Biomedical subjects

A Bernat

Publications and source records attributed to A Bernat.

At least 19 recordsLinked to original sources

PubMed2004

[Outcome of tunneled hemodialysis catheters as permanent vascular access].

UNLABELLED: Tunneled cuffed hemodialysis catheters (THC) are developed as a means of short hemodialysis access while a more permanent form of access are maturing. The aim of this study is to investigate the effectiveness, survival and complications of the THC used for long-term vascular access. METHODS: In a retrospective study we looked at 42 THC inserted between November 2000 and October 2003, in 40 elderly patients, with systemic disease or when other vascular access was not possible. RESULTS: Procedural complications occurred in 5 cases (11.9%), which included: local haemorrhage (3), hemothorax (1) and one fatal venous tear. 6 catheters (14.2%) were removed due to complications (non-function 3 and bacteraemia 3). The total incidence of THC related infections was 0.18 episodes/1,000 catheters-days. Patients were followed up for a mean 379 days (range 1-1,140) and a total of 15,946 catheter-days. Qb and KT/V achieved at one month were 278.3 +/- 34.1 ml/min and 1.48 +/- 0.27 respectively. At the end of the follow-up, 23 patients (54.7%) were alive with catheter functioning. One, three and twelve months survival was 90.4%, 73.1% and 59.5% respectively. CONCLUSION: The THC may be a useful alternative permanent vascular access for hemodialysis patients when others vascular access are not possible.

Aged↗

PubMed2003

Effect of SanOrg123781A, a synthetic hexadecasaccharide, on clot-bound thrombin and factor Xa in vitro and in vivo.

Factor (F)Xa and thrombin bound to the clot during its formation contribute to the propensity of thrombi to activate the coagulation system. The aim of this work was to study the inhibition of clot-bound FXa and clot-bound thrombin by SanOrg123781A, a synthetic hexadecasaccharide that enhances the inhibition of thrombin and FXa by antithrombin (AT). SanOrg123781A, designed to exhibit low non-specific binding to proteins other than AT, was compared with heparin. In buffer, heparin and SanOrg123781A inhibited FXa and thrombin at similar concentrations [concentration inhibiting 50% (IC50) of Xa and IIa activity were, respectively: heparin 120 +/- 7 and 3 +/- 1 ng mL-1; SanOrg123781A 77 +/- 5 and 4 +/- 1 ng mL-1]. In human plasma, the activity of both compounds was reduced, although the activity of heparin was much more affected than that of SanOrg123781A (IC50 values for inhibition of FXa and FIIa activity were, respectively: heparin 100 +/- 5 and 800 +/- 40 ng mL-1; SanOrg123781A 10 +/- 5 and 30 +/- 3 ng mL-1). We demonstrated, in agreement with our previous results, that the procoagulant activity of the clot is essentially due to clot-bound FXa and to some extent to clot-bound thrombin. We showed that heparin and SanOrg123781A were able to inhibit fragment F1+2 generation induced by clot-bound FXa with IC50 values of 2 +/- 0.5 micro g mL-1 and 0.6 +/- 0.2 micro g mL-1, respectively. Both compounds also inhibited clot-bound thrombin activity, the IC50 values of heparin and SanOrg123781A being 1 +/- 0.01 micro g mL-1 and 0.1 +/- 0.1 micro g mL-1, respectively. Moreover, both heparin and SanOrg123781A significantly inhibited fibrinopeptide A generated by the action of clot-bound thrombin on fibrinogen but also by free thrombin generated from prothrombin by clot-bound FXa with IC50 values of 4 +/- 0.6 and 1 +/- 0.1 micro g mL-1, respectively. As with clot-bound enzymatic activities, SanOrg123781A was three times more active than heparin in vivo on fibrinogen accretion onto a pre-existing thrombus and as activators of recombinant tissue-type plasminogen activator-induced thrombolysis. In conclusion, due to the specific activities of SanOrg123781A, this compound is much more active than heparin in the presence of plasma proteins, on clot-bound enzymes and in in vivo models of thrombosis/thrombolysis.

