Thus, the direct antioxidant actions of creatine appear to be limited to certain types of free radicals or reactive oxygen species. Sestili et al.  have found that creatine was not able to significantly counteract the concentrations of H2O2 and the compound tB-OOH that is derived from •OH and RO• radicals. With regard to levels of TBARS, our results are consistent with previous findings  that showed no change in hepatic TBARS levels in treadmill exercise-trained rats.
Taken in aggregate, these results for pro-oxidant markers underscore the findings of Sjodin BIRB 796 et al.  and Souza et al. , that is, predominantly aerobic exercise causes increased oxygen flow in the mitochondria and approximately five percent of this oxygen is not completely reduced, thereby forming ROS. As H2O2 levels rise, homeostasis requires increased production of antioxidant enzymes such as SOD, GSH-GPx and CAT to maintain the balance between oxidant production and the antioxidant system [8, 38, 39]. Our study results for SOD demonstrate decreased enzymatic activity in trained animals (T and TCR) when they were compared to group C rats. SOD is important
in the metabolism of O2•- that results in the formation of H2O2[34, 40, 41]. Thus, while SOD is an important combatant against oxidative stress, it also accelerates the formation of hydrogen peroxide, as occurs during physical exercise. In this situation, it has been suggested that Volasertib solubility dmso reduced SOD activity is mainly explained by the inhibitory effect of increased H2O2 production tuclazepam . In this study, a hypothesis may explain P5091 the decrease in SOD activity in response to CrS. Creatine may exert a sparing effect, i.e., creatine may act to neutralize ROS, resulting in down-regulation of the antioxidant system and specifically, the action of SOD. This hypothesis is based on research of antioxidant supplementation use that demonstrated inhibition of SOD, GSH-GPx and CAT activity [43, 44]. However, a notable finding from these studies was that unlike SOD, the
activity of GSH-GPx and CAT were increased in trained animals and CrS. Both GSH-GPx and CAT enzymes are present in most aerobic organisms and are responsible for conversion of intracellular H2O2 to water and oxygen [34, 40]. Our study demonstrated increase in GSH-GPx levels in exercised-trained rat groups T and TCr compared to control group animals. This finding may be explained by the fact that regular physical training activates transcription factors such as NF-κB and Nrf2, which are responsible for triggering various genes, including mitochondrial GSH-GPx [45, 46]. Moreover, the effect of training on the activity and expression of CAT is inconsistent and controversial . However, increased activity of this enzyme has been observed in rat liver , mice liver  and trained rat heart .