Depressed sarcoplasmic reticulum (SR) Ca(2+)-ATPase (SERCA2a) and Ca(2+)-release channels (ryanodine receptor RyR2) are involved in diabetic cardiomyopathy, however, the implication of intracellular calcium handling proteins in SR is undefined. It was hypothesized that the down-regulation of the intracellular calcium handling proteins of SR is closely related to an up-regulated endothelin (ET) system. Hydroxysafflor yellow A (HSYA) is expected to ameliorate cardiac insufficiency which is mediated by the depressed intracellular calcium handling system in diabetic rat heart. Diabetes was produced in male rats 8 weeks after an injection of streptozotocin (60 mg/kg i.p.) and HSYA was administered (100 mg/kg) by gavage in the last 4 weeks. Hemodynamic and echocardiographic changes, cardiac calcium handling proteins, serum biochemistry, ET system and redox were measured. The compromised cardiac function in diabetic rats was accompanied by a significant down-regulation of the expression of RyR2, FKBP12.6 as well as SERCA2a and PLB. These were closely linked with oxidative stress, an increased ET-1 and up-regulation of ECE, PropreET-1 and iNOS mRNA in diabetic cardiomyopathy. After a 4 week treatment with HSYA, all abnormalities were reversed significantly. In conclusion, diabetic cardiomyopathy was correlated with an abnormal expression of calcium handing proteins in SR and an activated ET-ROS (reactive oxygen species) system in the diabetic affected myocardium. HSYA significantly improved the cardiac function and down-regulated the ET system and ROS pathway, resulting in a reversal of the abnormalities of expression of calcium handing proteins and the cardiac performance in diabetic cardiomyopathy.