Objective To explore the therapeutical effect and its mechanism of tissue kallikrein (TK) on cerebral ischemic-reperfusion rat.Methods 36 rats were randomly divided into three groups: sham operation group, NS group [administrated with normal sodium 2 ml/(kg?d)], TK group [administrated with TK 17.5?10-3U/(kg?d)]. The NS and TK groups rats were injected intraperitoneally with NS or TK for three consecutive days. After that, neurological function and the infarct volume was appraised in each of group. Meanwhile, the ischemic tissue were detected by Nissl's staining. TUNEL staining and immunohistochemistry were used to examine the caspase-3,TNF-?,IL-1,NSE,GFAP,vWF expression in ischemic tissue.Results Compared with NS group, TK group significantly reduced the loss of neurological function and the infarct volume and improved the change of pathology in ischemic tissue(all P