Objective—To investigate the potential use of fluorescent- labeled annexin V, anti-human fibrinogen antibody, and anti-human thrombospondin antibody for detection of the activation of equine platelets by use of flow cytometry.
Sample Population—Platelets obtained from 6 Thoroughbreds.
Procedure—Flow cytometry was used to assess platelet activation as indicated by detection of binding of fluorescent-labeled annexin V, anti-human fibrinogen antibody, and anti-thrombospondin antibody to unactivated and ADP-, collagen-, platelet activating factor (PAF)-, and A23187-activated equine platelets. Human platelets were used as control samples. Determination of 14C-serotonin uptake and release was used to assess the extent of platelet secretion.
Results—Anti-human thrombospondin antibody failed to bind to equine platelets. Annexin V bound to platelets activated with PAF or A23187 when platelets had undergone secretion. Anti-human fibrinogen antibody bound to ADP-, PAF-, and A23817- activated platelets, but binding was not dependent on platelet secretion. The extent of binding of anti-fibrinogen antibody was less in equine platelets, compared with that for human platelets, despite maximal stimulation.
Conclusions and Clinical Relevance—Activation of equine platelets can be detected by use of fluorescent- labeled annexin V and anti-human fibrinogen antibody but not by use of anti-human thrombospondin antibody. These flow cytometric techniques have the potential for detection of in vivo platelet activation in horses at risk of developing thrombotic disorders. (Am J Vet Res 2002;63:513–519)