An Antibody Targeted To The Anionic Region Of Human Protease Activated Receptor 4 Inhibits Thrombosis Without Influencing Bleeding

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 2376-2376
Author(s):  
Michele M. Mumaw ◽  
Maria de la Fuente ◽  
Amal Arachiche ◽  
Daniel N. Nobel ◽  
Marvin T. Nieman
Keyword(s):  
Platelet Aggregation ◽  
Bleeding Time ◽  
Conflicts Of Interest ◽  
Preliminary Evidence ◽  
Human Platelets ◽  
Control Treatment ◽  
Dependent Manner ◽  
Protease Activated Receptors

Abstract Protease activated receptors (PARs) are G-protein coupled receptors which are activated by cleavage of their N-terminus by thrombin. This generates a tethered ligand which is then able to activate the corresponding receptor. Human platelets express PAR1 and PAR4, which both have crucial roles in mediating the response of platelets to injury. Our hypothesis is that PAR4 is an ideal target for new anti-platelet therapies because it is required for stable clot formation and has limited tissue distribution. We have previously determined a region on PAR4 that is required for efficient activation by thrombin. A polyclonal antibody (CAN12) targeted to this region of the PAR4 exodomain does not cross react to PAR1. Initial studies determined that CAN12 is able to block thrombin-induced human platelet aggregation with an IC50 of 10 ng/ml. Control IgG does not inhibit aggregation at 2 mg/ml. In mouse platelets, CAN12 inhibits P-selectin expression and integrin activation. In the Rose-Bengal mouse model of carotid artery thrombosis, CAN12 (1 mg/kg) administered 10 minutes prior to injury was able to completely inhibit the formation of a thrombus in a dose dependent manner. The antibody delayed thrombosis to greater than 90 min; the experiment was terminated at 90 minutes. In contrast, control treatment (2 mg/kg IgG or saline) resulted in complete occlusion at ∼40 minutes. Further, the minimal dose of CAN12 required for complete inhibition of thrombosis (0.5 mg/kg) administered fifteen minutes after injury also delayed thrombosis from ∼50 minutes to ∼80 minutes. This indicates that CAN12 is able to disrupt a thrombus after it has been initiated. Preliminary evidence indicates that CAN12 is able to delay the cleavage of PAR4. Importantly, CAN12 (2 mg/kg) treatment does not increase bleeding time or blood loss in the tail clip assay compared to control IgG (2 mg/kg) treatment. There was also no significant increase in bleeding in the saphenous vein assay. The mice treated with CAN12 (2 mg/kg) had an average bleeding time of 102 seconds for 12 clot formations in 20 minutes compared to the control mice (IgG 2 mg/kg) which had an average bleeding time of 143 seconds for 11 clot formations. These data demonstrate that we are able to inhibit platelet aggregation in vitro and thrombosis in vivo without influencing bleeding time. Overall, these studies provide insight towards the development of new anti-platelet therapies and, specifically, PAR4 as an antiplatelet therapy target. Disclosures: No relevant conflicts of interest to declare.

The Effects of Two Synthetic Glycoprotein II b/III a Antagonists, Ro 43-8857 and L-700,462, on Platelet Aggregation and Bleeding in Guinea-Pigs and Dogs: Evidence that Ro 43-8857 Is Orally Active

1993 ◽  
Vol 70 (05) ◽  
pp. 838-847 ◽  
Author(s):  
Nigel S Cook ◽  
Oliver Bruttger ◽  
Charles Pally ◽  
Alex Hagenbach
Keyword(s):  
Platelet Aggregation ◽  
Guinea Pigs ◽  
Bleeding Time ◽  
Ex Vivo ◽  
Human Platelets ◽  
Mesenteric Arteries ◽  
Duration Of Action ◽  
Orally Active

