Objective To study the effect of phospholamban antisense RNA (asPLB) on sarcoplasmic reticulum Ca2+-ATPase activity and cardiac function in rats with diabetes mellitus (DM) mediated by recombinant adeno-associated virus (rAAV) vector. Methods Six weeks after the induction of DM by streptozotocin injected intraperitoneally, the rats were divided into three groups, namely: DM-rAAV-asPLB group, DM-saline group and DM group (control group). The rats in the DM-rAAV-asPLB group were intramyocardially injected with rAAV-asPLB, the rats in the DM-saline group were injected with saline, and those in the control group did not receive any treatment. Six weeks after gene transfer, the expressions of PLB protein and PLB phosphorylation were detected by Western-blot, while the activity of sarcoplasmic reticulum (SR) Ca2+-ATPase and left ventricular function were measured. Results The PLB protein expression level was significantly higher whereas the PLB phosphorylation, SR Ca2+-ATPase activity and left ventricular function were significantly lower in the DM-saline group than in the control group. No significant difference was found in PLB protein expression level, PLB phosphorylation or SR Ca2+-ATPase activity between the DM-rAAV-asPLB group and the control group. The left ventricular function in the DM-rAAV-asPLB group was poorer than in the control group and was better than in the DM-saline group. Conclusion rAAV-asPLB can down-regulate PLB protein expression and up-regulate PLB phosphorylation and SR Ca2+ -ATPase activity, thus contributing to the improvement of in vivo left ventricular function. Objective To study the effect of phospholamban antisense RNA (asPLB) on sarcoplasmic reticulum Ca2 + -ATPase activity and cardiac function in rats with diabetes mellitus (DM) mediated by recombinant adeno-associated virus (rAAV) vector. Methods Six weeks after the induction of DM The rats in the DM-rAAV-asPLB group were intramyocardially injected with rAAV- asPLB, the rats in the DM-saline group were injected with saline, and those in the control group did not receive any treatment. Six weeks after gene transfer, the expressions of PLB protein and PLB phosphorylation were detected by Western-blot, while the Results of PLB protein expression level was significantly higher than the PLB phosphorylation, SR Ca2 + -ATPase activity and le ft ventricular function were significantly lower in the DM-saline group than in the control group. No significant difference was found in PLB protein expression level, PLB phosphorylation or SR Ca2 + -ATPase activity between the DM-rAAV-asPLB group and the control group. The left ventricular function in the DM-rAAV-asPLB group was poorer than in the control group and was better than in the DM-saline group. Conclusion rAAV-asPLB can down-regulate PLB protein expression and up-regulate PLB phosphorylation and SR Ca2 + -ATPase activity, thus contributing to the improvement of in vivo left ventricular function.