Cardiac function adaptations in hibernating grizzly bears (Ursus arctos horribilis)
Cardiac function adaptations in hibernating grizzly bears (Ursus arctos horribilis)
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DOI：
10.1007/s00360-009-0421-x
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发表时间：
2010-03-01
影响因子：
2
通讯作者：
Robbins, Charles T.
中科院分区：
文献类型：
--
作者：
Nelson, O. Lynne;Robbins, Charles T.
对冬眠哺乳动物心血管生理学的研究可能有助于深入了解进化适应；然而，用于处理野生动物的麻醉可能会影响感兴趣的心血管参数。为了克服这些潜在的偏差，我们研究了冬眠灰熊 (Ursus arctos horribilis) 在 4 年时间内的活动期、过渡期和冬眠期的功能性心脏表型，研究对象是有意识的熊而不是麻醉的熊。这些熊是圈养出生的，并在 5 个月至 4 岁时进行了一系列研究。心率在活动状态（82.6 +/- A 7.7 次/分钟）和冬眠状态（17.8 +/- A 2.8 次/分钟）之间存在显着差异。从活动状态到冬眠状态，舒张压和每搏输出量参数或左心房面积没有差异。左心室体积：冬眠期间质量显着增加，表明心室质量减少。左心室射血分数在活动状态和冬眠状态之间没有差异。相反，与活动状态（40.8 +/- A 1.9%）相比，冬眠期间总左心房排空分数显着降低（17.8 +/- A 2.8%）。冬眠期间心房收缩血流速度和心房收缩射血分数的降低也支持了心房功能的降低。 7.1 +/- A 2.8% 与活动状态期间的 20.7 +/- A 3% 相比。舒张心脏充盈周期的变化，尤其是心房对心室充盈的贡献，似乎是冬眠期间最显着的宏观功能变化。因此，我们认为心房功能的这些变化构成了冬眠期间的主要适应，它允许心肌在极低心率期间保存能量，避免心室扩张并保持健康。这些发现将有助于采取合理的方法来识别潜在的分子机制。
Research on the cardiovascular physiology of hibernating mammals may provide insight into evolutionary adaptations; however, anesthesia used to handle wild animals may affect the cardiovascular parameters of interest. To overcome these potential biases, we investigated the functional cardiac phenotype of the hibernating grizzly bear (Ursus arctos horribilis) during the active, transitional and hibernating phases over a 4 year period in conscious rather than anesthetized bears. The bears were captive born and serially studied from the age of 5 months to 4 years. Heart rate was significantly different from active (82.6 +/- A 7.7 beats/min) to hibernating states (17.8 +/- A 2.8 beats/min). There was no difference from the active to the hibernating state in diastolic and stroke volume parameters or in left atrial area. Left ventricular volume:mass was significantly increased during hibernation indicating decreased ventricular mass. Ejection fraction of the left ventricle was not different between active and hibernating states. In contrast, total left atrial emptying fraction was significantly reduced during hibernation (17.8 +/- A 2.8%) as compared to the active state (40.8 +/- A 1.9%). Reduced atrial chamber function was also supported by reduced atrial contraction blood flow velocities and atrial contraction ejection fraction during hibernation; 7.1 +/- A 2.8% as compared to 20.7 +/- A 3% during the active state. Changes in the diastolic cardiac filling cycle, especially atrial chamber contribution to ventricular filling, appear to be the most prominent macroscopic functional change during hibernation. Thus, we propose that these changes in atrial chamber function constitute a major adaptation during hibernation which allows the myocardium to conserve energy, avoid chamber dilation and remain healthy during a period of extremely low heart rates. These findings will aid in rational approaches to identifying underlying molecular mechanisms.