Abstract: AIM: To explore in vitro the effects of WR-2721,a cytoprotector of chemotherapy and radiation,on platelet activation induced by physiologic agonists ADP,collagen and PAF.METHODS: Blood,obtained from Chinese healthy volunteers aged 20 -35 years,was treated with physiologic agonists at the given concentrations:ADp1 μmol·L^-1,collagen 2 mg·L^-1,and PAF0.1 mg·L^-1.Then WR-2721 was added to the experimental system at final concentrations range of 10^-7 -10^-5 mol·L^-1.The effect of WR-2721 on platelet aggregation induced by the agonists was studied.Thromboxane B₂(TXB₂)levels and nitric oxide(NO)production were determined.RESULTS: WR-2721 inhibited both platelet aggregation and TXB₂ production induced by ADP,collagen and PAF,in a dose-dependent manner.When WR-2721 was added at the final concentration of 5μmol·L^-1,it significantly increased ADP,collagen and PAF-induced NO production,which suggested that NO release by activated platelets was involved in the inhibitory effect of WR-2721.CONCLUSION: WR-2721 can effectively inhibit platelet activation induced in vitro by physiologic agonists.It may be not only a cytoprotectant,but also a therapeutic agent.

Key words: WR-2721, ADP, thromboxane B₂, collagen, platelet activation