Abstract: To study the changes of Mysion Heavy Chain （MHC） and myocardial structure in heart failure rats induced by doxorbincin （ADR） , 22 male SD rats were divided into ①control group （n= 11） and ②ADR group （n= 11, ip 20 mg/kg ADR given intermittently within 16 days in 8 times）. Body weight of the rats，left ventricle mass to body weight ratio（LVM/BW），α-MHC and β-MHC were measured. The ultrastructural changes in myocardial cell were observed electromicrographically.Shifts of myosin from α-MHC to β-MHC occurred in ADR group in a form of the decrease of a-MHC （vs control P＜0.01）and the increase of β-MHC（vs control P＜0.01）. In ADR group, an increase in LVM/BW is found （vs control P＜0.01）. Ultrastructural changes of myocardial cell in heart failure rats were electromicroscopically observed as lysis of myocardial filament extension and aelveoli of plasmalemma, crests rupture and swellening of mitochondria in ADR group. The results suggest that the MHC may be involved in myocardium remodeling.

Key words: Doxorbincin, Mysion Heavy Chain, Heart failure, Rat