Liu B, Wang L C, Belke D D
Department of Zoology, University of Alberta, Edmonton, Canada.
Am J Physiol. 1993 Jan;264(1 Pt 2):R104-8. doi: 10.1152/ajpregu.1993.264.1.R104.
Chemically skinned papillary muscles from active and hibernating ground squirrels were used to determine whether the enhanced cardiac contractility observed in hibernation is due to a change in myofilament Ca2+ sensitivity. A similar preparation from rats was used to reflect the changes in a nonhibernator. When examined at pH 7.00 in all three groups and under physiological pH with varying temperatures in the ground squirrels, the calcium concentration at which muscle tension is at 50% maximum (pCa2+50) decreased significantly (P < 0.05) with decreasing temperature (25, 15, and 5 degrees C). When hibernating and active ground squirrels were compared, no significant difference in pCa2+50 was observed at 25 degrees C; however, the values at 15 and 5 degrees C were significantly higher (P < 0.05) in the hibernating squirrels. The results indicate that cardiac myofilament Ca2+ sensitivity decreases significantly at low temperature in both active and hibernating ground squirrels; however, the higher Ca2+ sensitivity in the hibernating squirrels at 15 and 5 degrees C could partially contribute to the enhanced cardiac contractility typically seen during hibernation.
利用来自活跃和冬眠地松鼠的化学去表皮乳头肌，来确定在冬眠期间观察到的心脏收缩力增强是否归因于肌丝对Ca2+敏感性的变化。使用来自大鼠的类似标本反映非冬眠动物的变化。当在所有三组中于pH 7.00进行检测时，以及在生理pH下于不同温度检测地松鼠时，肌肉张力达到最大张力50%时的钙浓度（pCa2+50）随着温度降低（25、15和5摄氏度）而显著降低（P<0.05）。当比较冬眠和活跃的地松鼠时，在25摄氏度下未观察到pCa2+50有显著差异；然而，在15和5摄氏度时，冬眠松鼠的pCa2+50值显著更高（P<0.05）。结果表明，在低温下，活跃和冬眠地松鼠的心肌肌丝对Ca2+的敏感性均显著降低；然而，在15和5摄氏度时，冬眠松鼠较高的Ca2+敏感性可能部分促成了冬眠期间通常所见的心脏收缩力增强。
