Effect of catalase (CAT) overexpression and antioxidant on LeTx-induced changes in ubiquitin-proteasome activity. Expression and activity of the ubiquitin-proteasome system were determined in myocardium from WT and catalase transgenic mice treated with or without lethal toxin. For positive control, a cohort of isolated cardiomyocytes from WT mice were incubated with H2O2 (250 μM) for 2 h in the presence or absence of the antioxidant NAC (500 μM). A: Representative gel blots in triplicates depicting ubiquitination; B: Ubiquitin expression; C: Chymotrypsin-like activity; and D: Caspase-like activity. Mean ± SEM, n = 6 mice or isolations per group, *P <0.05 vs. WT group, #P <0.05 vs. WT-LeTx group, ψ P <0.05 vs. WT-H2O2 group.