Animals↗

PubMed2002

Effect of new synthetic heparin mimetics on whole blood thrombin generation in vivo and in vitro in rats.

The effect of new heparin mimetics (synthetic oligosaccharides) was studied in vitro with regard to thrombin generation (TG) in rat platelet rich plasma (PRP) and whole blood (WB) and in vivo on stasis-induced venous thrombosis in the rat. TG in PRP and in WB was highly dependent on platelet count and strongly influenced by the haematocrit. The peak of TG appeared to be significantly higher in WB than in PRP whereas the endogenous thrombin potential (ETP) was not significantly different under either condition. The effect of hirudin, the synthetic pentasaccharide SR90107/Org31540 (SP) and heparin were measured on TG in PRP and WB. We then compared the effect of two new synthetic heparin mimetics (SR121903A and SanOrg123781) with potent and comparable antithrombin (AT) mediated activity against factor Xa and thrombin. These two compounds were made of a pentasaccharide with a high affinity to AT, prolonged at the non-reducing end by an oligosaccharide chain recognised by thrombin. In SR121903A, the charge density and charge distribution was analogous to that of heparin whereas in SanOrg123781 the charges were only located on the last 5 saccharides of the non-reducing end of the molecule. In PRP and in WB, SR121903A acted on the lag time and on the AUC whereas SanOrg123781 inhibited thrombin formation with no effect on the lag time. SanOrg123781 was more potent in inhibiting TG than SR121903A. This difference was due to the structures of the compounds that differed in their ability to be neutralised by platelet factor 4. The antithrombotic effect of the two compounds was examined in a venous thrombosis model in rats. We observed that SanOrg123781 was more active than SR121903A and heparin. Taken together, these results indicate that the activity of oligosaccharides is greatly influenced by the global charge density of the molecule and show that SanOrg123781 is a potent and promising antithrombotic drug candidate.

Animals↗

PubMed2002

Pharmacokinetics of new synthetic heparin mimetics.

Pharmacokinetics of oligosaccharides displaying various affinities for antithrombin (AT) allowed us to show that there was a close relationship between the plasma half-life of these antithrombotic oligosaccharides and their affinity for AT. Recently, we have described new heparin mimetics comprising an AT binding domain and a thrombin binding domain separated by a neutral methylated saccharide sequence. These compounds displayed strong anti-Xa and antii-IIA activities and, in contrast to heparin, escaped neutralisation by platelet factor 4. The aim of this work was to compare the pharmacokinetics of several of these heparin mimetics in rats. These compounds differed by their length, charge and affinity for AT (AT-binding domain). The results obtained indicate that the prolongation of the AT binding domain did not modify significantly their affinities for AT. However, an increase in the number of charges leads to a decrease in the half-life. When a methylated spacer was added in order to minimise the non-specific interactions to other proteins, half-lives of the heparin mimetic were in the same range than that of the pentasaccharide used as an AT binding domain. In conclusion, this study shows the influence of the charge of the oligosaccharides on their pharmacokinetics and underlinesthe importance of minimising their non-specific binding to plasma proteins in order to obtain compounds with predictive pharmacokinetics.

Animals↗

PubMed2001

Antiplatelet and antithrombotic activity of SL65.0472, a mixed 5-HT1B/5-HT2A receptor antagonist.

