School of Biological Sciences, Integrative Physiology Research Group, Heydon-Laurence Building (A08), The University of Sydney, NSW 2006, Australia.
Comp Biochem Physiol A Mol Integr Physiol. 2010 Mar;155(3):383-91. doi: 10.1016/j.cbpa.2009.12.008. Epub 2009 Dec 21.
Small mammals that remain active throughout the year at a constant body temperature have a much greater energy and food requirement in winter. Lower body temperatures in winter may offset the increased energetic cost of remaining active in the cold, if cellular metabolism is not constrained by a negative thermodynamic effect. We aimed to determine whether variable body temperatures can be advantageous for small endotherms by testing the hypothesis that body temperature fluctuates seasonally in a wild rat (Rattus fuscipes); conferring an energy saving and reducing food requirements during resource restricted winter. Additionally we tested whether changes in body temperature affected tissue specific metabolic capacity. Winter acclimatized rats had significantly lower body temperatures and thicker fur than summer acclimatized rats. Mitochondrial oxygen consumption and the activity of enzymes that control oxidative (citrate synthase, cytochrome c-oxidase) and anaerobic (lactate dehydrogenase) metabolism were elevated in winter and were not negatively affected by the lower body temperature. Energy transfer modeling showed that lower body temperatures in winter combined with increased fur thickness to confer a 25 kJ day(-1) energy saving, with up to 50% owing to reduced body temperature alone. We show that phenotypic plasticity at multiple levels of organization is an important component of the response of a small endotherm to winter. Mitochondrial function compensates for lower winter body temperatures, buffering metabolic heat production capacity.
在一年中保持恒温且活跃的小型哺乳动物在冬季需要更多的能量和食物。如果细胞代谢不受热力学负效应的限制，冬季体温降低可能会抵消在寒冷中保持活跃的能量成本增加。我们旨在通过测试以下假设来确定可变体温是否对小型恒温动物有利：即在野外大鼠（Rattus fuscipes）中，体温会季节性波动；在资源有限的冬季，这种波动可以节省能量并减少食物需求。此外，我们还测试了体温变化是否会影响组织特异性代谢能力。与夏季适应的大鼠相比，冬季适应的大鼠体温明显更低，皮毛更厚。冬季大鼠的线粒体耗氧量和控制氧化（柠檬酸合酶、细胞色素 c 氧化酶）和无氧（乳酸脱氢酶）代谢的酶的活性升高，而较低的体温并没有对其产生负面影响。能量传递模型表明，冬季较低的体温与较厚的皮毛相结合，可以节省 25 kJ·天(-1)的能量，其中高达 50%的能量节省仅来自于体温的降低。我们表明，在多个组织层次上的表型可塑性是小型恒温动物对冬季反应的重要组成部分。线粒体功能补偿了冬季较低的体温，缓冲了代谢产热能力。
