Avian thrombocytes express genes associated with platelet function and signal in response to platelet agonists collagen and thrombin. (A) Real-time quantitative PCR in thrombocytes and lymphocytes of select genes with a known role in platelet function. Shown is the log₂ difference in gene expression between chicken thrombocytes and lymphocytes. (B-E) 5-HT release from platelets or thrombocytes was measured after loading with [³H] 5-HT. Cells were stimulated with increasing doses of bovine thrombin (B) or equine type-I collagen (C). (D) Chicken thrombocytes were stimulated with collagen (3 μg/mL) in the presence of increasing doses of PP2. (E) PP2 (3μM) was used to inhibit 1.0 U/mL thrombin- or 3.0 μg/mL collagen-induced 5-HT release in either human platelets or chicken thrombocytes. An equivalent volume of DMSO solvent was added in no inhibitor controls. Mean ± SD is shown for all panels; n = 3 experiments per condition.