title: Phosphatidylserine surface expression and integrin alpha IIb beta 3 activity on thrombin/convulxin stimulated platelets/particles of different sizes.
abstract: Platelets stimulated by a combination of thrombin/convulxin have been shown to develop two to three populations characterized by different phosphatidylserine (PS) surface expression and integrin alpha IIb beta 3 activity. To determine how these markers are distributed on the surface of platelets/particles, we studied Annexin V and PAC-1 binding to platelets/particles of different sizes by flow cytometry analysis and evaluated influences of calpain and caspase inhibitors on thrombin/convulxin-activated platelets. Analysed platelets/particles were divided by their sizes, according to the standard size beads, into seven populations from 0.37 to 4.8 microm. PAC-1 binding/microm(2) was almost equal in platelets/particles ranging from 1.2 to 4.8 microm and was significantly lower on smaller-sized particles sizes (0.37-0.7 microm). PS surface exposure/microm(2) was high in the particles of 0.37-1.2 microm and very low in platelets (2.6-4.8 microm). Upon thrombin/convulxin stimulation caspase inhibitors prevented microparticle (MP) formation, while a calpain inhibitor stimulated MP formation. It was also shown that stimulated platelets are heterogeneous not only in their ability to activate alpha IIb beta 3 integrin complex and expose PS on their surface, but also in the distribution of activation markers, which strongly depends on platelet/particle size and that platelets/particles of different sizes provide different responses to the same stimulus.
authors.affiliation: Institute of Clinical Biochemistry and Pathobiochemistry, University of Würzburg, Würzburg, Germany.
authors.forename: Natalia
authors.initials: N
authors.lastname: Rukoyatkina
authors.forename: Antonija J
authors.initials: AJ
authors.lastname: Begonja
authors.forename: Jörg
authors.initials: J
authors.lastname: Geiger
authors.forename: Martin
authors.initials: M
authors.lastname: Eigenthaler
authors.forename: Ulrich
authors.initials: U
authors.lastname: Walter
authors.forename: Stepan
authors.initials: S
authors.lastname: Gambaryan
mesh_terms: D017304:Annexin A5 / Q000378:metabolism; D017209:Apoptosis / Q000187:drug effects; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism*; D048429:Cell Size; D002478:Cells, Cultured; D003435:Crotalid Venoms / Q000494:pharmacology; D004151:Dipeptides / Q000494:pharmacology; D054641:Dual Specificity Phosphatase 2 / Q000378:metabolism; D005434:Flow Cytometry / Q000379:methods; D006801:Humans; D037181:Lectins, C-Type; D010316:Particle Size; D010718:Phosphatidylserines / Q000097:blood*; D015539:Platelet Activation / Q000187:drug effects / Q000502:physiology; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000378:metabolism*; D011485:Protein Binding / Q000187:drug effects; D013917:Thrombin / Q000494:pharmacology*
chemical_list: D017304:Annexin A5; D003435:Crotalid Venoms; D004151:Dipeptides; D037181:Lectins, C-Type; D010718:Phosphatidylserines; D019039:Platelet Glycoprotein GPIIb-IIIa Complex; C071482:calpeptin; C028890:convulxin; D054641:Dual Specificity Phosphatase 2; D013917:Thrombin