*2.3. Effect of Resveratrol and CrO3 on the Antioxidant System*

The effect of the treatments on the antioxidant system was determined by evaluating glutathione (GSH) levels and the enzymatic activity of superoxide dismutase (SOD), glutathione peroxidase (GPx), and catalase (CAT). During the reduction of Cr(VI) to trivalent chromium [Cr(III)] superoxide radical (O2 •) is generated, which can be dismutated by SOD. While GPx and CAT, when interacting with hydrogen peroxide (H2O2), can inhibit the production of the hydroxyl radical (•OH), and GSH participates in one of the Cr(VI) reduction pathways [15]. The enzymatic activities of SOD, GPx, and CAT are shown in Figure 3. Data were analyzed with a one-way ANOVA. Treatment had a significant effect on SOD activity (*p* < 0.0001). The resveratrol group had higher SOD activity than the control group (C2) (*p* < 0.0001), and the resveratrol + CrO3 group showed an increase compared to the control groups (C1, *p* < 0.016; C2, *p* < 0.001), the resveratrol group (*p* < 0.019) and the CrO3 group (*p* < 0.0001). GPx activity was also significantly affected by treatment (*p* < 0.0001). The CrO3 treatment increased GPx activity compared to the control group C1 (*p* < 0.019) and the resveratrol + CrO3 group (*p* < 0.004). Resveratrol treatment alone also increased GPx activity compared to control group C2 (*p* < 0.0001). The resveratrol + CrO3 group had lower GPx activity than the resveratrol only group (*p* < 0.0001). There was also a significant effect of treatment on CAT activity (*p* < 0.0001). Resveratrol treatment increased CAT activity relative to the C2 control (*p* < 0.005), while treatment with CrO3 increased it compared to control group C1 (*p* < 0.034). CAT activity was lower in the resveratrol + CrO3 group than in the resveratrol group (*p* < 0.001) and the CrO3 group (*p* < 0.0002). Together, these results demonstrate that in the resveratrol + CrO3 mice, resveratrol restored GPx and CAT activity to levels similar to the controls. In the resveratrol + CrO3 group, SOD levels were higher than those of the control and CrO3 groups.

**Figure 3.** (**A**) Superoxide dismutase (SOD), (**B**) glutathione peroxidase (GPx), and (**C**) catalase (CAT) activities evaluated in peripheral blood at 48 h after treatments with resveratrol and CrO3 (*n* = 5 mice/group). Statistical significance was determined using one-way ANOVA followed by Tukey's post-hoc test: <sup>a</sup> *p* < 0.0001 vs. C2; <sup>b</sup> *p* < 0.016 vs. C1; <sup>c</sup> *p* < 0.001 vs. C2; <sup>d</sup> *p* < 0.019 vs. resveratrol; <sup>e</sup> *p* < 0.0001 vs. CrO3; <sup>f</sup> *p* < 0.0001 vs. C2; <sup>g</sup> *p* < 0.019 vs. C1; <sup>h</sup> *p* < 0.004 vs. resveratrol + CrO3; <sup>i</sup> *p* < 0.0001 vs. resveratrol; <sup>j</sup> *p* < 0.005 vs. C2; <sup>k</sup> *p* < 0.034 vs. C1; <sup>l</sup> *p* < 0.0002 vs. resveratrol + CrO3; <sup>m</sup> *p* < 0.001 vs. resveratrol. C1, Control 1, vehicle only (distilled water); C2, Control 2, vehicle only (ethanol 30%); CrO3, chromium trioxide.

The GSH levels are shown in Figure 4. There was a significant effect of treatment on GSH levels (*p* < 0.0001). There were no significant differences in GSH levels between CrO3-treated animals and any other group (*p* > 0.05), while resveratrol + CrO3 mice had significantly lower GSH levels than the controls (C1, *p* < 0.0001; C2, *p* < 0.0001), the resveratrol group (*p* < 0.0001), and the CrO3 only group (*p* < 0.0001).

**Figure 4.** Average glutathione (GSH) levels evaluated in peripheral blood erythrocytes 48 h after treatment with resveratrol and CrO3 (*n* = 5 mice/group). Statistical significance was determined using one-way ANOVA followed by Tukey's post-hoc test: <sup>a</sup> *p* < 0.0001 vs. C1; <sup>b</sup> *p* < 0.0001 vs. C2; <sup>c</sup> *p* < 0.0001 vs. resveratrol; <sup>d</sup> *p* < 0.0001 vs. CrO3. C1, Control 1, vehicle only (distilled water); C2, Control 2, vehicle only (ethanol 30%); CrO3, chromium trioxide.
