking on platelet and endothelial release reaction is suppressed in chronic smokers.

Whilst increased plasma beta-thromboglobulin (beta TG), platelet factor 4 and thrombospondin levels are regarded as reflecting the release reaction of platelets, tissue-type plasminogen activator (t-PA) and plasminogen activator inhibitor-1 (PAI-1) levels represent endothelial release reaction and/or damage. In this study including 12 smokers and 9 nonsmokers, we investigated the acute and chronic effect of smoking on these parameters and antithrombin III, protein S and fibrinogen, as well. Nonsmokers were found to have somewhat higher plasma levels of beta TG, t-PA and PAI-1 than chronic smokers, and 30 minutes after smoking two cigarettes, these levels and protein S levels of nonsmokers showed more prominent increases than of chronic smokers. It is speculated that chronic exposure to cigarette smoke may cause "exhaustion" or "receptor down-regulation" of platelets and endothelial cells, resulting with diminished release reaction of platelets and endothelium in response to acute smoking.

Evidence for the role of dialysis hypoxemia in the pathogenesis of hemodialysis-induced rise in tissue-type plasminogen activator.

It is well known that hemodialysis (HD) causes a rise in plasma tissue-type plasminogen activator (t-PA). Although there have been several suggested mechanisms responsible for this effect of HD, the precise cause has not been well understood yet. Another complication of HD, when performed with acetate-containing dialysate, is hypoxemia, which is commonly observed during the first hour of the session. The purpose of this study was to investigate the relationship between dialysis hypoxemia and HD-induced t-PA changes during the first two hours of HD. HD caused significant increase in plasma t-PA antigen levels. When individual t-PA profiles versus time were examined, two patterns were observed. Whilst ten subjects (%56) experienced minimal or no increase, t-PA antigen level of the remaining eight subjects began to rise at 30 minutes and continued at that level up to 90 minutes, when the last samples were drawn. The courses of pO2 were also different; whilst the former group had "early-onset and short-term" hypoxemia, the latter had "late-onset and prolonged" hypoxemia. The amount of increase in t-PA antigen and the amount of decrease in pO2 were correlated at 60 and 90 minutes of the HD session. Thus, it is concluded that dialysis hypoxemia may contribute to HD-induced rise in plasma t-PA levels. Further studies comparing different dialysates and dialyser membranes are required to confirm this hypothesis.

Effects of colchicine on inflammatory cytokines and selectins in familial Mediterranean fever.

OBJECTIVE: To evaluate whether basal levels of circulating cytokines and selectins exhibit a distinct profile in attack-free, non-colchicine taking familial Mediterranean fever (FMF) patients compared to normal healthy controls, and to determine the effect of colchicine treatment on these parameters. METHODS: Serum levels of interleukin (IL)-6, IL-8, tumor necrosis factor (TNF)-alpha, and soluble P-, E-, and L-selectin in attack-free, asymptomatic, non-colchicine using FMF patients (n = 11) and in normal controls (n = 10) were studied. Following 2 months of colchicine treatment the same parameters were evaluated again in the FMF patients. RESULTS: Before colchicine treatment the serum levels of all parameters except soluble P-selectin were significantly higher in FMF patients than in controls. After two months of treatment statistically significant decreases were observed in these parameters (p < 0.05). CONCLUSION: A distinct profile of IL-6, IL-8, TNF-alpha, and soluble E- and L-selectin levels was observed in FMF patients, which could reflect the presence of sustained inflammation in attack-free FMF patients. The effect of colchicine on these parameters suggests its therapeutic potential.

Synovial fluid cytokine levels in Behçet's disease.

OBJECTIVE: To investigate the synovial fluid levels of interleukin-1 beta (IL-1 beta), tumour necrosis factor-alpha (TNF-alpha), transforming growth factor-beta (TGF-beta), IL-1 receptor antagonist (IL-1ra), soluble IL-2 receptor (sIL-2r) and IL-8 in patients with Behçet's disease (BD) and to compare them to levels in rheumatoid arthritis (RA), and osteoarthritis (OA). METHODS: The cytokine levels of BD (n = 14), RA (n = 15) and OA (n = 15) patients were assessed by enzyme-linked immunosorbent method. RESULTS: Median synovial IL-1 beta and TNF-alpha levels were higher in RA compared to BD and OA patients. IL-1 beta levels were also higher in BD than OA whereas TNF levels were similar in these two groups. IL-1ra and TGF-beta activity in BD were higher than OA but lower than RA. sIL-2r and IL-8 levels were increased in BD and RA in comparison to OA patients. CONCLUSION: The arthritis of BD is non-erosive and accordingly, its synovial fluid contains lower levels of cytokines primarily involved in cartilage destruction, namely IL-1 beta and TNF-alpha, than RA. IL-1ra and TGF might serve as protective factors against erosion in the inflamed joints. High synovial fluid levels of sIL-2r and IL-8 probably reflect a non-specific inflammatory process.

Increased plasma levels of soluble selectins in patients with unstable angina.

