Cardioprotection from oxidative stress in the newborn heart by activation of PPARγ is mediated by catalase

► Catalase is upregulated in newborn but not adult heart by rosiglitazone via PPARγ. ► PPARγ activation is cardioprotective against oxidative stress by H2O2 in newborn. ► Rosiglitazone decreased measures of heart dysfunction caused by H2O2 in newborn. ► Cardioprotection by PPARγ activation is abolished by inhibition of catalase.