Liver homogenates obtained from lean (n=6) and Zucker fa/fa (n=6) animals were treated with: (A) either NADPH oxidase inhibitor, gp91ds-tat (50 μM), mitochondrial respiratory chain inhibitors, antimycin (10 μM) and rotenone (50 μM), and superoxide levels were determined by lucigenin (5 μM) chemiluminescence. (B) NADPH (100 μM) or NADH (100 μM) for 10 minutes at 37°C, and superoxide levels were determined as described above. These experiments were performed in the absence of NADPH regenerating system. Statistical analysis was performed using Student’s t-test and P<0.05 was considered statistically significant.