BACKGROUND: Inflammation plays an important role in the pathogenesis of unstable angina. Adhesion molecules, such as selectins, mediate the interactions between leukocytes, platelets and endothelial cells during inflammation and thrombogenesis. HYPOTHESIS: The purpose of this study was to determine whether soluble E-selectin, P-selectin and L-selectin levels are increased in patients with unstable angina (UA). METHODS: Soluble E-, P- and L-selectin levels were measured by enzyme-linked immunoassay in the peripheral blood of 23 patients with UA, 26 patients with stable angina (SA) and 15 control patients with angiographically normal coronary arteries. RESULTS: Soluble E-selectin levels were significantly higher in patients with UA (45+/-11 ng/ml) than in controls (30+/-8 ng/ml, P<0.001), or patients with SA (34+/-8 ng/ml, P=0.001). Similarly, plasma levels of P- and L-selectin were significantly higher in patients with UA (427+/-144 and 772+/-160 ng/ml, respectively) than in patients with SA (278+/-79 and 643+/-94 ng/ml, respectively, P<0.005 vs. UA for both), or control patients (189+/-43 and 601+/-126 ng/ml, respectively, P=0.001 vs. UA for both). CONCLUSIONS: Plasma levels of soluble selectins were increased in patients with UA compared with patients with SA or patients without angiographically visible coronary artery disease. Measurements of these adhesion molecules may be helpful as non-invasive markers of coronary plaque destabilization in UA.

Rational use of the PFA-100 device for screening of platelet function disorders and von Willebrand disease.

Two hundred and five patients referred for evaluation of platelet functions and 126 healthy controls were tested with the PFA-100 instrument. A cut-off value of 150 s for collagen/epinephrine (CEPI) closure time (CT) produced most acceptable sensitivity (90%), specificity (85.2%), and positive (82.6%) and negative (91.6%) predictivity values for screening of platelet function disorders and von Willebrand disease (vWD). All patients with vWD and Glanzmann thrombasthenia could be detected by PFA-100. Both CEPI and collagen/adenosine diphosphate (CADP) CTs were elevated in all of these cases. Sensitivity of the device was 81.6% for patients with platelet secretion defects. CADP CT was normal in 63.9% of the patients in this subgroup. Specificity (47%) and positive predictivity (57%) of the instrument were diminished in patients with low hemoglobin concentrations. Depending on the results, an algorithm was developed for screening of platelet function disorders and vWD with PFA-100.

Thrombopoietin and thrombospondin in renal allograft recipients.

Recipients of renal transplants appear to be at increased risk of thromboembolic events. Despite accumulating evidence for the hyperreactivity of platelets, the primary regulator of thrombopoiesis, thrombopoietin (TPO), has not yet been studied in renal transplant recipients. Thus, the aim of the present study was to quantify the levels of TPO and to assess its contribution to increased platelet reactivity in recipients of renal allografts. Serum concentrations of thrombospondin (TSP) were also determined in patients undergoing renal transplants in order to evaluate the role of this multifunctional protein in platelet hyperaggregability. Serum levels of TPO were significantly lower in renal transplant recipients (n = 27) than in healthy controls (30.8+/-20.6 pg/ml versus 129.9+/-113.6 pg/ml, P = 0.001). Serum concentrations of TPO were correlated neither with serum levels of creatinine nor duration of transplantation. However, levels of TPO were negatively correlated with platelet counts (r = -0.50, P = 0.007) in recipients of renal transplants. Plasma levels of TSP were higher in renal transplant patients than in the control group (104.5+/-54.7 ng/ml versus 63.4+/-41.5 ng/ml, P = 0.003). No significant correlation was found between levels of TPO and TSP. We conclude that, rather than the allograft function, the platelet mass determines the levels of TPO in recipients of renal transplants. Despite the low serum levels of TPO, and increased concentrations of TSP, TPO might still play a role in the hyperaggregability of platelets in patients undergoing renal transplants.

Increased systemic coagulation activity in patients with rheumatic mitral stenosis: assessment of the clinical and echocardiographic determinants.

In this study, we aimed to determine systemic coagulation activity in patients with rheumatic mitral stenosis and to define determinants of a possible prethrombotic state. Peripheral venous plasma level of thrombin-antithrombin III complex was measured in 84 consecutive patients with rheumatic mitral stenosis who had no left atrial thrombus by transesophageal echocardiography. The patients had significantly higher thrombin-antithrombin III complex values (mean +/- SD = 9.6+/-15.9 ng/ ml) compared with the healthy subjects (2.1+/-1.8 ng/ml) (P<0.001). Among many clinical and echocardiographic variables, severe mitral regurgitation (odds ratio = 6.7, P<0.001) and left atrial spontaneous echo contrast (odds ratio = 22.8, P<0.001) appeared as significant predictors of the increased systemic coagulation activity in multivariate logistic regression analysis. In conclusion, systemic coagulation activity is increased in the patients with rheumatic mitral stenosis, and coexistence of severe mitral regurgitation and presence of left atrial spontaneous echo contrast are determinants of this increment.

