Characterisation of species differences in the platelet ADP and thrombin response

Department of Molecular Pharmacology, Preclinical R and D, AstraZeneca R and D, Mölndal, 431 83 Mölndal, Sweden.
Thrombosis Research (Impact Factor: 2.45). 02/2006; 117(5):543-9. DOI: 10.1016/j.thromres.2005.04.026
Source: PubMed


A number of animal models are used to study platelet-dependent diseases. In the present investigation, we have used a simple flow cytometry assay to evaluate platelet function in man, rat, mouse, guinea pig and dog.
Platelet activation was evaluated in diluted whole blood by measuring fibrinogen binding to activated platelets using a polyclonal anti-human fibrinogen antibody that cross-reacts with fibrinogen from all species tested. The assay was used to evaluate platelet function with respect to ADP and thrombin sensitivity. The relative importance of the two platelet ADP receptors and total ADP in the thrombin response was also studied by using receptor-specific antagonists and apyrase, respectively.
Mouse platelets were most sensitive to both agonists. Unlike in man and dog the maximal response to ADP was greater than to thrombin in mouse, rat and guinea pig. P2Y(12) blockade was in all species equally effective as ADP removal in inhibiting thrombin-induced platelet activation whereas P2Y(1) blockade was almost ineffective.
The present study describes a simple platelet function test that can be used to evaluate platelet function in man, rat, mouse, guinea pig and dog. Platelets from the tested species differed in their sensitivity to ADP and thrombin. In contrast to human and canine platelets, mouse, rat and guinea pig platelets displayed a stronger maximal response to ADP than to thrombin. In terms of the relative contribution of P2Y(1) and P2Y(12) in the thrombin response, the P2Y(12) receptor was the key receptor in all species and its blockade gave equal effect as total removal of ADP.

7 Reads

  • [Show abstract] [Hide abstract]
    ABSTRACT: Thrombosis is a major cause of poor patency in synthetic vascular grafts for small diameter vessel (< 6 mm) bypass. Arteries have a host of structural mechanisms by which they prevent triggering of platelet activation and the clotting cascade. Many of these are present in vascular endothelial cells. These mechanisms act together with perpetual feedback at different levels, providing a constantly fine-tuned non-thrombogenic environment. The arterial wall anatomy also serves to promote thrombosis as a healing mechanism when it has been severely injured. Surface modification of synthetic graft surfaces to attenuate the coagulation cascade has reduced thrombosis levels and improved patency in vitro and in animal models. Success in this endeavor is critically dependent on the methods used to modify the surface. Platelets adhere to positively charged surfaces due to their own negative charge. They also preferentially attach to hydrophobic surfaces. Therefore synthetic graft development is concerned with hydrophilic materials with negative surface charge. However, fibrinogen has both hydrophilic and hydrophobic binding sites-amphiphilic materials reduce its adhesion and subsequent platelet activation. The self-endothelializing synthetic graft is an attractive proposition as a confluent endothelial layer incorporates many of the anti-thrombogenic properties of arteries. Surface modification to promote this has shown good results in animal models. The difficulties experienced in achieving spontaneous endothelialisation in humans have lead to the investigation of pre-implantation in vitro endothelial cell seeding. These approaches ultimately aim to result in novel synthetic grafts which are anti-thrombogenic and hence suitable for coronary and distal infrainguinal bypass.
    Journal of Biomedical Materials Research Part B Applied Biomaterials 07/2007; 82(1):100-8. DOI:10.1002/jbm.b.30710 · 2.76 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Adenosine A(2) agonists improve arterial patency in experimental models of recurrent thrombosis, an effect purportedly triggered by stimulation of platelet A(2) receptors and subsequent down-regulation of platelet function. However: (i) there is no direct evidence to substantiate this premise; and (ii) given the recognized differences among species in platelet signaling, it is possible that the mechanisms of A(2) receptor stimulation may be model-dependent. Accordingly, we applied an integrated in vivo and in vitro approach, using both canine and human models, to test the hypothesis that the anti-thrombotic effects of A(2) agonist treatment are due in part to inhibition of platelet activation. In Protocol 1, recurrent coronary thrombosis was triggered in anesthetized dogs by application of a stenosis at a site of arterial injury. Coronary patency and flow cytometric indices of platelet activation (P-selectin expression; formation of heterotypic aggregates) were compared in dogs pre-treated with the A(2) agonist CGS 21680 versus controls. In Protocols 2 and 3, blood samples were obtained from dogs and human volunteers. In vitro aggregation and platelet activation (assessed by impedance aggregometry and flow cytometry, respectively) were quantified in paired aliquots pre-incubated with CGS versus vehicle. In the canine models, CGS improved in vivo coronary patency and attenuated in vitro aggregation but, contrary to our hypothesis, did not evoke a down-regulation in platelet activation. In contrast, in human blood samples, CGS attenuated both in vitro aggregation and flow cytometric markers of platelet activation-aggregation. The mechanisms contributing to the anti-thrombotic effect of A(2) agonist treatment are species-dependent: adenosine A(2) receptor stimulation inhibits platelet activation in human, but not canine, models.
    Thrombosis Research 02/2008; 121(5):689-98. DOI:10.1016/j.thromres.2007.07.002 · 2.45 Impact Factor
Show more

Similar Publications