SummaryIn vitro platelet aggregation studies in whole blood were used to define the species-specificity profile of two synthetic GP-IIb/IIIa antagonists, Ro 43-8857 and L-700,462. Aggregation of rhesus monkey platelets was inhibited with a similar potency to human platelets, whereas both compounds were poor antagonists in mini-pig, rabbit or hamster blood. Compared to human platelets, Ro 43-8857 was 2-3-fold less active as an inhibitor of dog and guinea-pig platelet aggregation, whereas L-700,462 was, respectively, 4- and 14-fold less active in these species.In vivo investigations with these two compounds were performed in anesthetized guinea-pigs and conscious dogs, with bleeding times measured on small mesenteric arteries or on the inner jowl respectively. Ex vivo ADP-induced whole blood platelet aggregation was completely inhibited in guinea-pigs by Ro 43-8857 following intravenous administration of 0.1 mg/kg and intraduodenal administration of 3 mg/kg, with a duration of action exceeding 5 hours. Mesenteric bleeding times were prolonged by Ro 43-8857 only at doses causing supra-maximal inhibition of aggregation, suggesting these two effects could be partially dissociated. L-700,462 (3 mg/kg i. v.) was shorter acting than Ro 43-8857 in guinea-pigs (duration ~1 hour) and the antiaggregatory effect was accompanied by mesenteric bleeding time prolongations. In conscious dogs, ex vivo aggregation was inhibited to —80% by Ro 43-8857 (0.3 mg/kg i. v. or 10 mg/kg p. o.) and L-700,462 (1 mg/kg i.v.). However, bleeding time prolongations accompanied these anti-aggregatory effects with both compounds.In conclusion, we have shown clear differences between two synthetic GP-IIb/IIIa antagonists, both in terms of their species-specificity in vitro and in terms of their in vivo profile, and in particular the propensity to promote bleeding from mesenteric arteries in guinea-pigs. However, the ability of Ro 43-8857 to discriminate between anti-aggregatory and bleeding effects was not evident when the bleeding time measurements were performed on the dog jowl. This suggests that the species and/or vessels on which the bleeding time is performed, is also an important consideration when characterizing and comparing antiplatelet compounds, even with drugs acting via the same mechanism. These results are relevant for the future design of in vivo animal experiments to characterize this new class of compounds and in the interpretation of the data obtained to the clinical situation. The animal models described here are well suited for comparative studies of different GP-IIb/IIIa antagonists, providing information on in vivo potency, duration of action and effect-bioavailability following different routes of administration.Orally active GP-IIb/IIIa antagonists have not previously been described in the literature. The long duration of action and oral activity shown by Ro 43-8857 suggests a potential use of such compounds in arterial thrombotic disorders requiring chronic therapy.

Inhibition of Thrombosis by a Selective Fibrinogen Receptor Antagonist without Effect on Bleeding Time

1994 ◽  
Vol 72 (01) ◽  
pp. 119-124 ◽  
Author(s):  
Juerg F Tschopp ◽  
Curt Mazur ◽  
Kenneth Gould ◽  
Raymond Connolly ◽  
Michael D Pierschbacher
Keyword(s):  
Platelet Aggregation ◽  
Bleeding Time ◽  
Ex Vivo ◽  
Dependent Manner ◽  
Ic50 Values ◽  
Receptor Assays ◽  
Dose Dependent ◽  
Fibrinogen Deposition

SummaryMembrane glycoprotein αIIbβ3 on platelets plays a pivotal role in hemostasis by mediating RGD-(arginine-glycine-aspartic acid)-dependent platelet adhesion and aggregation. Antagonists of αIIbβ3 ligand binding function, such as antibodies, snake venom peptides, or synthetic RGD-containing peptides can completely inhibit platelet aggregation in vitro and cause significant prolongation of bleeding times when injected into experimental animals. The in vitro and in vivo properties of an αIIbβ3 specific RGD-containing peptide 2G (G(Ten)GHRGDLRCA) were compared to two non-specific RGD-containing peptides IN (G(Pen)GRGDTPCA) and 2H (GRGDSPDG). All three peptides have similar IC50 values in human patelet aggregation (14-22 μM) and ELISA-based μIIbβ3 receptor assays (0.2–0.3 αM) but show different inhibitory activity (IC50 values) in the αv㯂5 (2G = 10 μM; IN = 0.06 μM; 2H = 0.05 μM) and receptor assays (2G = 8.3 μM; IN = 0.06 μM; 2H = 0.04). The αIIbβ3 specific peptide 2G had no effect on monolayers of human saphenous vein endothelial cells while IN and 2H caused many cells to detach and contract. Peptides 2G and IN inhibited ADP-stimulated ex vivo platelet aggregation in dogs in a dose dependent manner. When complete inhibition (>90%) of ex vivo platelet aggregation was achieved with either a 10 mg/kg bolus followed by a 16mg/kg/h infusion of 2G or with a 15 mg/kg bolus and 24 mg/kg/h infusion of IN, peptide IN caused a dose-dependent increase of the template bleeding time, while peptide 2G had no effect, even at doses up to 15 mg/kg bolus followed by 24 mg/kg/h infusion. The in vivo properties of peptides 2G and 2H were also examined in a baboon ex vivo shunt model for their ability to block platelet uptake and fibrinogen deposition on small caliber GORE-TEX® grafts and for their effect on the hemostatic system. Systemic administration of peptide 2G at 10 mg/kg bolus followed by 10 mg/kg/h infusion (or at a 2-fold lower dose) abolished platelet uptake and fibrinogen deposition on the graft surface without affecting the hemostasis and template bleeding time of the animal. By contrast, peptide 2H caused a 3-4-fold increase in bleeding time at a dose of 10 mg/kg. The results suggest that efficacy and the effect of specific aIIbp3antagonists on bleeding time can be separated and that selective aIIbP3 receptor blockade may be an efficient and safe approach to improve the patency and the success rate pf small caliber vascular grafts and to treat unwanted platelet-dependent thromboses. While peptide 2G may represent a unique class of antithrombotic agent, the clinical use of this type of molecule would require a significant enhancement in potency.