The antiplatelet and antithrombotic activity of SL65.0472 (7-fluoro-2-oxo-4-[2-[4-(thieno [3,2-c]pyrin-4-yl) piperazin-1-yl]ethyl]-1,2-di-hydroquinoline-acetamide), a mixed 5-HT1B/5-HT2A receptor antagonist was investigated on 5HT-induced human platelet activation in vitro, and in rat, rabbit and canine platelet dependent thrombosis models. SL65.0472 inhibited 5-HT-induced platelet shape change in the presence of EDTA (IC50 values = 35, 69 and 225 nM in rabbit, rat and human platelet rich plasma (PRP)), and also inhibited aggregation induced in human PRP by 3-5 microM 5-HT + threshold concentrations of ADP (0.5-1 microM) or collagen (0.3 microg/ml) with mean IC50 values of 49 +/- 13 and 48 +/- 6 nM respectively. SL65.0472 inhibited thrombus formation when given both intravenously 5 min and orally 2 h prior to assembly of an arterio-venous (A-V) shunt in rats as from 0.1 and 0.3 mg/kg respectively. It was active in a rabbit A-V shunt model with significant decreases in thrombus weight as from 0.1 mg/kg i. v. and at 10 mg/kg p.o. The delay to occlusion in an electric current-induced rabbit femoral artery thrombosis model was increased by 251% (p <0.05) after 20 mg/kg p.o. SL65.0472 (30 microg/kg i.v.) virtually abolished coronary cyclic flow variations (7.2 +/- 1.0/h to 0.6 +/- 0.6/h, p <0.05) and increased minimum coronary blood flow (1.2 +/- 0.8 ml/min to 31.8 +/- 8.4 ml/min, p <0.05) in a coronary artery thrombosis model in the anaesthetised dog. Finally, SL65.0472 significantly increased the amount of blood lost after rat tail transection at 3 mg/kg p.o. Thus the anti-5-HT2A component of SL65.0472 is reflected by its ability to inhibit 5-HT-induced platelet activation, and platelet-rich thrombus formation.

Animals↗

PubMed2001

SR123781A, a synthetic heparin mimetic.

SR123781A, a synthetic hexadecasaccharide comprising an antithrombin (AT) binding domain, a thrombin binding domain, and a neutral methylated hexasaccharide sequence, was obtained from glucose through a convergent synthesis. SR123781A showed high affinity for human AT (Kd = 58 +/- 22 nM) and was a potent catalyst of its inhibitory effect with regard to factor Xa (IC50) = 77 +/- 5 ng/ml - 297 +/- 13 U/mg) and thrombin (IC50 = 4.0 +/- 0.5 ng/ml - 150 +/- 30 U/mg). SR123781A which acted exclusively via AT (no effect via heparin cofactor II at a concentration of 6 microg/ml) inhibited thrombin generation occurring via both the extrinsic and intrinsic pathways in vitro in human plasma. SR123781A did not compete for 3H-heparin binding to PF4 and did not activate platelets in the presence of plasma from patients with heparin-induced thrombocytopenia. After intravenous or subcutaneous administration to rats, rabbits or baboons, SR123781A displayed prolonged anti-factor Xa and anti-factor IIa activity ex vivo. After intravenous injection to baboons, decreases of the anti-factor Xa and anti-thrombin activities were parallel and disappeared with the same pharmacodynamics. Intravenous administrations of SR123781A strongly inhibited thrombus formation in an experimental model of thromboplastin-induced venous thrombosis in rats with an ED50 value of 18 +/- 0.1 microg/kg (vs 77 +/- 3 microg/kg for heparin). SR123781A inhibited arterial thrombus formation induced on a silk thread in an arterio-venous shunt and in the vena cava (ED50 values of 225 +/- 10 and 27 +/- 8 microg/kg, respectively). Compared to standard and low molecular weight heparin and to presently used drugs, SR123781A exhibited a highly favourable antithrombotic/bleeding ratio therefore showing that it might be considered as a promising compound in the treatment and prevention of various thrombotic diseases.

Animals↗

PubMed2001

HCV-RNA detection in liver bioptates--a comparison of automatic and 'home-made' protocols combined with a new procedure of HCV-RNA extraction.

