PubMed · 14958227
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P A OWREN. 1952. [Proconvertin].. https://pubmed.ncbi.nlm.nih.gov/14958227/
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The aim of this study was to investigate whole blood coagulation on low blood plasma protein adsorbing surfaces. For this purpose, the polycationic graft copolymer poly(L-lysine)-g-poly(ethylene glycol) (PLL-g-PEG), PLL-g-PEG grafted with a cell adhesive peptide containing the amino acid sequence -Arg-Gly-Asp- (RGD), and PLL-g-PEG with a control peptide -Arg-Asp-Gly- (RDG) were adsorbed onto titanium (oxide), forming stable monomolecular adlayers through electrostatic attraction. Free oscillation rheometry and complementary techniques were used to measure the coagulation time (CT) and other interactions of the surfaces with native whole blood, recalcified platelet-rich plasma (PRP), and recalcified citrated platelet-free plasma (PFP). The results show that the uncoated titanium surfaces (reference) activated platelets and quickly triggered the coagulation cascade via the intrinsic pathway, whereas the PLL-g-PEG surfaces displayed a prolonged CT, approximately 2-3 times longer compared to uncoated titanium. We hypothesise that blood coagulates outside the vascular system independent of low protein adsorption to or activation by surfaces, due to the absence of an active down-regulation of procoagulative processes by the vascular endothelium.
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Cellular microparticles support coagulation by exposure of negatively charged phospholipids and sometimes tissue factor. They are involved in inflammatory processes, the transfer of membrane antigens and bioactive molecules, and in the modulation of endothelial functions. Patients with disturbances in membrane vesiculation, leading to decreased numbers of circulating microparticles, present clinically with an increased bleeding tendency. In contrast, elevated numbers of microparticles are found in a great variety of diseases involving blood-vessel damage and hypercoagulability. Microparticles are also a major component of human atherosclerotic plaques. In view of their functional properties, cellular microparticles may be a missing link between cellular and plasmatic processes underlying atherosclerotic blood-vessel damage.