A Study On The Oxidative Stress Before And After Hibernation In Two Species Of Lizards At Different Altitudes

Phrynocephalus erythrurus,the highest living lizard in the world inhabited above 4500 m at Qinghai-Tibet Plateau,where hypobaric hypoxia and low ambient temperatures are certain environmental factors.Organisms living at high altitude suffered greater oxidative challenges than those living at low altitude.In the present study,oxidative stress and antioxidant defenses of P.erythrurus before and after hibernation in different tissues had been investigated.Another low altitude lizard Phrynocephalus przewalskii had been selected as a reference to varied geographically.The results of P.erythrurus between two periods indicated that levels of malondialdehyde and total antioxidant capacity in brain and skeletal muscle,hydrogen peroxide in liver and skeletal muscle were decreased after arousal from hibernation.By contrast,activities of superoxide dismutase and glutathione peroxidase in brain and skeletal muscle,catalase in liver and skeletal muscle,glutathione reductase in brain were increased.Results of oxidative stress and antioxidant defenses in P.przewalskii were similar with P.erythrurus.Moreover,compared with P.przewalskii,before hibernation,P.erythrurus had high levels of hydrogen peroxide,malondialdehyde and total antioxidant capacity in skeletal muscle,and activities of superoxide dismutase and catalase in three tissues,glutathione reductase in liver and skeletal muscle were also high.But activities of glutathione peroxidase in three tissues,glutathione reductase in brain were low.Results of oxidative stress and antioxidant defenses after hibernation were same as before hibernation.Data of Principal Component Analysis based on correlations of the investigated parameters indicated a clear separation in P.erythrurus and P.przewalskii during two periods.These distinct characteristics had showed that P.erythrurus had unique adaptive mechanisms to oxidative stress in hostile environment.In the second section,we studied the activities of citrate synthase and lactic dehydrogenase during pre-hibernation,acclimatization and post-hibernation per iods in P.erythrurus and P.przewalskii.The results showed that activities of enzymes decreased after acclimatization compared with pre-or post-hibernation.And activities of enzymes during post-hibernation were higher than pre-hibernation in some tissues,which was same in P.przewalskii.Compared with P.przewalskii,P.erythrurus had high activities of citrate synthase and lactic dehydrogenase in heart during two periods and in liver during pre-hibernation,but activities were low in liver during post-hibernation.Activities of citrate synthase were high in P.erythrurus in skeletal muscle,however,activities of lactic dehydrogenase were opposite.The differences of enzymes activities in P.erythrurus may be a low temperature adaptive strategy.