BACKGROUND: For HCV-RNA detection in liver tissue a generally accepted reference method has not been established yet. Therefore, we have developed a procedure of HCV-RNA extraction from liver tissue and compared two methods of HCV-RNA detection. MATERIALS AND METHODS: A set of 32 liver biopsy specimens, obtained from chronically HCV infected patients, has been examined. At the time of biopsy, serum HCV-RNA was detectable in 20 patients in RT-PCR automatic Cobas AmplicorTM Hepatitis C assay, ver. 2.0 (Roche Molecular Systems, Inc, Pleasanton, CA, USA) 2 serum samples were negative for HCV-RNA and 10 patients has not been tested. Liver tissue has been homogenized in the presence of CRSR-Green (Fast RNA Kit-Green, Bio101, Inc, Vista, CA, USA) and a mixture of phenol/chloroform/isoamylic alcohol, using a FastPrep homogenizator (Bio101, Inc, Vista, CA, USA). Then RNA has been isolated from the material obtained using the Total RNA Prep Plus procedure (A&A Biotechnology, Gdańsk, Poland). Presence of HCV-RNA was next tested by means either of 'home-made' nested RT-PCR procedure or the RT-PCR automatic Cobas AmplicorTM Hepatitis C assay, ver. 2.0. In case of an inhibition of PCR detected in the first run of automatic assay, both PCR procedures have been repeated. RESULTS: In 5 cases of automatic assay an inhibition of PCR reaction has been detected in the first run, the RT-PCR procedures has been then successfully repeated in the second run. The presence of HCV-RNA in the liver tissues was detected in a total of 22 cases (69%) by mean of automatic assay and in a total of 20 cases (63%) by means of 'home-made' RT-PCR procedure. Except for two cases of HCV-RNA positivity in a biopsy tissue, detected by means of automatic but not 'home-made' procedure, the results obtained employing the methods have been identical. In one serum HCV-RNA positive case, the presence of HCV RNA has not been detected in a liver tissue using both methods. CONCLUSIONS: Our procedure of RNA isolation combined either with automatic Cobas AmplicorTM Hepatitis C assay, ver. 2.0 or 'home-made' RT-PCR procedure may be useful for establishing presence of HCV-RNA in liver tissue. In this combination, the automatic assay seems to be more sensitive than the 'home-made' procedure.

Biopsy↗

PubMed2000

Effect of aspirin on platelet desaggregation induced by SR121566, a potent GP-IIb/IIIa antagonist.

Since results of recent clinical trial, performed in patients suffering from acute coronary syndromes, suggested that aspirin improved the efficacy of an anti-GP-IIb/IIIa therapy, this work was set to study the mechanism underlying such a mechanism of aspirin. SR121566 (3 mg/kg, i.v.), a new selective antagonist of the GP-IIb/IIIa complex inhibited thrombus formation which occurred following electrical stimulation of the carotid artery of rabbits. On rabbits pre-treated with aspirin (10 mg/kg, i.v.), a bolus injection of SR121566 produced a strong reversal of thrombosis compared with the effect obtained on rabbits treated with SR121566 alone. In vitro, the addition of SR121566 to human platelets during the ADP-induced aggregation process resulted in a reversal of the aggregation which was nearly complete when it was added 30 s after the induction of aggregation, but progressively decreased when SR121566 was added at later times. ADP-induced platelet aggregation in the presence of aspirin (1 mM) was comparable to that obtained in control platelet-rich plasma, but the addition of SR121566 at all time points of the aggregation process was followed by a complete reversal of the aggregation even at later time points (> 120 s). Histological examination of the platelet aggregates showed a clear-cut difference in the platelet content between control and aspirin-treated platelets which contained much more dense granules. Inhibition of the release of thrombospondin by aspirin may account for a significant part of its pro-desaggregating activity as demonstrated by the effect of the tetrapeptide VTCG, an inhibitor of the binding of thrombospondin to its receptor, which strongly potentiated the activity of SR121566 as a desaggregating agent. Therefore, our study shows that aspirin pretreatment promotes a 'thrombolytic' activity of GP-IIb/IIIa inhibitors and, in particular, of SR121566, a potent and selective member of this new class of compounds. This effect is mainly due to an inhibition of the release of the platelet granule content and in particular to thrombospondin. This observation may contribute to a greater efficacy of GP-IIb/IIIa inhibitors for the treatment of thrombosis in atherosclerotic patients.

