title: Platelet size distribution measurements as indicators of shear stress-induced platelet aggregation.
abstract: The mechanisms underlying shear stress-induced platelet aggregation (SIPA) were investigated by measuring changes in the platelet size distributions resulting from the exposure of human platelet-rich plasma (PRP) to well-defined shear stresses in a modified viscometer. Exposure of PRP to a shear stress of 100 dyne/cm2 for 1 min at 37 degrees C resulted in the loss of single platelets, an overall shift in the distribution to larger particle sizes, and the generation of platelet fragments. Treatment of PRP prior to shearing with a monoclonal antibody directed against platelet glycoprotein (GP) IIb-IIIa (integrin alpha IIb beta 3) at a concentration that completely inhibited ADP-induced platelet aggregation also inhibited SIPA. Furthermore, incubation of PRP with a recombinant fragment of von Willebrand factor (vWF) that abolishes ristocetin-induced platelet agglutination significantly inhibited but did not eliminate SIPA. Pretreatment of PRP with the tetrapeptides RGDS or RGDV, which constitute the GP IIb-IIIa peptide recognition sequences on fibrinogen and vWF, almost completely blocked platelet aggregation at 100 dyne/cm2, whereas the negative control peptide RGES had no discernible effect. Finally, incubation of PRP with a monoclonal antibody directed against the platelet vitronectin receptor (integrin alpha v beta 3) did not affect SIPA. These results indicate that both GP IIb-IIIa and GP Ib, the latter through its interaction with vWF, are required for SIPA at 100 dyne/cm2; that the interaction of GP IIb-IIIa with its adhesive ligands under shear stress can be inhibited by RGD-containing peptides; and that the vitronectin receptor on platelets, which shares the same beta 3 subunit as GP IIb-IIIa, plays no role in SIPA.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Biomedical Engineering, University of Tennessee, Memphis.
authors.forename: S M
authors.initials: SM
authors.lastname: Slack
authors.forename: L K
authors.initials: LK
authors.lastname: Jennings
authors.forename: V T
authors.initials: VT
authors.lastname: Turitto
mesh_terms: D000911:Antibodies, Monoclonal; D001792:Blood Platelets / Q000166:cytology* / Q000378:metabolism; D048429:Cell Size; D006023:Glycoproteins / Q000378:metabolism; D006801:Humans; D016023:Integrins / Q000378:metabolism; D010974:Platelet Aggregation; D019039:Platelet Glycoprotein GPIIb-IIIa Complex; D016024:Receptors, Cytoadhesin / Q000378:metabolism; D019030:Receptors, Vitronectin; D012212:Rheology; D013314:Stress, Mechanical; D019096:Vitronectin; D014841:von Willebrand Factor / Q000378:metabolism
chemical_list: D000911:Antibodies, Monoclonal; D006023:Glycoproteins; D016023:Integrins; D019039:Platelet Glycoprotein GPIIb-IIIa Complex; D016024:Receptors, Cytoadhesin; D019030:Receptors, Vitronectin; D019096:Vitronectin; D014841:von Willebrand Factor