Anti-Human VWF Monoclonal Antibody SZ-123 Prevents Arterial Thrombus Formation by Inhibiting VWF–collagen and VWF-Platelet Interactions in Rhesus Monkeys

Blood ◽  
2012 ◽  
Vol 120 (21) ◽  
pp. 5194-5194
Author(s):  
Yiming Zhao ◽  
Changgeng Ruan
Keyword(s):  
Monoclonal Antibody ◽  
Platelet Aggregation ◽  
Bleeding Time ◽  
Conflicts Of Interest ◽  
Ex Vivo ◽  
Thrombus Formation ◽  
Significant Prolongation ◽  
Arterial Thrombus

Abstract Abstract 5194 Objective: To investigate the in vivo antithrombotic efficacy of an anti-VWF monoclonal antibody SZ-123, and its potential underlying mechanism. Methods and Results: Cyclic flow reductions (CFRs) were measured in the femoral artery of monkeys before and after intravenous administration of SZ-123. Ex vivo VWF binding to collagen, platelet aggregation, platelet count and template bleeding time were performed as measurements of antithrombotic activity. In addition, plasma VWF, SZ-123 levels, and VWF occupancy were measured by ELISA. Administration of 0. 1, 0. 3, and 0. 6 mg/kg SZ-123 resulted in 45. 3%, 78. 2%, and 100% reduction in CFRs, respectively. When 0. 3 and 0. 6 mg/kg SZ-123 were administrated, 100% of VWF was occupied by the antibody. Moreover, 100% ex vivo inhibition of VWF-collagen binding and 60–95% inhibition of platelet aggregation were observed from 15 min to 1h. None of the doses resulted in significant prolongation of bleeding time. In vitro experiment also revealed that SZ-123 not only blocks collagen-VWF A3 interaction but also inhibits indirectly VWF A1 binding to GPIba induced by ristocetin. Conclusions: SZ-123 prevents in vivo arterial thrombus formation under high shear conditions by inhibiting VWF A3–collagen and VWF A1-platelet interactions and does not prolong bleeding time. Disclosures: No relevant conflicts of interest to declare.

Identification Of a Novel Small Molecule Inhibitor Of ASK1 As a Potent Anti-Platelet Agent

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 20-20
Author(s):  
Meghna Ulhas Naik ◽  
Maloney David ◽  
Ramya Turaga ◽  
Hidinori Ichijo ◽  
Ulhas P Naik
Keyword(s):  
Platelet Aggregation ◽  
Bleeding Time ◽  
Conflicts Of Interest ◽  
Thrombus Formation ◽  
Receptor Activation ◽  
Human Platelets ◽  
Dependent Manner ◽  
Genetic Ablation ◽  
Fibrinogen Receptor ◽  
Molecule Inhibitor

