Adherent platelets, secretion

Secretion of Granule Contents from Adherent Platelets... 

Platelets adherent to collagen change shape and spread out on the subendothelium. They release the contents of their storage granules (the dense granules and the alpha granules) secretion is also stimulated by thrombin. 

The work to be discussed here deals with platelet adhesion to protein coated surfaces. The protein coating, the cells on the surface and the moving fluid adjacent to the surface may be viewed as a system of interacting components. Flow is an important feature of this system since it brings new protein and cells to the system, augments the transport of cells to the surface and can cause the detachment of adherent cells. Each component of the system may influence the conditions of the other components. The variation of the surface concentrations of proteins on a solid substrate continues to be studied and remains a key area of interest. However, the action of immobilized cells on the substrate needs to be examined more carefully as well as their contribution of secreted substances to the fluid phase adjacent to the substrate and to the substrate protein itself Red cells, platelets and white cells may also adhere and detach from the substrate changing its make-up by yet another mechanism. 

The amount of ATP release from human platelets on SPEAs (an indication of hemocompatibility) was 2-fold lower than on the above nondegradable polymers. In addition, monocytes adherent onto saturated PEA induced far less secretion of proinflammatory cytokines such as interleukin (IL)-6 and IL-1 when compared with the tissue culture-treated polystyrene control. Therefore, saturated PEAs appear to support a more natural wound healing process by promoting reendothelialization and lowering inflammatory response. 

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