Effects of Doxycycline on Matrix Metalloproteinases in Rats after Myocardial Infarction

Objective: To observe the effects of doxycycline on matrix metalloproteinases-9(MMP-9) and ventricular remodeling(VRM) in rats after myocardial infarction and discuss its mechanisms. Methods: Forty-five healthy female Wistar rats were randomly allocated into three groups. The left coronary artery of rats was ligated in the experimental group and the control group, doxycycline 10 mg/(kg·d) in one milliliter saline were given to the rats in the experiment group by gastric lavage postoperation. On the other hand, rats in the sham-operated and control groups received one milliliter saline by tragastric lavage. All rats were killed seven days after surgery. The changes of left ventricular structure were observed by HE staining and the expression of MMP-9 in myocardial cells was examined by immunohistochemical methods. All the results were scanned and semi-quantitatively analyzed by computer image. Results: (1)Infarction was observed in experimental and control group, but the difference was not statistical (P 0.05). The expression of MMP-9 increased in the infracted zone in both groups and it was more significant in the control group. (2)The left ventricular cavity area in the experiment and the control group increased compared with the sham-operate group, moreover, the infracted zone got thinner and the left ventriculer cavity area was more spacial in the control group. Conclusion: The expression of MMP-9 in infracted zone of rats is strong and left ventricular remodeling happen one week after AMI. Doxycycline may inhibit ventricular remodeling by inhibiting the expression of MMP-9 in myocardial tissue.