title: Platelet aggregation through prothrombinase activation induced by non-aggregant doses of platelet agonists.
abstract: Activation of the prothrombinase complex, which catalyzes the formation of thrombin from prothrombin, is crucial for the (patho)physiological processes of hemostasis and thrombosis. We here report that washed platelets supplemented with prothrombin can be irreversibly aggregated with otherwise non-aggregant doses of adenosine diphosphate (10 micromol/l), thrombin (0.06 U/ml), or collagen (1 microg/ml). Prothrombinase-catalyzed prothrombin to thrombin conversion most probably supports this aggregation response, since inhibitors of thrombin (hirudin or heparin) and an inhibitor of activated factor X (DX-9065a) impair the response. A certain degree of agonist-induced platelet activation seems to be required for this prothrombin-supported aggregation response, since prothrombin alone does not induce aggregation, and blockade of glycoprotein Ia/IIa with a specific antibody inhibits the platelet aggregation response to collagen and prothrombin. These results may suggest that activation of the prothrombinase complex could be a common step of the platelet response to distinct agonists, which may be achieved at low levels of platelet stimulation.
authors.affiliation: Unit of Hematology and Medical Oncology, Hospital General Universitario Morales Meseguer, Murcia, Spain.
authors.forename: J
authors.initials: J
authors.lastname: Corral
authors.forename: R
authors.initials: R
authors.lastname: González-Conejero
authors.forename: C
authors.initials: C
authors.lastname: Martínez
authors.forename: J
authors.initials: J
authors.lastname: Rivera
authors.forename: M L
authors.initials: ML
authors.lastname: Lozano
authors.forename: V
authors.initials: V
authors.lastname: Vicente
mesh_terms: D000244:Adenosine Diphosphate / Q000494:pharmacology; D000818:Animals; D002417:Cattle; D003094:Collagen / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D004789:Enzyme Activation / Q000187:drug effects; D005170:Factor X / Q000494:pharmacology; D015951:Factor Xa / Q000494:pharmacology; D006801:Humans; D038982:Integrin alpha2beta1; D010974:Platelet Aggregation / Q000187:drug effects*; D011516:Prothrombin / Q000378:metabolism / Q000494:pharmacology; D038981:Receptors, Collagen / Q000037:antagonists & inhibitors; D013917:Thrombin / Q000494:pharmacology; D013925:Thromboplastin / Q000187:drug effects / Q000378:metabolism*
chemical_list: D038982:Integrin alpha2beta1; D038981:Receptors, Collagen; C468113:type I collagen receptor; D000244:Adenosine Diphosphate; D011516:Prothrombin; D005170:Factor X; D003094:Collagen; D013925:Thromboplastin; D013917:Thrombin; D015951:Factor Xa