Effect of Mild Hypothermia on the Immunoreactivity of tPA and PAI-1 after focal Cerebral Ischemia and Reperfusion in Rats

Objective:To observe the effect of mild hypothermia on the immunoreactivity of tissue plasminogen activator(tPA)and plasminogen activator inhabitor-1(PAI-1)after focal cerebral ischemia and reperfusion,and to investigate the change of them expression in different ischemic areas and at different time.In order to study their relationship and value.Methods:Reversible middle cerebral artery occlusion was performed with modified Koizumi's model.Rats were randomly divided into sham-operated group,normal ischemic/reperfusion group and mild hypothermia ischemic/reperfusion group.Normothermia ischemic group and hypothermia ischemia group were respectively reperfused for 4h,24h,74h,7d and 14d after ischemia for 2h.Brain mild hypothermia was achieved 30 minutes after ischemia and maintained to 4h.The neurological deficit scores were determined before killing,pathohistological changes of injured neurons were demonstrated by H-E staining and microscopy,and the expression of tPA and PAI-1was assayed by immunohistochemistry and computerized image analysis system.Results:The expression of tPA in mild hypothermia group significantly decreased compared with nomothermia group(P0.05),the expression of PAI-1.significantly increased(P0.05).Conclusion:Mild hypothermia can reduce expression of tPA and increase expression of PAI-1.In a focal model of transient cerebral ischemia reperfusion in rats.mild hypothermia treatment also resists the brain injured caused by transient cerebral ischemic reperfusion.