Adenosine Diphosphate↗

PubMed2000

Effect of factor Xa inhibitors on the platelet-derived microparticles procoagulant activity in vitro and in vivo in rats.

The aim of this study was to investigate the effect of factor Xa inhibitors on the prothrombinase activity of platelet-derived microparticles in vitro and in vivo. The factor Xa inhibitors studied were DX9065A (a direct factor Xa inhibitor) and Sanorg34006 (an antithrombin (AT)-mediated factor Xa inhibitor). Microparticles formed from the platelet surface following activation were isolated by size exclusion gel chromatography. After purification, their presence was detected by their procoagulant activity and by flow cytometry. Our results show that factor Xa and/or factor Va were present at the surface of the platelet-derived microparticles. Prothrombinase formed on the microparticles was inhibited by factor Xa inhibitors at IC50 values of 0.45+/-0.05 and 0.045+/-0.005 microM for DX9065A and AT-Sanorg34006 respectively. In an experiment aimed at determining the kinetics of microparticles formation we demonstrated that thrombin traces were sufficient to induce the formation of a significant quantity of microparticles. Both factor Xa inhibitors delayed the formation of microparticles by delaying thrombin generation. The thrombogenic effect of the microparticles were studied in vivo in a modified arterio-venous shunt model in the rat. In this model, the increase in the thrombus weigh due to microparticles or phospholipids did not differ significantly (33% and 23% respectively). In these conditions, prothrombinase activity seemed to play a lesser role in the thrombogenic effect than phospholipids. Nevertheless, factor Xa inhibitors were efficient and inhibited thrombus formation in a dose-dependent manner. These results demonstrate that platelet-derived microparticles display a potent prothrombotic effect in vivo and show that factor Xa inhibitors are potent antithrombotic compounds when thrombosis was induced by microparticles.

Animals↗

PubMed1999

Synthesis of thrombin-inhibiting heparin mimetics without side effects.

Unwanted side effects of pharmacologically active compounds can usually be eliminated by structural modifications. But the complex heterogeneous structure of the polysaccharide heparin has limited this approach to fragmentation, leading to slightly better-tolerated heparin preparations of low molecular mass. Despite this improvement, heparin-induced thrombocytopaenia (HIT), related to an interaction with platelet factor 4 (PF4) and, to a lesser extent, haemorrhages, remain significant side effects of heparinotherapy. Breakthroughs in oligosaccharide chemistry made possible the total synthesis of the pentasaccharide antithrombin-binding site of heparin. This pentasaccharide represents a new family of potential antithrombotic drugs, devoid of thrombin inhibitory properties, and free of undesired interactions with blood and vessel components. To obtain more potent and well-tolerated antithrombotic drugs, we wished to synthesize heparin mimetics able to inhibit thrombin, that is, longer oligosaccharides. Like thrombin inhibition, undesired interactions are directly correlated to the charge and the size of the molecules, so we had to design structures that were able to discriminate between thrombin and other proteins, particularly PF4. Here we describe the use of multistep converging synthesis to obtain sulphated oligosaccharides that meet these requirements.

Animals↗

PubMed1999

The antithrombotic efficacy of the GP IIb/IIIa antagonist SR121787 is potentiated by antithrombin-dependent factor Xa inhibition without an increase in the bleeding risk in the rabbit.

