Differential activation of platelets from normal and allergic ponies by PAF and ADP

Abstract.

Objective and Design: Altered platelet responsiveness has been demonstrated in human atopic dermatitis. This study has compared the in vitro function of platelets from normal ponies and those with the allergic skin disease, sweet itch.¶Subjects: Ponies with a clinical history of sweet itch and normal ponies were used as blood donors.¶Methods: PAF and ADP-induced platelet aggregation was measured and TxB₂ production quantitated at the time of maximal aggregation; 12-HETE was additionally measured in some samples. Agonist-induced release of ³[H]5-HT was also studied.¶Results: Although both PAF and ADP caused equine platelet aggregation, only PAF stimulated eicosanoid and 5-HT release. There were no differences between the responses of platelets from allergic and normal ponies to PAF or ADP (analysis of variance).¶Conclusions: There is no evidence of altered platelet responsiveness in ponies with sweet itch. The profile of responses to PAF and ADP suggest differential activation of intracellular signalling pathways in equine platelets.