Abstract: Objective To explore whether angiotensin-(1-7) [Ang-(1-7)] protects cardiac myocytes against high glucose (HG)-induced injury by inhibiting ClC-3 chloride channels. Method H9c2 cardiac cells were exposed to 35 mmol/L glucose for 24 h to establish a cell injury model. The cells were treated with Ang-(1-7) or the inhibitor of chloride channel (NPPB) in the presence of HG for 24 h to observe the changes in HG-induced cell injury. Cell counter kit 8 (CCK-8) assay was used to test the cell viability, and the morphological changes of the apoptotic cells were detected using Hoechst 33258 staining and fluorescent microscopy. The intracellular level of reactive oxygen species (ROS) was examined by DCFH-DA staining, SOD activity in the culture medium was measured using commercial kits, and the mitochondrial membrane potential (MMP) of the cells was tested with rodamine 123 staining. The expression level of cardiac ClC-3 chloride channels was detected with Western blotting. Results Exposure of H9c2 cardiac cells to 35 mmol/L glucose for 24 h markedly enhanced the expressions of cardiac ClC-3 channel protein (P<0.01). Co-treatment of the cells with 1 μmol/L Ang-(1-7) and HG for 24 h significantly attenuated HGinduced upregulation of ClC-3 channel protein expression (P<0.01). Co-treatment of the cells exposed to HG with 1 μmol/L Ang-(1-7) or 100 μmol/L NPPB for 24 h obviously ameliorated HG-induced injuries as shown by increased cell viability, enhanced SOD activity, decreased number of apoptotic cells, and reduced intracellular ROS generation and loss of MMP (P< 0.01). Conclusion ClC-3 channels are involved in HG-induced injury in cardiac cells. Ang-(1-7) protects cardiac cells against HG-induced injury by inhibiting ClC-3 channels.