title: Plasmin effect on platelet glycoprotein Ib-von Willebrand factor interactions.
abstract: We have studied the effect of streptokinase on platelets in platelet-rich plasma (PRP) and of plasmin on washed platelets. By three and one-half minutes after the addition of 50,000 IU/mL streptokinase to PRP, the maximum rate of ristocetin-induced platelet agglutination declined 40%, and by 60 minutes, it declined 70%. During the same time interval, the thrombin time increased from 20 seconds to over 120 seconds. At a concentration as low as 50 IU/mL, streptokinase reduced the maximum rate of ristocetin-induced platelet agglutination by 50% and prolonged the thrombin time to 1.5 times control value. Streptokinase added to PRP also caused inhibition of platelet aggregation following stimulation by 2.9 mumol/L adenosine diphosphate, 0.25 U/mL thrombin, and 0.025 mg/mL collagen. Plasmin, 0.05 to 1.0 CU/mL, reduced ristocetin-mediated agglutination of washed platelets in the presence of von Willebrand factor (vWF) from 66% of control to 2% of control, following a one-hour incubation. Autoradiograms produced following sodium dodecyl-polyacrylamide gel electrophoresis (SDS-PAGE) of plasmin-treated 125I-surface-labeled platelets demonstrated progressive loss of a protein with a molecular weight (mol wt) of 180,000; simultaneously, a protein with mol wt 135,000 appeared on autoradiograms produced following SDS-PAGE of the surrounding platelet medium. These proteins are similar in molecular weight to glycoprotein (gp) Ib, a platelet surface receptor for vWF, and glycocalicin, a proteolytic fragment of gpIb. By use of an enzyme-linked immunosorbent assay (ELISA) based immunoinhibition assay for glycocalicin, we were able to demonstrate that plasmin treatment of washed platelets released a glycocalicin-related antigen into the surrounding medium and that appearance of this material corresponding to loss of vWF-dependent, ristocetin-induced agglutination.
authors.forename: B
authors.initials: B
authors.lastname: Adelman
authors.forename: A D
authors.initials: AD
authors.lastname: Michelson
authors.forename: J
authors.initials: J
authors.lastname: Loscalzo
authors.forename: J
authors.initials: J
authors.lastname: Greenberg
authors.forename: R I
authors.initials: RI
authors.lastname: Handin
mesh_terms: D001779:Blood Coagulation Factors / Q000378:metabolism*; D004347:Drug Interactions; D005341:Fibrinolysin / Q000494:pharmacology*; D005557:Formaldehyde / Q000494:pharmacology; D006023:Glycoproteins / Q000032:analysis / Q000378:metabolism*; D006801:Humans; D066298:In Vitro Techniques; D007519:Isoantigens / Q000032:analysis; D008565:Membrane Proteins / Q000032:analysis / Q000378:metabolism*; D008970:Molecular Weight; D010974:Platelet Aggregation / Q000187:drug effects; D019038:Platelet Glycoprotein GPIb-IX Complex; D010980:Platelet Membrane Glycoproteins; D012310:Ristocetin / Q000378:metabolism; D013300:Streptokinase / Q000494:pharmacology; D014841:von Willebrand Factor / Q000378:metabolism*
chemical_list: D001779:Blood Coagulation Factors; D006023:Glycoproteins; D007519:Isoantigens; D008565:Membrane Proteins; D019038:Platelet Glycoprotein GPIb-IX Complex; D010980:Platelet Membrane Glycoproteins; C023592:glycocalicin; D014841:von Willebrand Factor; D012310:Ristocetin; D005557:Formaldehyde; D013300:Streptokinase; D005341:Fibrinolysin