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Cardiac hypertrophy occurs in response to different stimuli and is mainly characterized by an enlargement of cardiomyocyte size. During hypertrophy, cardiomyocytes undergo not only radical changes of the cellular architecture but also activation of signaling cascades that counteract the atrophy genes. Experimental studies highlighted that chronic low concentrations of H 2 O 2 , induce a hypertrophic phenotype, while higher levels of H 2 O 2 promote apoptosis. In this study, we explored the early and long-term hypertrophic effects of high concentrations of H 2 O 2 on H9c2 rat cardiomyocytes. We found that 2-h stimulation with 200 μM H 2 O 2 caused an early dramatic reduction of cell viability, accompanied, 5-days later, by increased cell size and up-regulation of atrial natriuretic peptide transcription. This hypertrophic phenotype is associated to increased Akt phosphorylation and a consequent reduction of the FOXO3a and atrogin-1 gene expression. Moreover, we observed that H 2 O 2 caused the overexpression of miR-212/miR-132 cluster concomitantly to a down-regulation of PTEN transcript without changes in its protein expression. Noteworthy, we found that the treatment of cardiomyocytes with H 2 O 2 further led to an increase of oxidized glutathione and glutathionylation of proteins, including PTEN. In conclusion, our results permit to reconstruct the molecular cascade triggering the cardiomyocyte hypertrophy upon high concentrations of H 2 O 2 . [ABSTRACT FROM AUTHOR]