title: The structural properties and contractile force of a clot.
abstract: When citrated plasma is recalcified, it forms a viscoelastic gel--a clot. The relationship between platelet contractility and clot rigidity was studied by using a rheological technique which simultaneously measured both the dynamic rigidity modulus and the contractile force during gel formation with platelet rich plasma (PRP). Protein network formation in a clot was accompanied by a contractile force throughout the clotting process. PRP demonstrated a maximum elastic modulus of 6,000 dynes/cm2 and a maximum contractile force/area of 1,500 dynes/cm2. The values of these parameters for a platelet-free clot (PFP) were 700 dynes/cm2 and less than 100 dynes/cm2 respectively. Sonicated control PRP and PRP from a Glanzmann thrombasthenia patient both clotted in a manner similar to PFP. Metabolic inhibitors, 2-deoxy-D-glucose and KCN (5 mM each), retarded the clotting curves of PRP. Cytochalasin B and E suppressed both structural rigidity and force generation in a concentration-dependent manner similar to their inhibitory effect on actin polymerization in platelets. Colchicine (2.5 mM) or vinblastine (0.11 mM) did not affect these clotting curves. Thrombin-activated, fixed platelets did not generate any force, nor did they significantly increase clot rigidity. Streptokinase induced a concurrent decrease of both rigidity and force in PRP clots. The elastic modulus of a PFP clot could be increased to 2,500 dynes/cm2 by externally straining the network with an axial force/area of 1,500 dynes/cm2. Our results indicate that clot structure formation in PRP is strongly coupled to the contractile force generated by the platelet microfilament system and that this force modulates clot rigidity.
mesh_terms: D001777:Blood Coagulation / Q000187:drug effects; D001792:Blood Platelets / Q000502:physiology* / Q000648:ultrastructure; D003078:Colchicine / Q000494:pharmacology; D003572:Cytochalasins / Q000494:pharmacology; D003599:Cytoskeleton / Q000502:physiology*; D003847:Deoxyglucose / Q000494:pharmacology; D004548:Elasticity; D006801:Humans; D011190:Potassium Cyanide / Q000494:pharmacology; D013300:Streptokinase / Q000494:pharmacology; D013917:Thrombin / Q000494:pharmacology; D014747:Vinblastine / Q000494:pharmacology
chemical_list: D003572:Cytochalasins; D014747:Vinblastine; D003847:Deoxyglucose; D013300:Streptokinase; D013917:Thrombin; D011190:Potassium Cyanide; D003078:Colchicine