Aloia R C, Raison J K
Department of Anesthesiology, Loma Linda University School of Medicine, CA 92350.
Biochim Biophys Acta. 1989 Jan 18;988(1):123-46. doi: 10.1016/0304-4157(89)90007-5.
For homeotherms the maintenance of a high, uniform body temperature requires a constant energy supply and food intake. For many small mammals, the loss of heat in winter exceeds energy supply, particularly when food is scarce. To survive, some animals have developed a capacity for adaptive hypothermia in which they lower their body temperature to a new regulatory set-point, usually a few degrees above the ambient. This process, generally known as hibernation, reduces the temperature differential, metabolic activity, as well as the energy demand, and thus facilitates survival during winter. Successful hibernation in mammals requires that the enzymatic processes are regulated in such a manner that metabolic balance is maintained at both the high body temperature of the summer-active animal (37 degrees C) and the low body temperature of the winter-torpid animal (approx. 5 degrees C). This means that the cellular membranes have thermal properties capable of maintaining a balanced metabolism at these extreme physiological temperatures. The available evidence indicates that, for some tissues, preparation for hibernation involves an alteration in the lipid composition and thermal properties of cellular membranes. Marked differences in the thermal response of cellular membranes have been observed on a seasonal basis and, in some membranes, differences in lipid composition have been associated with the torpid state. However, to date, no consistent changes in lipid composition which would account for, or explain, the changes in membrane thermal response, have been detected. An important point to emphasize is that the process of 'homeoviscous adaptation', which occurs in procaryotes and some poikilotherms during acclimation to low temperatures, is not a characteristic feature of most membranes of mammalian hibernators.
对于恒温动物来说，维持较高且恒定的体温需要持续的能量供应和食物摄入。对于许多小型哺乳动物而言，冬季的热量散失超过了能量供应，尤其是在食物匮乏时。为了生存，一些动物发展出了适应性低温的能力，即它们将体温降低到一个新的调节设定点，通常比环境温度高几度。这个过程通常被称为冬眠，它减小了温差、代谢活动以及能量需求，从而有助于在冬季生存。哺乳动物成功冬眠需要酶促过程以这样一种方式进行调节，即在夏季活跃动物的高体温（37摄氏度）和冬季蛰伏动物的低体温（约5摄氏度）下都能维持代谢平衡。这意味着细胞膜具有能够在这些极端生理温度下维持平衡代谢的热性质。现有证据表明，对于某些组织，冬眠的准备涉及细胞膜脂质组成和热性质的改变。在季节性基础上已观察到细胞膜热响应的显著差异，并且在一些细胞膜中，脂质组成的差异与蛰伏状态有关。然而，迄今为止，尚未检测到能够解释或说明膜热响应变化的脂质组成的一致变化。需要强调的一个重要点是，在原核生物和一些变温动物适应低温过程中发生的“同黏性适应”过程，并非大多数哺乳动物冬眠者细胞膜的特征。
