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

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, s weet itch. Subjects: Ponies with a clinical history of sweet itch and normal ponies we re used as blood donors. Methods: PAF and ADP-induced platelet aggregation was measured and TxB(2) p roduction quantitated at the time of maximal aggregation; 12-HETE was addit ionally 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 betw een the responses of platelets from allergic and normal ponies to PAF or AD P (analysis of variance). Conclusions: There is no evidence of altered platelet responsiveness in pon ies with sweet itch. The profile of responses to PAF and ADP suggest differ ential activation of intracellular signalling pathways in equine platelets.