Characterization of the equine platelet aggregation response.

Equine platelet aggregation responses to bovine collagen, adenosine diphosphate (ADP), serotonin, epinephrine, and arachidonate in a platelet aggregometer were recorded. Equine platelets exhibited irreversible aggregation when incubated with ADP at a final concentration of 10 microM and bovine collagen. A secondary aggregation wave was recorded from platelets from certain horses at final ADP concentrations of 1 to 5 microM. Serotonin and arachidonate induced a weak reversible aggregation response, but a response was not observed following epinephrine addition. Equine platelet aggregation was influenced by concentration of anticoagulant (sodium citrate). Platelet aggregation responses at 37 C were indistinguishable from those recorded at 39 C. Platelet aggregation responses also were altered if the aggregation tests were not performed within 4 hours of blood sample acquisition. An assessment of platelet aggregation from multiple blood samples from the same horse indicated that the procedures described provide a reliable method to assess equine platelet aggregation in vitro.