Objective: To explore the protective effect and mechanism of Danlou tablets (DT) on myocardial ischemia reperfusion injury (MIRI) in rats. Method: The 80 male healthy Wistar rats with body weight of (300±20) g were randomly divided into sham operation group

model group and Danlou tablets group. Rats in sham operation group and model group were administered with 0.5%CMC-Na solution at the daily dose of 10 mL·kg-1 by ig

and rats in the DT group were administered with 0.9 g·kg-1 Danlou tablets. After prophylactic administration for 7 days

the left anterior descending branch of the rats heart were ligatured for 50 minutes to create the models of myocardial ischemia reperfusion injury in rats. The levels of lactate dehydrogenase (LDH)

creatine kinase isoenzyme (CK-MB)

endothelin (ET) and nitric oxide (NO) in serum

and malondialdehyde (MDA) and myeloperoxidase (MPO) in myocardial tissues were detected after 2 h reperfusion in 6 rats of each group. Ultrasound was used to observe the cardiac ejection fraction (EF) before and after 48 h reperfusion. The 6 rats in each group were selected for TdT-mediated dUTP nick end labeling(TUNEL) staining to assess the apoptosis index of myocardial cells

and then the protein expression levels of Caspase-3

Bax and Bcl-2 protein in cardiac muscle tissues were detected by Western blot. Evans blue-TTC staining was used to assess the myocardial infarction area in the remaining rats. Result: After reperfusion for 2 h

as compared with model group

the levels of serum LDH

CK-MB and ET-1 in DT group were significantly reduced (P<0.05)

while the levels of NO

MDA and MPO were significantly elevated (P<0.05). After reperfusion for 48 h

as compared with model group

the EF values in Danlou tablets group were significantly elevated (P<0.05)

with obvious decreases in the myocardial infarction size and myocardial apoptosis index (P<0.05)

myocardial Caspase-3 and Bax protein expression levels in Danlou tablets group were significantly increased (P < 0.05

P < 0.01)

and Bcl-2 protein expression levels were decreased (P<0.05). Conclusion: Danlou tablets can protect endothelial cells

inhibit oxidative and inflammatory infiltration in the early stage of MIRI. The protective effect on myocardial ischemia reperfusion injury in rats of Danlou tablets may be related to inhibiting apoptosis

reducing myocardial infarct size and improving cardiac function in the late stage of MIRI.