Current antithrombotic therapy in acute coronary symptoms is only partially effective and exhibits bleeding complications. These experiments were designed to address the antithrombotic and hemorrhagic interactions of the novel glycoprotein (GP) IIb/IIIa antagonist SR121787 in combination with the indirect inhibitor of factor Xa, SR90107/ORG31540. Thrombogenesis was initiated by electrolytic injury of the intimal surface of the carotid artery, and thrombus formation was assessed by recording carotid blood flow and by measuring thrombus weight 45 min after electrical stimulation. SR121787 was an efficacious antithrombotic agent in this model (ED50 = 16.3+/-0.3 mg/kg, p.o.), whereas heparin (4.5 mg/kg, i.v.) and SR90107/ORG31540 [1 mg/kg (850 aXa anti-units/kg), i.v.] were only marginally effective (17 and 27% inhibition of carotid blood flow reduction, respectively). Coadministrations of heparin (4.5 mg/kg, i.v.) or SR90107/ORG31540 (0.5 mg/kg, i.v.) were found to potentiate the antithrombotic efficacy of threshold doses of SR121787 (5 or 10 mg/kg, p.o.). The enhancement of the antithrombotic efficacy of SR121787 by SR90107/ORG31540 was--contrary to the association of SR121787 with heparin--not accompanied by an increased blood loss from the incised rabbit ear. Coadministrations of heparin or SR90107/ORG31540 did not influence the ex vivo antiaggregatory activity of SR121787. SR121787 coadministration did not alter the systemic anticoagulant activities in heparin or SR90107/ORG31540-treated animals. These data suggest the potential for optimized antithrombotic treatment in acute coronary syndromes when a GP IIb/IIIa antagonist (SR121787) is combined with an antithrombin-dependent factor Xa inhibitor (SR90107/ORG31540).

Animals↗

PubMed1999

Interspecies comparison of the antiplatelet, antithrombotic, and hemorrhagic effects of SR 121566A, a novel nonpeptide GP IIb/IIIa antagonist.

We report the results from an interspecies comparison of the antiplatelet, antithrombotic, and hemorrhagic actions of SR 121566A, a novel nonpeptide antiplatelet agent with high affinity and specificity for the GP IIb/IIIa complex. SR 121566A exhibited in vitro antiplatelet activity against adenosine diphosphate (ADP)-induced aggregation with a rank order of potency [humans = baboons = dogs] > marmosets > guinea pigs > rabbits. These in vitro findings were predictive for the ex vivo antiplatelet potency after i.v. administration of SR 121566A to dogs, guinea pigs, and rabbits [median effective dose (ED50) values, 0.02, 0.05, and 0.15 mg/kg]. The antiplatelet actions of SR 121566A translated into an acute antithrombotic effect in an arteriovenous shunt model after i.v. administration in dogs, guinea pigs, rabbits, and marmosets (ED50, 0.08, 0.10, 0.50, and 0.007 mg/kg). Hemorrhagic effects of SR 121566A were observed in guinea pigs and rabbits at doses that represented 2-3 times the antithrombotic ED50, whereas in marmosets, no bleeding was observed at the antithrombotic ED90. These results demonstrate that SR 121566A exhibits favorable actions in terms of antithrombotic potency and hemostatic safety in different animal species, suggesting that, in humans, SR 121566A will be a good candidate as an antithrombotic compound.

Adenosine Diphosphate↗

PubMed1999

Effect of clopidogrel on thrombin generation in platelet-rich plasma in the rat.

Clopidogrel (25 mg/kg, p.o.), a potent and selective inhibitor of ADP-induced platelet aggregation, significantly inhibited, in the presence of platelets, ex vivo thrombin generation triggered by low concentrations of tissue factor. Clopidogrel reduced the area under the curve (23%, p <0.05) and the thrombin peak concentration (35%, p <0.05) but did not affect the lag phase of thrombin generation. Under the same experimental conditions, heparin (100 microg/ml) inhibited thrombin generation mostly by delaying and by reducing the burst of thrombin. In a stasis-induced venous thrombosis model in rats under low thrombogenic challenge, clopidogrel inhibited thrombus formation (ED50 = 7.9+/-1.5 mg/kg, p.o. - n = 10), confirming the existence of a close relationship between platelet activation and thrombin generation leading to blood coagulation and venous thrombosis.

Animals↗

PubMed1999

[New antithrombotic oligosaccharides].