Abstract Apoptosis signal-regulating kinase (ASK1) is a serine/threonine kinase, belonging to the MAP kinase-kinase-kinase family, which is activated in response to stress. However, its presence and role in platelets are not known. We found that ASK1 is expressed in platelets and is rapidly activated during platelet stimulation by various agonists in a dose-dependent manner. In addition, we found that TRAF2/6, known endogenous activators of ASK1, are expressed in platelets and associate with ASK1 upon platelet activation with agonists. Furthermore, genetic ablation of Ask1 significantly delayed tail-bleeding time (P=0.2x10-9). While WT mice showed an average bleeding time of 100 s, the Ask1 null mice had an average bleeding time of 576 s. A carotid artery injury induced by 10% FeCl3 showed a significantly increased (P=0.0003) time of occlusion and unstable thrombus formation in Ask1 null mice. Furthermore, we found that loss of Ask1 renders significant protection to the mice from pulmonary thromboembolism induced by a mixture of collagen and epinephrine as determined by increased survival and lack of large occlusive thrombi in the lung. We also found that ADP- and AYPGKF (PAR4 receptor peptide) -induced platelet aggregation was diminished in Ask1 null mice compared to WT mice. Furthermore, PAR4 peptide-induced alpha- and dense-granular secretion was also reduced in Ask1 null platelets compared to WT. Interestingly, we also found that Ask1 null platelets bind less FITC-fibrinogen compared to the WT upon activation by PAR4 peptide. Furthermore, thrombin failed to activate MKK6 and p38 in Ask1 knockout platelets, showing that Ask1 is indispensable for p38 activation by thrombin. These results indicated that ASK1 regulates platelet function by augmenting platelet secretion as well as fibrinogen receptor activation, making it an important target for combating thrombosis. We therefore synthesized a novel and highly specific ASK1 inhibitor, N-(6-(1H-imidazol-1-yl)imidazo[1,2-a]pyridin-2-yl)-4-(tert-butyl)benzamide (IPTB) based on the published report. IPTB has been found to be a very potent inhibitor that inhibits ASK1 activity at nM concentrations. IPTB is also highly specific to ASK1 and does not affect activities of related protein kinases such as ASK2, MEKK1, TAK1, and ERK1. We found that in human platelets, IPTB dose-dependently inhibits p38 activation induced by a variety of platelet agonists. Furthermore, IPTB dose-dependently inhibited ADP and PAR4 peptide-induced platelet aggregation. Interestingly, IPTB also dose-dependently inhibited platelet spreading on immobilized fibrinogen. Our results strongly suggest that the dose of IPTB could be adjusted so that it attenuates thrombosis without affecting hemostasis. This development would make IPTB a novel potential therapeutic agent to be used to combat thrombotic disorders. Disclosures: No relevant conflicts of interest to declare.

Fucoidan Is a Novel Platelet Agonist for CLEC-2 Receptor

Blood ◽  
2012 ◽  
Vol 120 (21) ◽  
pp. 94-94
Author(s):  
Bhanukanth Manne ◽  
Todd M Getz ◽  
Craig Hughes ◽  
Carol T Dangelmaier ◽  
Steve P Watson ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Animal Models ◽  
Platelet Activation ◽  
Conflicts Of Interest ◽  
Human Platelets ◽  
Lag Phase ◽  
Dependent Manner ◽  
Wild Type ◽  
Concentration Dependent Manner

