Abstract: Objective: To explore the effect of tectorigenin on myocardial fibrosis(MF) in the rats and clarify the related mechanism,and to provide reference for its clinical application. Methods: Sixty Wistar rats were randomly divided into normal control group,model group,positive drug (capropril) control group, and low,middle,high doses of tectorigenin groups(n=10).Except normal control group, the rats in other groups were used to construct MF models by subcutaneous injection of 5 mg·kg ^-1·d ^-1 isoproterenol (Iso) for 7 d.The rats in tectorigenin groups and captopril group were intragastricly administrated with different doses of tectorigenin (25,50,100 mg·kg^-1·d^-1)and captopril(10 mg·kg ^-1·d ^-1) from the second day after modeling for consecutive 28 d.Bl-420E+ biological function experiment system was used to detect the heart function; Heart mass index (HMI) and left ventricular mass index (LVMI) were measured after experiment.UV detection was used to measure the levels of malondialdehyde (MDA) and the activities of superoxide dismutase (SOD) in myocardial tissue.Microplate reader was used to measure the activities of lactic dehydrogenase(LDH) and creatine kinase(CK) and the levels of nitric oxide (NO)in serum.ELISA were used to detect the levels of collagen typeⅠ(ColⅠ) and collagen type Ⅲ (Col Ⅲ) in myocardium tissue of the rats.The pathological changes of myocardium tissue of the rats in various groups were observed by HE staining. Results: Compared with normal control group,the HR of rats in model groups was increased,and the left ventricular systolic pressure (LVSP) was decreased(P<0.01); the HMI and LVMI were increased(P<0.05), the levels of MDA in left ventricular myocardial tissue was increased(P<0.01), and the activity of SOD was decreased,the levels of serum ColⅠ,Col Ⅲ and the activities of LDH, CK were also increased(P<0.01);the level of NO in serum was decreased(P<0.01).Compared with model groups, the HR were decreased,LVSP were increased, and HMI and LVMI of the rats in different doses of tectorigenin groups were decreased in a dose-dependent manner; the levels of MDA were reduced;the activities of SOD were increased in myocardium tissue,and the CK activities and the ColⅠ and ColⅢ levels were decreased(P<0.05 or P<0.01);the LDH activities in middle and high doses of tectorgenin groups were decreased(P<0.01); and the levels of NO in serum in different doses of tectorigenin groups were significantlyincreased(P<0.05 or P<0.01). Conclusion: Tectorigenin could inhibit the MF induced by Iso in the rats, and its mechanism may be related to antioxidation,scavenging free radical and inhibition of collagen synthesis.

Key words: myocardial fibrosis, isoproterenol, collagen, tectorigenin, free radical