Abstract: Objective To determine whether nonivasive limb ischemic preconditioning (LIP) produces cardioprotective effect on ischemia-reperfused myocardium and to observe the roles of matris metalloproteinases (MMPs) in this effect. Methods LIP was performed in rats by a repeated three-cycle (5 min ischemia-5 min reperfusion) of hind limb everyday for three days. The rats were randomly divided 3 groups: I/R group, myocardial ischemic preconditioning (CIP) group and LIP group. The morphologic changes were observed using HE dyeing. The area at risk (AAR) and infarct area (IA) were determined using Trypan blue and triphenyl tetrazolium choride (TTC) staining respectively. The infarct size (IS) was defined as IA/AAR×100%.MMP-2、MMP-9 and TIMP-1 in different myocardial areas were determined by immunohistochemistry. Results During 30 min myocardial ischemia and subsequent 120 min reperfusion, the IS was （44.5±8.1）%. Compared with I/R, the myocardial swelling, interstitial hemorrhage and inflammatory cell infiltrate were decreased in both of CIP group and LIP group, and the IS was reduced 35.7% in CIP group and 42.9% in LIP group. The level of MMP-2, MMP-9 decreased in CIP group (42.1% and 43.3%) and LIP group was (41.2% and 46.6%) than those in I/R group, but the level of TIMP-1 increased in CIP group (40.0%) and LIP group (53.8%) than that in I/R group. CONCLUSION LIP could not only reduce the infarct area in myocardium but also prevent cardiac matrix from degrading following the myocardial ischemia-reperfusion. The MMPs play an important role in the myocardial protection provided by LIP.

Key words: limb, ischemic preconditioning, myocardium cardioprotection, ischemia/reperfusion injury, matris metalloproteinases