To assess redox status during hibernation with metabolic depression, oxidative stress parameters and antioxidant defense were assessed during different phases of hibernation including active period, hibernation, arousal, and post arousal period, in the liver and brain tissues of Duttaphrynus melanostictus. We hypothesized low levels of oxidative stress and antioxidant defense during the hibernation period in comparison to the summer active period due to hypometabolism and their subsequent increase during the arousal period following an increase in body temperature and metabolism. Contrary to our hypothesis increased oxidative stress with significantly higher lipid peroxidation, protein carbonylation, GSSG/GSH ratio, and elevated antioxidants defense consisting of higher catalase activity and high ascorbic acid content to control oxidative stress were found during hibernation. However, GSH and uric acid levels were found low with SOD activities at a steady level during hibernation. Supporting our hypothesis increased oxidative stress with high lipid peroxidation and GSSG/GSH ratio were found during arousal from hibernation owing to increased oxygen consumption and rewarming. Augmented catalase and SOD activities and nonenzymatic antioxidants (GSH, ascorbic acid, and uric acid) level were found to counteract oxidative stress during arousal periods as it was expected. A steady level of protein carbonylation indicating no oxidative damage during arousal from hibernation due to elevated antioxidant defense shows the significance of hibernation to overcome food and water scarcity and cold climatic condition. Decrease in antioxidants levels accompanying coming down of lipid peroxidation, protein carbonylation, and GSSG/GSH ratio to their lower levels during post arousal period showing normalcy in redox status as it was during active period indicates controllability of oxidative stress in hibernating toads.

To assess the oxidative assaults and antioxidant defense, oxidative stress markers, including lipid peroxidation level, protein carbonylation level, GSSG/GSH ratio and nonenzymatic antioxidants such as total glutathione, ascorbic acid and uric acid, in liver and brain tissues of hibernating common Asian toads, Duttaphrynus melanostictus, were compared with toads during active periods. Oxidative stress was found in both liver and brain tissues of hibernating common Asian toads in spite of depressed metabolism and low oxygen consumption. Significantly higher lipid peroxidation, protein carbonylation and an increased GSSG/GSH ratio were found in liver and brain tissues of hibernating toads, indicating oxidative stress. To counteract the stress, ascorbic acid was increased significantly in the liver and brain tissues of hibernating individuals in comparison to individuals during active periods. The uric acid level decreased in both the liver and brain tissues of hibernating toads, which may be due to its decreased rate of synthesis because of low xanthine oxidase activity at low body temperature and hypometabolism. The common Asian toad faced oxidative stress during hibernation, which was counteracted by augmented nonenzymatic antioxidant defense.