Impaired factor X and prothrombin activation associated with decreased phospholipid exposure in platelets from a patient with a bleeding disorder.
Platelets from a platelet factor 3-deficient patient, which was first described by Weiss et al (Am J Med 67:206, 1979), were found to be equally impaired in their ability to promote factor X and prothrombin activation. Compared to normal platelets, the patient's platelets showed upon stimulation with thrombin plus collagen a much slower generation and a considerably lower level of platelet prothrombin- and factor X-converting activities. Treatment of stimulated platelets with phospholipases revealed a decreased exposure of negatively charged phospholipid at the outer surface of the patient's platelets, relative to control's. We suggest that the combined impairment of prothrombin- and factor X-converting activities in this patient is due to a defect in the mechanism by which phosphatidylserine becomes exposed at the outer surface of stimulated platelets.
D001778:Blood Coagulation Disorders / Q000097:blood*; D001792:Blood Platelets / Q000201:enzymology*; D003094:Collagen / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D005165:Factor V / Q000502:physiology; D015943:Factor Va; D005170:Factor X / Q000096:biosynthesis*; D005260:Female; D006801:Humans; D010743:Phospholipids / Q000097:blood / Q000172:deficiency*; D011516:Prothrombin / Q000096:biosynthesis*; D013917:Thrombin / Q000494:pharmacology; D013925:Thromboplastin / Q000097:blood / Q000378:metabolism
D010743:Phospholipids; D015943:Factor Va; D005165:Factor V; D011516:Prothrombin; D005170:Factor X; D003094:Collagen; D013925:Thromboplastin; D013917:Thrombin