AIM: To explore the significance of platelet activation, fibrinolytic activity and the changes of vasoactive mediators in acute myocardial infarction in rabbits and the intervention of amiodarone and metoprolol. METHODS: Fifty New Zealand white rabbits were randomly assigned to five groups, ten for each. Group Ⅰ: sham group, group Ⅱ: acute myocardial infarction(AMI) group, group Ⅲ: AMI and lidocaine group, group Ⅳ: AMI and amiodarone group, group Ⅴ: AMI and metoprolol group.The middle point of left ventricular coronary artery was ligated (groupⅡ,Ⅲ, Ⅳ and Ⅴ ) or a sham ligation(group Ⅰ). Four hours later, blood was collected for measuring plasma concentration of TXB 2, 6-Keto-PGF 1?, ET, NO, plasma activity of t-Pa and PAI.After that, the heart was taken out to evaluate the infarction size(IS). RESULTS: Plasma concentration of TXB 2, ET, NO and plasma activity of PAI were significantly higher in groupⅡ,Ⅲ, Ⅳ and Ⅴ than those in group Ⅰ(P0.05).Compared to group Ⅱ, plasma concentration of ET, NO and PAI activity were significantly decresed (P