In the early eighties, following breakthroughs in oligosaccharide chemistry, the total chemical synthesis of pentasaccharides has been achieved, representing the antithrombin binding domain of heparin (the active site). The selective inhibitors of coagulation factor Xa thus obtained represent a new type of antithrombotic drugs. In a further step, based on the knowledge of the mechanism of antithrombin activation by heparin, oligosaccharides (pentadeca- to eicosasaccharides), comprising an antithrombin binding domain prolonged by a thrombin binding domain, were designed and synthesised in the Sanofi group. These compounds inhibit both factor Xa and thrombin, in the presence of antithrombin. Endowed with the full anticoagulant activity of heparin but devoid of undesired non-specific interactions, particularly with platelet factor 4 (PF4), they might represent "the ideal heparin-like antithrombotic".

Animals↗

PubMed1999

Effect of ciprofibrate on fibrinogen synthesis in vitro on hepatoma cells and in vivo in genetically obese Zucker rats.

In this study, we have shown that oncostatin M and interleukin-6 induce a dose- and time-dependent increase in fibrinogen levels in the conditioned medium of human hepatoma cells (HepG2). When HepG2 cells were treated simultaneously with oncostatin M or interleukin-6 and ciprofibrate (100 nmol/l), the production of fibrinogen in the conditioned media was strongly affected and a significant decrease in the mRNA levels of the fibrinogen beta chain was observed. Oncostatin-M- and interleukin-6-induced fibrinogen release was inhibited in a dose-dependent manner by ciprofibrate and, to lesser extent, by bezafibrate, fenofibric acid and clofibric acid. In vivo, increased plasma and platelet levels of fibrinogen were observed in genetically obese Zucker rats (fa/fa) compared with Zucker lean (fa/-) rats. In these rats, a 14-day oral treatment with ciprofibrate (10 mg/kg, per. os.) induced a statistically significant decrease (P > 0.05) in plasma concentrations of total cholesterol and triglyceride but also in plasma and platelet levels of fibrinogen. In order to determine the consequences of such an effect on fibrinogen, the ability of ciprofibrate to affect venous stasis was determined in a stasis-induced venous thrombosis model in Zucker rats. Under low thrombogenic challenge, ciprofibrate significantly inhibited thrombus formation (67+/-12%, P > 0.05), demonstrating for the first time that a potent hypolipemic compound exhibits an antithrombotic effect.

Animals↗

PubMed1998

Biochemical and pharmacological properties of SANORG 34006, a potent and long-acting synthetic pentasaccharide.

SANORG 34006 is a new sulfated pentasaccharide obtained by chemical synthesis. It is an analog of the "synthetic pentasaccharide" (SR 90107/ ORG 31540) which represents the antithrombin (AT) binding site of heparin. SANORG 34006 showed a higher affinity to human AT than SR 90107/ORG 31540 (kd = 1.4 +/- 0.3 v 48 +/- 11 nmol/L), and it is a potent and selective catalyst of the inhibitory effect of AT on factor Xa (1,240 +/- 15 anti-factor Xa U/mg v 850 +/- 27 anti-factor Xa U/mg for SR 90107/ORG 31540). In vitro, SANORG 34006 inhibited thrombin generation occurring via both the extrinsic and intrinsic pathway. After intravenous (IV) or subcutaneous (SC) administration to rabbits, SANORG 34006 displayed a long-lasting anti-factor Xa activity and inhibition of thrombin generation (TG) ex vivo. SANORG 34006 was slowly eliminated after IV or SC administration to rats, rabbits, and baboons, showed exceptionally long half-lives (between 9.2 hours in rats and 61.9 hours in baboons), and revealed an SC bioavailability near 100%. SANORG 34006 displayed antithrombotic activity by virtue of its potentiation of the anti-factor Xa activity of AT. It strongly inhibited thrombus formation in experimental models of thromboplastin/stasis-induced venous thrombosis in rats (IV) and rabbits (SC) (ED50 values = 40.0 +/- 3.4 and 105.0 +/- 9.4 nmol/kg, respectively). The duration of its antithrombotic effects closely paralleled the ex vivo anti-factor Xa activity. SANORG 34006 enhanced rt-PA-induced thrombolysis and inhibited accretion of 125I-fibrinogen onto a preformed thrombus in the rabbit jugular vein suggesting that concomitant use of SANORG 34006 during rt-PA therapy might be helpful in facilitating thrombolysis and preventing fibrin accretion onto the thrombus under lysis. Contrary to standard heparin, SANORG 34006 did not enhance bleeding in a rabbit ear incision model at a dose that equals 10 times the antithrombotic ED50 in this species and, therefore, exhibited a favorable therapeutic index. We suggest that SANORG 34006 is a promising compound in the treatment and prevention of various thrombotic diseases.

