Mitochondrial metabolism during daily torpor in the dwarf Siberian hamster: role of active regulated changes and passive thermal effects
Mitochondrial metabolism during daily torpor in the dwarf Siberian hamster: role of active regulated changes and passive thermal effects
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DOI：
10.1152/ajpregu.00310.2007
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发表时间：
2007-11-01
影响因子：
2.8
通讯作者：
Staples, James F.
中科院分区：
文献类型：
--
作者：
Brown, Jason C. L.;Gerson, Alexander R.;Staples, James F.
在日常的冬眠中，西伯利亚仓鼠，Photopus sungorus，代谢率降低了65%，与基础率相比，但所涉及的机制是有争议的。我们研究了肝脏线粒体呼吸，以确定代谢率降低中主动调节变化和被动热效应的可能作用。当在37 ℃下测定时，与正常体温相比，麻痹期间状态3（磷酸化）呼吸显著降低，但状态4（非磷酸化）呼吸没有降低，这表明在日常麻痹期间发生了主动调节的变化。使用自上而下的弹性分析，我们确定，这些活跃的变化，包括底物氧化能力降低和线粒体内膜的质子电导增加。在15 ℃时，线粒体呼吸至少比37 ℃时低75%，但在常温和麻木之间没有差异。这意味着主动调节的变化可能对减少高温下的呼吸作用更重要（即。例如，在进入过程中）和/或具有除了在低温下减少呼吸之外的效果。从37 ℃到15 ℃，呼吸作用的降低主要是由于迟钝和正常体温动物的底物氧化能力显著降低。质子泄漏和磷酸化动力学的温度依赖性变化取决于代谢状态;质子泄漏增加，但在体温正常的动物，而磷酸化活性降低，但在体温正常的动物。总的来说，我们已经表明，在这种物种的日常休眠期间，氧化磷酸化的主动和被动变化都发生了，这有助于减少代谢。
During daily torpor in the dwarf Siberian hamster, Phodopus sungorus, metabolic rate is reduced by 65% compared with the basal rate, but the mechanisms involved are contentious. We examined liver mitochondrial respiration to determine the possible role of active regulated changes and passive thermal effects in the reduction of metabolic rate. When assayed at 37 C, state 3 ( phosphorylating) respiration, but not state 4 (nonphosphorylating) respiration, was significantly lower during torpor compared with normothermia, suggesting that active regulated changes occur during daily torpor. Using top-down elasticity analysis, we determined that these active changes in torpor included a reduced substrate oxidation capacity and an increased proton conductance of the inner mitochondrial membrane. At 15 C, mitochondrial respiration was at least 75% lower than at 37 C, but there was no difference between normothermia and torpor. This implies that the active regulated changes are likely more important for reducing respiration at high temperatures (i. e., during entrance) and/or have effects other than reducing respiration at low temperatures. The decrease in respiration from 37 C to 15 C resulted predominantly from a considerable reduction of substrate oxidation capacity in both torpid and normothermic animals. Temperature-dependent changes in proton leak and phosphorylation kinetics depended on metabolic state; proton leakiness increased in torpid animals but decreased in normothermic animals, whereas phosphorylation activity decreased in torpid animals but increased in normothermic animals. Overall, we have shown that both active and passive changes to oxidative phosphorylation occur during daily torpor in this species, contributing to reduced metabolic