Adhesion of platelets

Adhesion of platelets to ligands such as collagen on the subendothelial matrix... 

CD42 represents the GPIb-IX-V complex, which is a receptor for von Wille-brand factor that is critical for the adhesion of platelets to damaged blood vessels. This marker is down-regulated on activation of platelets. 

Lee and Matsuda modified a segmented polyurethane film with a dithio-carbamate moiety and then initiated the polymerization of (ethylene glycol) methacrylate and N,N-dimethylacrylamide [35]. The resulting films were hy-drophihc and were shown to inhibit adhesion of platelets. Such films could be useful as anti-coagulant substrates for devices implanted in vivo. 

Fig. 11. Adsorption of 125I-labeled IgG and adhesion of platelet to the surface of PAAm-graft-ed PU films as a function of graft density (A) IgG (virgin, A), (O) platelet (virgin, )...

The adhesion of platelets to the subendothelial matrix via specific adhesive GPs is the initial step in primary hemostasis. Binding of platelets to the matrix results in rapid (Fig, 2) morphological conversion of platelets from flat discs to spiny spheres. 

Ruckenstein, E., A. Marmur and S. R. Rakower. 1976. Sedimentation and Adhesion of Platelets from Platelet Rich Plasma onto Glass Surface. submitted for publication. Ruekenstein, E. and D. C. Prieve. 1975. Dynamics of Cell Deposition on Surfaces. J. Theor. Biol., 51, 429-438. 

The specific platelet surface receptors that support these initial adhesive interactions are determined by the local fluid dynamic conditions of the vasculature and the extracellular matrix constituents exposed at the sites of vascular injury. Konstantopolous et al. (1998) and Alveriadou et al. (1993) demonstrated that under high shear conditions, the adhesion of platelets to exposed subendothelial surfaces of atherosclerotic or injured vessels presenting collagen and von Willebrand factor (vWF) is primarily mediated by the platelet glycoprotein (GP)Ib/IX/V complex. This primary adhesion to the matrix activates platelets, leading ultimately to platelet aggregation mediated... 

Relationships between Adsorption of Plasma Proteins and Adhesion of Platelets... 

Activation of Clotting and Adhesion of Platelets. It has been reported (45) that all uncharged hydrophobic surfaces adsorb the same proteins from plasma in the same undestructive way, but the adsorbed proteins are yet unidentified. 

Although the data show a relationship between the ability of a surface to adsorb fibrinogen out of plasma, the plasma s inability to convert this fibrinogen, and the tendency of platelets to adhere, it does not confirm that adsorption of fibrinogen must precede adhesion of platelets to all kinds of surface, or that surfaces which adsorb fibrinogen under these conditions will be bad biomaterials in vivo as heart valves, blood vessels, or canulae, or ex vivo as artificial kidney membranes—even though the latter are most likely to be impeded by any adsorbate. 

When a blood vessel wall is damaged, platelets are exposed to a variety of activating agents including collagen. The adhesion of platelets to vascular subendothelium is a... 

Tschopp TB, Weiss HJ, Baumgartner HR Decreased adhesion of platelets to subendothelium in von Willebrand s disease. J Lab Clin Med 83 296-300,1974... 

Zaidi TN, Mclntire LV, Farrell DH, Thiagarajan P. Adhesion of platelets to surface bound fiMnogen under flow. Blood 1996 88 2967-2972. 

Adhesion of platelets onto a damaged vascular sur ce is the primary event in the formaticHi ofd hemostatic plug. For perfect hemostatic performance, this initial adhesion step should be followed by further deposition of platelets onto the initial adherent layer rmtil an effective microthrombi is formed at the site of damage. Formation of s hemostatic plug is the result of a well recognized series of interactions among platelet glycoproteins, plasma adhesive proteins and components of the subendothelium. 

Fibronectin is present in plasma, subendothelium and platelet alpha granules. Despite containing the RGD sequence, the role of fibronectin in adhesive and cohesive properties of platelets seems less important. It has been suggested that plasma fibronectin would not be required for platelets to adhere on vascular extracellular matrices [45]. However, studies with plasma depleted of fibronectin seem to indicate that this adhesive protein could play a role in mediating adhesion of platelet and thrombus formation on collagen rich surfaces [46]. As will be commented on later, the mote recent studies suggest that vascular fibronectin would mediate platelet adhesion under certain experimental conditions [47]. 

Sixma JJ, Sakariassen KS, Beeser-Visser NH, Ott nhof-Rovers M, Boihuis PA Adhesion of platelets to human artery subendothelium effect of factor Vlll-von Will and factor of various multimeric conqx>sition. Blood 63 128-139,1984. 

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