This study investigated the effect of sample storage duration on the quantification of oxidative stress markers in the gastrocnemius, heart, and brain of mice submitted to a maximum swimming exercise. Thiobarbituric acid reactive substances (TBARSs), protein carbonyl derivatives, total antioxidant capacity (TAC), and the activity of superoxide dismutase (SOD) and catalase (CAT) were quantified in fresh tissues and in samples stored at -80°C for 1, 3, or 6 months, from exercised (n = 13) and nonexercised mice (n = 13). Except for protein carbonyl derivatives in the heart, the exercise resulted in the modification of all markers in all fresh-evaluated samples (p < 0.001). The storage duration did not modify the effect of exercise on protein carbonyl derivatives and TAC. TBARS was stable for 3 months in the gastrocnemius and for 1 month in frozen heart and brain. Accordingly, the exercise effect on TBARS levels observed in fresh samples was absent in the gastrocnemius frozen for 6 months (p = 0.98) and in the heart and brain frozen for 3 months (p = 0.07 and 0.28, respectively) or more (p = 0.21 for heart and p > 0.99 for brain). In addition, CAT and SOD activities were reduced by storage duration in all tissues evaluated (p < 0.05). Our findings show that sample storage duration alters the quantification of oxidative stress markers in mice submitted to maximum exercise, and its effect is tissue and marker dependent. Some recommendations to achieve more accurate and reproducible data in the exercise physiology and oxidative stress markers field are presented.
Keywords: antioxidant; biomarker; damage; freeze; preanalytical factors; redox status.