Production of reactive oxygen species (ROS) in differentiated primary rat preadipocytes cultured with (OTA+) or without the addition of ochratoxin A (OTA-) in cell culture medium and with the addition of quercetin (QCT) at various concentrations. The production of ROS was determined using a commercially available kit, and is expressed as a percentage of CM-H2DCFDA fluorescence relative to control (A). The expressions of NADPH oxidase 2 (Nox2; B), Nox4 (C), p22 (D), superoxide dismutase 1 (Sod1; E), Sod2 (F), Sod3 (G) and nuclear factor erythroid 2–related factor 2 (Nrf2; H) were determined by real-time PCR. Data were normalized to the gene expression of 40S ribosomal protein S29 (Rps29), the expression of which was not altered by the treatments. The results, presented as mean ± mean error (SEM), were analyzed by two-way ANOVA with factors QCT and OTA, followed by Bonferroni post-hoc test. The level of statistical significance considered for factor OTA was * p < 0.05; *** p < 0.001, and for factor QCT ## p < 0.01; ### p < 0.001.