title: Platelet heterogeneity: variation in coagulation complexes on platelet subpopulations.
abstract: OBJECTIVE
  Previous work has shown that platelets stimulated with the combination of thrombin and convulxin, a glycoprotein VI agonist, develop 2 populations with different levels of alpha-granule factor V bound to the platelet surface. To evaluate whether this phenomenon is restricted to alpha-granule components or is a feature that can be generalized to other coagulation factors, we studied the binding of factors V, VIII, IX, and X on the surface of platelets stimulated by convulxin and thrombin.
  
  
  RESULTS
  The relative amount of factors V, VIII, IX, and X on the surface of platelets stimulated with thrombin or convulxin plus thrombin was measured using flow cytometry. Simultaneous measurements of factor Xa and thrombin generation were obtained and correlated with the binding of coagulation factors on the platelet surface. The binding of factors V, VIII, IX, and X all increased on a subpopulation of platelets when stimulated with the combined agonists. The development of this platelet subpopulation is dependent on convulxin concentration and correlates with increases in factor Xa and thrombin generation.
  
  
  CONCLUSIONS
  The development of increased coagulation factor binding to a subpopulation of platelets is not limited to alpha-granule components. Convulxin-induced increases in thrombin generation are regulated by the proportion of platelets with increased coagulation factor binding.
authors.affiliation: University of North Carolina, Chapel Hill, NC 27599-7035, USA.
authors.forename: Christine L
authors.initials: CL
authors.lastname: Kempton
authors.forename: Maureane
authors.initials: M
authors.lastname: Hoffman
authors.forename: Harold R
authors.initials: HR
authors.lastname: Roberts
authors.forename: Dougald M
authors.initials: DM
authors.lastname: Monroe
mesh_terms: D001777:Blood Coagulation / Q000502:physiology*; D001792:Blood Platelets / Q000166:cytology* / Q000502:physiology*; D003435:Crotalid Venoms / Q000494:pharmacology; D005164:Factor IX / Q000378:metabolism; D005165:Factor V / Q000378:metabolism; D005169:Factor VIII / Q000378:metabolism; D005170:Factor X / Q000378:metabolism; D006490:Hemostatics / Q000378:metabolism / Q000494:pharmacology; D006801:Humans; D066298:In Vitro Techniques; D037181:Lectins, C-Type; D015539:Platelet Activation / Q000187:drug effects / Q000502:physiology*; D010980:Platelet Membrane Glycoproteins / Q000378:metabolism; D018179:Receptors, Thrombin / Q000378:metabolism; D013917:Thrombin / Q000378:metabolism / Q000494:pharmacology
chemical_list: D003435:Crotalid Venoms; D006490:Hemostatics; D037181:Lectins, C-Type; D010980:Platelet Membrane Glycoproteins; D018179:Receptors, Thrombin; C098341:platelet membrane glycoprotein VI; C028890:convulxin; D005165:Factor V; D005169:Factor VIII; D005164:Factor IX; D005170:Factor X; D013917:Thrombin