Animals↗

PubMed1998

SR142948A is a potent antagonist of the cardiovascular effects of neurotensin.

The novel compound SR142948A was compared with SR48692 as an antagonist of neurotensin-induced cardiovascular effects both in vitro and in vivo. SR142948A inhibited [125I]-neurotensin binding [median inhibitory concentration (IC50) = 0.24 +/- 0.01 nM], neurotensin-induced cytosolic free Ca2+ increase (IC50 = 19 +/- 6 nM), and prostacyclin production in human umbilical vein endothelial cells (IC50 = 17 +/- 3 nM) at much lower concentrations than did SR48692 (respective IC50 values, 14 +/- 5, 41 +/- 16, and 86 +/- 16 nM). Oral administration of SR142948A (10 microg/kg) resulted in significant inhibition of neurotensin-induced blood pressure changes, whereas SR48692 was active only at 10-fold higher doses. Furthermore, SR142948A administered i.v. in microg/kg quantities in the rat was as active as mg/kg doses of SR48692 on neurotensin-induced increase in hematocrit. SR142948A injected intradermally also significantly inhibited neurotensin-induced plasma extravasation at concentrations as low as 10 pmol/site, whereas 1,000 pmol/site of SR48692 were necessary to reach a significant inhibition. These data show that SR142948A is a novel, extremely potent antagonist of neurotensin-induced cardiovascular responses both in vitro and in vivo. SR142948A and SR48692 constitute a pair of nonpeptide neurotensin antagonists of different potency, which may be used to probe for the implication of neurotensin receptors in physiologic or pathologic phenomena.

Adamantane↗

PubMed1998

Effect of SR121566A, a potent GP IIb-IIIa antagonist on platelet-mediated thrombin generation in vitro and in vivo.

The effect of SR121566A, a new non-peptide GP IIb-IIIa antagonist was studied in vitro with regard to thrombin generation in platelet rich plasma and in vivo on stasis-induced venous thrombosis in the rabbit. SR121566A inhibited ADP-, arachidonic acid- and collagen-induced human platelet aggregation with IC50 values of 46 +/- 7.5, 56 +/- 6 and 42 +/- 3 nM, respectively. In the same experimental conditions, SR121566A strongly inhibited thrombin generation triggered by low concentrations of tissue factor. SR121566A reduced in a dose-dependent manner both the area under the curve and the thrombin peak concentration but did not affect the lag phase (defined as the time until 10 nM thrombin was generated). Aspirin (100 microg/ml) did not affect thrombin generation. One hour after intravenous administration to rabbits, SR121566A exhibited a potent ex vivo inhibitory effect against ADP-, arachidonic acid- and collagen-induced platelet aggregation. The ID50 were 0.6 +/- 0.25, 0.7 +/- 0.08 and 0.13 +/- 0.08 mg/kg, respectively. The ability of aspirin and SR121566A to affect venous stasis was determined in a stasis-induced venous thrombosis model in rabbits under high and low thrombogenic challenges. While aspirin was ineffective in both conditions, SR121566A significantly inhibited thrombus formation under low thrombogenic challenge demonstrating for the first time that a potent non-peptide platelet GP IIb-IIIa antagonist inhibits thrombin generation in vivo and exhibits a strong antithrombotic effect with regard to stasis-induced venous thrombosis. These results therefore confirm the existence of a close relationship between platelet activation and thrombin generation leading to blood coagulation but also emphasise the key role of platelets in the development of venous thrombosis, most likely through activation of the GP IIb-IIIa complex.

Animals↗