## 3 Results and Discussion
### Antioxidant Capacity of Mice Plasma--TEAC Assay  
The most commonly methods used for assessing total antioxidant capacity of plasma or serum are FRAP (Ferric Reducing Antioxidant Power) and TEAC (Trolox Equivalent Antioxidant Capacity). The mechanisms of measuring antioxidant capacity are different in these methods. For examples, FRAP assay measures the iron reducing ability of biological sample [43], while TEAC assay is based on inhibition of radical cation ABTS\({}^{\bullet+}\) (2,2\({}^{\prime}\)-azinobis (3-ethylbenzothazoline 6-sulfonate) inhibition [44].  
Antioxidant capacity of mice plasma was evaluated using TEAC assay, where potassium persulfate as radical-initiator of ABTS was used. The concentration-response curve of different Trolox solutions (0.25-2 mM) is shown in Figure 3a. The TEAC values of mice plasma, expressed as % inhibition of ABTS is shown in Figure 3b. Our results revealed significant decrease in the antioxidant capacity of mice plasma for Cd group, while Cd co-treatments with SeNPs did not affect the antioxidant capacity compared to the control group, suggesting selenium protection.  
Figure 2: Effects of cadmium and both form of selenium (SeNPs, purified and LSeNPs) on CREA level and LDH activity after 30 days treatments. All values were expressed as mean \(\pm\) SD for 10 mice in each group. Groups: Control-mice received only water; Cadmium group (Cd)-mice received orally 5 mg/kg CdCl\({}_{2}\); 0.1 SeNPs + Cd (0.1 mg/kg SeNPs + 5 mg/kg CdCl\({}_{2}\)); 0.2 SeNPs + Cd (0.2 mg/kg SeNPs + 5 mg/kg CdCl\({}_{2}\)); 0.4 SeNPs + Cd (0.4 mg/kg SeNPs + 5 mg/kg CdCl\({}_{2}\)); 0.1 LSeNPs + Cd (0.1 mg/kg LesNPs + 5 mg/kg CdCl\({}_{2}\)); 0.2 LSeNPs + Cd (0.2 mg/kg LSeNPs + 5 mg/kg CdCl\({}_{2}\)); 0.2 LSeNPs + Cd (0.2 mg/kg LSeNPs + 5 mg/kg CdCl\({}_{2}\)); 0.4 LSeNPs + Cd (0.4 mg/kg LSeNPs + 5 mg/kg CdCl\({}_{2}\)). Groups: SeNPs + Cd and LSeNPs + Cd at different concentration vs. control group: \({}^{\bullet}\)\(p\)\(<\) 0.05; \({}^{\bullet}\)\(p\)\(<\) 0.01; \({}^{\bullet}\)\(p\)\(<\) 0.001. Groups: SeNPs + Cd and LSeNPs + Cd at different concentration vs. cadmium group (Cd): \(\#\)\(\#\)\(p\)\(<\) 0.001.  
Total antioxidant capacity depending on the chemical reactions involved can be classified into two classes: hydrogen atom transfer and on single electron transfer methods. The TEAC assay is part of the last method, where the mechanism is based on the ability of a sample to transfer one electron to reduce radicals. The ABTS radical is soluble in both aqueous and organic solvent which allows the simultaneous evaluation of hydrophilic and lipophilic compounds being one of the advantages of TEAC method [43].  
Cadmium is unable to generate directly free radicals, but superoxide radical, hydroxyl radical could be generated indirectly [9]. The studies on animals shown the acute intoxication with cadmium increased antioxidant defense enzymes, including catalase, glutathione peroxidase, glutathione-S-transferase and superoxide dismutase [1,9,45]. Our results shows that both form of SeNPs were able to counteract the oxidative stress effects of Cd. Se antagonizes the toxicity of Cd through the action of Se-dependent antioxidant enzymes such as glutathione peroxidase and thioredoxin reductase [26]. Moreover, it is known that selenium pretreatment of rats intoxated with cadmium led to a significant decrease in MDA concentration, and increased levels of glutathione (GSH) and glutathione peroxidase (GPx) and thioredoxin reductase (TrxR) activities, when compared with those of cadmium-treated group; by this enzymatic mechanism it reduces the renal lipid peroxidation and induced a significant restoring of the antioxidant system affected by cadmium administration [46]. In humans (controlled trial study) selenium might reduce the oxidative stress by increasing total antioxidant capacity (TAC) and glutathione peroxidase (GPX) levels and decreasing serum malonaldehyde (MDA), both of which being crucial factors for reduction of oxidative stress [47].