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BACKGROUND Increased reactive oxygen species (ROS) and oxidative stress response lead to cardiomyocyte hypertrophy and apoptosis, which play crucial roles in the pathogenesis of heart failure. The purpose of current research was to explore the role of antioxidant N -acetylcysteine (NAC) on cardiomyocyte dysfunction and the underlying molecular mechanisms. METHODS AND RESULTS Compared with control group without NAC treatment, NAC dramatically inhibited the cell size of primary cultured neonatal rat cardiomyocytes (NRCMs) tested by immunofluorescence staining and reduced the expression of representative markers associated with hypertrophic, fibrosis and apoptosis subjected to phenylephrine administration examined by reverse transcription-polymerase chain reaction (RT-PCR) and western blot. Moreover, enhanced ROS expression was attenuated, whereas activities of makers related to oxidative stress response examined by individual assay Kits, including total antioxidation capacity (T-AOC), glutathione peroxidase (GSH-Px), and primary antioxidant enzyme Superoxide dismutase (SOD) were induced by NAC treatment in NRCMs previously treated with phenylephrine. Mechanistically, we noticed that the protein expression levels of phosphorylated phosphatidylinositol 3-kinase (PI3K) and AKT were increased by NAC stimulation. More importantly, we identified that the negative regulation of NAC in cardiomyocyte dysfunction was contributed by PI3K/AKT signaling pathway through further utilization of PI3K/AKT inhibitor (LY294002) or agonist (SC79). CONCLUSIONS Collected, NAC could attenuate cardiomyocyte dysfunction subjected to phenylephrine, partially by regulating the ROS-induced PI3K/AKT-dependent signaling pathway. [ABSTRACT FROM AUTHOR]