Living in a seasonal environment requires periodic changes in animal physiology, morphology and behaviour. Winter phenotype of small mammals living in Temperate and Boreal Zones may differ considerably from summer one in multiple traits that enhance energy conservation or diminish energy loss. However, there is a considerable variation in the development of winter phenotype among individuals in a population and some, representing the non-responding phenotype (non-responders), are insensitive to shortening days and maintain summer phenotype throughout a year. Differences in energy management associated with the development of different winter phenotypes should be accompanied by changes in antioxidant defence capacity, leading to effective protection against oxidative stress resulting from increased heat production in winter. To test it, we analysed correlation of winter phenotypes of Siberian hamsters ( Phodopus sungorus ) with facultative non-shivering thermogenesis capacity (NST) and oxidative status. We found that in both phenotypes acclimation to winter-like conditions increased NST capacity and improved antioxidant defence resulting in lower oxidative stress (OS) than in summer, and females had always lower OS than males. Although NST capacity did not correlate with the intensity of OS, shortly after NST induction responders had lower OS than non-responders suggesting more effective mechanisms protecting from detrimental effects of reactive oxygen metabolites generated during rewarming from torpor. We suggest that seasonal increase in antioxidant defence is programmed endogenously to predictively prevent oxidative stress in winter. At the same time reactive upregulation of antioxidant defence protects against reactive oxygen species generated during NST itself. It suggests that evolution of winter phenotype with potentially harmful characteristics was counterbalanced by the development of protective mechanisms allowing for the maintenance of phenotypic adjustments to seasonally changing environment.

中文翻译：

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异温啮齿动物抗氧化防御系统的预测和反应变化

生活在季节性环境中需要动物生理、形态和行为的周期性变化。生活在温带和寒带地区的小型哺乳动物的冬季表型可能与夏季表型有很大不同，其多种特征可以增强能量保存或减少能量损失。然而，群体中个体之间冬季表型的发展存在相当大的差异，并且一些代表无反应表型（无反应者）的人对缩短白天不敏感并全年保持夏季表型。与不同冬季表型的发展相关的能量管理差异应伴随着抗氧化防御能力的变化，从而有效防止冬季产热增加引起的氧化应激。为了测试它，我们分析了西伯利亚仓鼠（Phodopus sungorus）的冬季表型与兼性非颤抖产热能力（NST）和氧化状态的相关性。我们发现，在两种表型中，适应类似冬季条件的行为都会增加 NST 能力并改善抗氧化防御，从而导致氧化应激 (OS) 低于夏季，并且雌性的 OS 始终低于雄性。尽管 NST 能力与 OS 强度无关，但在 NST 诱导后不久，响应者的 OS 低于无响应者，这表明有更有效的机制可以防止从休眠状态复温期间产生的活性氧代谢物的有害影响。我们建议，抗氧化防御的季节性增加是内源性的，可以预测性地预防冬季的氧化应激。同时，抗氧化防御的反应性上调可防止 NST 本身产生的活性氧。这表明具有潜在有害特征的冬季表型的进化可以通过保护机制的发展来平衡，从而允许维持对季节性变化环境的表型调整。