Abstract: 【Abstract】 Objective To explore the role of p66shc in cardiomyocyte apoptosis induced by angiotensin (Ang)Ⅱ and the effect of estrogen pretreatment. Methods Neonatal rat cardiomyocytes were randomly divided into five groups: normal control, 10^－11 mol/L AngⅡ, 10^－9 mol/L AngⅡ, 10^－7 mol/L AngⅡ, and 10^－7 mol/L AngⅡ+estrogen treated groups. The cell viability was measured by MTT. The level of reactive oxygen species (ROS) and cell apoptosis rate were measured by flow cytometry. Mitochondrial membrane potential (MMP) was detected using a fluorescence microplate reader, and the protein expression of phosphorylated and total p66shc were detected using Western blot. Results With the increase of AngⅡconcentrations, cell viabilities and MMP levels decreased, whereas, the levels of ROS and cell apoptosis rates increased (P<0.05). Pretreatment with estrogen significantly attenuated the cardiomyocyte injury induced by AngⅡ (P<0.05). The protein expression of phosphorylated p66shc in the whole cell lysates and total p66shc in the mitochondria increased in a dose-dependent manner when cardiomyocytes were exposed to AngⅡ(P<0.05). Pretreatment with estrogen significantly down-regulated the protein expression of phosphorylated p66shc in the whole cell lysates and total p66shc in the mitochondria (P<0.05). Conclusion p66shc is involved in cardiomyocyte apoptosis induced by AngⅡ, and estrogen could attenuate AngⅡinduced cardiomyocyte injury through down-regulating the protein expression of p66shc.