Abstract Abstract 94 Fucoidan, a sulphated polysaccharide from fucus vesiculosus, decreases bleeding time and clotting time in hemophilia, possibly through inhibition of tissue factor pathway inhibitor (TFPI) (Prasad et al., Blood 111:672, 2008). The decrease in bleeding times in the hemophilia animal models by in vivo administration of fucoidan suggests the beneficial effect of fucoidan as a novel treatment. Furthermore, in vitro studies using platelet poor plasma from hemophilia animal models and human patients has shown that fucoidan inhibits TFPI thereby contributing to an increase in the extrinsic coagulation pathway activity. The effect of fucoidan on platelets however has not been studied. As it is known that the platelet count remains unaffected in hemophilia A patients and bleeding times are primarily measured to assess normal platelet function, we hypothesize that the decrease in bleeding times in the hemophilia animal models may be due to platelet activation by fucoidan. In this study, we demonstrate for the first time that fucoidan induces platelet activation in a concentration dependent manner. Fucoidan-induced platelet activation is completely abolished by the pan-Src family kinase (SFK) inhibitor, PP2, and in the absence of Syk and PLC-g2. Furthermore, fucoidan-induced platelet activation has a lag phase, which is reminiscent of platelet activation by collagen and by CLEC-2 receptor agonists. Platelet activation by fucoidan however was only slightly inhibited in FcRg-chain null mice indicating that fucoidan is not acting primarily through GPVI receptor. On the other hand, fucoidan-induced platelet activation was inhibited in CLEC-2 deficient mouse platelets revealing CLEC-2 as a physiological target of fucoidan. Thus, our data shows fucoidan as a novel CLEC-2 receptor agonist that activates platelets through an SFK-dependent signaling pathway. Further, the efficacy of fucoidan in hemophilia raises the possibility that decreased bleeding times could be achieved through activation of platelets. A) Fucoidan induces platelet activation: Washed aspirin-treated human platelets were stimulated with increasing concentrations of fucoidan at 37°C. Platelet aggregation was measured using a Lumi-aggregometer. The tracings are representative of data from at least three independent experiments. B) Effect of SFK inhibition on fucoidan-induced platelet activation: Washed aspirin-treated human platelets were pre-treated with SFK inhibitor PP2 10uM or PP3 (vehicle) at 37°C for 5 min followed by stimulation with fucoidan (50 ug/ml) for 3 minutes under stirred conditions. Platelet aggregation was measured using Lumi-aggregometer and effect on phosphorylation of Syk (Y525/26) and LAT (Y191) in the presence of SFK inhibitor PP2 an PP3 (control) were analyzed. The results are representative of data from platelets at least three independent experiments. C) Identifying a possible receptor for fucoidan on platelets: Wild type, FcRg-chain or CLEC-2 null murine platelets were stimulated with fucoidan (50 ug/ml) at 37°C under stirred conditions and aggregation was measured using Lumi-aggregometer. A) Fucoidan induces platelet activation: Washed aspirin-treated human platelets were stimulated with increasing concentrations of fucoidan at 37°C. Platelet aggregation was measured using a Lumi-aggregometer. The tracings are representative of data from at least three independent experiments. . / B) Effect of SFK inhibition on fucoidan-induced platelet activation: Washed aspirin-treated human platelets were pre-treated with SFK inhibitor PP2 10uM or PP3 (vehicle) at 37°C for 5 min followed by stimulation with fucoidan (50 ug/ml) for 3 minutes under stirred conditions. Platelet aggregation was measured using Lumi-aggregometer and effect on phosphorylation of Syk (Y525/26) and LAT (Y191) in the presence of SFK inhibitor PP2 an PP3 (control) were analyzed. The results are representative of data from platelets at least three independent experiments. . / C) Identifying a possible receptor for fucoidan on platelets: Wild type, FcRg-chain or CLEC-2 null murine platelets were stimulated with fucoidan (50 ug/ml) at 37°C under stirred conditions and aggregation was measured using Lumi-aggregometer. Disclosures: No relevant conflicts of interest to declare.

The Effects of Brinolase (Fibrinolytic Enzyme from Aspergillus Oryzae) on Platelet Aggregation of Dog and Man

1972 ◽  
Vol 28 (01) ◽  
pp. 031-048 ◽  
Author(s):  
W. H. E Roschlau ◽  
R Gage
Keyword(s):  
Platelet Aggregation ◽  
Aspergillus Oryzae ◽  
Degradation Products ◽  
Blood Platelet ◽  
Human Platelets ◽  
Fibrinolytic Enzyme ◽  
Inhibitory Effects ◽  
Blood Platelet Aggregation

SummaryInhibition of blood platelet aggregation by brinolase (fibrinolytic enzyme from Aspergillus oryzae) has been demonstrated with human platelets in vitro and with dog platelets in vivo and in vitro, using both ADP and collagen as aggregating stimuli. It is suggested that the optimal inhibitory effects of brinolase occur indirectly through the generation of plasma fibrinogen degradation products, without compromising platelet viability, rather than by direct proteolysis of platelet structures.

scholarly journals Antithrombotic Effect of Crotalin, a Platelet Membrane Glycoprotein Ib Antagonist From Venom of Crotalus atrox

