Department of Veterinary Clinical Sciences, Washington State University, 100 Grimes Way, Room 17, Pullman, WA 99164, USA.
J Comp Physiol B. 2010 Mar;180(3):465-73. doi: 10.1007/s00360-009-0421-x. Epub 2009 Nov 26.
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 +/- 7.7 beats/min) to hibernating states (17.8 +/- 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 +/- 2.8%) as compared to the active state (40.8 +/- 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 +/- 2.8% as compared to 20.7 +/- 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.
关于冬眠哺乳动物心血管生理学的研究可能提供有关进化适应的见解；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，我们在 4 年的时间里，在意识而非麻醉状态下，研究了活跃、过渡和冬眠期的灰熊（Ursus arctos horribilis）的功能性心脏表型。这些熊是圈养出生的，从 5 个月到 4 岁进行了连续研究。心率在活跃状态（82.6 +/- 7.7 次/分钟）和冬眠状态（17.8 +/- 2.8 次/分钟）之间有显著差异。在舒张和每搏量参数或左心房面积方面，从活跃状态到冬眠状态没有差异。左心室容量/质量在冬眠期间显著增加，表明心室质量减少。左心室射血分数在活跃状态和冬眠状态之间没有差异。相比之下，左心房总排空分数在冬眠期间（17.8 +/- 2.8%）显著低于活跃状态（40.8 +/- 1.9%）。心房收缩血流速度和心房收缩射血分数在冬眠期间也降低，分别为 7.1 +/- 2.8%和 20.7 +/- 3%，表明心房室功能降低。舒张期心脏充盈周期的变化，特别是心房室对心室充盈的贡献，似乎是冬眠期间最明显的宏观功能变化。因此，我们提出，心房室功能的这些变化构成了冬眠期间的主要适应，使心肌能够在极低心率期间节约能量、避免心室扩张并保持健康。这些发现将有助于合理地确定潜在的分子机制。
