Effect of gRb1 on cell death in H2O2-exposed cardiomyocytes. Cells were loaded with propidium iodide (PI, 5 μM) and pretreated with gRb1 (0.01, 0.1 or 1 μM) for 2 h and co-treated with H2O2 (0.5 mM) for 2 h or exposed to H2O2 alone for 2 h. The cell death was increased by H2O2, which was concentration-dependently reduced by pretreatment with gRb1, &p < 0.05, #p < 0.01 vs H2O2 alone. The results are presented as mean ± S.E.M.