Effect of Fibrinogen on Platelet Reactivity Measured by the VerifyNow P2Y12 Assay.

The VerifyNow assay is based upon the ability of activated platelets to cross-link beads coated with fibrinogen. However, fibrinogen is an abundant protein of blood, and therefore it may affect test results by competing with fibrinogen of beads for binding to platelets. To test this assumption, we assessed the influence of artificial alteration of fibrinogen level in blood samples obtained from donors (n = 9) and patients on clopidogrel therapy (n = 8) on the results of the VerifyNow P2Y12 assay. Fibrinogen level was altered by adding to blood samples 1/10 volume of fibrinogen solution (10.56 g/liter) or corresponding buffer. Relative to baseline, addition of buffer significantly increased platelet reactivity, whereas addition of fibrinogen decreased it. Analysis of the relationship between change in platelet reactivity values (dBase and dPRU) and change in fibrinogen concentration (dFg) revealed strong negative correlations: dBase = -63.3 × dFg - 27.1 (r = -0.924, p < 0.0005) and dPRU = -54.4 × dFg - 21.8 (r = -0.764, p < 0.0005). Thus, the results of our experiments suggest that: (i) blood fibrinogen strongly influences results of the VerifyNow P2Y12 assay, and (ii) correcting for fibrinogen effect may be needed to improve the accuracy of the test in the measuring of antiplatelet effect of clopidogrel therapy.

[Action of a nitric oxide donor dinitrosyl complex of iron with glutathione on hemodynamics in rats and monkeys].

We studied action of a nitric oxide donor, dinitrosyl complex of iron (DNIC) with glutathione as a ligand on the hemodynamics of normotensive Wistar rats, spontaneously hypertensive rats (SHR), and monkeys. Intravenous DNIC introduction (2-120 mg/kg) rendered fast (1-2 min) hypotensive effect combined with increased heart rate by 10-25%. Second phase of the effect in Wistar rats was characterized by slowed recovery of arterial pressure and heart rate up to initial level. A gradual DNIC breakdown in blood occurred during this period associated with increased NO accumulation in organs with intensive oxidative metabolism (liver, heart, and kidney). Duration of hypotensive effect in all animals depended on dose, this dependence was most expressed in SHR.

[Changes of parameters of hemodynamics and systems of neurohumoral regulation in patients with implanted cardiac pacemakers after switching from DDD to VVI pacing mode].

To study complex of pathogenetic changes arising during VVI mode single chamber ventricular pacing we temporarily (for 1 hour) switched pacing mode from dual (DDD) to single (VVI) chamber stimulation in 11 patients. Parameters studied were cardiac output (CO), total peripheral vascular resistance (TPVR), levels of precursors of atrial and inactive fragment of brain natriuretic peptides (pro-ANP and NT-pro-BNP, respectively), noradrenaline, aldosterone, and renin activity in blood plasma. Reprogramming of pacing mode was associated with 21.4% lowering of CO and 11.4% elevation of TPVR according to impedance cardiography data, and augmentation of pro-ANP secretion from 429.79 to 620.22 fmol/l. At the background of VVI pacing there was a tendency to increase of noradrenaline blood concentration without significant changes of aldosterone concentration and plasma renin activity.

[The anticoagulant properties of the endothelium studied by the standard venous occlusion test]. / Izuchenie antikoaguliantnykh svoistv éndoteliia s pomoshch'iu standartnogo venookliuzivnogo testa.

Venous occlusion (VO) during which thrombin (Th) is postulated to be generated is routinely used for evaluation of fibrinolytic potential of endothelium (E). This study was performed to find out whether VO can also be used for assessment of anticoagulant function of E. VO was performed in 98 male patients (pts) with ischemic heart disease. Levels of protein C (PrC) which is related to Th binding by thrombomodulin and fibrinopeptide A (FpA)--a marker of presence of free Th--were determined together with some other factors of coagulation and fibrinolysis. Differences between pre- and postVO PrC levels fluctuated from -54.8% to +57.3%. According to reaction of PrC to VO pts were divided into 2 groups: 13 pts with increase or no change and 17 pts with decrease (consumption) of PrC. In pts without PrC consumption there was a significant increase in FpA. In pts with PrC consumption FpA was unchanged. In pts with PrC consumption exceeding its median value for this group (14%) PAI-1 antigen level fell significantly (-8.4 + 4%) during VO. Thus PrC consumption after VO indicates that TH is effectively removed from blood stream by endothelial factors. Absence of consumption of PrC is a sign of ineffective anticoagulant function of E. Increase in PrC level during VO in some pts may be due to its escape from tissue depot.

[Tissue plasminogen activator, its inhibitor and other factors of the blood fibrinolytic system in stable coronary heart disease]. / Tkanevoi aktivator plazminogena, ego ingibitor i drugie faktory fibrinoliticheskoi cictemy krovi pri stabil'noi ishemicheskoi bolezni serdtsa.

The activity of tissue plasminogen activator (TPA), its rapid inhibitor (TPAL), C protein (Cp), plasminogen, alpha 2-antiplasmin, antithrombin III was evaluated and the levels of fibrinogen-fibrin degradation products and fibrinogen (F) were measured in 51 males with persistent coronary heart disease (CHD) and 16 without coronary atherosclerosis and atherosclerosis of other sites, which were matched for age and CHD risk factors. The patients were found to have elevated TRAI levels (17.3 +/- 1.2 IU/ml versus 12.2 +/- 2.2 IU/ml in the controls; p less than 0.05), increased TPA release (75.5 +/- 9.2 IU/ml versus 47.5 +/- 7.9 IU/ml in the controls; p less than 0.03) in response to venous occlusion, and lower Cp levels (-7.7 +/- 2.5%; p less than 0.01). The level of F correlated with the severity of coronary atherosclerosis. The patients with primary angina pectoris displayed higher TPA release than did those with chronic CHD. The presented facts are associated with overt changes occurring in the response of the endothelium in the patients, primarily, in early CHD.

