We compared both the rate and extent of platelet aggregation with the extent of fibrinogen receptor expression and specific Fg binding to activated platelets, as a function of ADP concentration. Human citrated platelet-rich plasma (diluted ten-fold) was maximally pre-activated by incubating with adenosine diphosphate (ADP) at room temperature and then stirred. Platelet aggregation was determined from the decrease in the total number of particles. The number of fibrinogen receptors or bound Fg was measured from mean fluorescence values obtained with FITC-labelled IgM monoclonal antibody PAC1, and the IgG monoclonal antibody, 9F9, respectively, using flow cytometry. The expression of fibrinogen receptors occurs within seconds of activation. The fraction of platelets with fluorescence values above one critical threshold value increased with increasing activator concentration and correlated linearly with the fraction of platelets recruited into aggregates for ADP (r $>$ 0.9). Aggregation was not rate-limited by fibrinogen receptor expression nor by Fg binding. It appears that each platelet expresses $>$90% of its maximal Fg receptors at a critical ADP concentration i.e, occupancy of ADP receptors. This, in turn, leads to rapid Fg occupancy and platelet aggregation.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.60500 |
| Date | January 1991 |
| Creators | Mooney, Robert Francis |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Master of Science (Department of Physiology.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001243215, proquestno: AAIMM72058, Theses scanned by UMI/ProQuest. |
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