Glutathione redox balance in hibernating Chinese soft-shelled turtle Pelodiscus sinensis hatchlings

Glutathione (GSH) system is a critical component of antioxidant defense, which is important for hibernating survive of turtle hatchlings. The present work measured changes at the mRNA level of genes involved in GSH synthesis, GSH reduction and GSH utilization, as well as enzyme activity, in Pelodiscus sinensis hatchlings during hibernation. Samples were taken in the field at pre-hibernation (17°C, Mud temperature (MT)), hibernation (5.8°C, MT) and arousal (20.1°C, MT). Cerebral total GSH content decreased during hibernation, recovered after arousal along with a stable ratio of GSH/GSSG. Hepatic total GSH increased after arousal and pushed the ratio of GSH/GSSG to a more reduced status. Cerebral glutathione reductase (GR) mRNA and activity were depressed during hibernation then recovered after arousal. However, hepatic GR mRNA elevated during hibernation but its activity did not change. Tissue-specific changes of GR activity and mRNA may promote these tissue-specific changes of GSH redox. Hibernation caused little effect on mRNA level of glutathione synthetase (GS) while arousal induced them in the brain and liver. Most Glutathione-S-transferase (GST) isoform mRNAs did not change in both brain and liver during hibernation, then induced after arousal. Cerebral and hepatic GST activities kept stable throughout the entire experiment. Our results showed that GSH system may play a more important role in antioxidant defense in the liver while mainly maintaining stable redox balance in the brain of hibernating P. sinensis hatchings.