Determinants of soluble CD23 antigen levels in hemodialysis patients: effect of 1.25 dihydroxyvitamin D3 and recombinant human erythropoietin treatment.

BACKGROUND: The immunodeficiency of end-stage renal disease (ESRD) paradoxically coexists with T cell and monocyte activation. In spite of well known defective antibody responses in ESRD, the functional status of B cells in the immune system dysregulation of uremia is still controversial. Soluble CD23 (sCD23) antigen is a recently identified B cell activation marker and is also involved in T cell activation process. Effects of parathyroid hormone (PTH), red blood cells and ferritin on T and B cell functions have been shown both in vivo and in vitro. PATIENTS AND METHODS: In this study, serum levels of sCD23 in hemodialysis patients were determined to evaluate the functional status of B cells and possible linkages between this cytokine and PTH levels, ferritin levels, red blood cell counts were investigated. RESULTS: Serum sCD23 levels were significantly elevated in hemodialysis patients relative to healthy controls (12.5+/-8.4 micro/l vs. 2.4+/-1.1 micro/l, p<0.001). Serum sCD23 levels were negatively correlated with red blood cell count (r = -0.61, p = 0.009) and serum PTH levels (r = -0.62, p = 0.008), while positively correlated with serum ferritin levels (r = 0.63, p = 0.007) in hemodialysis patients. We also investigated the immunumodulator effects of 1.25 dihydroxyvitamin D3 (1.25OHD3) and recombinant human erythropoietin (rHu-Epo) treatment in hemodialysis patients. 1.25OHD3 treatment for eight weeks did not change serum sCD23 levels in hemodialysis patients (n = 8). On the other side, rHu-Epo administration for 16 weeks led to a decrease in serum sCD23 levels (17.7+/-8.6 microg/l vs. 9.8+/-3.5 microg/l, p = 0.007) in these patients (n = 9). CONCLUSION: These results suggests that similar to T cells, B cells are activated in uremia and the degree of this activation is correlated with red blood cell count, serum parathyroid hormone levels and iron status of the hemodialysis patients. Moreover, B cell activation could be altered by recombinant human erythropoietin therapy in hemodialysis patients.

Thrombomodulin levels in Behçet's disease with and without the factor V Leiden mutation.

The plasma levels of thrombomodulin (TM) in 34 patients with Behçet's disease and 79 healthy control subjects were studied. Eight patients had the factor V Leiden (FVL) mutation. The TM level was significantly lower in patients with the FVL mutation than in patients without the mutation and in the healthy controls (p < 0.05 and p < 0.01). However, there was no difference in overall mean plasma TM concentration between the patients without the mutation and the healthy controls.

Interleukin-1, -6, and -8 levels in juvenile chronic arthritis.

The immunoinflammatory pathogenesis of juvenile chronic arthritis (JCA) involves the activation of many pathways including various cytokines. We have evaluated the levels of interleukin(IL)-1, IL-6 and IL-8 in 29 JCA patients. The age range was 1-16 with a mean of 10.1. A disease activity score was developed on the basis of: 1. constitutional symptoms and/or morning stiffness, 2. presence of joint swelling, 3.warmth, 4.limited range of motion, and 5.joint pain. This score correlated very significantly with laboratory disease activity markers such as erythrocyte sedimentation rate (ESR) and CRP (both p = 0.006) and also correlated with IL-1 and IL-6 levels. The levels of IL-1 decreased in four of the five patients with improved disease activity. IL-6 but not IL-1 correlated significantly with the number of inflamed joints (p = 0.013); IL-6 also strongly correlated with rheumatoid factor supporting this cytokine's role in B cell induction (p = 0). Haemoglobin values correlated negatively with the activity index, ESR, CRP, IL-1 and IL-6. IL-8 did not correlate with disease activity markers. In the systemic patients all cytokines tended to be higher. Our data suggest that interleukins 1 and 6 are effective in the pathogenesis of JCA. Whether cytokines may be used for monitoring therapy may be clarified with further studies.

Bloodstream thrombopoietin in rheumatoid arthritis with thrombocytosis.

Thrombopoietin (TPO) is the major regulator of growth and differentiation of megakaryocytes. Recent studies have shown that TPO may also act as an acute-phase reactant, and it has been suggested as a component of inflammatory reactions. In this study our objective was to investigate serum TPO levels in patients with rheumatoid arthritis, a complex chronic inflammatory disorder not uncommonly associated with thrombocytosis. Bloodstream TPO concentrations were assessed in 13 RA patients with platelet counts between 450 and 650 x 10(9)/l, 10 RA patients with platelet counts >650 x 10(9)/l, 15 RA patients with normal platelet counts and 12 healthy controls. RA patients with normal platelet counts had TPO levels comparable with healthy controls. TPO concentrations in patients with mild thrombocytosis were significantly elevated, whereas patients with markedly increased thrombocyte counts had prominently decreased TPO levels. These results indicate that TPO seems to be associated with reactive thrombocytosis in RA patients with active disease. In patients with extremely increased thrombocytosis serum TPO levels might be regulated by increased platelet mass via receptor-mediated uptake and metabolism.