Objective To explore the molecular mechanism of blood_stasis syndrome (BSS) by studying the changes of gene expression of endothelin (ET) and constit utive nitric oxide synthase (cNOS) in vascular endothelial cells (VEC) cultured w ith BSS rabbit serum. Methods ET_1 mRNA expression and cNOS mRNA expression were analyzed by semi_quantitative reverse transcription and polymerase chain re action method. Results ET_1 mRNA expression level was increased and cNOS mRN A expression level was decreased in VEC cultured with BSS rabbit serum (Group A) as compared with VEC cultured with normal rabbit serum (Group B) or without rab bit serum (Group C) (P

0.05).The results of electrocardiography and the laboratory ex-amination showed that neither ANWin cluding natural Calculus Bovis nor A NWincluding in -vitro cultured Calc ulus Bo-vis had obviously toxic and side effe cts in treating epidemic encephalitis B.Conclusion ANW including in -vitro cul-tured Calculus Bovis has an markedly effect in the treatment of epidemic e ncephalitis B.