Blood ◽  
1998 ◽  
Vol 91 (5) ◽  
pp. 1582-1589
Author(s):  
Mei-Chi Chang ◽  
Hui-Kuan Lin ◽  
Hui-Chin Peng ◽  
Tur-Fu Huang
Keyword(s):  
Platelet Aggregation ◽  
Latent Period ◽  
Bleeding Time ◽  
Thrombus Formation ◽  
Platelet Membrane ◽  
Dependent Manner ◽  
Glycoprotein Ib ◽  
Platelet Surface ◽  
Dose Dependent

A potent platelet glycoprotein Ib (GPIb) antagonist, crotalin, with a molecular weight of 30 kD was purified from the snake venom ofCrotalus atrox. Crotalin specifically and dose dependently inhibited aggregation of human washed platelets induced by ristocetin with IC50 of 2.4 μg/mL (83 nmol/L). It was also active in inhibiting ristocetin-induced platelet aggregation of platelet-rich plasma (IC50, 6.3 μg/mL). 125I-crotalin bound to human platelets in a saturable and dose-dependent manner with a kd value of 3.2 ± 0.1 × 10−7 mol/L, and its binding site was estimated to be 58,632 ± 3,152 per platelet. Its binding was specifically inhibited by a monoclonal antibody, AP1 raised against platelet GPIb. Crotalin significantly prolonged the latent period in triggering platelet aggregation caused by low concentration of thrombin (0.03 U/mL), and inhibited thromboxane B2formation of platelets stimulated either by ristocetin plus von Willebrand factor (vWF), or by thrombin (0.03 U/mL). When crotalin was intravenously (IV) administered to mice at 100 to 300 μg/kg, a dose-dependent prolongation on tail bleeding time was observed. The duration of crotalin in prolonging tail bleeding time lasted for 4 hours as crotalin was given at 300 μg/kg. In addition, its in vivo antithrombotic activity was evidenced by prolonging the latent period in inducing platelet-rich thrombus formation by irradiating the mesenteric venules of the fluorescein sodium-treated mice. When administered IV at 100 to 300 μg/kg, crotalin dose dependently prolonged the time lapse in inducing platelet-rich thrombus formation. In conclusion, crotalin specifically inhibited vWF-induced platelet agglutination in the presence of ristocetin because crotalin selectively bound to platelet surface receptor-glycoprotein Ib, resulting in the blockade of the interaction of vWF with platelet membrane GPIb. In addition, crotalin is a potent antithrombotic agent because it pronouncedly blocked platelet plug formation in vivo.

scholarly journals Antithrombotic Effect of Crotalin, a Platelet Membrane Glycoprotein Ib Antagonist From Venom of Crotalus atrox

Blood ◽  
1998 ◽  
Vol 91 (5) ◽  
pp. 1582-1589 ◽  
Author(s):  
Mei-Chi Chang ◽  
Hui-Kuan Lin ◽  
Hui-Chin Peng ◽  
Tur-Fu Huang
Keyword(s):  
Platelet Aggregation ◽  
Latent Period ◽  
Bleeding Time ◽  
Thrombus Formation ◽  
Platelet Membrane ◽  
Dependent Manner ◽  
Glycoprotein Ib ◽  
Platelet Surface ◽  
Dose Dependent

AbstractA potent platelet glycoprotein Ib (GPIb) antagonist, crotalin, with a molecular weight of 30 kD was purified from the snake venom ofCrotalus atrox. Crotalin specifically and dose dependently inhibited aggregation of human washed platelets induced by ristocetin with IC50 of 2.4 μg/mL (83 nmol/L). It was also active in inhibiting ristocetin-induced platelet aggregation of platelet-rich plasma (IC50, 6.3 μg/mL). 125I-crotalin bound to human platelets in a saturable and dose-dependent manner with a kd value of 3.2 ± 0.1 × 10−7 mol/L, and its binding site was estimated to be 58,632 ± 3,152 per platelet. Its binding was specifically inhibited by a monoclonal antibody, AP1 raised against platelet GPIb. Crotalin significantly prolonged the latent period in triggering platelet aggregation caused by low concentration of thrombin (0.03 U/mL), and inhibited thromboxane B2formation of platelets stimulated either by ristocetin plus von Willebrand factor (vWF), or by thrombin (0.03 U/mL). When crotalin was intravenously (IV) administered to mice at 100 to 300 μg/kg, a dose-dependent prolongation on tail bleeding time was observed. The duration of crotalin in prolonging tail bleeding time lasted for 4 hours as crotalin was given at 300 μg/kg. In addition, its in vivo antithrombotic activity was evidenced by prolonging the latent period in inducing platelet-rich thrombus formation by irradiating the mesenteric venules of the fluorescein sodium-treated mice. When administered IV at 100 to 300 μg/kg, crotalin dose dependently prolonged the time lapse in inducing platelet-rich thrombus formation. In conclusion, crotalin specifically inhibited vWF-induced platelet agglutination in the presence of ristocetin because crotalin selectively bound to platelet surface receptor-glycoprotein Ib, resulting in the blockade of the interaction of vWF with platelet membrane GPIb. In addition, crotalin is a potent antithrombotic agent because it pronouncedly blocked platelet plug formation in vivo.

