Objective:To study the expression of Fas and FasL in hyperthyroid cardiopathy and to explore its possible effect and clinical significance in the pathogenesis of the hyperthyroid cardiopathy.Methods:Twenty New Zealand rabbits were randomly divided into two groups: control group(n =10) and experimental group(n =10).Hyperthyroidism animal model was established by peritoneal injection of Levothyroxine(L-Thy) in experimental group.All the rabbits were followed up for 4 weeks.Every 7 days blood samples were obtained.Serum TT3 and TT4 were measured with radioimmunoassays(RIAs).Electrocardiogram(ECG) was performed to determine heart rate(HR).All the rabbits underwent echocardiography and the thickness of IVS?LV?LA?LVPW and LVEF were measured at the end of the follow-up period.Ventricular tissues were collected at 4th weeks.Cardiac hypertrophy index

cardiomyocyte diameter

structural change were detected.Cardiac fibrosis was displayed by Masson stain and collagen volume fraction(CVF)was measured using pathological image analytic system.Protein of Fas and FasL were localized by immunohistochemistry and semi-quantified with pathological image analytic system.Results: In experimental group

the thickness of IVS?LV?LA?LVPW

cardiac quality index

cardiomyocyte diameter

collagen volume fraction(CVF) and the expression of Fas in left atrium and left ventricle increased obviously(P<0.05).Conclusion:L-Thy could induce myocardial hypertrophy

structural change of cadiomyocyte

myocardium interstitial fibrosis and cell apoptosis.The system of Fas/FasL may correlate with the pathogenesis and course of the hyperthyroid cardiopathy.