Abstract: Objective To establish the rat experimental model of heart failure with thyroid dysfunction by using low-dose Isoprenaline(ISO). Methods In accordance with the dosage and route of administration of ISO, the rats were randomly divided into 6 experiment groups and the control group with 2 ml saline by intraperitoneal injection.Before administration and on 10 day after administration, echocardiography was conducted and CK, LDH, FT₃, FT₄ were detected. On 11 day the animals were sacrificed and the hearts were sampled for TTC staining. Results (1)No death in group 3mg.kg^-1.d^-1, the survival rate in group 5 mg·kg^-1·d^-1×3 d,10 kg^-1·d^-1×3 d and 6 mg·kg^-1·d^-1×7d were 50%, 60%, 80% respectively; (2) compared with the control group,left ventricular fractional shortening (FS) was significantly decreased in all groups (P<0.05), and group 6 mg·kg^-1·d^-1×7 d was lower than the others(P<0.05); (3) CK and LDH increased more significantly after administration, and serum FT₃ concentration in group 6 mg·kg^-1·d^-1×7 d obviously lower than group 10 mg·kg^-1·d^-1×3 d (P<0.05); (4) the myocardial infarction area in experimental group was more obvious compared with the control group(P<0.05), the percentage of the myocardial infarction weight was more visible in group 6 mg·kg^-1·d^-1×7 d compared with group 10 mg·kg^-1·d^-1×3d (P=0.02). Conculusion The best dosage and route of administration was that administering ISO (6 mg·kg^-1·d^-1) by intraperitoneal injection, the total dose was done twice with one hour interval,continuous administration for 7 days. This experiment provided an easy way to establish the animal model of heart failure with thyroid dysfunction, which was reproducible,credibie, stable and had low mortality and a high success rate.

Key words: Isoprenaline, Thyroid dysfunction, Low T₃ syndrome, Heart failure, Myocardial infarction, Animal model, Rats