Antioxidant Defense Systems In Tissues Of Lizards During Hibernation And Effect Of Melatonin On These Systems In Tissues Of Hibernating Lizards

Hibernation is a physiological adaptation to environmental factors in animals. It also can increase survival during extreme conditions. Lizard, phrynocephalus przewalskii, which is a natural hibernator is endemic to China. This study was designed to investigate the lipid peroxidation and antioxidant defense systems in tissues of a lizard during hibernation and the effect of melatonin (MT) on lipid peroxidation and antioxidant defense systems in tissues of a hibernating lizard.一. Lipid peroxidation and antioxidant defense systems in tissues of a lizard during hibernation.This study was designed to investigate the extent of hydrogen peroxide and malonic dialdehyde (MDA), the level of total anti-oxidation capability (T-AOC) and the activities of superoxide dismutase (SOD), catalase (TAS) and glutathione peroxidase (GPx) in brain, heart and liver of lizard in six stages during hibernation. The six stages involved euthermic state (25℃), prehibernation (10-12℃), after hibernating for a week and a month (2-4℃), and arousing from hibernation for a week and two weeks (10-12℃). From euthermic state to long-term hibernation, lipid peroxidation was showed to increase in brain except the stage of prehibernation. However in heart and liver, lipid peroxidation was showed to increase from prehibernation to long-term hibernation but never exceeded the level of awaken animals. A high level of antioxidant protection was maintained in the monitored tissues except liver after hibernation for a week and a month. The results suggested that, in the hibernating lizards, a physiological mechanism was employed to prevent irreversible structural damage to the main organs and provide for their normal functioning at a low body temperature.二. Effect of melatonin on lipid peroxidation and antioxidant defense systems in tissues of hibernating lizards.We injected different concentration of melatonin including 1mg/kg and 5mg/kg to hibernating lizards for a month and investigate the effect of MT on lipid peroxidation and antioxidant defense systems in tissues of hibernating lizards. The results showed that after continuous administration of MT, the level of MDA decreased and the activities of CAT and GPx increased significantly in brain and heart of hibernating lizards. But in liver, the content of MDA increased and the activity of SOD decreased. The experiment reflected that the strong anti-oxidation capability of MT can significantly assist antioxidant defense system in heart of hibernating lizards.