Objective:To study the influence of rt-PA and urokinase on the expression of matrix metalloproteinase(MMP-9) and hemorrhagic transformation after thrombolysis therapy in rats.Methods:A focal cerebral ischemia model of rat was established through embolization of left middle cerebral artery with autologous blood clots.rt-PA and urokinase were intravenously administrated 6 hours after ischemia at a dose of 10 mg/kg and 4 000 μ/kg.At the 24th hour after ischemia

all rats were killed.The expression of MMP-9 was detected with immunohistochemical staining and cerebral hemorrhage was quantified by spectrophotometer assay.Results:The expression of MMP-9 was increased after ischemia

and MMP-9 was significantly further upregulated after rt-PA and urokinase had been intravenously administrated.The average optical density(AOD) of MMP-9 in the sham operated group was 0.086±0.008

and increased to 0.158±0.010 after cerebral ischemia for 24 hours and then further increased to 0.225±0.034 and 0.228±0.022 in the rt-PA and urokinase thrombolytic therapy groups.Transformation and quantified intracerebral hemorrhage were significantly higher in the therapy groups as compared with the ischemic group.However

there was no difference between rt-PA group and urokinase group.Conclusion:rt-PA and urokinase treatment both increase the levels of MMP-9 after ischemia.MMP-9 might be involved in the hemorrhagic transformation after thrombolytic therapy with rt-PA and urokinase.