title: Role of platelet GpIIb/IIIa receptors in the modulation of platelet plasminogen activator inhibitors type-1 (PAI-1) release.
abstract: This study was undertaken to determine the role of platelet glycoprotein (GP) IIb/IIIa receptors in the modulation of plasminogen activator type-1 (PAI-1) release from human platelets as compared to other platelet functions. To address this issue, the effect of various agonists on human platelet aggregation, [125I]fibrinogen binding and the release of PAI-1 was examined in normal and Glanzmann's thrombasthenic (GT) platelets. In control subjects, maximum platelet aggregation and PAI-1 secretion were observed within 5 min in response to the different agonists including thrombin, collagen, adenosine diphosphate (ADP), and arachidonic acid. Agonist-induced platelet GpIIb/IIIa receptor activation was confirmed by [125I]fibrinogen binding analysis. In contrast, platelets from GT subjects demonstrated a lack of fibrinogen binding and a lack of an aggregatory response to all agonists tested except to the GPIb- mediated aggregation induced by ristocetin. However, GT platelets demonstrated normal responsiveness in secreting PAI-1 in response to the various agonists. Similarly, when platelet GpIIb/IIIa receptors were blocked in normal platelets by the tripeptide Arg-Gly-Asp (RGD) or the tetrapeptide Arg-Gly-Asp-Ser (RGDS) at 10(-3) M, agonist-induced platelet aggregation and fibrinogen binding were blocked, but platelet PAI-1 release was not blocked. Furthermore, flow cytometric analysis using dual fluorescence markers for the platelet GPIIb/IIIa membrane receptors (FITC-labeled cyclic RGD analog, XL086) and for the alpha granule (PE-monoclonal antibody for P-selectin) demonstrated a dissociation between the platelet GPIIb/IIIa receptors and granular secretion. These results suggest a lack of a role for platelet GpIIb/IIIa receptors in the modulation of platelet PAI-1 release.
authors.affiliation: Du Pont Merck Pharmaceutical Company, Cardiovascular Diseases Research, Experimental Station, Wilmington, DE 19880-0400.
authors.forename: S A
authors.initials: SA
authors.lastname: Mousa
authors.forename: J
authors.initials: J
authors.lastname: Bozarth
authors.forename: M
authors.initials: M
authors.lastname: Forsythe
authors.forename: P
authors.initials: P
authors.lastname: Tsao
authors.forename: L
authors.initials: L
authors.lastname: Pease
authors.forename: T M
authors.initials: TM
authors.lastname: Reilly
mesh_terms: D000595:Amino Acid Sequence; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism*; D005340:Fibrinogen / Q000378:metabolism; D005434:Flow Cytometry; D006801:Humans; D066298:In Vitro Techniques; D008969:Molecular Sequence Data; D009842:Oligopeptides / Q000494:pharmacology; D017395:Plasminogen Activator Inhibitor 1 / Q000378:metabolism*; D010974:Platelet Aggregation; D010980:Platelet Membrane Glycoproteins / Q000378:metabolism*
chemical_list: D009842:Oligopeptides; D017395:Plasminogen Activator Inhibitor 1; D010980:Platelet Membrane Glycoproteins; C047981:arginyl-glycyl-aspartic acid; D005340:Fibrinogen; C046617:arginyl-glycyl-aspartyl-serine