Maximum rates of sustained metabolic rate in cold-exposed Djungarian hamsters (Phodopus sungorus): the second wind
Maximum rates of sustained metabolic rate in cold-exposed Djungarian hamsters (Phodopus sungorus): the second wind
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DOI：
10.1007/s00360-010-0476-8
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发表时间：
2010-05
期刊：
影响因子：
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通讯作者：
T. Ruf;B. Grafl
中科院分区：
文献类型：
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作者：
T. Ruf;B. Grafl
Djungarian仓鼠（Phodopus sungorus）可以忍受短期暴露于低至−70°C的环境温度（Tas），但令人惊讶的是，以前似乎在Tas ≥−2°C时达到最大可持续代谢率（SusMR）。我们假设，荣格仓鼠的SusMR可能会受到动物先前冷适应程度和Tachanges时间模式的影响，例如平均Tadeclines。在+5 ° C冷适应6周后，仓鼠达到了比先前确定的高35%的SusMR率，并且能够在Ta −9°C下保持正能量平衡。然而，无论平均冷负荷是恒定的还是由Tas在+3 ° C和低至−25°C之间以小时为间隔的循环引起的，SusMR都不受影响。在平均Tas为+3 ° C至-3 °C时，仓鼠的体重和能量消耗显著降低，但在较低Tas（-5 ° C至-9 °C）时能够保持稳定的体重。这些结果表明，先前的冷适应深刻影响仓鼠的SusMR和体重调节可能发挥不可或缺的一部分，在保持正能量平衡，在冷暴露。由于瞬时冷负荷的程度对SusMR没有影响，我们假设Djungarian仓鼠的能量周转限制不是由承受极端温度的能力决定的（即，外周限制），但由于能量摄入的中枢限制。
Djungarian hamsters (Phodopus sungorus) tolerate short-term exposure to ambient temperatures (Tas) down to −70°C, but surprisingly, previously appeared to reach maximum sustainable metabolic rate (SusMR) when kept atTas as high as ≥−2°C. We hypothesized that SusMR in Djungarian hamsters may be affected by the degree of prior cold acclimation and temporal patterns ofTachanges experienced by the animals, as averageTadeclines. After cold-acclimation at +5°C for 6 weeks, hamsters reached rates of SusMR that were 35% higher than previously determined and were able to maintain positive energy balances down toTa−9°C. SusMR was unaffected, however, by whether mean cold load was constant or caused byTas cycling between +3°C and as low as −25°C, at hourly intervals. At meanTas between +3 and −3°C hamsters significantly reduced body mass and energy expenditure, but were able to maintain stable body mass at lowerTas (−5 to −9°C). These results indicate that prior cold-acclimation profoundly affects SusMR in hamsters and that body mass regulation may play an integral part in maintaining positive energy balance during cold exposure. Because the degree of instantaneous cold load had no effect on SusMR, we hypothesize that limits to energy turnover in Djungarian hamsters are not determined by the capacity to withstand extreme temperatures (i.e., peripheral limits) but are due to central limitation of energy intake.