title: Platelet phosphatidylserine exposure and procoagulant activity in clotting whole blood--different effects of collagen, TRAP and calcium ionophore A23187.
abstract: We have studied the effects of different platelet agonists on phosphatidylserine (PS) exposure and clotting times in blood without anticoagulants. Similar reductions in clotting time were obtained for collagen, TRAP-6 or calcium ionophore A23187 (50 micro mol/L), in spite of huge differences in PS expression [6.7 +/- 2.4%, 2.3 +/- 0.5% and 99.9 +/- 0.1%, respectively (mean +/- SD, n = 5)]. Furthermore, the clotting times were much longer for samples with A23187 exposing the same amounts of PS as samples with collagen or TRAP-6. Annexin V reversed the clotting time reduction, but could not prevent coagulation. Addition of phospholipid vesicles containing 20% PS neither affected the clotting times nor induced clotting in recalcified, platelet-free plasma. We conclude that platelet PS exposure is necessary, but not sufficient, for the coagulation amplification observed when platelets are stimulated via physiological receptors in a whole blood environment.
authors.affiliation: Department of Biomedicine and Surgery, Division of Clinical Chemistry, University Hospital, SE-581 85 Linköping, Sweden. sofra@ifm.liu.se
authors.forename: Sofia
authors.initials: S
authors.lastname: Ramström
authors.forename: Mats
authors.initials: M
authors.lastname: Rånby
authors.forename: Tomas L
authors.initials: TL
authors.lastname: Lindahl
mesh_terms: D017304:Annexin A5 / Q000494:pharmacology; D001777:Blood Coagulation / Q000187:drug effects*; D001792:Blood Platelets / Q000378:metabolism / Q000648:ultrastructure; D000001:Calcimycin / Q000494:pharmacology; D003094:Collagen / Q000494:pharmacology; D006801:Humans; D008081:Liposomes / Q000494:pharmacology; D010446:Peptide Fragments / Q000494:pharmacology; D010718:Phosphatidylserines / Q000378:metabolism / Q000502:physiology*; D015539:Platelet Activation / Q000187:drug effects / Q000502:physiology*
chemical_list: D017304:Annexin A5; D008081:Liposomes; D010446:Peptide Fragments; D010718:Phosphatidylserines; C082835:thrombin receptor peptide (42-47); D000001:Calcimycin; D003094:Collagen