Arginine vasopressin release from human platelets after irreversible aggregation

1990 ◽  
Vol 78 (1) ◽  
pp. 113-116 ◽  
Author(s):  
Giovanni Anfossi ◽  
Elena Mularoni ◽  
Mariella Trovati ◽  
Paola Massucco ◽  
Luigi Mattiello ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Arginine Vasopressin ◽  
Platelet Rich Plasma ◽  
Human Platelets ◽  
Vasopressin Release ◽  
Irreversible Aggregation ◽  
Local Release

1. The release of arginine vasopressin from human platelets was investigated in platelet-rich plasma after irreversible aggregation induced by adenosine 5′-pyrophosphate, collagen, sodium arachidonate, thrombin and adrenaline in vitro. 2. Arginine vasopressin levels were significantly higher in the supernatant from stimulated platelet-rich plasma than from unstimulated samples, reaching 3.5 × 10−12 (range 1.6–12.5 × 10−12) mol/l in the absence of an aggregating agent, 8.8 × 10−12 (range 4.2–17.5 × 10−12) mol/l after adenosine 5′-pyrophosphate, 13.7 × 10−12 (2.2–63.2 × 10−12) mol/l after collagen, 7.8 × 10−12 (2.2–14.6 × 10−12) mol/l after sodium arachidonate, 7.8 × 10−12 (2.2–16.3 × 10−12) mol/l after thrombin and 12.2 × 10−12 (4.8–32.1 × 10−12) mol/l after adrenaline. 3. An arginine vasopressin level of 18 × 10−12 mol/l, which can be achieved physiologically, increased the sensitivity of platelets to adenosine 5′-pyrophosphate and collagen in vitro; the same concentration of arginine vasopressin caused a potentiation of the effect of catecholamines on the response of platelets to sodium arachidonate. 4. These results indicate that intraplatelet arginine vasopressin is released during aggregation and suggest that a local release of arginine vasopressin could occur after complete platelet aggregation in vivo.

scholarly journals Survival and recovery of human platelets stored for five days in a non- plasma medium

Blood ◽  
1986 ◽  
Vol 67 (3) ◽  
pp. 672-675 ◽  
Author(s):  
GA Adams ◽  
SD Swenson ◽  
G Rock
Keyword(s):  
Platelet Aggregation ◽  
Human Blood ◽  
Blood Platelets ◽  
Human Platelets ◽  
Plasma Medium ◽  
Release Reaction ◽  
In Vivo Recovery ◽  
Human Blood Platelets

Abstract Human blood platelets were stored for five days as concentrates in 60 mL of: (a) plasma; (b) non-plasma medium with anticoagulant; and (c) non-plasma medium without anticoagulant. All preparations were equally functional when tested for platelet aggregation and release reaction in response to single agonist or synergistic pairs of agonists in vitro. Platelets stored in non-plasma medium with anti-coagulant had lower kallikrein, fibrino(gen)peptide A, lactate, and beta-thromboglobulin than did plasma controls after five days. In vivo recovery and survival of platelets stored in non-plasma medium with anticoagulant were 51.2% +/- 4.3% and 8.7 +/- 0.3 days, respectively, which were not statistically different from plasma controls of 39.2% +/- 4.9% and 7.2 +/- 0.8 days, respectively. It is concluded that platelets can be stored for five days in a non-plasma medium and still have good in vivo recoveries and survivals.

Sign in / Sign up

Export Citation Format

Share Document