[Unstable angina: tissue plasminogen activator, tissue plasminogen activator inhibitors, protein C and other factors of the blood fibrinolytic system]. / Nestabil'naia stenokardiia: tkanevyi aktivator plazminogena, ingibitor tkanevogo aktivatora plazminogena, protein C i drugie faktory fibrinolitecheskoi sistemy krovi.

The authors examined the activities of plasminogen activator, its inhibitor, the levels of C protein, antithrombin III, alpha 2-antiplasmin, plasminogen, fibrinogen, fibrinogen/fibrin degradation products in 22 patients with unstable angina by using the vein occlusive test. No significant differences were found in the examined parameters while comparing the group of stable angina patients and healthy subjects. It was concluded that thrombogenesis disturbances in unstable angina were regional and the recording of peripheral blood fibrinolytic parameters failed to detect any changes characteristic of unstable angina.

[Signs of thrombin formation in venous occlusion in patients with ischemic heart disease and the role of the protein C activation system in its utilization]. / Priznaki obrazovaniia trombina pri venoznoi okkliuzii u bol'nykh ishemicheskoi bolezn'iu serdtsa i rol' sistemy aktivatsii proteina C v ego utilizatsii.

Elevated levels of fibrin peptide A were found in venous occlusion only in the patients unconsuming C protein, which indicates that there is a relationship between the thrombin production processes during venous occlusion and the C protein system functioning, the anticoagulant function of the endothelium in particular. Moreover, this makes it possible to employ the standard venous occlusion test to make an integral assessment of endothelial function.

[Effects of low doses of activated protein C in experimental arterial thrombosis in rats]. / Vliianie malykh doz aktivirovannogo proteina C na éksperimental'nyi arterial'nyi thromboz u krys.

Activated C protein (ACP) is a physiological anticoagulant enzyme that is capable to inactivate factors Va and VIIIa, thereby having a wide spectrum of antithrombotic effects. Low-dose ACP was tested for its ability to affect anodic current-induced arterial thrombosis in the rat. ACP given in low doses (15 micrograms/kg, 7% of total C protein in the rat) was found to produce a marked antithrombotic effect. With this, the activated partial thromboplastin time remained virtually unchanged, and its antithrombotic action was equal to that of heparin administered in a dose of 125 U/kg. In the authors' opinion, ACP may form the basis for designing a highly effective antithrombotic agent.

[Plasminogen activator inhibitor and protein C: their relation to plasma lipids and lipo- and apoproteins in ischemic heart disease of different duration]. / Ingibitor aktivatora plazminogena i protein C: sviaz' s lipidami, lipo- i apoproteinami plazmy pri ishemicheskoi bolezni serdtsa razlichnoi prodolzhitel'nosti.

The levels of plasminogen activator inhibitor (PAI), protein C (pC), total cholesterol (TC), high and low density lipoprotein cholesterols (HDLC and LDLC), apolipoproteins A1 (apoA1) and B (apoB) were measured in 45 patients with coronary heart disease angiographically documented and 10 healthy subjects without coronary heart disease and coronary atherosclerosis as evidenced by coronary angiography and provocative tests. Twenty three patients had primary angina (PA) with a duration of less than 3 months, twenty two patients presented with chronic coronary heart disease (CCHD) with a duration of more than 4 months. In general, a negative correlation between PAI and HDLC levels in the patients under study (r = -0.413; p = 0.02), it was higher in PA (r = -0.687; p = 0.02), but disappeared in CCHD (r = 0.027). The content of PAI correlated with the cholesterol index (r = 0.654; p less than 0.001 in the whole group), more greatly in PA (r = 0.865; p = 0.001) than in CCHD (r = 0.506, NS). There was a good correlation between the levels of pC and apoB in the whole group (r = 0.606; p less than 0.001) and in PA (r = 0.662; p = 0.001), but not in CCHD (r = 0.288, NS). The content of pC also correlated with a apoB/apoA1 ratio (r = 0.445; p = 0.002 in the whole group of patients). This correlation was significantly positive in PA (r = 0.455; p = 0.044), but not in CCHD (r = 0.022). Thus, higher levels of PAI coincided with atherogenic changes in those of HDLC, and an increase in the content of pC was in agreement with that of apoB. The interrelationships are particularly typical of early stages of CHD.

[Isolation and characterization of a protein C activator from the moccasin snake venom]. / Vydelenie i kharakteristika aktivatora proteina C iz iada mokassinovogo shchitomordnika.

The protein C activator detectable in the venom of the Southern Copperhead snake (Agkistrodon contortrix contortrix) was isolated by a combination of chromatofocusing on PBE-94 in the range pH9-7 and gel-filtration on Sephadex G-100 column. The peak protein C activator from Sephadex G-100 column appeared as double diffuse bands with apparent molecular weight of 37,700 and 31,400 after electrophoresis in the presence of sodium dodecylsulfate and 2-mercaptoethanol. The isolated enzyme does not clot human fibrinogen and when mixed with normal plasma generates activity of Protein C. It can be used for the measurement of protein C functional activity.