AimTo investigate the effect of hypoxia postconditioning on mitochondrial reactive oxygen species (ROS) and cardiomyocyte apoptosis induced by hypoxia/reoxygenation.MethodsThe model of cultured cardiomyocytes with hypoxia/reoxygenation (H/R) was established and the cardiomyocytes were divided into 3 groups, including control group, H/R group (hypoxia 3 h and reoxygenation 6 h), and hypoxia postconditioning (PC) group (3 intermittent cycles of 5 min H/R immediately after hypoxia 3 h, then reoxygenation for 6 h).Cardiac mitochondria and sarcolemma were isolated by differential centrifugation.ROS was detected with fluorescent probes and cardiomyocyte apoptosis was detected with flow cytometry.The expressions of Bcl-2 and Bax proteins in the cardiac mitochondria and sarcolemma were measured by Western blot.ResultsBoth mitochondrial ROS and the number of apoptotic cardiomyocytes reduced significantly in PC group compared with H/R group.Bcl-2 levels increased while Bax levels decreased in cardiac mitochondria and sarcolemma of PC group.ConclusionPC attenuated ROS and cardiomyocyte apoptosis induced by H/R, which potentially mediated by upregulating the expression of Bcl-2 and downregulating the Bax in mitochondria and sarcolemma.